Publications by C.P-A. Bourque

A stand dynamic model for red pine plantations with different initial densities

Mon, 16 Jan 2012

A stand dynamic model was developed to predict the growth response in even-aged forest planations of different initial planting densities. The model is based on the integration of three subcomponents: height growth, self-thinning, and diameter increment. The integrated model uses the height of dominant trees to simulate stand response to site quality and internal growth potential. An extended self-thinning submodel is used to simulate mortality in stands due to crowding and inter-tree competition. A diameter increment submodel is used to link the height growth and self-thinning submodels. The height growth submodel is based on an application of the "Pipe Model" theory. The three-parameter self-thinning submodel is developed from an extended self-thinning law that captures self-thinning in stands before they attain full stocking. The diameter increment model is based on the assumption that diameter increment is related to height growth and available growing space described by stand density. The integrated model is applied to data collected from a 45-year-old red pine (Pinus resinosa Ait.) plantation subsectioned with different initial planting densities. For the data used, only two parameters were required to capture 99% of measured variation in height growth. Additional data from sites with different planting intensities are required to formulate a more generalized height growth model. The slope of the linear self-thinning limit for red pine is approximately -1.5. Model predictions are consistent with field measurements.

Modelled potential species distribution under current and projected future climates for the Acadian Forest Region of Nova Scotia, Canada.

Fri, 05 Apr 2013

Predicting the effects of woodcutting and moose browsing on forest development in Gros Morne National Park, Newfoundland, Canada

Mon, 26 Apr 2010

Long-term scenario analysis was used to predict the effects of domestic harvesting and moose (Alces alces) on forest growing stock, species composition, and age-class distribution for two groups of managed forest blocks dominated by balsam fir (Abies balsamea [L.] Mill.) in Gros Morne National Park (GMNP), western Newfoundland. Four scenarios were examined. The first scenario assumed no timber harvesting and light moose browsing. Tranition rules applied to this scenario came from neighbouring industrial forests, where moose populations are regulated by hunting. The other test scenarios use GMNP-specific transition rules to address increased moose browsing in the park, where hunting has been prohibited since the park’s inception in 1973. One of the three tested scenarios was also given a “no timber harvest treatment” so that the effects of moose browsing on park forests may be quantified by comparison with the first scenario. The two remaining test scenarios were designed to address compound effects of timber harvesting and moose browsing within the park, each representing an alternative management scenario currently being implemented in GMNP. For both harvest scenarios, the overall achievable wood volume was found to be at least five orders of magnitude lower than growing stock, thus providing sufficient volume for the ongoing domestic wood-cutting program (1973-2060) in the park. The proposed levels of woodcutting were predicted to have little impact on forest growing stock and old-growth forest after 160 years of management, but not on maintaining white birch (Betula papyrifera Marsh.), which is already in low numbers. In contrast, moose browsing, although it was predicted to have little effect on age-class distribution, was estimated to cause a 12% to 32% reduction in growing stock over a 160-year planning horizon, depending on the scenario. This was characterized by a 47% to 50% reduction in growing stock of balsam fir and a 50% to 87% reduction in white birch, and a commensurate expansion in low-density black spruce (Picea mariana [Mill.] B.S.P.) and grassland cover.

A wetness index using terrain-corrected surface temperature and normalized difference vegetation index derived from standard MODIS products: an evaluation of its use in a humid forest-dominated region of eastern Canada

Tue, 02 Oct 2007

In this paper, we develop a method to estimate land-surface water content in a mostly forest-dominated (humid) and topographically varied region of eastern Canada. The approach is centered on a temperature-vegetation wetness index (TVWI) that uses standard 8-day MODIS-based image composites of land surface temperature (Ts) and surface reflectance as primary input. In an attempt to improve estimates of TVWI in high elevation areas, terrain-induced variations in Ts are removed by applying grid, digital elevation model-based calculations of vertical atmospheric pressure to calculations of surface potential temperature. Here, surface potential temperature corrects Ts to the temperature value to what it would be at mean sea level (i.e., ~101.3 kPa) in a neutral atmosphere. The vegetation component of the TVWI uses 8-day composites of surface reflectance in the calculation of normalized difference vegetation index (NDVI) values. TVWI and corresponding wet and dry edges are based on an interpretation of scatterplots generated by plotting surface potential temperature as a function of NDVI. A comparison of spatially averaged field measurements of volumetric soil water content (VSWC) and TVWI for the 2003-2005 period revealed that variation with time to both was similar in magnitudes. Growing season, point mean measurements of VSWC and TVWI were 31.0% and 28.8% for 2003, 28.6% and 29.4% for 2004, and 40.0% and 38.4% for 2005, respectively. An evaluation of the long-term spatial distribution of land-surface wetness generated with the new surface potential temperature-NDVI function and a process-based model of soil water content showed a strong relationship (i.e., r2 = 95.7%).

A simple net ecosystem productivity model for gap filling of tower-based fluxes: an extension of Landsberg’s equation with modifications to the light interception term

Fri, 17 Aug 2007

Net ecosystem productivity (NEP) is a key ecological variable in forestry and carbon sequestration sciences. Advances in eddy-covariance instrumentation in recent years have improved the accuracy to which productivity in ecosystems can be measured. However, equipment failure, power outages, system maintenance shutdowns, and inclement weather frequently introduce gaps in the measurement data stream, which can reduce the integrity, usefulness, and interpretation of the data. To compensate for these limitations, a simple NEP model with few automatically adjustable parameters is developed to improve gap filling of discontinuous time series. Initial model formulation and parameter-value determination are founded on 2004 growing-season NEP measurements collected at eight Fluxnet-Canada (FCRN) stations (i.e., eight ecosystems) from across Canada's southern commercial forest zone. A preliminary inter-equation comparison of three commonly used flux equations, all with photosynthetically active radiation (PAR) as the independent variable, revealed that the three equations provided similar mean description of NEP. In this paper, we use Landsberg's equation (Landsberg, J.J., 1977. Some useful equations for biological studies. Exp. Agric. 13, 272-286) in modelling NEP. Initial parameter values of the Landsberg's equation were shown to depend on forest species composition, stand age, and existing site conditions. Further analysis indicated that on average for a 9-day period for the Atlantic Maritime balsam fir site in New Brunswick, Landsberg's equation represented mean NEP very well for cloudy days, but performed poorly when light conditions deviated from average conditions. We hypothesized that variation in the level of diffuse and direct radiation contributed to differences in light response. As Landsberg's equation does not explicitly address (I) light quality, i.e., level of diffuse to direct illumination, and (ii) vertical canopy structure, a simple NEP model combining Landsberg's equation with a two big-leaf (sunlit versus shade leaf model concept) and multiple-layer canopy light transmission formulation was developed for modelling the day-to-day variation in NEP and for gap filling. Results from these enhancements captured more of the NEP peaks (coefficient of determination, r2 = 0.70) than were previously modelled with the unaltered form of Landsberg's equation (r2 = 0.63). Model sensitivity suggested partitioning the canopy in four canopy layers provided the best overall improvement in NEP calculations; beyond four layers, model improvement was minor.

A study in sampling of pre-commercial thinned plots in New Brunswick. Internal Report.

Wed, 16 May 2007

In recent years, inconsistent assessment results from routine harvest block surveys for different parts of New Brunswick have raised concerns among foresters about the required sampling intensity for pre-treatment precommercial thinning conditions in softwood and hardwood stands. The primary objective of this report is to determine the required sample plot number for four groups of harvest blocks size (10, 20, 30, and 40 ha) at three confidences levels (90, 95, and 99%) at the request of the New Brunswick Silviculture Technical Group. A secondary objective of this report is to determine the influence of limiting to the upper level of 33 crop-tree stems/plot (49 5000 stems / ha) on density determination and required sample plot number. The required number of sample plots is determined by classic statistical methods and Monte Carlo modelling techniques. High variation in stem densities of all species combined, softwoods, and hardwoods was observed for individual regeneration plots and harvest blocks. Between one to two regeneration plots / ha for all species and hardwoods at 90% confidence level appears to provide a reliable estimate of the mean crop-tree density for most harvest blocks of this study. For softwood mean density estimates, between two to three regeneration plots / ha are required for adequate sampling of most of the harvest blocks. Although the analysis of an upper limit of 33 crop-trees / ha showed no significant differences to an actual density count at the harvest block level, the impact on the productivity of the silvicultural worker conducting per-commercial thinning prescriptions is beyond the scope of this report. The impact on productivity of the silvicultural worker because of significant stem density differences at the regeneration plot level is not known. Extreme variation of individual regeneration plots and some harvest blocks may be reduced by fewer and larger sample plots or stratification of the harvest blocks based on ecological or landscape features, such as the Depth-to-water Map.

Site influences on net ecosystem productivity in managed Abies balsamea stands

Mon, 23 Apr 2007

This paper investigates site influences on net ecosystem productivity (NEP) in 15 managed balsam fir stands in SW New Brunswick, Canada. Flux towers in 2 of the 15 stands provide a short-term measurement of NEP and site micrometeorology for the June 29-November 30, 2004 period. Site conditions between Charlie Lake (CL01) and Nashwaak Lake (NWL) flux sites for the 2004 period reveal few differences. The greatest differences occur in soil temperature and soil water content (SWC), with CL01 being the warmer and wetter of the two sites. These differences, particularly in SWC are hypothesized to be responsible for the 29% increase in NEP at CL01 for the 2004 period. Slope position (SP, an index of potential soil wetness, indicates because of physiographic position NWL has dryer soils. Stem analysis of 42 trees from the two sites show that over the lifetime of the stands, mean annual increment at CL01 was 4.8 compared with 4.5 m3 ha-1 yr-1 for the NWL. Relating SI to SP revealed that Si co-varies with SP in a parabolic fashion. Excessively wet or dry soils are shown to have reduced site productivity, while soils and intermediate SWC promote improved stand growth.

Optimizing carbon sequestration in commercial forests by integrating carbon management objectives in wood supply modeling

Tue, 10 Apr 2007

This paper provides a methodology for generating forest management plans, which explicitly maximize carbon (C) sequestration at the forest-landscape level. This paper takes advantage of concepts first presented in a paper by Meng et al. (2003) by integrating C-sequestration objective functions in existing wood supply models. Carbon-stock calculations performed in Woodstock TM (RemSoft Inc.) are based on C yields generated from volume table data obtained from local Forest Development Survey plots and a series of wood volume-to-C content conversion factors specified in von Mirbach (2000)). The approach is used to investigate the impact of three deomnstration forest-management scenarios on the C budget in a 110,000 ha forest in south-central New Brunswick, Canada. Explicit demonstration scenarios addressed include (1) maximizing timber extraction either by clearcut or selection harvesting for greatest revenue generation, (2) maximizing total C storage in the forest landscape and in wood products generated from harvesting, and (3) maximizing C storage together with revenue generation. The level of clearcut harvesting was greatest for scenario 1 (>/=15 X 10⁴ cubic meters of wood and >/=943 ha of land per harvesting period), and least for scenario 2 (=0 cubic meters per harvesting period) where selection harvesting dominated. Because softwood saw logs were worth more than pulpwood ($60 m^-3 vs. $40 m^-3) and were strategic to the long-term storage of C, the production of softwood was generally the preferred harvesting method across scenarios. Only in scenario 1 did levels of clearcut harvesting occasionally exceed those of selection harvesting, mainly in the removal of old, dilapidated stands early in the simulation (i.e., during periods 1 through 3). Scenario 2 provided the greatest total C-storage increase over 80 years (i.e., 14 X 10⁶ Mg C, or roughly 264 Mg ha ^-1) at a cost of $111 per Mg C due to lost revenues. Scenarios 3 and 1 produced reduced storage rates of roughly 9 X 10⁶ Mg C and 3 X 10⁶ Mg C, respectively; about 64% and 22% of the total, 80-year C storage calculated in scenario 2. The bulk of the C in scenario 2 was stored in the forest, amounting to about 76% of te total C sequestered.

Using site and climate variables to explain forest productivity in Nova Scotia (Abstract)

Thu, 08 Mar 2007

Understanding the ecological processes that govern forest development over time and predicting future stand growth and yield from these processes are one of the primary challenges in forest management planning. Tree growth is controlled by solar radiation, water availability, nutrient availability and site variables such as temperature and precipitation. Decision making and planning in forests of variable land and forest conditions, such as those in Nova Scotia, require methods of estimating forest site productivity for each of the important tree species. Therefore, the objective of this paper is to determine the degree to which the five main environmental variables (i.e., solar radiation, soil fertility, soil drainage, temperature, and precipitation) explain variation in tree and stand growth in Nova Scotia. Potential forest productivity maps will be created for each of the main environmental variables, showing potential productivity classes from “very low” to “high”. Significant differences in the growth rate relationships will be used to refine the individual environmental variable maps. A site quality map based on the five potential productivity maps may provide a useful means for estimating site potential as a basis for silvicultural and sustainable forest management decisions.

A model of canopy-level photosynthesis and its application in gap filling of flux data

Fri, 20 Apr 2007

Data gaps in flux data has been a serious problem for many years. Although many different methods have been developed for gap filling of eddy covariance measurements, including net ecosystem productivity (NEP) measurements, there lacks a standard, commonly acceptable solution for gap filling. This paper describes a simple, but ecologically based method for gap filling of NEP measurements. The model couples processes of photosynthesis and stomatal conductance through the dynamic calculation of the internal carbon dioxide (CO2) concentration in leaves. The model contains three response functions, one for temperature, CO2 concentration, and light intensity. To account for light variation in the canopy, the canopy is divided into four layers of equal depth with each layer being assigned a proportion of the total canopy LAI, i.e., LAI resident volume in a layer to the total crown volume, assuming conical crowns. The canopy layers are subdivided into portions of shaded and sunlit leaves to capture the daily variation in incident solar radiation and photosynthesis. Because of the model’s simplicity and low input data requirement, model parameters are readily optimized with either the Simplex or Levenberg-Marquardt’s numerical convergence rules for periods when data exist. Comparison of model results to field measurements provide reasonable agreement, yielding r2 = 0.77.

Photosynthetic light use efficiency of three biomes across an east–west continental-scale transect in Canada

Fri, 08 Dec 2006

Late-summer carbon fluxes from Canadian forests and peatlands along an east-west continental transect

Tue, 05 Dec 2006

Net ecosystem productivity (NEP) during August 2003 was measured by using eddy covariance above 17 forest and 3 peatland sites along an east-west continental-scale transect in Canada. Measured sites included recently disturbed stands, young forest stands, intermediate-aged conifer stands, mature deciduous stands, mature conifer stands, fens, and an open shrub bog. Diurnal courses of NEP showed strong coherence within the different ecosystem categories. Recently disturbed sites showed the weskest diurnal cycle; and intermediate-aged conifers, the strongest. The western treed fen had a more pronounced diurnal pattern than the eastern shrub bog or the Saskatchewan patterned fen. All but three ring were clearly afternoon C sinks. Ecosystem respiration was highest for the young fire sites. The intermediate-aged conifer sites had the highest maximum NEP (NEP_MAX) and gross ecosystem productivity (GEP_MAX), attaining rates that would be consistent with the presence of a strong terrestrial C sink in regions where these types of forest are common. These results support the idea that large-scale C cycle modeling activities would benefit from information on the age-class distribution and disturbance types within larger grid cells. Light use efficiency followed a pattern similar to that of NEP_MAX and GEP_MAX. Four of the five recently disturbed sites and all three of the peatland sites had low water use efficiencies.

Regneration response on different microsites following site preparation and direct aerial seeding in southwestern Nova Scotia

Fri, 14 Jul 2006

Regeneration response on different microsites following site preparation and direct aerial seedling in southwestern Nova Scotia. (Abstract)

Wed, 31 May 2006

Timely regeneration of harvested forest land is arguably the most important aspect of forest management. Not only does the resulting regeneration have an impact on the future allowable annual cut and timber resource, but it also contributes to biodiversity, wildlife habitat, aesthetics, and management responsibilities. In order to be more competitive, forest industries in Canada must develop more cost-efficient, silvicultural methods that promote ecologically sustainable forest management. In 2003, Bowater Mersey Paper Company Ltd. began experimenting with aerial seeding of spruce as a cost-efficient method to regenerate partially stocked harvest blocks in southwestern Nova Scotia. Factors leading to the respectively unfavourable and successful results of the 2003 and 2005 direct aerial seeding operations were examined as a seniro B.Sc.F. thesis; the resulting information is provided here. Soil moisture was identified as a major environmental factor influencing survival of newly germinated seedlings on these sensitive sites. Recent increases in annual temperatures may be a primary factor in spruce seedling mortality on these sites in Nova Scotia. The rate of seeding was identified as a contributing factor for successful regeneration stocking of harvest blocks. A predictive tool is being developed using a slope-to-position map, because of the relationship of soil moisture to seedling survival. Although more research is required to refine the microsite relationships of spruce geneneration with the slope-to-position map, operational recommendations for direct aerial seeding based on results to date will be provided. The future direction of the study will also be made available to the audience.

Modeling carbon sequestration with CO2Fix and a timber supply model for use in forest management planning

Tue, 28 Mar 2006

Carbon (C) dynamics and forest management have become integrated in recent years, largely due to the Kyoto Protocol stipulating that forest C changes may be accountable in an emissions framework. A C stock modeling framework for forest managers is introduced in this paper. Empirical growth and yield models are used to develop sustainable timber supply for forest companies. These models use linear programming to solve the complex mathematical problem of timing and allocation of forest harvest and silviculture interventions. In this paper, we evaluated the effects of “business as usual” forest management versus management objectives to maximize C sequestration. Goal programming was used to minimize the deviation of two goals for C forest management: maximizing C in the forest, and maximizing the return on investment (net present value of forest timber products). Species-specific wood-to-C content conversion factors were used to parameterize the amount of C in forest stands on Canadian Forces Base Gagetown forest lands in New Brunswick, Canada. Goal programming reduced the loss of revenue associated with increasing C stocks in the forest. Partial harvesting and high valued end-products tended to increase C stocks and provided a higher return on investment in the simulations.

Spatial extent of winter thaw events in eastern North America: historical weather records in relation to yellow birch decline

Tue, 06 Sep 2005

An algorithm (Weather Reader) was developed and used to analyze daily weather records from all existing Canadian and American weather stations of eastern North America (in excess of 2100 stations), from 1930 through 2000. Specifically, the Weather Reader was used to compile daily minimum, mean, and maximum air temperatures for weather stations with at least 30 years of data, and was used to calculate accumulated degree days for winter thaw-freeze events relelvant to yellow birch (Betula alleghaniensis Britt.) from beginning to end. A thaw-freeze event relevant to yellow birch was considered to take place when (i) the station daily maximum temperature reached or exceeded +4 C after being below freezing for at least 2 months of the winter, (ii) sufficient growing degree days accumulated (>50 growing degree days) to cause the affected yellow birch trees to prematurely deharden, and (iii) the daily minimum temperature dropped below -4 C causing roots and/or shoots of dehardened trees to experience freeze-induced injury and possibly dieback. The threshold temperature of +4 C represents the daily temperature above which biological activity occurs in yellow birch. The staiton growing degree day summaries were subsequently spatially interpolated with the Kriging function in GS+ and mapped in ArcView GIS in order to display the geographic extent of the most severe thaw-freeze events. The ArcView maps were then compared with the extent of historically observed yellow birch decline. It was found that the years 1936, 1944, and 1945 were particularly uncharacteristic in terms of region-wide winter thaw-freeze extremes, and also in terms of observed birch decline events during 1930-1960. An overlay of suspected accumulated birch decline based on thaw-freeze mapping and observed decline maps prepared by Braathe (1995), Auclair (1987, and Auclair et al. (1997) for 1930-1960 demonstrated similar geographic patterns. The thaw-freeze projection for 1930-1960 was shown to coincide with 83% of the birch decline map appearing in Braathe (1995) and 55% of the geographic range of yellow birch in eastern North America. Thaw-freeze mapping was also applied to two significant events in 1981. Greatest impact was recorded to occur mostly in southern Quebec and Ontario, and several American Great Lake States, specifically in northern Michigan and New York, where the greatest growing degree day accumulation prior to refreeze in late February (February 28th) was projected to have occurred; and in southern Quebec, most of Atlantic Canada, and Maine, prior to a late spring frost in mid-April (April 17).

Carbon and biomass partitioning in balsam fir (Abies balsamea)

Tue, 26 Jul 2005

Balsam fir (Abies balsamea (L.) Mill.) was extensively sampled to investigate the effects of forest management practices, site location, within-crown position, tree component (i.e., stem, foliage, branches, and roots), and tree social classes on biomass and carbon (C) partitioning at the individual tree level and across ecological regions. The sites were located in three ecologically distinct forest regions of west-central New Brunswick, Canada. There were no significant differences in %C content of trees across ecological regions or across tree social classes. However, at the individual tree level, significant differences were evident in biomass and C allocation between different parts of the tree, between treatment types (i.e., unmanaged and precommercially thinnned stands) and between within-crown positions, indicating the need for separate estimates of biomass and C content of tree components to obtain more precise estimates of quantities at the stand level. Calculating stand C content based on constant allocation values, as is commonly done, produced errors of up to 15% compared with the values calculated in this study. Three allometric equations of biomass and C that account for partitioning among different parts of the tree were developed and compared: (1) a third-order polynomial, (2) a modified inverse polynomial, and (3) a modified Weibull equation. Diameter at breast height (DBH) was used as the only explanatory variable to describe fresh biomass, dry biomass, and C content. All regressions derived showed a high correlation with DBH, with most r2 values > 0.95. A comparison of the equation results showed that the modified Weibull equation gave consistent results with the best overall fit and was the simplest of the three equations investigated. The regressions can be used to estimate forest biomass and tree C content at the stand level, given specific information on DBH.

Modeling stream water nutrient concentrations and loadings in response to weather conditions and forest harvesting

Tue, 30 Aug 2005

A process-based biogeochemistry model, ForNBM, was used to simulate stream water nutrient concentrations and monthly and cumulative stream nutrient loadings according to the monthly air temperature and precipitation records at the Nashwaak Experimental Watershed in central New Brunswick, Canada. Compared with the field measurement data from 1973 to 1985, the simulation results show that the best simulation of stream water nutrient concentrations is for Mg2+ with r2 = 0.59, and the poorest is for NH4+-N with r2 = 0.48. The best simulation of the monthly stream nutrient loadings is for Ca2+ with r2 = 0.66, and the poorest is for NO3--N with r2 = 0.53. All simulations of the cumulative stream nutrient loadings have r2 values more than 0.90.

Seasonal precipitation and air temperature played the most important role in determining the patterns of the stream nutrient concentrations and loadings. The stream nutrient concentrations were high during the winter and low during the spring. The peak values of the stream nutrient loadings appeared in the springs and the low values appeared in the winters. Although snowmelt diluted the stream water nutrient concentrations during the springs, it resulted in high stream nutrient loadings due to stream flooding.

According to the assessments of the model simulations and the field measurements, the increased watershed soil nutrient losses through the stream exports after forest harvesting may not cause the decline of the watershed soil productivity because (1) the annual increments of the stream nutrient exports were small, with 2.34 kg ha-1 year-1 for NO3--N, 0.93 for NH4+-N, 3.34 for Ca2+, 0.30 for Mg2+, and 5.21 for K+ and (2) the increased watershed soil nutrient losses occurred during the stage of forest regeneration when vegetation growth requires low soil nutrient supply.

A test and application of the model ForNBM in a northeastern Ontario jack pine (Pinus banksiana lamb.) stand

Mon, 10 May 2004

The model, ForNBM, was used to simulate biomass growth, soil temperature, hydrology, and nutrient cycling in a jack pine forest in northeastern Ontario. Simulated forest biomass growth, water, and nutrient fluxes were compared with up to 9 years of field measurements. The results show that r2-values between predicted and measured monthly soil leaching of five main nutrient ions (NO3--N, NH4+-N, Ca, Mg, and K) range from 0.65 to 0.98, with the best simulation for Ca and the worst for NO3--N. Predicted biomass growth, biomass nutrient content, and cumulative nutrient leaching strongly agree with measurements (all r2-values >0.9). For the given jack pine stand, the model predicts that N and K supply for jack pine uptake mainly came from soil organic matter mineralization (61 and 60%, respectively). Ca supply is mainly from soil mineral weathering (50%) and K supply from both soil mineral weathering and organic matter mineralization (30 and 30%, respectively). As such, clear-cutting of the jack pine forest may result in a minimal overall degradation of nutrient supply, especially for N and K, for future forest biomass growth.

Combining carbon sequestration objectives with timber management planning

Wed, 07 Jan 2004

This paper presents a new approach to assessing carbon (C) sequestration in commercial forests at spatial sclaes relevant to forest managers. The approach combines C-sequestration objectives with timber and non-timber (i.e., wildlife habitat) management objectives. As a demonstration, the approach is applied to a 105,000 ha special management area in northern New Brunswick, Canada over a simulated time horizon of 80 years. Carbon stock calculations are carried out by multiplying a series of simple wood volume-to-C conversion factors to wood supply projections generated with the Woodstock wood supply (RemSoft Inc.) and CWIZ linear programming software. Basic input requirements to the wood supply model include (i) current forest stand inventory and forest age structure, (ii) growth and yield curves for naturally developing stands, (iii) modified growth and yield curves to describe post-treatment stand response, (iv) non-timber objectives, and (v) specific harvesting prescriptions, including extent of application area and intensity. Spatial blocking of stands is carried out by importing the treatment schedule from the 80-year plan and by providing spatial constraints such as green-up delays and adjacency rules over a 25-year planning horizon. Model projection indicates that carbon stock in the forest of the special management area will increase in the next 40 years under the proposed harvesting plan and start to decrease thereafter. Under the no-disturbance scenario (both natural and man-made), the carbon stock in the forest will increase for the next 60 years and start to decline thereafter. For the whole planning period, C stock in the forest following current industrial practices will be less than naturally growing forest without any form of disturbance. Although model calculations are not exact, combining C objectives with timber management objectives provides a good framework for assessing C sequestration in commercial forests, given the excellent quality of the forest input data regarding above-ground biomass. Improvements to modelled C-sequestration projections may take place as scientific information about the details of the C cycle in managed forests becomes available.

Thaw effects on cold-hardiness parameters in yellow birch

Thu, 23 May 2002

One-year-old, cold-hardened, container-grown yellow birch (Betula alleghaniensis Britt.) seedlings were exposed to cold treatments after being pretreated with a simulated winter thaw. Freezing injury to roots and shoots was assessed by relative electrolyte leakage and triphenyltetrazolium chloride reduction. Growth characteristics were also determined after 60 days under greenhouse conditions. Relative electrolyte leakage and triphenyltetrazolium chloride reduction measurements showed that roots became increasingly damaged with decreasing cold-treatment temperatures. However, plants pretreated with thaws showed significantly lower stem increment, shoot length, and leaf area in response to the cold temperatures than did the unthawed plants. Variation in these growth parameters was also significantly correlated with both root and shoot freezing injury parameters. Cold hardiness under different thaw pretreatments was assessed using the highest freezing temperature that caused significant injury, referred to as the critical temperature. For seedlings without the thaw pretreatment, shoot and root critical temperatures were estimated as -52.5 and 23.8 C, respectively. Following 12 days of thaw, these temperatures increased to -24.08 C for shoots and -13 C for roots. Twelve days of thaw, or growing degree-day (>4 C) accumulations greater than 66 during a thaw, could sufficiently deharden roots and shoots such that they would be susceptible to freezing damage at ambient temperatures commonly encountered in the Canadian Maritimes. We also observed that root pressure declined significantly with increasing root freezing injury. Sufficient root pressure is required for springtime refilling of xylem embolisms caused by winter cavitation of the vessels in this species. Weak root pressure caused by freezing injury would represent a risk of shoot dieback and tree decline due to the remaining embolisms reducing water flow to the developing foliage. The rapid reduction of shoot cold hardiness may also indicate the threat of late-spring frosts to this species. These induced changes are especially important under climate change scenarios that suggest increases in winter temperatures and changes in seasonality in eastern Canada.

Simulations of pre- and post-harvest soil temperature, soil moisture, and snowpack for jack pine

Thu, 31 May 2001