Recent publications

Comparing growth and fine root distribution in monocultures and mixed plantations of hybrid poplar and spruce.

Wed, 15 May 2013 14:26:01 MST

Disease prevention, biodiversity, productivity improvement and ecological considerations are all factors that contribute to increasing interest in mixed plantations. The objective of this study was to evaluate early growth and productivity of two hybrid poplar clones, P. balsamifera x trichocarpa (PBT) and P. maximowiczii x balsamifera (PMB), one improved family of Norway spruce (Picea glauca (PA)) and one improved family of white spruce (Picea abies (PG)) growing under different spacings in monocultures and mixed plots. The plantations were established in 2003 in Abitibi-Témiscamingue, Quebec, Canada, in a split plot design with spacing as the whole plot factor (1 × 1 m, 3 × 3 m and 5 × 5 m) and mixture treatments as subplot factor (pure: PBT, PMB, PA and PG, and 1:1 mixture PBT:PA, PBT:PG, PMB:PA and PMB:PG). Results showed a beneficial effect of the hybrid poplar-spruce mixture on diameter growth for hybrid poplar clones, but not for the 5 × 5 m spacing because of the relatively young age of the plantations. Diameter growth of the spruces decreased in mixed plantings in the 1 × 1 m, while their height growth increased, resulting in similar aboveground biomass per tree across treatments. Because of the large size differences between spruces and poplars, aboveground biomass in the mixed plantings was generally less than that in pure poplar plots. Leaf nitrogen concentration for the two spruce families and hybrid poplar clone PMB was greater in mixed plots than in monocultures, while leaf nitrogen concentration of clone PBT was similar among mixture treatments. Because of its faster growth rate and greater soil resources demands, clone PMB was the only one showing an increase in leaf N with increased spacing between trees. Fine roots density was greater for both hybrid poplars than spruces. The vertical distribution of fine roots was insensitive to mixture treatment.

Mobilizing sustainable forest bioenergy in Canada.

Wed, 15 May 2013 09:48:50 MST

Unequal recombination and evolution of the mating-type (MAT) loci in the pathogenic fungus Grosmannia clavigera and relatives.

Wed, 15 May 2013 09:27:23 MST

Sexual reproduction in fungi is regulated by the mating-type (MAT) locus where recombination is suppressed. We investigated the evolution of MAT loci in eight fungal species belonging to Grosmannia and Ophiostoma (Sordariomycetes, Ascomycota) that include conifer pathogens and beetle symbionts. The MAT1-2 idiomorph/allele was identified from the assembled and annotated Grosmannia clavigera genome, and the MAT locus is flanked by genes coding for cytoskeleton protein (SLA) and DNA lyase. The synteny of these genes is conserved and consistent with other members in Ascomycota. Using sequences from SLA and flanking regions, we characterized the MAT1-1 idiomorph from other isolates of G. clavigera and performed dotplot analysis between the two idiomorphs. Unexpectedly, the MAT1-2 idiomorph contains a truncated MAT1-1-1 gene upstream of the MAT1-2-1 gene that bears the high-mobility-group domain. The nucleotide and amino acid sequence of the truncated MAT1-1-1 gene is similar to its homologous copy in the MAT1-1 idiomorph in the opposite mating-type isolate, except that positive selection is acting on the truncated gene and the alpha(a)-box that encodes the transcription factor has been deleted. The MAT idiomorphs sharing identical gene organization were present in seven additional species in the Ophiostomatales, suggesting that the presence of truncated MAT1-1-1 gene is a general pattern in this order. We propose that an ancient unequal recombination event resulted in the ancestral MAT1-1-1 gene integrated into the MAT1-2 idiomorph and surviving as the truncated MAT1-1-1 genes. The a-box domain of MAT1-1-1 gene, located at the same MAT locus adjacent to the MAT1-2-1 gene, could have been removed by deletion after recombination due to mating signal interference. Our data confirmed a 1:1 MAT/sex ratio in two pathogen populations, and showed that all members of the phiostomatales studied here including those that were previously deemed asexual have the potential to reproduce sexually. This ability can potentially increase genetic variability and can enhance fitness in new, ecological niches.

Steps in the biosynthesis of fuscumol in the longhorn beetles Tetropium fuscum (F.) and Tetropium cinnamopterum Kirby.

Wed, 15 May 2013 05:51:33 MST

Fuscumol ((2S,5E)-6,10-dimethyl-5,9-undecadien-2-ol) was recently identified as the male-produced aggregation pheromone of the brown spruce longhorn beetle, Tetropium fuscum (F.), and the eastern larch borer, Tetropium cinnamopterum Kirby. Several other species use this homoterpenoid alcohol motif, its ketone, or its acetate as part of their pheromone system. Investigation of the biosynthesis of this compound in these two Tetropium species demonstrated that geranylacetone ((5E)-6,10-dimethyl-5,9-undecadien-2-one) and farnesol ((2E,6E)-3,7,11-trimethyl-2,6,10-dodecatrien-1-ol) are both intermediates in this process. This was accomplished by applying deuterium-labeled geranylacetone and deuterium-labeled farnesol in separate experiments to the abdominal sterna of live T. fuscum and T. cinnamopterum and analyzing the deuterium labeling in the fuscumol and geranylacetone emitted by the insects with solid-phase microextraction (SPME) and GC/MS analysis. Deuterium labeling studies also showed that nerolidol ((3S,6E)-3-hydroxy-3,7,11-trimethyl-1,6,10-dodecatriene) and 2,3-epoxyfarnesol are not intermediates in fuscumol or geranylacetone synthesis in T. fuscum or T. cinnamopterum. Tissue-specific expression of T. fuscum farnesyl diphosphate synthase (TfFPPS), an enzyme expected to provide a key fuscumol precursor, was measured. TfFPPS transcripts were relatively abundant in male midguts, but were also present at significant levels in other tissues.

Efficacy of the pheromone, (3Z)-lactone, and the host kairomone, (3Z)-hexenol, at detecting early infestation of the emerald ash borer, Agrilus planipennis.

Mon, 13 May 2013 07:47:35 MST

The invasive emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), is a major pest of ash trees, Fraxinus spp., in its introduced range in North America. Field studies were conducted to quantify the efficacy of traps baited with kairomone and pheromone lures for early detection of A. planipennis infestation. A trapping experiment demonstrated that green traps baited with the kairomone (3Z)-hexenol detected at least one adult A. planipennis in 55.3% of plots with ‘nil to low’-density infestations and in 100% of plots with ‘moderate to high’-density A. planipennis infestations. Mean trap captures increased significantly with increasing infestation density. In terms of the optimal number of traps per plot, when one (3Z)-hexenol-baited trap was placed per plot, the trap detected populations in 62% of the plots with ‘low to moderate’-density infestations through branch sampling. Detectability was increased to 82% when two traps were placed per plot. Finally, addition of female-produced (3Z)-lactone pheromone to traps significantly increased detection rates at both the trap and plot level, as compared with traps baited with the host volatile, (3Z)-hexenol, alone (88 vs. 60%, respectively). Our results are the first to demonstrate the efficacy of baited green sticky traps for detecting low-density A. planipennis infestations, particularly when the (3Z)-lactone pheromone is used. This combination is therefore recommended for development of early-detection protocols against A. planipennis.

Growth decline and divergent tree ring isotopic composition (δ13C and δ18O) contradict predictions of CO2 stimulation in high altitudinal forests.

Fri, 10 May 2013 12:57:11 MST

Human-induced changes in atmospheric composition are expected to affect primary productivity across terrestrial biomes. Recent changes in productivity have been observed in many forest ecosystems, but low-latitude upper tree line forests remain to be investigated. Here, we use dendrochronological methods and isotopic analysis to examine changes in productivity, and their physiological basis, in Abies religiosa (Ar) and Pinus hartwegii (Ph) trees growing in high-elevation forests of central Mexico. Six sites were selected across a longitudinal transect (Transverse Volcanic Axis), from the Pacific Ocean toward the Gulf of Mexico, where mature dominant trees were sampled at altitudes ranging from 3200 to 4000 m asl. A total of 60 Ar and 84 Ph trees were analyzed to describe changes in growth (annual-resolution) and isotopic composition (decadal-resolution) since the early 1900s. Our results show an initial widespread increase in basal area increment (BAI) during the first half of the past century. However, BAI has decreased significantly since the 1950s with accentuated decline after the 1980s in both species and across sites. We found a consistent reduction in atmosphere to wood ¹³C discrimination, resulting from increasing water use efficiency (20–60%), coinciding with rising atmospheric CO₂. Changes in ¹³C discrimination were not followed, however, by shifts in tree ring δ¹⁸O, indicating site- and species-specific differences in water source or uptake strategy. Our results indicate that CO₂ stimulation has not been enough to counteract warming-induced drought stress, but other stressors, such as progressive nutrient limitation, could also have contributed to growth decline. Future studies should explore the distinct role of resource limitation (water vs. nutrients) in modulating the response of high-elevation ecosystems to atmospheric change.

Competition theory – science and application in mixed forest stands: review of experimental and modelling methods and suggestions for future research

Fri, 10 May 2013 11:56:21 MST

Competition in forest stands has long been of interest to researchers. However, much of the knowledge originates from empirical studies that examined the effects of competition. For instance, many studies were focused on the effects of the presence of herbaceous species on the development of tree seedlings or the decrease in individual tree growth with increases in stand density. Several models that incorporate competitive effects have been developed to predict tree and stand growth, but with simplified representations of competitive interactions. While these studies provided guidance useful for forest management, they contributed only partially to furthering our understanding of competitive mechanisms. Also, most competition studies were conducted in single-species stands. As competitive interactions occurring in mixed stands are characterized by a higher degree of complexity than those in single-species stands, a better understanding of these mechanisms can contribute to developing optimal management scenarios. The dynamics of forest stands with at least two species may be affected not only by competition, but also by facilitation or complementarity mechanisms. Thus, knowledge of the mechanisms may provide insight into the relative importance of intra- versus inter-specific competition and whether competition is symmetric or asymmetric. Special attention to the implementation of field experimental designs is warranted for mixed stands. While traditional spacing trials are appropriate for single-species stands, the examination of competitive interactions in mixed stands requires more complex experimental designs to examine the relative importance of species combinations. Forest productivity models allow resource managers to test different management scenarios, but again most of these models were developed for single-species stands. As competitive interactions are more complex in mixed stands, models developed to predict their dynamics will need to include more mechanistic representations of competition.

A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera, Mymaridae), with comments on its sister genus Kikiki, and discussion on small size limits in arthropods.

Thu, 09 May 2013 09:02:21 MST

A new genus and species of fairyfly, Tinkerbella nana (Hymenoptera: Mymaridae) gen. n. and sp. n., is described from Costa Rica. It is compared with the related genus Kikiki Huber and Beardsley from the Hawaiian Islands, Costa Rica and Trinidad. A specimen of Kikiki huna Huber measured 158 μm long, thus holding the record for the smallest winged insect. The smallest size possible, as measured by body length, for flying insects and wingless arthropods is discussed.

Synopsis of adventive species of Coleoptera (Insecta) recorded from Canada. Part 2: Staphylinidae.

Tue, 30 Apr 2013 12:16:04 MST

A synopsis of adventive species of Staphylinidae (Coleoptera) in Canada is provided. Of the over 1654 rove beetle species recorded from Canada, 156 species in 76 genera and 13 subfamilies are reported as adventive, constituting about 9.4% of the fauna. The majority of adventive species belong to two subfamilies, Staphylininae (51 species) and Aleocharinae (49), and the genera with the most species are Philonthus (16), Atheta (8), Aleochara (7) and Quedius (7). All 156 adventive species are reviewed, including diagnostic features (supported by 156 colour habitus photos and 230 black and white images of diagnostic characters), native range, detailed distribution in Canada (with 151 distribution maps), general distribution in the USA, early Canadian and North American records and habitat information. New jurisdictional records are Atheta longicornis (Gravenhorst) from Alberta, Philonthus sanguinolentus (Gravenhorst) from eastern Canada (Ontario) and Xantholinus longiventris Heer from Canada (British Columbia).

Impact of salvage logging on stand structure and beetle diversity in boreal balsam fir forest, 20 years after a spruce budworm outbreak.

Tue, 30 Apr 2013 09:48:24 MST

Spruce budworm outbreaks represent the most important natural disturbance in the boreal balsam fir (Abies balsamea (L.) Mill.) forest of Canada, killing trees over wide areas and thus generating large amounts of dead wood. This disturbance is part of the dynamic processes occurring within balsam fir forests, and its effects on biodiversity need to be understood in order to move closer towards sustainable forest management. We described stand structure and used beetles as biodiversity indicators to compare the ecological value of salvaged stands, managed afterwards with three different silvicultural treatments, with unsalvaged stands, 20 years after the last spruce budworm outbreak. Our experimental design involved five replicated stands of each of the four disturbance types for a total of 20 stands. A total of 3124 Coleoptera belonging to 47 families and 269 taxa were captured over 3 months of sampling. Results showed that habitat attributes still differed 20 years after a spruce budworm outbreak between unsalvaged and treated salvaged stands, such as more abundant and diverse dead wood in unsalvaged stands. Salvage logging and silvicultural treatments led to different beetle communities than in unsalvaged stands, even though abundance and richness did not change significantly. Most indicator species identified were saproxylic and associated with unsalvaged stands, suggesting salvage logging generated the largest changes to the original ecosystem while additional effects of the silvicultural treatments were less pronounced. This may result from the 67% reduction in downed dead wood volumes (e.g., 138 m³/ha in unsalvaged stands vs 46 m³/ha in managed stands). Even if this volume of dead wood is still relatively high, it is less diverse than in unsalvaged stands and includes almost no recent dead wood. Salvage logging affected saproxylic beetle communities, suggesting that the retention of naturally disturbed stands may help in implementing ecosystem management in boreal balsam fir forest and move closer towards sustainable management.