Publications by J.A. Trofymow

Gross and aboveground net primary production at Canadian forest carbon flux sites

Wed, 27 Mar 2013

Simultaneous biometric measurements of aboveground net primary production (ANPP) and eddy-covariance measurements of gross primary production (GPP) were made at 18 forest stands with 80 site-years of data across Canada – to assess the fraction of photosynthesis that is used to produce plant tissues and the consistency of carbon allocation patterns across forest ecosystems. The stands included boreal and temperate forests and spanned very young to mature stand ages. Across all sites, ANPP averaged 298 ± 138 gCm^-2 yr^-1 (mean ± 1 s.d.), with the highest values for temperate white pine plantations (307–630 gCm^-2 yr^-1) and harvested Douglas-fir stands (219–459 gCm^-2 yr^-1), and the lowest values for boreal harvested jack pine stands (97–185 gCm^-2 yr^-1). ANPP more than doubled from newly established (≤12 years) to young (13–25 years) stands, then stabilized in young to mature (≥51 years) stands but with diverging trends among species. Inter-site variations in ANPP and GPP were closely related to site characteristics, in particular, to leaf area index, which explained 66% of the variation in ANPP and 80% of the variation in GPP, and absorbed photosynthetically active radiation, which explained 80% of the variation in ANPP and 82% of the variation in GPP. Both ANPP and GPP were also positively correlated with mean annual air temperature, mean annual precipitation, and total soil nitrogen in the upper 10 cm of the mineral soil. ANPP was strongly, positively correlated with GPP and the ANPP/GPP ratio was relatively constant (0.29 ± 0.06), with no consistent differences among species or age classes. The results support the use of a constant ANPP/GPP ratio as a reasonable assumption in models of forest productivity for boreal and northern temperate forests. A similar conclusion is reached for the NPP/GPP ratio when published values of belowground NPP are considered.

An emphasis on fungi and forest or prairie soils. Selected papers from the 2011 Soil Ecology Society conference.

Wed, 05 Sep 2012

This special issue of Applied Soil Ecology contains a selection of peer-reviewed papers presented at the 13th biennial meeting of the Soil Ecology Society (SES) held in Kelowna, B.C., Canada on May 24–27, 2011 on the Okanagan campus of the University of British Columbia. This conference invited presentations on all applied soil ecology research topics, and papers in this special issue examine the roles and interactions of microbes and soil fauna in soil processes in different soil ecosystems, including forests, prairie, and agro-ecosystems. In this introduction, in addition to a synopsis of the conference and papers in the special issue, research topics of the 13 articles in this special issue were compared with 326 articles published in Applied Soil Ecology from 2010 to 2012 to reveal trends and emphasis in research and publications. Although the SES 2011 meeting was not organized around a specific theme, research topic terms show papers in this special issue were more dominated by studies on mycorrhizal fungi and on forest or prairie soils when compared to recent ASE articles.

Decomposition and change in N and organic composition of small-diameter Douglas-fir woody debris over 23 years. (Includes Supplementary Data)

Thu, 21 Jun 2012

Managing second-growth forests for multiple benefits requires enhanced information on decomposition of woody debris generated during forestry operations. Experimental thinning and biomass sampling at the Shawnigan Lake Research Forest on southern Vancouver Island facilitated retrospective sampling of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stem sections (4.9–21.5 cm diameter) from 0 to 23 years after cutting. A sigmoidal pattern of density loss was observed, while a single-exponential fit gave a decay rate (k) of 0.058 year^–1. Initial N concentrations were higher in bark than in sapwood and heartwood, and all increased during decay, while C/N ratios declined to around 175 for wood and 70 for bark. Nitrogen contents initially increased but tended to decline after about 50% C loss. Solid-state ^13C nuclear magnetic resonance spectroscopy showed little change in organic composition, consistent with white-rot fungal decay, with only a few 19-year samples showing large increases in lignin typical of extensive brown-rot decay. Hydrolyzable monosaccharides of wood and bark were dominated by glucose followed by mannose, xylose, galactose, and arabinose. For wood, the mole fraction of mannose decreased with decomposition, whereas those of glucose, arabinose, and galactose increased slightly and that of xylose remained constant for both brown and white rot. Our results support indications that decomposition of smaller diameter woody debris from managed conifer forests will likely be dominated by white-rot fungi, leaving residues high in cellulose rather than in lignin.

The carbon balance of two lodgepole pine stands recovering from mountain pine beetle attack in British Columbia

Mon, 05 Mar 2012

Disturbances play an important role in determining the C balance of North American forests. This study used the eddy covariance (EC) technique to examine the impact of mountain pine beetle (MPB) (Dendroctonus ponderosae) outbreak on the gross ecosystem photosynthesis (P_g), ecosystem respiration (R_e) and net ecosystem production (NEP), of two lodgepole pine-dominated stands in the central interior of British Columbia. MPB-06, an 85-year-old stand, was first attacked in 2006 and by 2010 only ∼16% of the trees remained healthy. MPB-03, a 110-year-old stand with a developed secondary structure (tree seedlings and saplings, sub-canopy and canopy trees that survive the attack), was first attacked in 2003 and by 2007 had >95% pine canopy mortality. Annual NEP increased each year at MPB-06, from −81 g C m^-2 in 2007 to 64 g C m^-2 in 2010, due to an increase in P_g from 440 g C m^-2 in 2007 to 576 g C m^-2 in 2010. Annual R_e was more conservative, −ranging from 512 g C m^-2 in 2010 to 557 g C m^-2 in 2008. At MPB-03, NEP increased from −57 g C m^-2 in 2007 to 3 and 6 g C m^-2 in 2008 and 2009 before falling to −26 g C m^-2 in 2010. Between 2007 and 2010, P_g and R_e ranged from 430 to 516 g C m^-2 and from 487 to 513 g C m^-2, respectively. Variation in NEP at both sites was mainly a result of changes in P_g. At MPB-03, P_g was reduced by drought during the 2009 and 2010 growing seasons. An empirical logistic equation best described the relationship between R_e and soil temperature at 5-cm depth (T_s), and the relationship varied significantly over the four years at both sites. At both sites, over the 4 years the ratio of the growing season totals of modelled R_e using nighttime and daytime NEP data was well within 15% with the exception of 2010 at MPB-06. Growing season averages of foliar net assimilation followed a similar trend as average growing season P_g, increasing from 2007 to 2009 at MPB-06, and decreasing in response to drought in 2009 and 2010 at MPB-03. Growing season water use efficiency (P_g/evapotranspiration) increased from 2.2 to 2.8 g C (kg H₂O)^-1 from 2007 to 2010 at MPB-06, and ranged from 1.7 to 2.0 g C (kg H₂O)^-1 between 2007 and 2010 at MPB-03. Spring NEP was an important determinant of the annual C balance at both sites.

Fine root density distribution and biomass in second- and third-growth Douglas-fir stands on Vancouver Island, British Columbia

Wed, 02 Nov 2011

Fine root and ectomycorrhizal root density and biomass were quantified in 2003 and 2004 by sequential soil coring in a 54-yearold second-growth stand and 3- and 14-year-old third-growth stands of Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) at Fluxnet–Canada research sites on east–central Vancouver Island, British Columbia. We investigated the relationships of fine root mass and carbon concentration (%C) with soil depth, stand age, and soil substrate. Fine root %C varied significantly with stand age, was lower in the forest floor (LFH) and deeper mineral soil than in shallow soil horizons, and was lower for ectomycorrhizal (EM) versus non-EM roots. These results suggest that differences in root %C associated with soil depth and forest stage should be accounted for when scaling root data for carbon (C) budgets. Total fine root density (mass/soil volume) in the LFH was highest in the 54-year-old stand and declined with depth in mineral soil; whereas total, live, and live conifer root density in the mineral soil was generally highest in the 14-year-old stand, intermediate in the 54-year-old stand, and lowest in the 3-year-old stand. Ectomycorrhizal fine root density was highest in the 54-year-old stand, intermediate in the 14-year-old stand, and lowest in the 3-year-old stand; especially so in the LFH and shallowest mineral soil. Total fine root biomass (mass/area) generally increased with stand age in the LFH, but patterns were less definite in mineral soil. When the LFH and mineral soil were combined, total fine root biomass was lowest in the 3-year-old and highest in the 14- and 54-year-old stands. Ectomycorrhizal fine root biomass was significantly higher in the 54-year-old than in either the 14- or 3-year-old stands. The higher fine root biomass in the 14-year-old stand was unexpected; however, the higher EM root biomass in the 54-year-old stand suggests that a greater proportion of carbon is allocated to the ephemeral absorptive structures of the EM fungi in forests at this age.

Determination of ecosystem carbon-stock distributions in the flux footprint of an eddy-covariance tower in a coastal forest in British Columbia.

Fri, 05 Aug 2011

An important consideration when interpreting eddy-covariance (EC) flux-tower measurements is the spatial distribution of forest land surface cover and soil type within the EC flux-tower footprint. At many EC flux-tower sites, there is a range of geospatial data available with the ability to estimate the spatial distribution of forest land cover and soils. Developing methods that utilize multiple geospatial data sets will result in more thorough estimates of ecosystem C stock distributions. The objective of this study was to develop, apply, and validate methods to obtain comprehensive estimates of the spatial distribution of ecosystem C stock components from live-tree, detritus, and soil pools within an EC flux-tower footprint. First, a set of geospatial data sets was collected and assessed for its predictive ability for the measured aboveground C stocks. Next, large tree and snag aboveground C stocks were estimated using two methods: (i) a geospatial regression model, and (ii) most similar neighbor (k-MSN) spatial prediction methodology, and the results were compared with those of a multiple linear regression model using light detection and ranging (LiDAR) data alone. Finally, we applied the spatial prediction methodology to estimate the spatial distribution of other C stock components (including soil C and woody debris).

Including the effects of water stress on decomposition in the Carbon Budget Model of the Canadian Forest Sector CBM-CFS3

Mon, 07 Feb 2011

Decomposition of plant detritus and humified organic matter in terrestrial ecosystems is a primary source of atmospheric carbon dioxide (CO2), yet the dynamics of decomposition are not well understood, particularly their response to climate change. The Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) presently includes a sub-model to simulate the decomposition of dead organic matter carbon pools using base decay rates modified by temperature quotients. In this study, representation of litter decomposition was improved in the CBM-CFS3 by reducing decay rates under limited moisture conditions. Water stress effects were determined from comparisons of model predictions with data from a 12-year national litterbag decomposition study—the Canadian Intersite Decomposition Experiment (CIDET). Several simple water-stress modifiers based on precipitation and potential evapotranspiration were tested, and parameters were simultaneously fit by minimizing the least-squared error. The best-fitting formulation used the annual average of the ratio of monthly precipitation to monthly potential evapotranspiration, and increased the explained variance by 8%. Water-stress modifiers were applied to decay rates to predict carbon stocks at 516 ground plots from a national soil plot database. The addition of the water-stress modifier modestly increased litter and humified organic matter carbon stocks at dry locations and decreased these carbon stocks at non-water-stressed locations. The new ability to lower decay rates of certain dead organic matter pools under limited moisture conditions in the CBM-CFS3 has the potential to reduce bias in carbon flux predictions for those regions and for future climate change scenarios where moisture limits decomposition processes.

Impact of mountain pine beetle on the net ecosystem production of lodgepole pine stands in British Columbia

Thu, 08 Apr 2010

British Columbia (BC), Canada is experiencing a severe mountain pine beetle (MPB) (Dendroctonus ponderosae) epidemic extending over an area of 135,000 km2. The widespread mortality of lodgepole pine (Pinus contorta var. latifolia) caused by the beetle has significant implications for BC's timber supply and Canada's carbon (C) budget. This study used the eddy-covariance technique to examine how the beetle is impacting the net ecosystem production (NEP) of two attacked lodgepole pine-dominated stands in the central interior of BC. MPB-06 is an 83-year-old stand that was first attacked in 2006. At the start of 2007 roughly 60% of the canopy had been attacked and by October 2008 only 21% of the trees remained healthy. MPB-03, a 110-year-old stand, had >95% pine canopy mortality as a result of a 2003 beetle attack, and also differed from MPB-06 in that it had a more developed secondary structure (consisting of tree seedlings and saplings and sub-canopy and canopy trees) that survived the beetle attack. Eddy-covariance measurements were also conducted in two stands near MPB-06 harvested in 2005 and 1997 (CC-05 and CC-97) for approximately three-week periods each during the 2007 growing season. MPB-06 had an annual NEP of -82 and -33 g C m-2, while MPB-03 had an NEP of -56 and 4 g C m-2 in 2007 and 2008, respectively. In the 2007 and 2008 growing seasons (May–September), MPB-06 was a sink of 12 and 52 g C m-2, while MPB-03 was a sink of 17 and 68 g C m-2, respectively. The productivity at MPB-06 resulted from an increase in photosynthesis by the remaining healthy trees and understory vegetation, while at MPB-03 the secondary structure and understory vegetation showed a strong capacity to sequester C due to an opening up of the stand as a result of canopy mortality. Average daily values of NEP during the measurement periods at CC-97 and CC-05 were -0.37 and -0.87 g C m-2, respectively, showing that even 10 years following harvesting, these stands are likely to remain growing season C sources. That MPB-06 and MPB-03 were growing season C sinks suggests that deferring the harvest of stands with significant levels of secondary structure could prevent MPB-attacked forested areas from becoming C sources over extended periods.

Implications of differing input data sources and approaches upon forest carbon stock estimation

Mon, 29 Mar 2010

Site index is an important forest inventory attribute that relates productivity and growth expectation of forests over time. In forest inventory programs, site index is used in conjunction with other forest inventory attributes (i.e., height, age) for the estimation of stand volume. In turn, stand volumes are used to estimate biomass (and biomass components) and enable conversion to carbon. In this research, we explore the implications and consequences of different estimates of site index on carbon stock characterization for a 2,500-ha Douglas-fir-dominated landscape located on Eastern Vancouver Island, British Columbia, Canada. We compared site index estimates from an existing forest inventory to estimates generated from a combination of forest inventory and light detection and ranging (LIDAR)-derived attributes and then examined the resultant differences in biomass estimates generated from a carbon budget model (Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3)). Significant differences were found between the original and LIDAR-derived site indices for all species types and for the resulting 5-m site classes (p<0.001). The LIDAR-derived site class was greater than the original site class for 42% of stands; however, 77% of stands were within ±1 site class of the original class. Differences in biomass estimates between the model scenarios were significant for both total stand biomass and biomass per hectare (p<0.001); differences for Douglas-fir-dominated stands (representing 85% of all stands) were not significant (p=0.288). Overall, the relationship between the two biomass estimates was strong (R 2=0.92, p<0.001), suggesting that in certain circumstances, LIDAR may have a role to play in site index estimation and biomass mapping.

Stoichiometric controls on carbon, nitrogen, and phosphorus dynamics in decomposing litter

Thu, 04 Mar 2010

The mineralization of nitrogen and phosphorus from plant residues provides an important input of inorganic nutrients to the soil, which can be taken up by plants. The dynamics of nutrient mineralization or immobilization during decomposition are controlled by different biological and physical factors. Decomposers sequester carbon and nutrients from organic substrates and exchange inorganic nutrients with the environment to maintain their stoichiometric balance. Additionally, physical losses of organic compounds from leaching and other processes may alter the nutrient content of litter. In this work, we extend a stoichiometric model of litter nitrogen mineralization to include (1) phosphorus mineralization, (2) physical losses of organic nutrients, and (3) chemical heterogeneity of litter substrates. The enhanced model provides analytical mineralization curves for nitrogen and phosphorus as well as critical litter carbon:nutrient ratios (the carbon:nutrient ratios below which net nutrient release occurs) as a function of the elemental composition of the decomposers, their carbon-use efficiency, and the rate of physical loss of organic compounds. The model is used to infer the critical litter carbon:nutrient ratios from observed nitrogen and phosphorus dynamics in about 2600 litterbag samplings from 21 decomposition data sets spanning artic to tropical ecosystems. At the beginning of decomposition, nitrogen and phosphorus tend to be immobilized in boreal and temperate climates (i.e., both C:N and C:P critical ratios are lower than the initial ratios), while in tropical areas nitrogen is generally released and phosphorus may be either immobilized or released, regardless of the typically low phosphorus concentrations. The critical carbon:nutrient ratios we observed were found to increase with initial litter carbon:nutrient ratios, indicating that decomposers adapt to low-nutrient conditions by reducing their carbon-use efficiency. This stoichiometric control on nutrient dynamics appears ubiquitous across climatic regions and ecosystems, although other biological and physical processes also play important roles in litter decomposition. In tropical humid conditions, we found high critical C:P ratios likely due to high leaching and low decomposer phosphorus concentrations. In general, the compound effects of stoichiometric constraints and physical losses explain most of the variability in critical carbon:nutrient ratios and dynamics of nutrient immobilization and release at the global scale.

Aboveground large tree mass estimation in a coastal forest in British Columbia using plot-level metrics and individual tree detection from lidar

Mon, 29 Mar 2010

Plot-level large tree and snag aboveground mass (TSAM) in a second-growth coastal Douglas-fir forest stand in British Columbia was estimated using light detection and ranging (lidar) combining metrics from individually identified trees and snags and plot-level lidar canopy return density. Individual trees were identified using the tree variable window (TreeVaW) algorithm, which identifies tree crowns using a circular moving filter and the relationship between tree height and crown diameter. A multiple linear regression model was then developed to predict plot-level TSAM as determined from ground plots. The predicted heights of individually identified trees were very accurate (r2 = 0.92, SEE = 0.69 m). Plot TSAM was predicted with an r2 = 0.75 and SEE = 29.68 Mg/ha using lidar density and height metrics alone, and a slightly lower r2 = 0.71 and SEE = 31.95 Mg/ha using lidar density metrics with individually identified tree heights. Using individual tree metrics did not improve plot-level TSAM estimation, since a large component of TSAM is contained in complex canopy levels where individual trees are difficult to identify.

Re-establishment of ectomycorrhizae from refugia bordering regenerating Douglas-fir stands in Vancouver Island

Tue, 26 Jan 2010

The objective of this study was to determine the influence of refugia on the rate of recovery of ectomycorrhizal (EM) diversity in clearcut and replanted Douglas-fir (Pseudotsuga menziesii) forests in British Columbia, Canada. Transects were established at two locations on southern Vancouver Island: Northwest Bay and Koksilah. The transects extended from 15 m inside the remaining 90(+)-year-old (mature) or old-growth Douglas-fir-dominated reference stands, to 45 m inside adjacent younger second-growth stands. The average ages of the latter were 6.0 years (regeneration), 27 years (sapling), 57 years (young forest), and 85+ years (mature forest). Diversity of EM was measured in soil cores sampled at five stations along each transect. A total of 83 EM taxa were found. The most common taxa were Cenococcum geophilum, "Pseudotsugaerhiza baculifera", Rhizopogon vinicolor and Piloderma fallax. Analyses of variance and covariance showed that species richness and proportion root colonization were drastically reduced with increasing distance from reference stands. The reduction was smaller for the transitions from reference stand to sapling stands, and insignificant in transitions to young or mature regenerating forest. Despite the full recovery of EM abundance to pre-harvest levels, which occurred approximately 55 years after replanting, differences in community composition remained after 60 years. Future studies should examine particular host-species and also mixed host-species scenarios that could accelerate the recovery process. Silvicultural practices aimed at promoting the re-establishment of EM fungi would include prompt replanting of harvested sites, using small cut-block sizes, minimal destruction of the forest floor, and green-tree retention.

Decreasing uncertainty in CBM-CFS3 estimates of forest soil C sources and sinks through use of long-term data from the Canadian Intersite Decomposition Experiment

Tue, 26 Jan 2010

Dead organic matter submodel parameters of the Carbon Budget Model of the Canadian Forest Sector 3 (CBM-CFS3) were verified using litterbag decomposition data from the Canadian Intersite Decomposition Experiment (CIDET). This national experiment provided 12 years of decomposition time series data from 18 sites across Canada for calibration of decay parameters for foliar litter (very fast decay pool) and aboveground fine woody debris (fast decay pool). Time series of measured carbon remaining were compared to model predictions to improve the model's decomposition algorithm, which includes base decay rates, temperature response coefficients, and the proportion of carbon transferred from quickly decaying dead organic matter pools to the slow humified pool. A statistical approach was developed to optimize several model parameters simultaneously by minimizing residual errors. For foliar litter, which is contained in the aboveground very fast pool in CBM-CFS3, the asymptotic form of the decay function used in the model was consistent with the measured time series for both needle and leaf litter. Optimized decay parameters had a smaller base decay rate (0.36 yr-1 at a 10o C reference temperature), a larger temperature quotient (Q10=2.7), and a slightly larger proportion transferred to the slow pool (0.185) compared to the default model decay parameters. The absolute error between predicted and measured carbon remaining was reduced from 14.1% to 7.6% when the optimized parameters were used in place of the default parameters. Potential model modifications were tested to assess if additional climate variables would further improve model predictions. Adding summer precipitation as a decay modifier and simulating first-year leaching with winter precipitation resulted in modest improvements. For wood blocks, which are contained in the aboveground fast pool in CBM-CFS3, the data were not well represented by the model's asymptotic form of decay. Instead, colder sites had a linear decay rate, and the remaining sites had a variable decay rate that would be better described by a sigmoidal function. Four potential modifications to the decay algorithm were tested to estimate improvements in model predictions of fast pool decay. These included a temperature-dependent time delay, a sigmoidal function for decay, and the addition of a holding pool that had either a delayed transfer or a decayed transfer. These modifications reduced the errors by about 1.9%, 3.4%, 2.2% and 2.6%, respectively. Their implementation in the model would, however, require the introduction and simulation of additional pools. This effort would be justifiable only if more long-term decay data were available to improve model parameterization. Such data are expected in the future from ongoing long-term decomposition experiments.

Chemical Changes During 6 Years of Decomposition of 11 Litters in some Canadian forest sites. Part 1. Elemental Composition, Tannins, Phenolics, and Proximate Fractions

Mon, 30 Nov 2009

Slowing or even cessation of litter decomposition with time is well-known, but there is insufficient understanding of the chemical changes that contribute to increasing recalcitrance. Samples from the Canadian Intersite Decomposition Experiment (CIDET) were used to determine 6-year chemical changes for all 11 litters from a site with rapid initial decomposition (Morgan Arboretum, MAR) and for three litters at three colder sites. Six-year mass remaining was 17–37% at MAR, with higher values at the colder sites. Atomic C/N ratios declined and phenolics and condensed tannins generally decreased to minimal values. However, for the three species compared across four sites, phenolics and tannins showed small increases for species with the lowest initial values and also tended to increase with increasing mass loss. For the foliar litters at MAR, there was an average increase in proportion of acid-unhydrolyzable residue (AUR) and decreases in proportions of acid-hydrolyzable (ACID) and extractable fractions, with final AUR/(ACID + AUR) ratios within 0.55–0.66. Principal component analysis showed that foliar litters (and to a lesser extent wood) became more alike after 6 years, decomposition being associated with increase of Fe, Al, N, and AUR concentrations and decrease of K, Mg, tannins, phenolics, and non-polar and water-soluble fractions. However, litters were also affected by site soil chemistry, with some high 6-year accumulations of Ca, Mg, Fe, Al, Mn, and Mg at two sites. Increasing recalcitrance likely arises from increasing dominance of complex, less-soluble organic structures, collectively represented by AUR, together with increases in heavy elements such as Al and Fe, which also specifically bind and stabilize organic matter.

Chemical Changes During 6 Years of Decomposition of 11 Litters in Some Canadian Forest Sites. Part 2. 13C Abundance, Solid-State 13C NMR Spectroscopy and the Meaning of “Lignin”

Mon, 30 Nov 2009

There is still a poor understanding of how changes in the organic composition of litter contribute to slowing or even cessation of decomposition. Using 13C nuclear magnetic resonance (NMR) spectroscopy of samples from the Canadian Intersite Decomposition Experiment (CIDET), we asked whether increasing lignin per se could account for the well-known increase in acid-unhydrolyzable residue (AUR), and secondly, using three litters from four sites with different mean annual temperatures, whether changes in organic composition would follow similar trajectories with C mass loss. At 6 years, there was 16–39% C remaining for 10 foliar litters and wood blocks at a site with rapid initial decomposition, and higher amounts remaining for three species at three colder sites. 13C NMR spectra obtained with rapid cross-polarization (CP) mainly showed increasing similarity among the foliar litters, although wood showed little change in composition. Foliage generally showed loss of O- and di-O-alkyl C, mainly from carbohydrate, and increase in alkyl, aromatic, phenolic and carboxyl C. However, O-alkyl C loss was limited, especially for litters with slow initial decomposition, and many litters showed relatively small changes in intensity distribution. Quantitative 13C (“BD”) spectra showed similar trends, but even smaller changes in C composition, and 6-year CP difference spectra showed that C was lost across the whole range of structures. Changes in delta 13C were small and variable, but could be correlated to some extent with loss of carbohydrates versus tannins. Lignin was not selectively preserved, and the increase of resistant structures derived from lignin, tannins, and cutin collectively accounts for increasing AUR. Compositional changes of NMR C fractions across sites with different temperatures were small and inconsistent, likely due to the influence of other site factors; however, changes in their contents did largely follow consistent trajectories with %C remaining.

Leaf litter decomposition—Estimates of global variability based on Yasso07 model

Fri, 20 Nov 2009

Litter decomposition is an important process in the global carbon cycle. It accounts for most of the heterotrophic soil respiration and results in formation of more stable soil organic carbon (SOC) which is the largest terrestrial carbon stock. Litter decomposition may induce remarkable feedbacks to climate change because it is a climate-dependent process. To investigate the global patterns of litter decomposition, we developed a description of this process and tested the validity of this description using a large set of foliar litter mass loss measurements (nearly 10,000 data points derived from approximately 70,000 litter bags). We applied the Markov chain Monte Carlo method to estimate uncertainty in the parameter values and results of our model called Yasso07. The model appeared globally applicable. It estimated the effects of litter type (plant species) and climate on mass loss with little systematic error over the first 10 decomposition years, using only initial litter chemistry, air temperature and precipitation as input variables. Illustrative of the global variability in litter mass loss rates, our example calculations showed that a typical conifer litter had 68% of its initial mass still remaining after 2 decomposition years in tundra while a deciduous litter had only 15% remaining in the tropics. Uncertainty in these estimates, a direct result of the uncertainty of the parameter values of the model, varied according to the distribution of the litter bag data among climate conditions and ranged from 2% in tundra to 4% in the tropics. This reliability was adequate to use the model and distinguish the effects of even small differences in litter quality or climate conditions on litter decomposition as statistically significant.

Forest management and maintenance of ectomycorrhizae: A case study of green tree retention in south-coastal British Columbia

Tue, 14 Jul 2009

Assessment of ectomycorrhizal (EM) colonization was carried out in a variable green tree retention experimental block near Powell River, British Columbia. We hypothesized that increasing retention level enhances colonization of EM fungi onto seedlings in harvested areas. We also investigated the role of isolated trees in EM maintenance. Transects were established in treatments where 0% (a clearcut), 5%, 10%, and 30% of trees were retained. Douglas-fir seedlings (Pseudotsuga menziesii) were planted at 5, 15, 25 and 45 m from the remaining forest edge and excavated 18 months later for analysis of EM colonization. Within the forest, soil cores and sporocarp surveys provided information on EM species potentially available for colonization of seedlings. We observed a total of 85 EM morphotypes. The edge effects—declines with distance from the forest, observed in the 0% retention treatment—were diminished in the higher-retention treatments. EM richness and root colonization increased insignificantly with increasing tree retention when the influence of ubiquitous early-stage EM fungi and inherent microsite differences were accounted for. EM diversity next to isolated trees was greater than at 10 m from the trees, but lower than at 5 m from the forest edge. We discuss the implications of these relationships and the role of isolated trees in the context of these exploratory findings. While these results suggest certain trends, they are for a single installation and their applicability to forests elsewhere in the region needs further study.

Assessing tower flux footprint climatology and scaling between remotely sensed and eddy covariance measurements

Mon, 15 Jun 2009

We describe pragmatic and reliable methods to examine the influence of patch-scale heterogeneities on the uncertainty in long-term eddy-covariance (EC) carbon flux data and to scale between the carbon flux estimates derived from land surface optical remote sensing and directly derived from EC flux measurements on the basis of the assessment of footprint climatology. Three different aged Douglas-fir stands with EC flux towers located on Vancouver Island and part of the Fluxnet Canada Research Network were selected. Monthly, annual and interannual footprint climatologies, unweighted or weighted by carbon fluxes, were produced by a simple model based on an analytical solution of the Eulerian advection-diffusion equation. The dimensions and orientation of the flux footprint depended on the height of the measurement, surface roughness length, wind speed and direction, and atmospheric stability. The weighted footprint climatology varied with the different carbon flux components and was asymmetrically distributed around the tower, and its size and spatial structure significantly varied monthly, seasonally and inter-annually. Gross primary productivity (GPP) maps at 10-m resolution were produced using a tower-mounted multi-angular spectroradiometer, combined with the canopy structural information derived from airborne laser scanning (Lidar) data. The horizontal arrays of footprint climatology were superimposed on the 10-m-resolution GPP maps. Monthly and annual uncertainties in EC flux caused by variations in footprint climatology of the 59-year-old Douglas-fir stand were estimated to be approximately 15–20% based on a comparison of GPP estimates derived from EC and remote sensing measurements, and on sensor location bias analysis. The footprint-variation-induced uncertainty in long-term EC flux measurements was mainly dependent on the site spatial heterogeneity. The bias in carbon flux estimates using spatially-explicit ecological models or tower-based remote sensing at finer scales can be estimated by comparing the footprint-weighted and EC-derived flux estimates. This bias is useful for model parameter optimizing. The optimization of parameters in remote-sensing algorithms or ecosystem models using satellite data will, in turn, increase the accuracy in the upscaled regional carbon flux estimation.

Applicability of Diffuse Reflectance Fourier Transform Infrared Spectroscopy to the Chemical Analysis of Decomposing Foliar Litter in Canadian Forests

Mon, 15 Jun 2009

Diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy was used to compare changes in organic chemistry of 10 species of foliar litter undergoing in situ decomposition for 1 to 12 years at four forested sites representing a range of climates in Canada. Three types of foliar litter (conifer, black spruce; deciduous, trembling aspen; and a grass, fescue) were studied on all four sites plus seven additional types (Douglas, fir; western red cedar; white birch; jack pine; beech; bracken fern; and tamarack) studied at the warmest site (Morgan Arboretum [MAR]). For all litter samples, DRIFT spectra were collected, and carbon and N were contents determined. A subset of samples (10 types x 5 years for MAR, three types x 5 years for the other sites) was analyzed by classical chemical methods for proximate fractions. Spectra for subsets of chemically analyzed samples from MAR were used to prepare partial least squares calibration equations for each chemical variable. These calibrations were then used to predict chemical concentrations for samples in a reserved subset, in intervening years, and from the three other sites, and then validated against measured values. Results indicated a trend of decline in proportion of nonpolar and water-soluble extractables with an increase in proportion of acid unhydrolyzable residue. The DRIFT was demonstrated as a fast and simple analysis method for analyzing large numbers of samples to give good estimates of litter chemistry. A single nondestructive sampling using as little as 0.1 g of sample gave reasonable values of carbon, N, and proximate fractions.

Prediction of Nuclear Magnetic Resonance Carbon Fractions in Decomposing Forest Litter Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Partial Least Squares Regression

Mon, 15 Jun 2009

A diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy method was developed to enable DRIFT to be used as a substitute for 13C-nuclear magnetic resonance (13C-NMR) spectroscopy in predicting specific functional groups containing carbon. As part of the Canadian Intersite Decomposition Study, samples of 10 foliar litter types (trembling aspen, American beech, bracken fern, black spruce, Douglas-fir, plains rough fescue, jack pine, tamarack, white birch, western redcedar) and one wood type (western hemlock) at one site and a subset of three foliar litters (trembling aspen, black spruce, plains rough fescue) at three other colder sites undergoing field exposure for 12 years were annually collected. The DRIFT spectra were collected for all samples, with a subset of litter samples also analyzed by 13C-NMR spectroscopy with cross-polarization and magic-angle spinning. Partial least squares calibrations were calculated from the DRIFT spectra for the seven NMR regions representing specific carbon-containing functional groups. These calibrations were then used to predict the proportion of each NMR region in each sample. A single nondestructive sampling using as little as 0.5 g of sample gave measurements for all of the NMR regions. The DRIFT was demonstrated as a fast and simple analysis method for analyzing large numbers of samples to give fair estimates of the NMR regions for each litter type at all four sites.

CBM-CFS3: a model of carbon-dynamics in forestry and land-use change implementing IPCC standards

Wed, 31 Dec 2008

The scientific community, forest managers, environmental organizations, carbon-offset trading systems and policy-makers require tools to account for forest carbon stocks and carbon stock changes. In this paper we describe updates to the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) implemented over the past years. This model of carbon-dynamics implements a Tier 3 approach of the Intergovernmental Panel on Climate Change (IPCC) Good Practice Guidance for reporting on carbon stocks and carbon stock changes resulting from Land Use, Land-use Change and Forestry (LULUCF). The CBM-CFS3 is a generic modelling framework that can be applied at the stand, landscape and national levels. The model provides a spatially referenced, hierarchical system for integrating datasets originating from different forest inventory and monitoring programs and includes a structure that allows for tracking of land areas by different land-use and land-use change classes. Ecosystem pools in CBM-CFS3 can be easily mapped to IPCC-defined pools and validated against field measurements. The model uses sophisticated algorithms for converting volume to biomass and explicitly simulates individual annual disturbance events (natural and anthropogenic). Several important scientific updates have been made to improve the representation of ecosystem structure and processes from previous versions of CBM-CFS. These include: (1) an expanded representation of dead organic matter and soil carbon, particularly standing dead trees, and a new algorithm for initializing these pools prior to simulation, (2) a change in the input data requirement for simulating growth from biomass to readily available merchantable volume curves, and new algorithms for converting volume to biomass, (3) improved prediction of belowground biomass, and (4) improved parameters for soil organic matter decay, fire, insect disturbances, and forest management. In addition, an operational-scale version of CBM-CFS3 is freely available and includes tools to import data in standard formats, including the output of several timber supply models that are commonly used in Canada. Although developed for Canadian forests, the flexible nature of the model has enabled it to be adapted for use in several other countries.

Modeling forest leaf-litter decomposition and N mineralization in litterbags, placed across Canada: a 5-model comparison

Mon, 05 Jan 2009

The performances of five carbon (C) and nitrogen (N) cycling models (FLDM, CENTURY, SOMM, DOCDOM and CANDY) were compared for their ability to quantify mass and N remaining in 10 g leaf-litterbags across the wide range of litter types and sites of the Canadian Intersite Decomposition Experiment (CIDET), over a 6-year period. These models differ in their structure and assumptions, number of compartments, predictor variables and coefficients. Calibrated model outputs displayed similar but not identical trends for mass and N remaining, but differed substantially in mass and N contents per model-defined compartments. The quality of fit between model calculations and data varied as follows: FLDM>CENTURY>DOCMOD>CANDY>SOMM for mass remaining (0.73 < r2 < 0.92), and FLDM>DOCMOD>CENTURY>SOMM>CANDY for the changing N concentrations inside the bags (0.40 < r2 < 0.80). FLDM calculations were the most consistent by CIDET site (21), litter type (10), and years of litterbag retrieval (1993–1998). Best-fitted models were used to project mass remaining and N concentrations inside the bags over the next 50 years, using mean July and January air temperatures, and annual precipitation and initial litter composition as independent predictor variables. Projected model outputs converged for mass remaining, but diverged for the N concentrations, i.e., (1±0.5) g and (2±1)% at year 50, respectively.

Modeling forest leaf-litter decomposition and N mineralization in litterbags, placed across Canada: a 5-model comparison

Tue, 23 Dec 2008

N2O emissions and carbon sequestration in a nitrogen-fertilized Douglas fir stand

Wed, 05 Nov 2008

This study investigated how nitrogen (N) fertilization with 200 kg N/ha of a 58-year-old West Coast Douglas fir stand influenced its net greenhouse gas (GHG) global warming potential (GWP) in the first year after fertilization. Effects of fertilization on GHG GWP were calculated considering changes in soil N2O emissions, measured using the static chamber technique and the soil N2O gradient technique; eddy covariance (EC) measured net ecosystem productivity (NEP); and energy requirements of fertilizer production, transport, and its aerial spreading. We found significant N2O losses in fertilized plots compared to a small uptake in nonfertilized plots. Chamber-measured N loss in the fertilized plots was about 16 kg N2O/ha in the first year, which is equivalent to 10 kg N/ha or 5% of the applied fertilizer N. Soil N2O emissions measured using the gradient technique, however, exceeded the chamber measurements by about 50%. We also compared a polymer-coated slow-release urea with regular urea and found that the former delayed N2O emissions but the year-end total loss was about the same as that from regular urea. Change in NEP due to fertilization was determined by relating annual NEP for the nonfertilized stand to environmental controls using an empirical and a process-based model. Annual NEP increased by 64%, from 326 g C m-2, calculated assuming that the stand was not fertilized, to the measured value of 535 g C m-2 with fertilization. At the end of the year, net change in GHG GWP was -2.28 t CO2 /ha compared to what it would have been without fertilization, thereby indicating favorable effect of fertilization even in the first year after fertilization with significant emissions of N2O.

Derivation of a spatially explicit 86-year retrospective carbon budget for a landscape undergoing conversion from old-growth to managed forests on Vancouver Island, BC

Thu, 23 Oct 2008

To understand the influence of disturbance, age–class structure, and land use on landscape-level carbon (C) budgets during conversion of old-growth forests to managed forests, a spatially explicit, retrospective C budget from 1920 through 2005 was developed for the 2500 ha Oyster River area of Fluxnet-Canada's coastal BC Station. We used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), an inventory-based model, to simulate forest C dynamics. A current (circa 1999) forest inventory for the area was compiled, then overlaid with digitized historic disturbance maps, a 1919 timber cruise map, and a series of historic orthophotographs to generate a GIS coverage of forest cover polygons with unique disturbance histories dating back to 1920. We used the combined data from the historic and current inventory and forest change data to first estimate initial ecosystem C stocks and then to simulate forest dynamics and C budgets for the 86-year period. In 1920, old-growth forest dominated the area and the long-term landscape-level net ecosystem C balance (net biome productivity, NBP) was a small sink (NBP 0.2 Mg C/ ha/year). From 1930 to 1945 fires, logging, and slash burning resulted in large losses of biomass C, emissions of C to the atmosphere, and transfers of C from biomass to detritus and wood products (NBP ranged from -3 to -56 Mg C/ha/year). Live biomass C stocks slowly recovered following this period of high disturbance but the area remained a C source until the mid 1950s. From 1960 to 1987 disturbance was minimal and the area was a C sink (NBP ranged from 3 to 6 Mg C/ha/year). As harvest of second-growth forest began in late 1980s, disturbances again dominated the area's C budget, partially offset by ongoing C uptake by biomass in recovering young forests such that the C balance varied from positive to negative depending upon the area disturbed that year (NBP from 6 to -15 Mg C/ha/year). Despite their high productivity, the area's forests are not likely to attain C densities of the landscape prior to industrial logging because the stands will not reach pre-logging ages. Additional work is underway to examine the relative role historic climate variability has had on the landscape-level C budget.

The global stoichiometry of litter nitrogen mineralization

Mon, 08 Sep 2008

Plant residue decomposition and the nutrient release to the soil play a major role in global carbon and nutrient cycling. Although decomposition rates vary strongly with climate, nitrogen immobilization into litter and its release in mineral forms are mainly controlled by the initial chemical composition of the residues. We used a data set of ~2800 observations to show that these global nitrogen-release patterns can be explained by fundamental stoichiometric relationships of decomposer activity. We show how litter quality controls the transition from nitrogen accumulation into the litter to release and alters decomposers’ respiration patterns. Our results suggest that decomposers lower their carbon-use efficiency to exploit residues with low initial nitrogen concentration, a strategy used broadly by bacteria and consumers across trophic levels.

Litter decomposition and nitrogen and phosophorus dynamics in peatlands and uplands over 12 years in central Canada

Wed, 18 Jun 2008

Comparison of MODIS, eddy covariance determined and physiologically modelled gross primary production (GPP) in a Douglas-fir forest stand

Mon, 15 Jun 2009

Quantification of the magnitude of net terrestrial carbon (C) uptake, and how it varies inter-annually, is an important question with future potential sequestration influenced by both increased atmospheric CO2 and changing climate. However the assessment of differences in measured and modeled C accumulation is a challenging task due to the significant fine scale variation occurring in terrestrial productivity due to soil, climate and vegetation characteristics as well as difficulties in measuring carbon accumulation over large spatial areas. The Moderate Resolution Imaging Spectroradiometer (MODIS) offers a means of monitoring gross primary production (GPP), both spatially and temporally, routinely from space. However it is critical to compare and contrast the temporal dynamics of the C and water fluxes with those measured from ground-based networks, or estimated using physiological models. In this paper, using a number of approaches, our objective is to determine if any systematic biases exists in either the MODIS, or the modeled estimates of fluxes, relative to the measurements made over an evergreen, needleleaf temperate rainforest on Vancouver Island, Canada. Results indicate that 8-day GPP as predicted with a simple physiological model (3PGS), forced using local meteorology and canopy characteristics, matched measured fluxes very well (r2 = 0.86, p < 0.001) with no significant difference between eddy covariance (EC) and modeled GPP (p < 0.001). In addition, modeled water supply closely matched measured relative available soil water content at the site. Using canopy characteristics from the MODIS fraction of photosynthetically active radiation (fPAR) algorithm, slightly reduced the correspondence of the predictions due to a large number of unsuccessful retrievals (83%) due to sun angle, snow and cloud. Predictions of GPP based on the MODIS GPP algorithm, forced using local meteorology and canopy characteristics, were also highly correlated with EC measurements (r2 = 0.89, p < 0.001) however these estimates were biased under predicting GPP. Estimates of GPP based on the most recent MODIS reprocessing (collection 4.5) remained highly correlated (r2 = 0.88, p < 0.001) yet were also the most biased with the estimates being 30% less than the EC-measured GPP. Most of the variance in GPP at the site was explained by the absorbed photosynthetically active radiation. We also compared the nighttime respiration as measured over 2 years at the site with the minimum 8-day MODIS land surface temperature and found a significant relationship (r2 = 0.57), similar to other studies.

Modeling mass and nitrogen remaining in litterbags for Canadian forest and climate conditions

Wed, 17 Oct 2007

A new Forest Litter Decomposition Model (FLDM) is presented to simulate mass, N and carbon/nitrogen ratios (C/N) according to the 1992-1998 leaf litterbag data of the Canadian Intersite Decomposition Experiment (CIDET). This experiment involved 10 litter types, with litterbags placed on the ground of 18 upland and 3 wetland sites across Canada. The calibrated model, based on first-order reaction kinetics, calculates total mass, N concentration and C/N for each litter type and location using: three compartments (fast, slow, and very slow); four parameters for compartment initialization; three for compartment-based decay; three to assess the climate influence on decay; and one each to determine the rate of N-mineralization and the final C/N ratio. With FLDM, the initial fast fraction is determined from the initial water-extractable and acid-hydrolyzable or acid-unhydrolyzable portions of the litter; the initial ash content determines the ratio between the slow and very slow fractions. Mean July and January air temperatures, and annual precipitation, determine the climate effect on litter decay. Initial N concentration and the upland-wetland difference determine the N-mineralization coefficient. Model performance was fairly consistent by litter type, location, and year: r2 ranged from 0.83 to 0.97, from 0.64 to 0.92 and from 0.54 to 0.93 for mass remaining, N concentration and C/N, respectively.

Estimating branch production in trembling aspen, Douglas-fir, jack pine, black spruce, and balsam fir

Wed, 22 Aug 2007

Measuring net primary productivity of trees requires the measurement of total wood production of branches. Recent work on balsam fir (Abies balsamea) has shown that branch-wood production can be estimated as a function of foliage production. We extend the analysis to four other species found in the Canadian forest: black spruce (Picea mariana), jack pine (Pinus banksiana), Douglas-fir (Pseudotsuga menziesii), and trembling aspen (Populus tremuloides). Results show that the ratio of annual branch-wood production to annual foliage production is about 1.0 for conifer species (between 0.86 and 1.12) and 0.56 for aspen during a nondrought year. An analysis using field measurements of litterfall and stem-diameter increment from selected forested sites shows that branch-wood production accounts for a smaller proportion of aboveground net primary productivity in trembling aspen (15%–20%) than in conifer species (25%). Also, litterfall capture of small branches (<1 cm diameter) accounts for only 33% of branch detritus production in conifers and 50% in trembling aspen. This study supports the use of an alternative method for estimating branch-wood production that reduces the potential bias in field estimates of net primary productivity.

Estimating canopy structure of Douglas-fir forest stands from discrete-return LiDAR

Mon, 09 Jul 2007

Variations in vertical and horizontal forest structure are often difficult to quantify as field-based methods are labour intensive and passive optical remote sensing techniques are limited in their capacity to distinguish structural changes occurring below the top of the canopy. In this study the capacity of small footprint (0.19 cm), discrete return, densely spaced (0.7 hits/m-2), multiple return, Light Detection and Ranging (LiDAR) technology, to measure foliage height and to estimate several stand and canopy structure attributes is investigated. The study focused on six Douglas-fir [Pseudotsuga menziesii spp. menziesii (Mirb.) Franco] and western hemlock [Tsuga heterophylla (Raf.) Sarg.] stands located on the east coast of Vancouver Island, British Columbia, Canada, with each stand representing a different structural stage of stand development for forests within this biogeoclimatic zone. Tree height, crown dimensions, cover, and vertical foliage distributions were measured in 20 m × 20 m plots and correlated to the LiDAR data. Foliage profiles were then fitted, using the Weibull probability density function, to the field measured crown dimensions, vertical foliage density distributions and the LiDAR data at each plot. A modified canopy volume approach, based on methods developed for full waveform LiDAR observations, was developed and used to examine the vertical and horizontal variation in stand structure. Results indicate that measured stand attributes such as mean stand height, and basal area were significantly correlated with LiDAR estimates (r 2 = 0.85, P < 0.001, SE = 1.8 m and r 2 = 0.65, P < 0.05, SE = 14.8 m2 ha-1, respectively). Significant relationships were also found between the LiDAR data and the field estimated vertical foliage profiles indicating that models of vertical foliage distribution may be robust and transferable between both field and LiDAR datasets. This study demonstrates that small footprint, discrete return, LiDAR observations can provide quantitative information on stand and tree height, as well as information on foliage profiles, which can be successfully modelled, providing detailed descriptions of canopy structure.

Carbon dioxide fluxes in coastal Douglas-fir stands at different stages of development after clearcut harvesting

Mon, 15 Jun 2009

Forests play a significant role in the global carbon (C) cycle. Variability in weather, species, stand age, and current and past disturbances are some of the factors that control stand-level C dynamics. This study examines the relative roles of stand age and associated structural characteristics and weather variability on the exchange of carbon dioxide between the atmosphere and three different coastal Douglas-fir stands at different stages of development after clearcut harvesting. The eddy covariance technique was used to measure carbon dioxide fluxes and a portable soil chamber system was used to measure soil respiration in the three stands located within 50 km of each other on the east coast of Vancouver Island, British Columbia, Canada. In 2002, the recently clearcut harvested stand (HDF00) was a large C source, the pole/sapling aged stand (HDF88) was a moderate C source, and the rotation-aged stand (DF49) was a moderate C sink (net ecosystem production of -606, -133, and 254 g C m-2 year-1, respectively). Annual gross ecosystem production and ecosystem respiration also increased with increasing stand age. Differences in stand structural characteristics such as species composition and phenology were important in determining the timing and magnitude of maximum gross ecosystem production and net ecosystem production through the year. Both soil and ecosystem respiration were exponentially related to soil temperature in each stand with total ecosystem respiration differing more among stands than soil respiration. Between 1998 and 2003, annual net ecosystem production ranged from 254 to 424 g C m-2 year-1 over 6 years for DF49, from -623 to -564 g C m-2 year-1 over 3 years for HDF00, and from -154 to -133 g C m-2 year-1 over 2 years for HDF88. Interannual variations in C exchange of the oldest, most structurally stable stand (DF49) were related to variations in spring weather while the rapid growth of understory and pioneer species influenced variations in HDF00. The differences in net ecosystem production among stands (maximum of 1000 g C m-2 year-1 between the oldest and youngest stands) were an order of magnitude greater than the differences among years within a stand and emphasized the importance of age-related differences in stand structure on C exchange processes.

Spatial patterns and competition of tree species in a Douglas-fir chronosequence on Vancouver Island

Mon, 23 Oct 2006

While the successional dynamics and large-scale structure of Douglas-fir forest in the Pacific Northwest region is well studied, the fine-scale spatial characteristics at the stand level are still poorly understood. Here we investigated the fine-scale spatial structure of forest on Vancouver Island, in order to understand how the three dominant species, Douglas-fir, western hemlock, and western redcedar, coexist and partition space along a chronosequence comprised of immature, mature, and old-growth stands. We quantified the changes in spatial distribution and association of the species along the chronosequence using the scale-dependent point pattern analyses pair-correlation function g(r) and Ripley's L-function. Evidence on intra- and inter-specific competition was also inferred from correlations between nearest-neighbor distances and tree size. Our results show that 1) the aggregation of Douglas-fir in old-growth was primarily caused by variation in local site characteristics, 2) only surviving hemlock were more regular than their pre-mortality patterns, a result consistent with strong intra-specific competition, 3) inter-specific competition declined rapidly with stand age due to spatial resource partitioning, and 4) tree death was spatially randomly distributed among larger overstory trees. The study highlights the importance of spatial heterogeneity for the long-term coexistence of shade-intolerant pioneer Douglas-fir and shade-tolerant western hemlock and western redcedar.

Decomposition, delta 13C, and the “lignin paradox”

Thu, 25 May 2006

The natural abundance of 13C (delta 13C) generally increases with decomposition of organic matter. This is contrary to the expected decrease, as lignin is hypothesized to accumulate relative to isotopically heavier cellulose. Our objective was to test the hypothesis that 13C depletion should be observed for gymnosperm logs that typically develop advanced brown-rot decay with high lignin content. With increasing lignin concentration [previously determined by nuclear magnetic resonance (NMR)], delta 13C tended to become more negative for samples of Pseudotsuga menziesii, Tsuga heterophylla, Thuja plicata, and unidentified species from Coastal Forest Chronosequence sites of southern Vancouver Island. For a larger sample set without NMR analysis, delta 13C was significantly more depleted for the highest decay classes, and total C was negatively correlated with delta 13C, consistent with the higher total C of lignin than of cellulose. Relationships of total C and delta 13C with density were much weaker. We discuss causes for the variability of delta 13C in coarse woody debris from these sites, and how the apparent paradox in the predicted change of delta 13C with decomposition is largely due to the confusion of lignin, the biopolymer produced by higher plants, with the acid-unhydrolyzable residue (AUR) of the proximate analysis procedure commonly used to assess litter quality in decomposition studies.

Litter decomposition affected by climate and litter quality—Testing the Yasso model with litterbag data from the Canadian intersite decomposition experiment

Wed, 01 Mar 2006

Litterbag experiments provide valuable data for testing the accuracy of predictions of decomposition from soil carbon models. The soil carbon model Yasso describes litter decomposition based on basic climate and litter quality information, and was calibrated using European litterbag data. In this study, we tested the predictive capabilities of Yasso using independent litterbag data for 10 foliage litter types decomposed for 6 years at 18 upland forest sites across Canada (CIDET).

The model underestimated mass of leaf litters remaining on CIDET sites, with only a small systematic error in predicting the effects of climate when effective temperature sum was used as the temperature variable in the model. The overall rate of decomposition was predicted correctly when mean annual temperature was used as the temperature variable, but then the model substantially overestimated climatic effects.

The model correctly predicted differences in decomposition rates among litter types in the early years of decomposition, but underestimated them in later years. The decomposition rate of the litter type richest in phenolic compounds (larch needles) was systematically overestimated, and that of the litter type richest in O-alkyl compounds (grass leaves) was systematically underestimated. Accounting for these factors would improve the general applicability of the model. However, accounting for the initial nitrogen concentration of litter did not improve the accuracy of the model unless the initial lignin (i.e., acid unhydrolyzable residue) content was also taken into account.

We conclude that the model Yasso accounts for most of the effects of climate and initial litter quality on the decomposition of a range of foliage litter types under varying climate conditions. Recalibration of the reference decomposition rates used in the model may improve the accuracy when applying the model outside of Europe.

Patterns of decomposition and carbon, nitrogen, and phosphorus dynamics of litter in upland forest and peatland sites in central Canada

Tue, 05 Apr 2005

We tested whether upland or peatland location affected rates of litter decomposition and nutrient dynamics. We examined the patterns of mass loss and carbon (C), nitrogen (N), and phosphorus (P) gain, retention, or loss in 11 forest tissues over 6 years at three upland and three peatland sites in the Low Boreal, High Boreal, and Low Subarctic zones of central Canada. After 6 years of decomposition, the average litter mass remaining ranged from 35% for fescue grass to 75% for western redcedar needles and 94% for wood blocks placed on the soil surface, with exponential decay coefficients (k) of –0.16, –0.05, and –0.01, respectively. At one pair of sites, the mass remaining and the k values indicated that faster decomposition occurred in the upland site than in the nearby peatland site. The reverse was the case in a second pair. No overall pattern was apparent in the third. In general, Douglas-fir needles decomposed significantly faster in peatland than upland sites, and the reverse pattern occurred for bracken fern. Most foliar litters retained their original N mass and lost P as they decomposed. There were few major differences between N and P dynamics in litters decomposing at upland and peatland sites, though N and P retention in some cases was greater at the peatland sites. These results suggest that longer term (>6 years) differences in decomposition rate and differences in litter quality account for larger C accumulation in peatland than in upland soils.

Diversity of ectomycorrhizae on experimentally planted Douglas-fir seedlings in variable retention forestry sites on southern Vancouver Island

Wed, 05 Jan 2005

Studies were done on Vancouver Island of ectomycorrhizal (EM) communities at four distances (5-45 m) from isolated forest patches in three second-growth (SG) and three old-growth (OG) Douglas-fir sites subject to variable retention harvesting. We tested the hypothesis that retention of mature trees enhances colonization and diversity of EM fungi on seedlings planted in adjacent areas. In total 41 EM morphotypes were described, with mean diversity of 3.47 morphotypes and root colonization of 62% per seedling. Overall, root colonization declined with distance (72% at 5 m vs. 52% at 45 m), as did EM diversity (4.7 at 5 m vs. 2.9 at 45 m). For individual sites, the distance effect was significant for root colonization at four sites and for EM diversity at three to four sites. This suggests that variable retention is important for the recovery of ectomycorrhizal biota in harvested sites. Seedling root colonization was significantly lower in SG sites than in OG sites. Though EM diversity did not differ with stand age, OG sites had potentially more total (34) and unique (14) EM morphotypes than did SG sites (total 27, unique 7). Differences with stand age might be related to the relative abilities of EM fungi to disperse to regenerating second-growth forests.

Functional role of Collembola in successional coastal temperate forests on Vancouver Island, Canada

Wed, 31 Dec 2003

The interrelationships among collembolan feeding groups (FG), decomposition rates, microbial biomass, and forest successional stage were studied at three sites in Douglas-fir dominated stands on the dry leeward side of Vancouver Island, BC, Canada. Each site contained a basic suite (or chronosequence) of four stages of stand development: old-growth (>248 years), regeneration (7–9 years), immature (35–46 years), and mature (80–102 years).

Principal component analysis (PCA) was used to identify four collembolan feeding groups on the basis of gut contents. Three of the feeding groups (FG 1–3) were fungal-feeders, but differed from one another in the types of fungal material consumed. The last group (FG 4) comprised species that ingested particulate organic matter (POM). Significant positive correlations between microbial biomass and collembolan abundance were obtained for the fungal-feeding Collembola (FG 1–3), but not for the detritivorous FG 4. The proportional representation of collembolan species feeding on darkly pigmented fungi (FG 1) was reduced in the regeneration stands, where species feeding on particulate organic matter predominated.

Over the 4 years of this study, the mass loss of decomposing wood chips in litterbags was not significantly influenced by the age of the forest in which the bags were placed. In contrast, the mass loss of needle litter was significantly reduced in regeneration stands. Multiple regressions based on the abundance of the different feeding groups of Collembola provided better estimates of the mass loss of decomposing litter or wood chips than did regressions based on total collembolan numbers.

Abundance, species diversity, and community structure of Collembola in successional coastal temperate forests on Vancouver Island, Canada

Wed, 31 Dec 2003

The ecological implications of the conversion of old-growth temperate rainforests to managed forests have generated much discussion worldwide. This paper examines the effects of such a conversion on different aspects of the biodiversity of the soil collembolan fauna, and attempts to determine the time that will be required for the collembolan fauna to approach the abundance and community structure seen in old-growth forests. The study also investigates the potential of using different measures of species diversity and community structure as indicators of old-growth conditions in forest soils. The study was carried out in three chronosequence sites in Douglas-fir dominated stands on the dry leeward eastern side of Vancouver Island, BC, Canada. Each of the three sites contained stands representing four stages of stand development: regeneration (7–9 years), immature (35–46 years), mature (80–102 years) and old-growth (>248 years). The Collembola were extracted from litterbags containing needle litter or wood chips, and from the forest floor (LFH) layer in the late autumn of four successive years.

Overall abundance of Collembola was highest in the old-growth and lowest in the regeneration stands. Although population numbers in the immature and mature forests were significantly higher than in regeneration stands, they still had not achieved the levels observed in old-growth forests. In the forest floor, species richness was low in regeneration stands compared to later stages of stand development, but did not differ significantly among immature, mature and old-growth stands. Measures of species diversity based on Shannon's and Simpson's indices of diversity did not differ significantly according to the stage of stand development.

It was not possible to distinguish individual collembolan species that could be used as indicators of old-growth conditions. The same species occurred in most or all stand ages, with differences being determined by changes in relative and absolute abundance of the species comprising the community. However, principal component analysis of data on the Collembola of needle litterbags and the LFH layer showed that the collembolan community of the regeneration stands could be clearly differentiated from those of the forested stands. In addition, the collembolan communities of 80–102-year-old forests could still be distinguished from those of the old-growth forests. In contrast, the collembolan fauna of decomposing wood chips was very similar in all stand ages, with the exception of the regeneration stands.

Attributes and indicators of old-growth and successional Douglas-fir forests on Vancouver Island

Mon, 20 Oct 2003

The Douglas-fir forests of coastal British Columbia are within the most heavily modified forest ecosystem types in coastal BC and local land managers are developing new forestry practices to retain elements of old growth within the managed forest area. To determine how successful these practices are requires the selection and monitoring of appropriate attributes and knowledge on how they change with stand development. In this paper we summarize previously published results from an extensive data set on four Douglas-fir dominated sites located on eastern Vancouver Island. Data were collected as part of the Coastal Forest Chronosequences project which was addressing questions on (1) how does conversion to managed forests impact species and forest structural diversity and (2) how does this diversity recover in older second-growth stands. Each site contained four stands, a postharvest chronosequence: regeneration (R, 5–10 years), immature (I, 25–45 years), and maturing (M, 75–95 years) stands, and an old growth (O, >240 years) control stand. Over 20 attributes are summarized including structural attributes, and at three sites, detailed biodiversity and process attributes. All old-growth plots exceeded the minimum age criteria and some but not all of the minimum structural attribute criteria for old-growth Douglas-fir forests in the US Pacific Northwest, reflecting regional or site type differences. Most structural attributes showed their greatest change within the first 100 years, although older stands (M and O) still differed based on tree and snag sizes and tree mass or basal area. Most species abundance and richness attributes and process attributes clearly differentiated R from the forested stages but were of less value for differentiating among older (M and O) stands. Arboreal lichen abundance and species richness; the abundance of cryptogams, achlorophyllus plants, litter collembola, and specific species of fungi and carabids; litter fall and gap fraction were the exception, these attributes clearly differentiating M from O stands. In postharvest stands, the overall pattern of change with succession for most attributes, as inferred from the chronosequence, was confirmed to be very different from a previously published conceptual model for post-fire succession. Compared to the post-fire model, the greatest changes in the postharvest stands occurred early in stand development, associated with canopy closure. Although stand structural attributes can clearly be used to distinguish old-growth features in managed forest stands, none-the-less it is important to monitor and demonstrate, at least for a selection of nonstructural attributes, that forestry practices are effective in maintaining biodiversity and associated processes of old-growth forests in the managed forest area.

Stand structure and species composition in chronosequences of forests on southern Vancouver Island

Thu, 28 Nov 2002

Overstory stand structure was measured in 32 plots in a Canadian Forest Service study on the effects of converting coastal old-growth forest into managed forest. Stand density, tree height, tree diameter at breast height (DBH), crown depth, stem biomass and basal area (BA) of living stems, and density and mass of snags were measured in a chronosequence of three post-harvest stands (R - regeneration (3-8 years); I - immature (25-45 years); M - mature (65-86) years), and O - an old-growth control (> 200 years) at each of eight study sites on Vancouver Island. Four sites were within the very dry CWHxm and four in the very wet CWHvm biogeoclimatic subzones. Results of this study demonstrate that variability and complexity of overstory structure and composition in coastal forests increases with stand age, and that stands on the west side of the island (CWHvm) were more variable and structurally diverse than those on the east side (CWHxm).

Overstory structure attributes collected for Vancouver Island forests in the CWHxm and CWHvm compare favorably to those of others in the Pacific Northwest. However, old-growth plots do not match US Pacific Northwest definitions of old-growth Douglas-fir as well, likely due to regional differences in climate or because chronosequences were on medium to poor sites. Overstory attribute summaries from this study provide some direction for defining old-growth characteristics. However, the variability of many of these attributes is such that more data are required to rationalize a rigorous definition that will withstand scientific and operational scrutiny.

Rates of litter decomposition over 6 years in Canadian forests: influence of litter quality and climate

Tue, 04 Jun 2002

The effects of litter quality and climate on decomposition rates of plant tissues were examined using percent mass remaining (MR) data of 10 foliar litter types and 1 wood type during 6 years exposure at 18 upland forest sites across Canada. Litter-quality variables used included initial nutrient contents (N, P, S, K, Ca, Mg) and carbon fractions (determined by proximate analysis and 13C nuclear magnetic resonance spectroscopy). Climate variables used included mean annual temperature; total, summer, and winter precipitation; and potential evaptranspiration. A single-exponential decay model with intercept was fit using the natural logarithm of 0- to 6-year percent MR data (LNMR) for all 198 type by site combinations. Model fit was good for most sites and types (r2 = 0.64–0.98), although poorest for cold sites with low-quality materials. Multiple regression of model slope (K f ) and intercept (A) terms demonstrated the im-portance of temperature, summer precipitation, and the acid-unhydrolyzable residue to N ratio (AUR/N) (r2 = 0.65) for K f , and winter precipitation and several litter-quality variables including AUR/N for A (r2 = 0.60). Comparison of ob-served versus predicted LNMR for the best overall combined models were good (r2 = 0.75–0.80), although showed some bias, likely because of other site- and type-specific factors as predictions using 198 equations accounted for more variance (r2 = 0.95) and showed no bias.

Harvesting and climate effects on organic matter characteristics in British Columbia coastal forests

Fri, 22 Mar 2002

As part of investigations into the effects of harvesting old-growth forest, we characterized carbon in five organic matter pools in eight forest chronosequences of coastal British Columbia. Each chronosequence comprised stands in four seral stages from regeneration (3-8 yr) to old-growth (>250 yr), with second-growth stands mostly of harvest origin. Stands were located in two biogeoclimatic subzones with contrasting climate (wetter, slightly cooler conditions on the west coast of Vancouver Island than on the east). Carbon concentrations in fine woody debris (FWD), forest floor (LFH), fine roots from LFH, and two water-floatable fractions from 10 to 30 cm mineral soil (MIN-ROOT, 2-8 mm and MIN-FLOAT, <2 mm) showed no significant effects due to climate, seral stage, or site. There were some significant differences in N concentrations, but none related to seral stage. Carbon-13 cross-polarization with magic-angle spinning (CPMAS) nuclear magnetic resonance (NMR) spectra with principal component analysis of relative areas also showed little harvesting effect, but greater variation related to input of coarse woody debris (CWD) vs. roots high in tannin. Overall, there tended to be more spectral features associated with wood and lignin in the west; whereas some MIN-ROOT samples from the drier east side had aromatic intensity attributed to charcoal. The minimal effects of one harvest on organic matter are most likely due to the large legacy effect; however, more intensive management will probably result in less CWD retention, less charcoal input, and less microsite variability in these pools of poorly decomposed organic matter.

Derivation and validation of Canada-wide coarse-resolution leaf area index maps using high-resolution satellite imagery and ground measurements

Tue, 19 Feb 2002

Leaf area index (LAI) is one of the surface parameters that has importance in climate, weather, and ecological studies, and has been routinely estimated from remote sensing measurements. Canada-wide LAI maps are now being produced using cloud-free Advanced Very High-Resolution Radiometer (AVHRR) imagery every 10 days at 1-km resolution. The archive of these products began in 1993. LAI maps at the same resolution are also being produced with images from the SPOT VEGETATION sensor. To improve the LAI algorithms and validate these products, a group of Canadian scientists acquired LAI measurements during the summer of 1998 in deciduous, conifer, and mixed forests, and in cropland. Common measurement standards using the commercial Tracing Radiation and Architecture of Canopies (TRAC) and LAI-2000 instruments were followed. Eight Landsat Thematic Mapper (TM) scenes at 30-m resolution were used to locate ground sites and to facilitate spatial scaling to 1-km pixels. In this paper, examples of Canada-wide LAI maps are presented after an assessment of their accuracy using ground measurements and the eight Landsat scenes. Methodologies for scaling from high- to coarse-resolution images that consider surface heterogeneity in terms of mixed cover types are evaluated and discussed. Using Landsat LAI images as the standard, it is shown that the accuracy of LAI values of individual AVHRR and VEGETATION pixels was in the range of 50-75%. Random and bias errors were both considerable. Bias was mostly caused by uncertainties in atmospheric correction of the Landsat images, but surface heterogeneity in terms of mixed cover types were also found to cause bias in AVHRR and SPOT VEGETATION LAI calculations. Random errors come from many sources, but pixels with mixed cover types are the main cause of random errors. As radiative signals from different vegetation types were quite different at the same LAI, accurate information about subpixel mixture of the various cover types is identified as the key to improving the accuracy of LAI estimates. © 2002 Elsevier Science Inc. All rights reserved.

Environmental Science Advisory Committee Report: 2000 Annual Report. Department of National Defence - CFB Esquimalt

Tue, 10 Jan 2006

The Department of National Defence Science Advisory Committee (ESAC) - CFB Esquimalt was established in 1994 under a letter of understanding as a technical advisory committee reporting to the joint Department of National Defence/ Canadian Forest Service Forest Resource Management Committee. ESAC is a multiagency committee composed of representatives from the Department of National Defence, Canadian Forest Service and Canadian Wildlife Service and representatives from Universities and other interested provincial agencies. The committee has the responsibility of providing professional expertise, advice and supervision of research being conducted on CFB Esquimalt properties and providing opportunities for dissemination of the research results.

A comparison of digital and film fisheye photography for analysis of forest canopy structure and gap light transmission

Thu, 03 Oct 2002

Due to the scarcity and high cost of conventional film-based hemispherical photographic systems, some forest scientists are now using multi-purpose, consumer-grade digital cameras for the analysis of forest canopy structure and gap light transmission. Although the low cost of digital cameras and direct capture of digital images appear to offer significant advantages over film camera systems, relatively little is known about their technical differences from an applications perspective. In this study, we compared the performance of a popular digital camera (Nikon Coolpix 950 with FC-E8 fisheye) with a conventional film camera (Nikon F with Nikkor 8mm fisheye) under different stand structures and sky conditions. Our findings show that the Nikon Coolpix 950 digital camera produced hemispherical canopy photos with substantial color blurring towards the periphery of the exposure. We believe that chromatic aberration associated with the camera's lens optics may be the source of this phenomenon; however, other factors may have also contributed to the diminished image sharpness. Color blur influenced (i) the size, shape, and distribution of canopy gaps; (ii) the accuracy of edge detection and the binary division of pixels into sky and canopy elements, and (iii) the magnitude, range, and replication of canopy openness, leaf area, and transmitted global radiation results. The Nikon Coolpix 950 produced canopy openness measures that were 1.4 times greater than film estimates in 22 of the 36 photo pairs. Cloud cover and sky brightness also influenced the spectral characteristics of the lateral chromatic aberration (halos), and thus had an added and unpredictable effect on canopy openness. Setting the Nikon Coolpix 950 to record in black and white, and shooting only under uniformly overcast skies will help to minimize the unpredictable effects of chromatic aberration. Nevertheless, we recommend a cautious approach when undertaking canopy measurements with the Nikon Coolpix 950, particularly when stands are dense and canopy openness falls below 10%. High-quality (1:4) JPEG compression had no significant influence on mean canopy openness; however, lower XGA and VGA image resolutions combined with 1:4 JPEG compression produced mean canopy openness results that were significantly lower than openness data extracted from uncompressed, full-resolution TIFF photos.

Environmental Science Advisory Committee Report: 1999 Annual Report. Department of National Defence - CFB Esquimalt

Tue, 10 Jan 2006

Characterization of soil P in coastal forest chronosequences of southern Vancouver Island: effects of climate and harvesting disturbance

Mon, 19 Feb 2001

Limitation of tree growth due to inadequate (P) supply has been found for young plantations following harvesting of old-growth in high rainfall areas of coastal British Columbia. To understand the reasons for P limitation, we investigated P chemistry in mineral soil to 50 cm depth in sites from the Coastal Forest Chronosequence project on Vancouver Island. This allowed comparison of biogeoclimatic subzone (higher rainfall on west than east coast sites) and of time from harvesting disturbance (seral stage). Available (Bray 1) P was significantly higher (P<0.001) on the drier east side (up to 50 mg kg-1 ), than on the west side (< 5 mg kg-1 ), although total P values were less divergent (694 mg kg-1, east and 534 mg kg-1, west). There were no significant seral stage effects on total and available P. Extraction with 0.5 M NaOH recovered 50 - 60 % of total P, except for samples from 10 - 30 cm depth on the west side, for which only 20% was recovered, an effect not found for C. Analysis of the NaOH extracts by 31P nuclear magnetic resonance (NMR) spectroscopy showed much higher proportions of orthophosphate P on the east side. West side extracts were higher in organic P forms, especially diesters, typical of forest ecosystems with restricted nutrient cycling and high precipitation. On the west side, low concentrations of available P, higher proportions of organic P in NaOH extracts, and depression of NaOH extractability at 10 - 30 cm are consistent with P being a limiting nutrient for tree growth, a problem that may be exacerbated by harvesting disturbance.

Variability in litter quality and its relationship to litter decay in Canadian forests.

Wed, 20 Dec 2000

Predicting the effects of climate change on litter decomposition requires an improved understanding of the link between organic composition and the parameters used to define litter quality. Carbon-13 nuclear magnetic resonance spectroscopy with cross-polarization and magic-angle spinning (CPMAS NMR) was used to characterize 36 foliar litters, including the species used in Canadian Intersite Decomposition Experiment (CIDET), a Canada-wide long-term litter decomposition study. The litters showed a wide range of organic composition, qualitatively interpreted as the sum of component biopolymers (mainly carbohydrates, cutin, tannins, and lignin). Only weak correlations were found between NMR parameters and Klason lignin (KLIG); however, cluster analysis based on elemental, NMR and proximate analysis gave good separation of botanical classes. NMR also had little predictive value for 3-year CIDET mass losses, which were negatively correlated with both KLIG and KLIG/N. Mass loss generally decreased in the following order: grass > pioneer broad-leafed deciduous > conifer (deciduous and evergreen) > American beech (a fagaceae) > wood. Predictive models for 3-year CIDET mass loss derived from linear regression with elemental, proximate and NMR analyses were superior to those using only NMR parameters, with the best model based on KLIG, N and Ca. Although providing no molecular-level understanding, KLIG integrates the most insoluble lignin, cutin, and tannin components. Limitations and possible improvements for NMR evaluation of litter quality are discussed.

Nutrient concentrations and nitrogen mineralization in forest floors of single species conifer plantations in coastal British Columbia.

Thu, 23 Nov 2000

We examined the extent to which nutrient concentrations and C and N mineralization rates in forests floors under different tree species are predictable from the chemistry of foliar litter and its rate of decomposition. We studied replicated single species plantations of western redcedar (Thuja plicata Donn ex D. Don), western hemlock (Tsuga heterophylla (Raf.) Sarg.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), and Sitka spruce (Picea sitchensis (Bong.) Carr.) at four locations. Nutrient concentrations in forest floors correlated poorly with litter nutrient concentrations; the only significant relationships were for Ca and K. Nitrogen mineralization correlated weakly with forest floor C/N ratio, and differed more among sites than among species. None of the litter chemistry parameters were related to net N mineralization rates. Decomposition was fastest in hemlock litter, intermediate in Douglas-fir litter and lowest in cedar litter. Litter also decomposed more rapidly on hemlock forest floors than on cedar forest floors. Rates of N mineralization in the forest floors were not related to rates of decomposition of foliar litter. Differences among sites in N mineralization rates were related to the understory vegetation composition, particularly the amount of the ericaceous shrub salal, which in turn was related to slope position. These site factors appeared to override the effect of tree species on rates of N mineralization.

Developing an online database of descriptions of ectomycorrhizae

Thu, 14 Sep 2000

Ectomycorrhizae are the mutually beneficial symbioses of fungi and fine roots, and are responsible for the uptake of nutrients that support tree growth.Many species of fungi form ectomycorrhizae with conifers; most are Basidiomycetes or Ascomycetes that form large mushrooms found in forests. It is, therefore, important to investigate how forest management practices affect the health, growth patterns, physiological function,and taxonomic diversity of ectomycorrhizae. Identification of ectomycorrhizae is fundamental to such research. To date, several hundred detailed descriptions of ectomycorrhizae have been published in books,journal articles,and on a compact disk database called DEEMY (DEtermination of EctoMYcorrhizae ), but hundreds more are unavailable in researchers 'private databases. The Database of Descriptions of Ectomycorrhizae (DDE) web site aims to be a comprehensive tool for the identification of ectomycorrhizae by bringing together as many published and unpublished descriptions as possible. A search function, available to all users, has been programmed to act as an electronic synoptic key. The DDE system also allows qualified researchers to add their unpublished descriptions to the database, and to update these descriptions as needed. The DDE database currently contains 338 descriptions; 318 from DEEMY and 20 from A Manual of Concise Descriptions of Ectomycorrhizae (CDE). Entry of descriptions and search profiles is done using a web form with all the characters in the CDE checklist and links to the CDE illustrated glossary.

Relationship of readings from the LI-COR canopy analyzer to total one-sided leaf area index and stand structure in immature Douglas-fir

Mon, 28 Aug 2000

Estimation of leaf area is important in predicting potential growth. This estimation is often done by means of a photometer, such as the LI-COR plant canopy analyzer, but such instruments generally give biased estimates. Consequently, conversion factors are required to convert output from the photometer to the actual leaf area index (LAI). Foliar biomass was estimated in a 52-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand which had been treated with three levels of thinning and three levels of fertilization 28 years previously. The four treatment extremes (no thinning or fertilization up to heavy thinning and heavy fertilization) were sampled for foliage. Projected leaf areas were calculated from these biomass samples using specific leaf areas derived in a previous biomass sampling. Total one-sided leaf area was then computed by dividing the projected leaf areas by 0.9 to allow for lateral leaf curvature. In addition, LAI-2000 readings were taken in the same plots and then factors were derived to convert LAI-2000 readings to total one-sided LAI. These conversion factors were found to vary strongly with quadratic mean diameter, stand density, mean dbh, mean height and stand basal area. The effect of live crown height was minimal. These should allow the prediction of the conversion factor based on two or three of these highly correlated factors.

Assessing bias from boles in calculating leaf area index in immature Douglas-fir with the LI-COR canopy analyzer

Sat, 26 Aug 2000

Measurements of leaf area index (LAI) taken with photometers such as the LAI2000 are biased by boles and branches which stop part of the light from reaching the photometer. We estimated how much of the sky would be obscurred by boles in an immature stand of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) that was stem-mapped and of known diameter, height and height-to-live-crown. These yielded gap fractions which were then converted to bole area index (BAI) via the algorithm used by the LAI2000. The mean BAI, as a fraction of the effective leaf area index (LAIe) calculated by the LAI2000, ranged from <0.01 for Douglas-fir at 24 years of age to about 0.1 at 48 years. Comparing readings on Douglas-fir trees defoliated by root rot with readings on fully foliated trees yielded a proportion of 0.41, which included branches. Measurements were also taken on clumps of maple (Acer macrophyllum Pursh) and alder (Alnus rubra Bong.) both before and after leaf-fall, yielding corresponding proportions, including branches, of 0.41 and 0.25, respectively. The values obtained this way are probably upper limits. The contributions of boles may be appreciable, particularly in mature unthinned stands with closed canopies.

Canopy openness and leaf area in chronosequences of coastal temperate rainforests

Sat, 26 Aug 2000

We examined spatial and temporal differences in canopy openness and effective leaf area (Le) in a series of eight forest chronosequences located on southern Vancouver Island, British Columbia. Structural attributes were measured on the west and east side of the island in immature, mature, and old-growth stands using hemispherical photography and the LAI-2000 plant canopy analyzer (PCA). Old-growth forest canopies were distinct from those of younger stands: they were more open, more heterogeneous in their openness, and maintained a lower stand Le. Although the overall developmental trajectories of forests were similar across the study sites, site-to-site differences in the rate and magnitude of these temporal changes indicated that site-specific factors also play a significant role in determining the character of forest canopies and their development. The most significant changes in canopy structure did not emerge until the later stages of stand development (150-200 years). Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) dominated east-side forests were, on average, more open, more heterogeneous, and had a lower stand Le than the stands dominated by western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western redcedar (Thuja plicata Donn.) forming the west-side chronosequences. Shoot clumping, along with other evidence, suggested that species-related differences in leaf display and the geometry of branching structure might have contributed significantly to these regional patterns.

Environmental Science Advisory Committee Report: 1998 Annual Report. Department of National Defence - CFB Esquimalt

Tue, 10 Jan 2006

Validation of Canada-wide LAI/FPAR maps from satellite imagery

Wed, 24 Oct 2001

Expérience canadienne sur las décomposition interstationnelle (CIDET) Rapport sur l'implantation des stations et sur le projet

Sat, 26 Aug 2000

This report details the background to the establishment of the Canadian Intersite Decomposition Experiment (CIDET). The objectives of the study were: (a) to investigate the long-term rates of litter decomposition and nutrient mineralization over a broad range of forested ecoclimatic regions in Canada; (b) to study the relationship between decomposition rates, substrate quality and climate; (c) to assess the relative importance of site factors and microclimate on decomposition rates; (d) to assess the influence of site moisture regimes on decomposition rates; and (e) to test specific hypotheses on the observed pattern of litter decomposition.

The study was established in 1992 and involved the preparation of almost 11 000 litter bags containing samples of sets of 12 standard litter types. Ten sets were placed in each of four replicate plots on 21 sites (18 upland and 3 wetland) representing a range of forested ecoclimatic regions. Each year for ten years, one set of bags is removed per plot and analyzed for mass loss and carbon, nitrogen and phosphorous content.

The 21 sites cover a broad range of conditions from the wet (yearly precipitation 1782 mm), mild (9.3oC mean annual temperature) Douglas-fir and western hemlock forested sites in the pacific cordilleran ecoclimatic region, to the dry (261 mm), cold (-9.8oC), black spruce forested sites in the subarctic. Surface soil chemical properties generally reflected soil type, with brunisols and regosols having the lower %C and %N and higher pH's than podzols. In general sites in the pacific cordilleran or cool temperate were warmer, wetter and had forests with higher basal area, mean DBH, and height that those in the other ecoclimatic regions. Sites in the boreal, subarctic and transitional grassland formed a board group that could be distinguished from the cordilleran which were at a higher elevation and had forests with generally lower stand densities.

CIDET is a cooperative study involving 20 researchers from the Canadian Forest Service, universities and provincial ministries The successful establishment of CIDET complements similar studies underway in the U.S. and Europe. Together these studies will increase our understanding of the relationship between climate, litter quality, and decomposition processes.

Litter decomposition rates in Canadian forests

Fri, 21 Jul 2000

The effect of litter quality and climate on the rate of decomposition of plant tissues was examined by the measurement of mass remaining after 3 years' exposure of 11 litter types placed at 18 forest sites across Canada. Amongst sites, mass remaining was strongly related to mean annual temperature and precipitation and amongst litter types the ratio of Klason lignin to nitrogen in the initial tissue was the most important litter quality variable. When combined into a multiple regression, mean annual temperature, mean annual precipitation and Klason lignin:nitrogen ratio explained 73% of the variance in mass remaining for all sites and tissues. Using three doubled CO2 GCM climate change scenarios for four Canadian regions, these relationships were used to predict increases in decomposition rate of 4-7% of contemporary rates (based on mass remaining after 3 years), because of increased temperature and precipitation. This increase may be partially offset by evidence that plants growing under elevated atmospheric CO2 concentrations produce litter with high lignin:nitrogen ratios which slows the rate of decomposition, but this change will be small compared to the increased rate of decomposition derived from climatic changes.

Environmental Science Advisory Committee Report: 1997 Annual Report. Department of National Defence - CFB Esquimalt

Tue, 10 Jan 2006

Chronosequences for research into the effects of converting coastal British Columbia old-growth forests to managed forests: an establishment report

Sat, 26 Aug 2000

A program of multidisciplinary research was initiated in 1991 by the Canadian Forest Service to study the changes caused by converting old-growth coastal temperate forests to managed forests. In 1992, plots were established on ten sites on southern Vancouver Island — five sites in Douglas-fir dominated stands on the dry leeward east side of Vancouver Island in very dry variants of the coastal western hemlock zone (CWHxm), and five sites in western hemlock dominated stands on the wetter windward west side of the island in very wet variants of the zone (CWHvm). Each site contained a basic suite of four seral stands — a chronosequence — representing four stages of stand development: regeneration, immature, mature and old growth. Chronosequences were selected so that stands within a site were on similar, slope, elevation and aspect. Most second-growth stands selected were of harvest origin and burned, though mature stands at three sites were of wild–fire or landslide origin.

This report details the background to the establishment of the coastal forest chronosequence experiment and thus serves as an important reference for future reports and publications. The report includes: information on site selection criteria, plot layout and maps; a general introduction to the ecology, physiography, geology and climate of the study area (southern Vancouver Island); and ecosystem descriptions for each site and plot including general site environment, soil descriptions, soil chemistry, general stand characteristics and lists of indicator plant species. Methods for ecosystem description are provided and results summarized and compared between subzones and among sites and seral stages. Brief summaries of each of the 18 studies of ecosystem structure, processes and diversity carried out on these sites during the first 5-year period of the experiment (1992 – 1997) are also provided. Structure studies examined differences in coarse woody debris, overstory and canopy gap distributions; process studies included investigations of changes in site carbon and nutrient levels, transformations of carbon pools, microenvironments and detrital carbon fluxes (litter fall, soil respiration and decomposition); biodiversity studies included characterization of various groups of soil fauna, carabid beetles, mycorrhizal fungi, mushrooms, salamanders, canopy lichens and vascular plants. During the first 5-year period, most of the more detailed process and diversity studies were conducted on east island Douglas-fir dominated sites. Future studies on ecosystem processes and diversity are planned for west island sites.

Chronosequence research offers scientists the opportunity to examine, over a period of a few years, long–term changes in forest succession. The knowledge gained from studies from these sites will assist foresters in improving their stewardship of these forest lands, upon which forest productivity and biodiversity ultimately depend.

The Canadian intersite decomposition experiment (CIDET): Project and site establishment report

Sat, 26 Aug 2000

Comparison of communities of ectomycorrhizal fungi in old-growth and mature stands of Douglas-fir at two sites on southern Vancouver Island

Sat, 26 Aug 2000

An old-growth and a mature stand, each of fire origin and similar in drainage, slope, and exposure, were selected at each of two sites. Soil cores were collected in spring and fall for 2 years in each stand. Ectomycorrhizae were separated into types based on detail examination of morphology and anatomy. All root tips were separated and counted. Sixty-nine morphological types were distinguished. Nineteen accounted for >1% of the 17 500 root tips examined, and 14 types were found in >=5% of the 120 soil cores. Only three types were found in >=20% of the cores. Total richness was approximately 100 fungi. Nine codominant mycosymbionts each colonized 2.8-24% of all tips and together colonized 67% of all tips. Cenococcum geophilum Fr. was the most abundant, followed by a Rhizopogon vinicolor Fr.-like species, an unidentified Piloderma-like species, Lactarius rubrilacteus Hesler & Smith, Piloderma fallax (Libert) Stalpers, and four unidentified species. Old-growth and mature stands had similar richness and diversity of ectomycorrhizal types. There was no evidence that any types were more abundant or frequent in one age-class than in the other.

Introduction to the Coastal Forest Chronosequence Project

Sat, 26 Aug 2000

Structure, processes, and diversity in successional forests of coastal British Columbia

Sat, 26 Aug 2000

Developmental Trends of Canopy Structure in Coastal Forests of British Columbia

Sat, 26 Aug 2000

Coarse woody debris in the coastal forests of southern Vancouver Island

Sat, 26 Aug 2000

Changes in ecosystem mass and carbon distributions in coastal forest chronosequences

Sat, 26 Aug 2000

Changes in ecosystem nutrient concentrations and content on coastal forest chronosequences

Sat, 26 Aug 2000

Chemical and 31P NMR characterization of soil P in coastal forest chronosequences of southern Vancouver Island: effects of climate and disturbance

Sat, 26 Aug 2000

Detrital carbon fluxes and microbial activity in successional Douglas-fir forests

Sat, 26 Aug 2000

Characterization and transformations of organic carbon pools by 13C CPMAS NMR in coastal forest chronosequences of southern Vancouver Island

Sat, 26 Aug 2000

Collembolan succession and stump decomposition in Douglas-fir

Sat, 26 Aug 2000

Comparison of communities of ectomycorrhizal fungi in old-growth and mature stands of Douglas-fir on southern Vancouver Island

Sat, 26 Aug 2000

Soil microarthropod abundance and species richness in successional Douglas-fir forests

Sat, 26 Aug 2000

Microfungal diversity in successional Douglas-fir forests

Sat, 26 Aug 2000

Distribution of ectomycorrhizas in microhabitats in mature and old-growth stands of Douglas-fir on southeastern Vancouver Island

Sat, 26 Aug 2000

Knowledge of the functional diversity of ectomycorrhizas is needed to design forest management practices that sustain both commercial yield of timber and biological diversity. We surveyed the distribution of ectomycorrhizal types in logs, stumps, the forest floor and mineral soil, in mature (90-y) and old-growth (290, 440 y) stands of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco]. Ectomycorrhizal abundance (root-tips 1-1 of soil) and frequency (occurrence in soil cores) were related to soil chemical characteristics and habitats. Density of ectomycorrhizal rooting was greater in the forest floor (LFH) over mineral soil (114 tips 1-1) than in mineral soil (28) or logs (46). Logs contained more ectomycorrhizal root tips and more types of ectomycorrhizas than stumps. Piloderma fallax (Libert) Stalpers preferred woody substrate; two unidentified types, including "Pseudotsugarhiza baculifera" (Piloderma?) (Mueller, W. R. and Agerer, R. (1996) "Pseudotsugaerhiza baculifera" + Pseudotsuga menziesii (Mirb) Franco. In Descriptions of Ectomycorrhizae, ed. R. Agerer, pp. 95-100. Einhorn-Verlag, 73502 Schwabisch Gmund, Munich.), were found almost exclusively in the forest floor and coarse woody debris and another unidentified type (CDE3) was found only in mineral soil. There was little correlation between ectomycorrhizal abundance and chemical content of soil cores, perhaps due to heterogeneity of soil environment within cores. Future studies might best focus on particular fungi or microhabitats.

13C CPMAS NMR spectroscopy and chemical analysis of coarse woody debris in coastal forests of Vancouver Island

Sat, 26 Aug 2000

The coastal forests of British Columbia have large accumulations of coarse woody debris, and information on this pool is considered essential in developing sustainable management practices. We characterized coarse woody debris (7-12 and >12 cm diameter) in forest chronosequences of four age classes located on east and west sides of Vancouver Island. For three species (Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western hemlock (Tsuga heterophylla (Raf.) Sarg), western redcedar (Thuja plicata Donn.)) and unidentifed samples, increases in decay class (I to V, assigned in the field) were associated with decreasing density, and small increases in concentrations of C, N, and P. Sulfur concentrations (0.6 to 2.4 g/kg) were higher than those found elsewhere for wood and did not show any significant changes with decay class. Carbon-13 nuclear magnetic resonance spectroscopy with cross polarization and magic-angle spinning (13C CPMAS NMR) was used to analyse organic components in a subset of samples >12 cm. Logs up to decay class III generally showed little change in composition or a slight increase in polysaccharide C. After this, polysaccharide was lost more quickly and logs of decay class V were composed almost entirely of lignin, a pattern consistent with decay by brown-rot fungi. However, two samples of western redcedar decay class III and IV showed accumulation of polysaccharide, the pattern expected from white-rot fungi. The results of the density, chemical and NMR analysis indicate that for management purposes, a system with fewer decay classes would suffice.

Special issue on Structure, Process, and Diversity in Successional Forests of Coastal British Columbia

Sat, 26 Aug 2000

Arboreal lichens in successional forests on southern Vancouver Island

Sat, 26 Aug 2000

Changes in the relative abundance and diversity of arboreal lichens on young branches were studied on chronosequence plots established on southern Vancouver Island by the Canadian Forest Service at four sites in the Very Dry Maritime (CWHxm) and four sites in the Very Wet Maritime (CWHvm) Coastal Western Hemlock (CWH) biogeoclimatic subzones. A total of 32 stands were sampled. Each site had a chronosequence of stands of four age classes: old growth (176-435 years), regeneration (3-9 years), immature (32-43 years), and mature (66-99 years) stands. The branches examined had been sampled for foliar nutrient analysis study being conducted on these sites. Entire branches were collected from the upper crown of three trees of each species found in each plot. To supplement this undirected sample, a more directed sample was conducted at one site in the CWHxm (Koksilah) where lichens on older windfall branches and on the bark were also sampled. Lichen individuals were counted and identified to the species level. Many young branches had no lichens or had recent immigrants only. On young branches or older substrates, more species were found in mature or old-growth plots than in immature or regenerating plots. Branches from old-growth plots had more highly structured and richer communities, and more species of crustose lichens. There were more species of lichens on Douglas-fir, which predominates on the drier sites, than on other conifers, and the drier sites in the CWHxm had a richer lichen flora than those in the wetter CXHvm.

Environmental Science Advisory Committee Report: 1996 Annual Report. Department of National Defence - CFB Esquimalt

Tue, 10 Jan 2006

A method for estimating canopy openness, effective leaf area index, and photosynthetically active photon flux density using hemispherical photography and computerized image analysis techniques

Sat, 26 Aug 2000

Indirect optical techniques have been used increasingly in place of more laborious and often-destructive direct methods to derive stand-level estimates of gap fraction distribution, canopy openness, and effective leaf area index. Hemispherical canopy photography, combined with digital image analysis, is one indirect technique that has proven to be a fast and efficient way to measure various attributes of canopy structure and to predict seasonal patterns of forest canopy light transmission.

The Canadian Forestry Service, Pacific Forestry Centre, utilized hemispherical photography and paired LAI-2000 Plant Canopy Analyzers to measure gap fraction distribution, canopy openness, effective leaf area index, and seasonally-integrated understory light levels in several age sequences of Coastal Western Hemlock and Douglas-fir forests on southern Vancouver Island, British Columbia, Canada. The main purpose of the research was to document some of the structural changes caused by the conversion of old-growth temperate forests to second growth. This report describes the general theory, practical application, and technical shortcomings associated with the hemispherical photography and image-processing component of this project. The field and analytical methodologies used in this research are presented as a case study for those interested in similar ecological applications.

Current hemispherical image analysis systems have not kept pace with evolving digital technologies, computer hardware and software, or scientific models. A number of improvements must therefore be made to realize the full potential of this technique. Hemispherical models do not take into account the effects of local weather conditions, nor do they compensate for the effects of regional landform geometry and site orientation on the distribution of direct and diffuse solar radiation. Post-processing techniques that would correct for some of these deficiencies are possible, but only if intermediate summary data are made accessible to the end-user.

13C nuclear magnetic resonance spectroscopy with cross-polarization and magic-angle spinning investigation of the proximate-analysis fractions used to assess litter quality in decomposition studies

Sat, 26 Aug 2000

Proximate analysis is often used in decomposition studies to characterize the organic components of foliar litter. The percent weight residue remaining after extraction by nonpolar and polar solvents and H2SO4 hydrolysis (Klason lignin, KL) is commonly used as a measure of litter quality and a modelling parameter. While KL is associated with resistance to decay, its nature is not well understood and it has long been suspected that it incorporates nonlignin components. We used solid-state 13C nuclear magnetic resonance (NMR) spectroscopy to characterize litter, extracted residue, and the KL fraction of five species. NMR shows that cutin and condensed tannin are both significant components of litter and its extraction residues, in addition to lignin and carbohydrate. Hydrolysis with H2SO4 removes carbohydrates and amino acids, leaving the KL fraction derived from cutin, tannin, and lignin. Tannin retention in KL was also demonstrated by a hydrolysis study of purified tannins and a brown-rot lignin, using both NMR and the proanthocyanidin assay for condensed tannins. Although the NMR results are qualitative at this stage, it is clear that KL has limited use as a parameter controlling litter decomposition, and that other biopolymers should not be ignored in conceptual models, chemical analysis, and experimental design.

Coarse woody debris in chronosequences of forests on southern Vancouver Island

Sat, 26 Aug 2000

We examined trends of coarse woody debris (CWD) abundance in chronosequence plots established by the Canadian Forest Service on the drier east side (CWHxm subzone) and the wetter west side (CWHvm subzone) of southern Vancouver Island. Overall, total biomass of CWD on the east side was substantially (and significantly) lower than on the west side. Mean total biomass in the chronosequences ranged from 17 Mg/ha to 38 Mg/ha on the east side and 65 Mg/ha to 191 Mg/ha on the west side.

We found that total biomass of CWD followed a U-shaped curve over the chronosequence in three of four sites on the west side (CWHvm), while no overall trend was detectable for total biomass in the east side (CWHxm). Further, in both subzones, CWD was skewed to lower decay classes in younger stands, and more normally distributed in older stands. On the east side, CWD in young stands was biased to small size class CWD, and more uniformly distributed in older stands. Conversely, on the west side, CWD tended to be biased to larger size classes in all age classes. Finally, on the east side, Douglas-fir was the most common species among classified CWD; on the west side, western hemlock and western redcedar were most common.

On both the east side (CWHxm) and west side (CWHvm), variance in CWD loadings among plots was substantial. This may have limited our ability to detect some trends, and suggests that other factors besides those examined in this study influence CWD abundance. Finally, it is possible that the regenerating, immature and most mature stands examined in this study are not following the same developmental trajectory as old stands because they were initiated after harvesting while old stands were initiated after natural disturbances. Further studies comparing CWD characteristics in harvested and naturally disturbed stands would improve understanding of the differences in CWD dynamics that result from different disturbance types.

Piloderma fallax (Libert) Stalpers and Pseudotsuga menziesii (Mirb.) Franco

Tue, 20 Sep 2005

Environmental Science Advisory Committee Report. 1995 Annual Report. Department of National Defence - CFB Esquimalt

Fri, 13 Aug 2004

The Department of National Defence Environmental Science Advisory Committee (ESAC) - CFB Esquimalt was established in 1994 under a letter of understanding as a technical advisory committee reporting to the joint Department of National Defence / Canadian Forest Service Forest Resource Management Committee. ESAC is a multiagency committee composed of representatives from the Department of National Defence, Canadian Forest Service and Canadian Wildlife Service and representatives from Universities and other interested provincial agencies. The committee has the responsibility of providing professional expertise, advice and supervision of research being conducted on CFB Esquimalt properties and providing opportunities for dissemination of the research results. The committee set up a formal permitting system to facilitate the tracking of proposals to do research on CFB Esquimalt lands. During 1995 a total of 22 proposals were received and 20 permits were issued. The committee met four times during the year to review policy and proposals. To facilitate the communication and transfer results of research on DND properties to member agencies as well as amongst researchers working on CFB Esquimalt lands, the committee cosponsored two workshops during the year. One sponsored jointly by the committee and Environment Canada was open to all project proponents who had done research on DND lands during the year. The other was held at the Pacific Forestry Centre and was for the project proponents who had conducted work under a joint proposal coordinated by the Canadian Wildlife Service and funded by DND Headquaters. The purpose of this report is to provide background on the committee, its terms of reference and information on the permitting process. As well the report provides research summaries of reports for permitted projects completed in 1995 and annual reports for permitted projects continuing in following years. A cumulative bibliography of reports on environmental research conducted on CFB Esquimalt lands since 1994 and available at the Pacific Forestry Centre Libray is also provided.

Fate of urea and urea formaldehyde nitrogen in a one-year laboratory incubation with Douglas-fir forest floor

Sat, 26 Aug 2000

In a 1 yr laboratory incubation of a Douglas-fir forest floor (FH) the effects of two different kinds of organic N compounds, fast-release urea (U) and slow-release ureaformaldehyde (UF), on N transformations were studied. Compounds labelled with 15N were used to follow the mineralization and distribution of added N in the following pools: NH4+-N, (NO2- + NO3-)-N, soluble organic N, microbial biomass N and total N in the soil residue. The effects of U and UF on microbial activity (CO2 production), microbial biomass (FE and SIR) and on the numbers of autotrophic nitrifiers (MPN) were also studied. The pattern of transformation of N was quite different. In the U-treated soils the added N contributed mostly to the exchangeable NH4+ pool, whereas in the UF-treated soils the highest amount of the added N was found in the soil residue. In the U-treated soils the amount of NH4+ was constant throughout the experiment, but the 15N in it was diluted by mineralization of native organic N. In the UF-treated soils the accumulation of exchangeable NH4+ started slowly and increased steadily. However, the atom % 15N excess in the NH4+ pool stayed constant, as it did in the soil residue. This unchanged 15N enrichment of NH4+ indicates formation of a UF-humic complex. Higher atom % 15N excess in the UF-treated soils in the exchangeable NH4+ pool (2.8%) than in the soil residue (1.5%) suggests also that the UF-N entered the active organic N pool in the soil. The results presented here help to explain earlier field observations, where UF was shown to improve the N status of forest soil, and the applied N was retained in an available N pool.

Influence of body size of soil fauna on litter decomposition and 15N uptake by poplar in a pot trial

Sat, 26 Aug 2000

We combined the advantages of litter-basket and microcosm techniques to study the decomposition of 15N tagged Douglas-fir litter and uptake of labelled N by poplar plants. This was done in microcosms in the greenhouse under artificial summer and winter conditions. The microcosms contained litter baskets that excluded certain soil fauna based on body size. Litter baskets of varying mesh-size containing 15N-enriched defaunated litter were embedded in a simulated coniferous forest floor of unlabelled organic and mineral soil layers. Four litter-basket treatments were established: 1, 5 mm mesh allowing entry of all fauna, but macropredators were excluded; 2, 5 mm mesh, but macropredators were included; 3, 0.5 mm mesh with entrance for mesofauna only; and 4, 48 µm mesh allowing only the microfauna to enter the baskets. After 40 weeks, the development of faunal populations outside the litter baskets was similar in each treatment, except for the absence of macropredators and a greater number of millipedes in treatment 1. Fauna colonizing the litter baskets clearly differed among treatments. No treatment differences were detected in plant biomass and in the uptake of total-N by poplar. However, the 15N content in treatment 4 plants was significantly lower than in others. On a simple net loss basis, significantly larger amounts of the N and litter remained in the litter baskets with the 5 mm mesh than with smaller mesh (treatments 3 and 4). However, the dilution of 15N in litter baskets indicated translocation of external organic matter into litter baskets, confirming the limitations of conventional litter bag methods that use N content and gravimetric measurements only. After including translocation and adjustment of 15N content in litter baskets and surrounding pot soil, actual losses of N and mass were reversed: treatment 3>1>2>4, with treatment 4 being significantly less than others. Top predators had no apparent influence on any of the functional variables measured, suggesting that nutrient dynamics are mainly regulated by interactions occurring near the base of the detrital foodweb.

A manual of concise descriptions of North American ectomycorrhizae including microscopic and molecular characterization

Sat, 26 Aug 2000

Microbial respiration and biomass (substrate-induced respiration) in soils of old-growth and regenerating forests on northern Vancouver Island, British Columbia

Sat, 26 Aug 2000

In studying the basal respiration, microbial biomass (substrate-induced respiration, SIR), and metabolic quotient (qCO2) in western redcedar (Thuja plicata Donn ex D. Don)-western hemlock [(Tsuga heterophylla (Raf.) Sarg.] ecosystems (old-growth forests, 3- and 10-year-old plantations) on northern Vancouver Island, British Columbia, Canada, we predicted that (1) soil basal respiration would be reduced by harvesting and burning, reflecting the reduction in microbial biomass and activities; (2) the microbial biomass would be reduced by harvesting and slash-burning, due to the excessive heat of the burning or due to reduced substrate availability; (3) microbial biomass in the plantations would tend to recover to the pre-harvesting levels with growth of the trees and increased substrate availability; and (4) microbial biomass measured by the SIR method would compare well with that measured by the fumigation-extraction (FE) method. Decaying litter layer (F), woody F (Fw) and humus layer (H) materials were sampled four times in the summer of 1992. The results obtained supported the four predictions. Microbial biomass was reduced in the harvested and slash-burned plots. Both SIR and FE methods provided equally good estimates of microbial biomass in the samples [SIR microbial C (mg g-1)=0.227+0.458 FE microbial C (mg g-1), r=0.63, P=0.0001] and proved suitable for microbial biomass measurements in this strongly acidic soil. Basal respiration was significantly greater in the old-growth forests than in the young plantations (P<0.05) in both F and H layers, but not in the Fw layer. For the 3- and 10-year-old plantations, there was no difference in basal respiration in F, Fw, and H layers. Basal respiration was related to changes in air temperature, precipitation, and the soil moisture content at the time of sampling. The qCO2 values were higher in the old-growth stands than in the plantations. Clear-cutting followed by prescribed burning did not increase soil microbial respiration, but CO2 released from slash-burning and that contributed from other sources may be of concern to increasing atmospheric CO2 concentrations.

Litter quality and its potential effect on decay rates of materials from Canadian forests

Sat, 26 Aug 2000

Decomposition is influenced by a wide array of factors including macroclimate, microclimate, soil biota, soil nutrients, substrate piece size and substrate quality. To separate the influence of some of these factors a 10-year study, the Canadian Intersite Decomposition Experiment, was established in 1992 to measure the decay of 11 standard litter types on a range of forest types at 21 sites across Canada. As part of the study we analyzed the initial elemental contents (N, P, S, K, Ca, Mg) and C fractions (extractables, cellulose, hemicellulose, lignin) by 13C NMR and wet chemical proximate analysis in a total of 37 primarily foliar litter types representative of the range of species found at the different CIDET sites. Litter types especially non-conifer species varied greatly in their qualities. Principal component analyses showed that the litter types could be distinguished by the elemental macronutrient contents through the ratio of N+P+K:S, by proximate chemical analyses through the ratio of water soluble:acid fractions, and by NMR through the ratio of O-alkyl:alkyl C. Litter quality data were used in three simple models of litter decay to predict how the mass loss of the different litter types could vary. Two models using a linear or single exponential decay equation and litter lignin and N content predicted a 2-5 fold difference in total mass loss for the different litter types. A third model using a summed exponential decay equation for three chemical fractions and a ligno-cellulose index predicted that for all but one litter type, variation in mass loss between types would be less than a 20%.

Influence of micro- and macro-habitat factors on collembolan communities in Douglas-fir stumps during forest succession

Sat, 26 Aug 2000

We studied the relative importance of micro- and macro-habitat factors on collembolan communities in decaying stumps in three Douglas-fir ecosystems. Each ecosystem contained four seres: regeneration (3-8 years old), immature (25-45 years old), mature (65-85 years old), and old-growth stands (over 200 years old). Stumps were classified, depending on stage of wood decay as: sound, moderate decay, and advanced decay. The relationship between collembolan communities and habitat factors was determined by canonical correspondence analysis (CCA) and detrended correspondence analysis (DCA).

Macrohabitat factors (stand age and study site) were the most important ones affecting species distribution. When data were pooled for season and stump decay stages, collembolan communities were characteristically grouped by seres, particularly for the regeneration and old growth. However, only a few species were characteristic of a particular sere, notably Vertagopus alpa, Hymenaphorura cocklei, and Folsomia stella in old-growth forests, and Anurophorus septentrionalis and Ballistura libra in regeneration seres. In contrast to collembolan species, microhabitat factors in the stump were influenced more by season than by stand age or site. DCA-ordination indicated that within an individual season, microhabitat factors, especially %C, %P and microbial biomass, were important determinants of collembolan distribution.

Common and abundant collembolan species tended to be positively correlated with %C, but negatively correlated with %N, %P, numbers of nematodes and microbial biomass. We suggest that collembolan numbers were not directly related to the first four factors and that the negative correlation with microbial biomass was caused by excessive grazing on fungi by the Collembola.

Characterization of organic matter in a forest soil of coastal British Columbia by NMR and pyrolysis-field ionization mass spectrometry

Sat, 26 Aug 2000

Organic matter in the soil profile under a young Douglas-fir stand in coastal British Columbia was characterized by examining intact samples of fresh litterfall and organic horizons (LF, H), and fractions (floatables, humic acid [HA], fulvic acid [FA], humid [HU]) from the three mineral horizons (Ae, Bm, BC). Some 30-40% of the carbon in the mineral horizons was found in poorly-decomposed plant material floatable in water, a fraction whose characteristics changed little with depth, and which contained over 1% Fe. The proportion of soil C in HA plus FA was approximately 8%, but the ratio of C in FA/HA increased with depth. Solid-state 13C NMR spectra of litterfall, LH and H samples showed effects of decomposition, in particular a decrease in O-alkyl C from litterfall to LH to H, and degradation of resolution from LF to H. For the mineral soil fractions, both floatables and de-ashed HU ('HUd' prepared by HCl/HF treatment) indicated high levels of the original plant biopolymers, including a large alkyl component. Solution 13C spectra of the HAs from mineral horizons showed little difference with depth, except that peaks due to lignin were more pronounced for the Bm HA. The NMR spectra of FAs were high in O-alkyl and carboxyl C. Pyrolysis-field ionization mass spectrometry confirmed and extended the results from NMR and chemical analyses, in particular demonstrating the accumulation of suberin in some fractions and the leaching and decomposition of lignin components with increasing depth in the mineral horizons. The general features of the HA, FA and HUd from this forest soil, and the effects of decomposition and pedogenesis were similar to those widely found for agricultural and forest soils. However, the accumulation of suberin, and the leaching and decomposition of lignin are particularly associated with forest soils. The low proportion of soil C in HA and FA, and the high proportion in poorly decomposed, iron-rich plant fragments suggest that decomposition is somewhat limited at this site, which is classified as having low fertility. The high accumulations of alkyl C from suberin may also indicate, or contribute to inhibition of decomposition.

An introduction to the coastal forest chronosequences

Tue, 16 Aug 2005

An overview of the stand characteristics of the intensively studied chronosequence plots

Tue, 16 Aug 2005

Assessing the effects of forestry practices on carbon and nutrient dynamics in coastal forests: an introduction to Project PC-71-20

Tue, 16 Aug 2005

Effects of converting coastal old-growth forests to managed forests: changes in site carbon and nutrient contents during post-disturbance succession

Tue, 16 Aug 2005

Long-term recovery and availability of 15N-fertilizer applied to immature Douglas-fir

Tue, 16 Aug 2005

Soil microbial activity in coastal Douglas-fir forests

Tue, 16 Aug 2005

The Canadian Intersite Decomposition Experiment (CIDET): long-term rates of leaf litter and wood decay

Tue, 16 Aug 2005

Testing the performance of FORCYTE-11 against results from the Shawnigan Lake thinning and fertilization trials on Douglas-fir

Sat, 26 Aug 2000

This project was undertaken to test and evaluate the performance of the FORCYTE-11 model using data from Forestry Canada's thinning and fertilization trials of Douglas-fir at Shawnigan Lake, British Columbia. The project was divided into two distinct phases. In phase I, FORCYTE-11 was run using the standard Vancouver Island Douglas-fir input data provided by the model's authors. The model was used to simulate four treatments at Shawnigan Lake and its performance was evaluated using statistical and graphical techniques on 21 variables. In phase II of the project the model was calibrated using data from the Shawnigan Lake control plots and the simulations and evaluation were repeated for the same four treatments and 21 variables. Additional runs were made for all 15 treatments to compare the model and data rankings of the treatments for three variables.

Phase I results indicated the model was not well calibrated for the Shawnigan Lake site. Simulation of tree growth on the control plots was inaccurate. Foliage biomass increased too rapidly in the simulations for all treatments. At crown closure the model predicted N limitation resulting in an extreme underestimate of foliage biomass on the control plots. Simulation of foliage biomass was more accurate for thinned or fertilized plots. Decomposition processes were not well calibrated. The model predicted humus levels of about 20 Mg ha-1 yet actual soils data indicated a humus level in excess of 100 Mg ha-1.

The model was calibrated in phase II of the project using data from the Shawnigan Lake control plots. Salal was added to the simulation as a competitor for the Douglas-fir. Resulting simulations of tree biomass growth were generally improved. Simulation of foliage biomass accumulation was more realistic, but was still underestimated on the control plots. Predictions of density dependent mortality in unthinned treatments improved slightly. The simulation of soil humus levels was more accurate. The calibrated FORCYTE-11 model was able to accurately simulate some of the tree growth responses to thinning and fertilization at Shawnigan Lake. The model's simulations of 15 treatments underestimated stemwood volume and volume increment in treatments with low fertilization. Estimates improved with increasing levels of fertilization although in some cases volume and volume increment were overestimated. This bias was more extreme for unthinned treatments. The model's ability to rank treatments for volume and stem density decreased with the length of the simulation. Model rankings for volume increment were best at the beginning and end of the simulation. At no time did model and data treatment rankings significantly differ from each other (5% level).

FORCYTE-11 was difficult to calibrate,but the calibrated version was relatively easy to use. Model simulations may be improved by incorporating additional stocking, growth, and yield data from higher quality sites. A calibrated version of the model should be useful as both a management simulator and a research tool.

Annual rates and elemental concentrations of litter fall in thinned and fertilized Douglas-fir

Sat, 26 Aug 2000

Overstory litter fall, primarily needles, was collected for 15 years within control and treated plots in a stand of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) located near Shawnigan Lake, British Columbia. Treated plots were thinned or fertilized, or both; thinned plots had two-thirds of their basal area removed, fertilized plots were treated with 448 kg·ha-1 of either urea or ammonium nitrate, and half the fertilized plots were refertilized at the same rate 9 years later. The annual rate of litter fall in control plots averaged 1890 kg·ha-1. In control plots significant yearly variations were observed in litter-fall mass and concentrations of K, Mg, and Ca but not N or P. Thinning decreased rates of litter fall by 80%, but rates returned to control-plot levels after 13-15 years in unfertilized plots and after 8-10 years in fertilized plots. Fertilization without thinning depressed litter fall in the year of treatment but increased the rate by 20-80% in subsequent years. Litter-fall N concentrations increased by 40-80% the year of fertilization and then began declining 3-6 years later. Nitrogen fertilization reduced litter-fall P, K, and Mg concentrations for 8, 4 and 1 year(s), respectively, following fertilization. The effects were greater in ammonium nitrate plots than in urea plots. Rates of litter fall correlated poorly with stand density but well with basal area and stemwood increment. Correlations with the latter two variables varied with time and treatment.

FORCYTE-11 and intensive management of Douglas-fir: Examination of some of the model's short- and long-term predictions of biomass production

Sat, 26 Aug 2000

Concern over the long-term productivity of forests with intensive biomass harvest has led to the development of FORCYTE-11, an ecosystem-based model which can be used to examine the impacts of different management schemes. Although calibrated and used to examine management impacts for several of forest types, the model has not been tested against an independent data set. FORCYTE-11 predictions were compared to 15 years of data from a thinning and fertilization experiment in a low site quality, 40-year-old stand of Pseudotsuga menziesii at Shawnigan Lake, B.C. (east coast of Vancouver Island). Data for 23 variables were compared but only data on stand biomass and density are reported in this paper. Initial comparisons with the uncalibrated model showed that model simulations were reasonable, with growth in treated plots tending to be more accurately predicted than in control plots. This was probably due to the model's weakness in its simulation of decomposition and soil organic matter. After calibration with control plot data and inclusion of an understory species, Gaultheria shallon, model fit improved, but its accuracy showed strong biases which varied with the thinning and fertilization treatments. The model was able to correctly predict the rankings of all 15 treatments. Using the control plot dataset for Shawnigan Lake, FORCYTE-11 was then used to examine the effects of intensive forest management on long-term productivity. The model predicted that yield would decline the most over time with short-rotation, whole-tree harvest. Effects of initial site conditions caused high biomass yields in either the first or second rotation, depending upon rotation length. Iterative simulations with the model suggested that to keep yield constant with successive rotations, large fertilizer additions were needed, especially with short-rotations. The model proved quite sensitive to variation in N inputs through precipitation, cumulative 360-year yields declined by 18% when N inputs were reduced from 2.0 to 0.5 kg N (ha yr)-1.

Mycorrhizas

Sat, 26 Aug 2000

Effects of phosphorus and sulphur fertilization on the growth of thinned and urea fertilized Douglas-fir at Shawnigan Lake, B.C.

Sat, 26 Aug 2000

Roots in Forest Soils: Biology and Symbioses. Introduction

Sat, 26 Aug 2000

Rates of rhizodeposition and ammonium depletion in the rhizophere of axenic oat roots

Sat, 26 Aug 2000