Recent publications

Seed abscission schedules and the timing of post-fire salvage of Picea mariana and Pinus banksiana.

Fri, 14 Jun 2013 08:58:38 MST

For aerial seedbank species, the seed abscission schedule following fire is of practical interest as it affects the optimal timing of post-fire salvage operations designed to maximize natural regeneration. It is also of theoretical interest as we would expect that the rapid deterioration of the better (very thin duff or exposed mineral soil) post-fire seedbeds due to leaf-fall from regenerating plants ought to select for rapid dissemination of seeds following burning. Nonetheless, there are no published reports of the abscission schedule of an aerial seedbank species that include the full temporal range from the fire date to several years after. In northwestern Quebec, we used eight burnt, non-salvaged stands, four dominated by black spruce (Picea mariana) and four dominated by jack pine (Pinus banksiana), in three different fires to examine the seed abscission schedule of these aerial seedbank species for the first 3 years after fire. We found that (1) the abscission schedules of populations of each species differed between fires and (2) black spruce dispersed seeds from the cones at a significantly slower rate than jack pine at all fires. Extrapolating from the regressions (all fires lumped), we conclude that approximately 90% of jack pine and black spruce seeds will have been dispersed by 1 and 5 years, respectively, after a fire. Further, we argue that due to its protracted abscission schedule, early post-fire salvage will invariably require that black spruce be planted. The approach adopted here should be useful for optimizing post-fire salvage timing for all commercially valuable species with aerial seedbanks.

Casey’s conundrum, a review of the genus Semanotus Mulsant(Coleoptera: Cerambycidae: Cerambycinae: Callidiini) in North America

Wed, 12 Jun 2013 16:32:48 MST

The North American species of Semanotus Mulsant, 1839 are reviewed. Semanotus ligneus (Fabricius, 1787), Semanotus amplus amplus (Casey, 1912) new status, S. amplus basalis (Casey, 1924) new status, Semanotus amplus sequoiae Van Dyke, 1923 new status, Semanotus conformis Casey, 1924 new status, Semanotus terminatus Casey, 1912 new status, Semanotus amethystinus (LeConte, 1853), Semanotus juniperi (Fisher, 1915), and Semanotus litigiosus (Casey, 1891) are recognized as valid. A key to the North American fauna, as well as to Semanotus japonicus Lacordaire, 1869 and Semanotus australis Giesbert, 1993 is included. A morphometric study was conducted using 37 measured characters from adults of S. litigiosus. Data were examined using stepwise discriminant analysis to determine which characters aid in the diagnosis of taxa, and their amounts of resolving power using canonical variates analysis. Morphometrics revealed significant sexual dimorphism among taxa and suggested that three taxa were present, however, only two taxa could be reasonably separated using observable characters. Phylogenetic analysis using a hypothetical ancestor as out-group returned a single most parsimonious tree for North American Semanotus.

The genomic architecture and association genetics of adaptive characters using a candidate SNP approach in boreal black spruce.

Fri, 07 Jun 2013 12:49:06 MST

Background: The genomic architecture of adaptive traits remains poorly understood in non-model plants. Various approaches can be used to bridge this gap, including the mapping of quantitative trait loci (QTL) in pedigrees, and genetic association studies in non-structured populations. Here we present results on the genomic architecture of adaptive traits in black spruce, which is a widely distributed conifer of the North American boreal forest. As an alternative to the usual candidate gene approach, a candidate SNP approach was developed for association testing.

Results: A genetic map containing 231 gene loci was used to identify QTL that were related to budset timing and to tree height assessed over multiple years and sites. Twenty-two unique genomic regions were identified, including 20 that were related to budset timing and 6 that were related to tree height. From results of outlier detection and bulk segregant analysis for adaptive traits using DNA pool sequencing of 434 genes, 52 candidate SNPs were identified and subsequently tested in genetic association studies for budset timing and tree height assessed over multiple years and sites. A total of 34 (65%) SNPs were significantly associated with budset timing, or tree height, or both. Although the percentages of explained variance (PVE) by individual SNPs were small, several significant SNPs were shared between sites and among years.

Conclusions: The sharing of genomic regions and significant SNPs between budset timing and tree height indicates pleiotropic effects. Significant QTLs and SNPs differed quite greatly among years, suggesting that different sets of genes for the same characters are involved at different stages in the tree’s life history. The functional diversity of genes carrying significant SNPs and low observed PVE further indicated that a large number of polymorphisms are involved in adaptive genetic variation. Accordingly, for undomesticated species such as black spruce with natural populations of large effective size and low linkage disequilibrium, efficient marker systems that are predictive of adaptation should require the survey of large numbers of SNPs. Candidate SNP approaches like the one developed in the present study could contribute to reducing these numbers.

Climate change-induced shifts in fire for Mediterranean ecosystems.

Wed, 05 Jun 2013 17:21:29 MST

Aim: Pyrogeographical theory suggests that fire is controlled by spatial gradients in resources to burn (fuel amount) and climatic conditions promoting combustion(fuel moisture). Examining trade-offs among these environmental constraints is critical to understanding future fire activity. We evaluate constraints on fire frequency in modern fire records over the entire Mediterranean biome and identify potential shifts in fire activity under an ensemble of global climate projections.

Location: The biome encompassing the Mediterranean-type ecosystems (MTEs).

Methods: We evaluate potential changes in fire over the 21st century in MTEs based on a standardized global framework. Future fire predictions are generated from statistical fire-climate models driven by ensembles of climate projections under the IPCC A2 emissions scenario depicting warmer–drier and warmer–wetter syndromes. We test the hypothesis that MTEs lie in the transition zone discriminating fuel moisture versus fuel amount as the dominant constraint on fire activity.

Results: Fire increases reported in MTEs in recent decades may not continue throughout the century. MTEs occupy a sensitive portion of global fire-climate relationships, especially for precipitation-related variables, leading to highly divergent fire predictions under drier versus wetter syndromes. Warmer–drier conditions ould result in decreased fire activity over more than half the Mediterranean biome by 2070–2099, and the opposite is predicted under a warmer–wetter future. MTEs encompass, however, a climate space broad and complex enough to include spatially varied fire responses and potential conversions to non-MTE biomes.

Main conclusions: Our results strongly support the existence of both fuel amount and fuelmoisture constraints on fire activity and show their geographically variable influence throughout MTEs. Climatic controls on fire occurrence in MTEs lie close to ‘tipping points’, where relatively small changes in future climates could translate into drastic and divergent shifts in fire activity over the Mediterranean biome, mediated by productivity alterations.

Service canadien des forêts. En primeur. Reconstruire des édifices publics au Japon grâce à l'expertise canadienne en construction en charpente en bois. Juin 2013.

Tue, 04 Jun 2013 14:45:24 MST

Canadian Forest Service Spotlight. Rebuilding public structures in Japan with Canada wood frame expertise. June 2013.

Tue, 04 Jun 2013 14:42:29 MST

Incorporating weather sensitivity in inventory-based estimates of boreal forest productivity: A meta-analysis of process model results.

Tue, 04 Jun 2013 13:23:26 MST

Weather effects on forest productivity are not normally represented in inventory-based models for carbon accounting. To represent these effects, a meta-analysis was conducted on modeling results of five process models (ecosys, CN-CLASS, Can-IBIS, InTEC and TRIPLEX) as applied to a 6275 ha boreal forest landscape in Eastern Canada. Process model results showed that higher air temperature (T_a) caused gains in CO₂ uptake in spring, but losses in summer, both of which were corroborated by CO₂ fluxes measured by eddy covariance (EC). Seasonal changes in simulated CO₂ fluxes and resulting inter-annual variability in NEP corresponded to those derived from EC measurements. Simulated long-term changes in above-ground carbon (AGC) resulting from modeled NEP and disturbance responses were close to those estimated from inventory data. A meta-analysis of model results indicates a robust positive correlation between simulated annual NPP and mean maximum daily air temperature (T_amax) during May–June in four of the process models. We therefore, derived a function to impart climate sensitivity to inventory-based models of NPP': NPP_i = NPP_i + 9.5 (T_amax −16.5) where NPP_i and NPP'_i; are the current and temperature-adjusted NPP, 16.5 is the long-term mean T_amax during May–June, and T_amax is that for the current year. The sensitivity of net CO₂ exchange to T_a is nonlinear. Although, caution should be exercised while extrapolating this algorithm to regions beyond the conditions studied in this landscape, results of our study are scalable to other regions with a humid continental boreal climate dominated by black spruce. Collectively, such regions comprise one of the largest climatic zones in the 450 Mha North American boreal forest ecosystems.

A sequential sampling plan for counts of Adelges tsugae on individual eastern hemlock trees.

Tue, 04 Jun 2013 07:16:00 MST

A sequential sampling plan was developed to estimate density of sistens of the invasive exotic hemlock woolly adelgid, Adelges tsugae (Annand), by counting adelgids on new shoots of four branch tips sampled from the lower half of the live crown of individual, asymptomatic eastern hemlock trees. The y-intercepts and slopes for the relationship between observed mean and variance of A. tsugae counts were similar for North Carolina and for 2 years of data collected from Virginia; thus, data were pooled to create one regression equation that was used to develop a count-based sequential sampling plan. Validation data sets were obtained in West Virginia and by randomly selecting half of the trees sampled in North Carolina and Virginia, trees not used previously to develop the sampling plan. Validation of the combined North Carolina-Virginia sampling plan showed that the model performed as specified. This plan should allow for estimation of adelgid population changes on a tree over time, provided the tree has not declined due to A. tsugae infestation. This plan can also be used to assess chemical or biological treatment effects on A. tsugae, provided such treatments do not fundamentally alter the mean-variance relationship.

Effects of prescribed burning and harvesting on ground-dwelling spiders in the Canadian boreal mixedwood forest.

Fri, 24 May 2013 16:23:49 MST

The ‘Natural Disturbance Paradigm’ for forest management seeks to meet conservation goals by modeling industrial harvest in fire-driven forest systems on patterns associated with wildfire. Fire suppression and increased forest harvesting may have detrimental effects on biodiversity, and therefore prescribed burning is suggested to retain legacies of wildfire not emulated under natural disturbance based approaches. The merits of this approach are being tested in the EMEND experiment in the Canadian boreal mixedwood forest. We compared responses of ground-dwelling spiders between sites subjected to prescribed post-harvest burning and retention harvest during three seasons during the first 7 years after disturbance. Overall, 38,661 adult spiders representing 190 species were collected. Estimated species richness was highest in undisturbed sites in all 3 years. Burning had the strongest negative effect on species richness 1–2 years after treatment; however, richness was higher in burns than in harvested sites 5–6 years postdisturbance. Species turnover was highest within controls but tended to increase over time between burned and harvested plots. Lower turnover in burned and harvested sites may reflect habitat homogenization by disturbance, suggesting a management and conservation challenge in relation to naturally disturbed and undisturbed areas. Species were grouped into disturbance-specialists, disturbance-tolerant, disturbance-generalists and generalists; 22 species were significant indicators for untreated sites, 18 for the burn and three for the harvest treatments. No major differences were observed in the spider fauna between harvested and burned areas within the first 6–7 years post-disturbance, and little evidence of recovery toward the pre-harvest fauna was evidenced. However, long term experiments may improve understanding of natural disturbance processes and improve management of boreal forests.

A second-generation diagnostic single nucleotide polymorphism (SNP)-based assay, optimized to distinguish among eight poplar (Populus L.) species and their early hybrids.

Thu, 23 May 2013 14:13:35 MST

Rapid identification of Populus L. species and hybrids can be achieved with relatively little effort through the use of primer extension-based single nucleotide polymorphism (SNP) genotyping assays. We present an optimized set of 36 SNP markers from 28 gene regions that diagnose eight poplar species (Populus angustifolia James, Populus balsamifera L., Populus deltoides Bartram, Populus fremontii Watson, Populus laurifolia Ledeb., Populus maximowiczii Henry, Populus nigra L., and Populus trichocarpa Torr. & Gray). A total of 700 DNA sequences from six Populus species (1–15 individuals per species) were used to construct the array. A set of flanking and probe oligonucleotides was developed and tested. The accuracy of the SNP assay was validated by genotyping 448 putatively “pure” individuals from 14 species of Populus. Overall, the SNP assay had a high success rate (97.6 %) and will prove useful for the identification of all Aigeiros Duby and Tacamahaca Spach. species and their early-generation hybrids within natural populations and breeding programs. Null alleles and intraspecific polymorphisms were detected for a few locus/species combinations in the Aigeiros and Tacamahaca sections. When we attempted to genotype aspens of the section Populus (Populus alba L., Populus grandidentata Michx., Populus tremula L., and Populus tremuloides Michx.), the success rate of the SNP array decreased by 13 %, demonstrating moderate cross-sectional transferability.