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Rare species are an ecologically important component of biological communities, but may be at risk of decline as a result of human disturbance and other sources of environmental change. Rare species are also ecologically idiosyncratic, making their occurrence difficult to predict a priori, and leading to efforts to find surrogate measures of rare species occurrence to inform conservation decisions. Using floristic data collected at 602 sites in the western Canadian boreal forest, we studied relationships between rare species occurrence, species richness and habitat type, with rarity defined according to the classification system developed by Rabinowitz (in: Synge (ed) The biological aspects of rare plant conservation, Wiley, Somerset, 1981). Relative to similar studies in other temperate regions, we found that a smaller proportion of species were classified as rare in our study region, and that common species dominate the flora. Regional-scale relationships were positive between richness and the occurrence of rare species; however, due to variation in these relationships among habitat types, richness is not a suitable surrogate for a site's conservation value with respect to species rarity. [ABSTRACT FROM AUTHOR]

The capacity of forests to recover after disturbance, i.e., their resilience, determines their ability to persist and function over time. Many variables, natural and managerial, affect forest resilience. Thus, understanding their effects is critical for the development of sound forest conservation and management strategies, especially in the context of ongoing global environmental changes. We conducted a representative review, meta-analysis, of the forest literature in this topic (search terms “forest AND resilience”). We aimed to identify natural conditions that promote or jeopardize resilience, assess the efficacy of post-disturbance management practices on forest recovery, and evaluate forest resilience under current environmental changes. We surveyed more than 2,500 articles and selected the 156 studies (724 observations) that compared and quantified forest recovery after disturbance under different contexts. Context of recovery included: resource gradients (moisture and fertility), post-disturbance biomass reduction treatments, species richness gradients, incidence of a second disturbance, and disturbance severity. Metrics of recovery varied from individual tree growth and reproduction, to population abundance, to species richness and cover. Analyses show management practices only favored recovery through increased reproduction (seed production) and abundance of recruitment stages. Higher moisture conditions favored recovery, particularly in dry temperate regions; and in boreal forests, this positive effect increased with regional humidity. Biomass reduction treatments were only effective in increasing resilience after a drought. Early recruiting plant stages benefited from increased severity, while disturbance severity was associated with lower recovery of remaining adult trees. This quantitative review provides insight into the natural conditions and management practices under which forest resilience is enhanced and highlights conditions that could jeopardize future resilience. We also identified important knowledge gaps, such as the role of diversity in determining forest resilience and the lack of data in many regions. [ABSTRACT FROM AUTHOR]

Nest predation studies often use artificial nests to secure sample sizes and nest distribution patterns that allow empirically testing differences in predation rates between ecological units of interest. These studies rely on the assumption that natural and artificial nests experience similar or consistent relative predation rates across ecological gradients. As this assumption may depend on several factors (for example differences in predator community, nest construction, parental care patterns), it is important to test whether artificial nests provide adequate and comparable estimates of predation rates to natural nests. In this study, we compare predation rates of above-ground natural open-cup nests, artificial nests and natural nests with artificial eggs along a forest gradient from edge to interior (interior, transition zone and edge) and within two nest visibility classes (visible and concealed). Our aim was to determine whether nest structure affects comparability between nest types along these ecological gradients in boreal forests. Our results indicated important contributions of nest type, nest visibility and location along the forest edge-interior gradient, but no variable had strong significant effects on predation rates, except exposure time that showed lower predation rates at longer exposure times. Predation rates in visible and concealed nests remained similar for all nest types, but not along the forest edge-interior gradient. Here, artificial nests showed much lower predation rates than natural nests, whereas natural nests with artificial eggs tended to have higher predation rates than natural nests. We conclude that artificial nests in boreal forests represent an adequate measure of relative nest predation risk in open-cup natural nests along some ecological gradients, but results on predation rates along forest edge-interior gradients obtained from artificial nests should be interpreted with care. [ABSTRACT FROM AUTHOR]

The effective sustainable management of introduced woody species requires understanding of the mechanisms which affect successful colonization in different forest habitats. We studied the spontaneous spread of the alien species – Northern red oak ( Quercus rubra ) in the Scots pine ( Pinus sylvestris ) forest located in Poland. We analysed the impacts of seed source distance, presence of and distance from linear structures (public and forest roads) in the landscape, as well as microhabitat diversity, on the distribution of juvenile red oaks. We also studied the effects of types of acorn deposition sites (under shrubs, within clumps of Vaccinium myrtillus , in the open), and ways of seed burial (in moss wefts, in rodent corridors) by animal seed hoarders on seed germination and seedling growth. Field data were collected in six transect lines divided into 3300 plots (1 m 2 each). We found that Q. rubra efficiently colonizes Scots pine monoculture. Results of spatially explicit hierarchical generalized linear models showed that distance from acorn sources and occurrence of sparse shrub layers are the most important predictors of Q. rubra ecological success, defined as establishment of juvenile specimens. The presence of roads – potential migration corridors for avian and mammalian acorn consumers/dispersers – favoured non-random red oak spread. The “nurse effect” of native understory components on red oak seed germination and seedling growth was indicated by higher numbers of juvenile specimens as well as by higher proportions of germinated seeds noted under shrubs than in open areas (without shrubs) or within clumps of V. myrtillus . All red oaks developed from seeds buried in compact moss wefts or in spacious caches and corridors created by rodents in the moss layer, which indicated a positive “burial effect”. We conclude that microhabitats make the Scots pine forests very suitable for Q. rubra invasion. Because of the wide distribution of numerous red oak stands in European temperate forests and the presence of numerous oak seed dispersers, the continuous colonization of widespread Scots pine monocultures by Q. rubra must be expected. [ABSTRACT FROM AUTHOR]

Nutrient optimization has been proposed as a way to increase boreal forest production, and involves chronic additions of liquid fertilizer with amounts of micro- and macro-nutrients adjusted annually to match tree nutritional requirements. We used a short-term (maintained since 2007) and a long-term (maintained since 1987) fertilization experiment in northern Sweden, in order to understand nutrient optimization effects on soil microbiota and mesofauna, and to explore the relationships between plant litter and microbial elemental stoichiometry. Soil microbes, soil fauna, and aboveground litter were collected from the control plots, and short- and long-term nutrient optimization plots. Correlation analyses revealed no relationships between microbial biomass and litter nutrient ratios. Litter C:N, C:P and N:P ratios declined in response to both optimization treatments; while only microbial C:P ratios declined in response to long-term nutrient optimization. Further, we found that both short- and long-term optimization treatments decreased total microbial, fungal, and bacterial PLFA biomass and shifted the microbial community structure towards a lower fungi:bacterial ratio. In contrast, abundances of most fungal- and bacterial-feeding soil biota were little affected by the nutrient optimization treatments. However, abundance of hemi-edaphic Collembola declined in response to the long-term nutrient optimization treatment. The relative abundances (%) of fungal-feeding and plant-feeding nematodes, respectively, declined and increased in response to both short-term and long-term treatments; bacterial-feeding nematodes increased relative to fungal feeders. Overall, our results demonstrate that long-term nutrient optimization aiming to increase forest production decreases litter C:N, C:P and N:P ratios, microbial C:P ratios and fungal biomass, whereas higher trophic levels are less affected. [ABSTRACT FROM AUTHOR]

Fire as a dominant disturbance has profound implications on the terrestrial carbon cycle. We present the first ever multi-decadal, spatially-explicit, 30 meter assessment of fire regimes across the forested ecoregions of Canada at an annual time-step. From 1985 to 2015, 51 Mha burned, impacting over 6.5% of forested ecosystems. Mean annual area burned was 1,651,818 ha and varied markedly (σ = 1,116,119), with 25% of the total area burned occurring in three years: 1989, 1995, and 2015. Boreal forest types contained 98% of the total area burned, with the conifer-dominated Boreal Shield containing one-third of all burned area. While results confirm no significant national trend in burned area for the period of 1985 to 2015, a significant national increasing trend (α = 0.05) of 11% per year was evident for the past decade (2006 to 2015). Regionally, a significant increasing trend in total burned area from 1985 to 2015 was observed in the Montane Cordillera (2.4% increase per year), while the Taiga Plains and Taiga Shield West displayed significant increasing trends from 2006 to 2015 (26.1% and 12.7% increases per year, respectively). The Atlantic Maritime, which had the lowest burned area of all ecozones (0.01% burned per year), was the only ecozone to display a significant negative trend (2.4% decrease per year) from 1985 to 2015. Given the century-long fire return intervals in many of these ecozones, and large annual variability in burned area, short-term trends need to be interpreted with caution. Additional interpretive cautions are related to year used for trend initiation and the nature and extents of spatial regionalizations used for summarizing findings. The results of our analysis provide a baseline for monitoring future national and regional trends in burned area and offer spatially and temporally detailed insights to inform science, policy, and management. [ABSTRACT FROM AUTHOR]

Abstract: Understorey vegetation comprises the majority of species diversity and contributes greatly to ecosystem functioning in boreal forests. Although patterns of understorey abundance, species diversity and composition associated with forest stand development are well researched, mechanisms driving these patterns remain largely speculative. We sampled fire‐origin stands of varying stand ages and overstorey compositions on mesic sites of the boreal forest of Canada and used structural equation modelling (SEM) to link time since fire (stand age), light availability and heterogeneity, substrate heterogeneity and soil nitrogen to understorey vegetation cover and species diversity. The most parsimonious model for total understorey cover showed a positive direct effect of stand age (r = .43) and an indirect effect via mean light level (0.18) and shrub cover (−0.11), with a positive total effect (0.50); the per cent broadleaf canopy had a direct negative effect (−0.22) and an indirect effect via shrub cover (−0.11). The model for total understorey species richness showed an indirect effect of stand age via mean light (0.24), light heterogeneity (0.10) and substrate heterogeneity (0.07), with a positive total effect (0.52); per cent broadleaf canopy had an indirect effect via light heterogeneity (0.09), and substrate heterogeneity (−0.10). Soil nitrogen did not significantly influence either understorey cover or species richness. The models for vascular plants followed similar trends to those for total understorey cover and species richness; however, there was an opposite indirect effect of light heterogeneity for both cover and species richness of non‐vascular plants. Shrub cover had positive direct and negative direct and indirect effects on both vascular and non‐vascular cover and species richness. Synthesis. Our findings indicate that understorey cover and species diversity are driven by time since disturbance, light availability as influenced by overstorey and shrub layers, but with important additional effects mediated by light and substrate heterogeneity. Non‐vascular understorey vegetation is more strongly determined by time since disturbance than vascular vegetation, and negatively affected by broadleaf tree abundance. The overall results highlight the importance of colonization, light availability and heterogeneity, substrate specialization and growth dynamics in determining successional patterns of boreal forest understorey vegetation. [ABSTRACT FROM AUTHOR]

Large differences in productivity and species composition are characteristic for the boreal forest and nitrogen (N) availability has been deemed the proximate cause of this variation. We used a modified microdialysis technique to assess N availability through monitoring in situ inorganic and organic soil N fluxes in the presence and absence of mass flow in two forest ecosystems of contrasting fertility, a nutrient rich Norway spruce forest and a nutrient poor Scots pine forest. This was enabled by using solutions of different osmotic potentials as perfusates. In the absence of mass flow, amino acids dominated soil N fluxes of both ecosystems representing 62 and 82% of total flux in the nutrient rich and the nutrient poor ecosystem respectively. In the presence of mass flow, N flux increased by nine times in the nutrient rich and four times in the nutrient poor soil and nitrate comprised a greater share of total N flux. Our results suggest that mass flow may be a strong driver for plant N acquisition in boreal forests through delivering higher amounts of amino acids and NO 3 − to plant roots and mycorrhizas. These results points to a strong interaction between water and N availabilities, the former enhancing the supply of the latter through enabling high rates of transpiration. [ABSTRACT FROM AUTHOR]

Aim The dominant role of Tilia in primeval forests of Scandinavia has long been recognized, but the timing and mechanisms for its decline have not been completely unravelled. A particular uncertainty involves the balance between climate and human activities as the drivers of the change. One reason for the uncertainty is the challenge in evaluating the past cover of the genus owing to its poorly dispersed pollen; another is that a multi-site study would be required to trace subregional differences. To overcome these obstacles, we here apply two different analytical methods to pollen data from 42 sites in two distinct vegetation zones of Sweden. Location Temperate and hemi-boreal vegetation zones of southern Sweden. Methods Generalized additive mixed models (GAMM) were used to model the development of Tilia and cereal pollen percentages over time. Twelve sites were used for reconstruction of local cover of Tilia using the landscape reconstruction algorithm (LRA). Results Before 4000 cal. bp the Tilia mean pollen percentages were similar in the two vegetation zones. Thereafter, values in the hemi-boreal zone declined, with less Tilia since around 3000 cal. bp. In contrast, Tilia did not decrease in the temperate zone until this past millennium. The LRA application revealed that in some forests a large cover of Tilia remained considerably longer than has traditionally been estimated by pollen percentages alone. Main conclusions By using a large coherent dataset we found significant differences in how the abundance and distribution of Tilia changed through time between two adjacent vegetation zones. We interpret the initial decline in the northern hemi-boreal zone to be driven by cooling climate, and the later decline in the southern temperate zone to be driven more by human land-use. [ABSTRACT FROM AUTHOR]

Specific activities of artificial (Cs, Sr) and natural (К, Th, Ra) radionuclides in background soils of southern and middle taiga of Komi Republic have been estimated with consideration for the landscape-geochemical features of the territory. It has been shown that their accumulation and migration in soils are determined by the following factors: position in relief, texture, and organic matter content. No anomalous zones with increased contents of radionuclides in soils have been revealed. [ABSTRACT FROM AUTHOR]

Isaac Newton's approach to developing theories in his book Principia Mathematica proceeds in four steps. First, he defines various concepts, second, he formulates axioms utilising the concepts, third, he mathematically analyses the behaviour of the system defined by the concepts and axioms obtaining predictions and fourth, he tests the predictions with measurements. In this study, we formulated our theory of boreal forest ecosystems, called NewtonForest, following the four steps introduced by Newton. The forest ecosystem is a complicated entity and hence we needed altogether 27 concepts to describe the material and energy flows in the metabolism of trees, ground vegetation and microbes in the soil, and to describe the regularities in tree structure. Thirtyfour axioms described the most important features in the behaviour of the forest ecosystem. We utilised numerical simulations in the analysis of the behaviour of the system resulting in clear predictions that could be tested with field data. We collected retrospective time series of diameters and heights for test material from 6 stands in southern Finland and five stands in Estonia. The numerical simulations succeeded to predict the measured diameters and heights, providing clear corroboration with our theory. [ABSTRACT FROM AUTHOR]

Biological nitrogen fixation ( BNF) performed by moss-associated cyanobacteria is one of the main sources of new nitrogen (N) input in pristine, high-latitude ecosystems. Yet, the nutrients that limit BNF remain elusive. Here, we tested whether this important ecosystem function is limited by the availability of molybdenum (Mo), phosphorus (P), or both., BNF in dominant mosses was measured with the acetylene reduction assay ( ARA) at different time intervals following Mo and P additions, in both laboratory microcosms with mosses from a boreal spruce forest and field plots in subarctic tundra. We further used a 15N2 tracer technique to assess the ARA to N2 fixation conversion ratios at our subarctic site., BNF was up to four-fold higher shortly after the addition of Mo, in both the laboratory and field experiments. A similar positive response to Mo was found in moss colonizing cyanobacterial biomass. As the growing season progressed, nitrogenase activity became progressively more P limited. The ARA : 15N2 ratios increased with increasing Mo additions., These findings show that N2 fixation activity as well as cyanobacterial biomass in dominant feather mosses from boreal forests and subarctic tundra are limited by Mo availability. [ABSTRACT FROM AUTHOR]

Coarse woody debris (CWD) is an important microhabitat in forests, particularly for bryophytes and lichens. Many have suggested that this is because CWD provides a uniquely stable and humid surface microclimate, which facilitates epixylic flora, although few have adequately tested this hypothesis. Consequently, it is uncertain whether the apparent relationship between CWD and epixylic vegetation is because CWD regulates moisture, or because moisture is simply correlated with other important CWD traits. This study tested the moisture-capacitor hypothesis of epixylic flora-CWD association by measuring the surface moisture availability directly on CWD under thinned and unthinned forest canopies, and (1) comparing (a) cumulative moisture levels, and (b) variation in moisture levels with ambient and adjacent forest floor microclimates, (2) testing whether associations with log and canopy properties are stronger through direct or indirect pathways, and (3) testing whether desiccation-sensitive functional groups respond more strongly to surface moisture than other groups. Path models were built using canopy cover and log physical traits (log covering, size, acidity, and hardness) as predictors, surface moisture indices as mediators, and epixylic functional group cover as outcome variables. Forest floor and CWD microclimates were equally stable and humid, regardless of canopy cover. Log and canopy properties were more strongly related to epixylic group cover directly than indirectly (through surface moisture). Synthesis : The CWD moisture-capacitor hypothesis is rejected: CWD traits can influence surface moisture availability, but (1) log surface moisture does not differ from the forest floor, and (2) log and canopy properties are more strongly associated with epixylic taxa directly than as mediated through microclimate. [ABSTRACT FROM AUTHOR]

Determining optimal forest management to provide multiple goods and services, also referred to as Ecosystem Services (ESs), requires operational-scale information on the suitability of the forest for the provisioning of various ESs. Remote sensing allows wall-to-wall assessments and provides pixel data for a flexible composition of the management units. The purpose of this study was to incorporate models of ES provisioning potential in a spatial prioritization framework and to assess the pixel-level allocation of the land use. We tessellated the forested area in a landscape of altogether 7500 ha to 27,595 pixels of 48 × 48 m 2 and modeled the potential of each pixel to provide biodiversity, timber, carbon storage, and recreational amenities as indicators of supporting, provisioning, regulating, and cultural ESs, respectively. We analyzed spatial overlaps between the individual ESs, the potential to provide multiple ESs, and tradeoffs due to production constraints in a fraction of the landscape. The pixels considered most important for the individual ESs overlapped as much as 78% between carbon storage and timber production and up to 52.5% between the other ESs. The potential for multiple ESs could be largely explained in terms of forest structure as being emphasized to sparsely populated, spruce-dominated old forests with large average tree size. Constraining the production of the ESs in the landscape based on the priority maps, however, resulted in sub-optimal choices compared to an optimized production. Even though the land-use planning cannot be completed without involving the stakeholders' preferences, we conclude that the workflow described in this paper produced valuable information on the overlaps and tradeoffs of the ESs for the related decision support. [ABSTRACT FROM AUTHOR]

The predominant input of available nitrogen (N) in boreal forest ecosystems originates from moss-associated cyanobacteria, which fix unavailable atmospheric N2, contribute to the soil N pool, and thereby support forest productivity. Alongside climate warming, increases in atmospheric CO2 concentrations are expected in Canada's boreal region over the next century, yet little is known about the combined effects of these factors on N fixation by forest floor cyanobacteria. Here we assess changes in N fixation in a common forest floor, moss-associated cyanobacterium, Nostoc punctiforme Hariot, under elevated CO2 conditions over 30 days and warming combined with elevated CO2 over 90 days. We measured rates of growth and changes in the number of specialized N2 fixing heterocyst cells, as well as the overall N fixing activity of the cultures. Elevated CO2 stimulated growth and N fixation overall, but this result was influenced by the growth stage of the cyanobacteria, which in turn was influenced by our temperature treatments. Taken together, climate change factors of warming and elevated CO2 are expected to stimulate N2 fixation by moss-associated cyanobacteria in boreal forest systems. [ABSTRACT FROM AUTHOR]

In this study we sought answers to two questions (i) What is the relative influence of silvicultural disturbances on species richness in northern temperate and boreal forests? and (ii) In a scenario where emulating natural disturbances is applied, do collinearity and hierarchical structure exist among climate, soils, disturbance of the forest canopy and forest floor, exotic species, and species richness? By capitalizing on the NEBIE plot network, a large-plot experimental study designed to evaluate the effects of intensification of silviculture on fiber production and biodiversity. We demonstrate that silvicultural disturbances act with contemporary climate, soils, and historic fire regimes to influence plant species richness in northern temperate and boreal forests in Ontario, Canada. Relationships between various factors and plant species richness (total and for each life form: woody, herbaceous, bryophyte, and lichen) were analyzed using general linear (GLM) and structural equation modelling (SEM). Results of GLM indicate that climate accounted for the overwhelming percentage of variation in species richness of each of the plant life form groupings (>50% and often >70%), while soil properties, canopy structure, silvicultural practices, and degree of natural disturbance each accounted for on the order of 10% or less of variation in species richness. Results of fitted SEM suggested strong collinearity and hierarchy among climate, soils, historic fire regimes, and silviculture systems; however, the effect of silvicultural intensity on plant species richness was independent of climate, soils, and historic fire regimes. [ABSTRACT FROM AUTHOR]

The variability of chlorophyll a fluorescence (ChlF) parameters of forest tree species was investigated in 209 stands belonging to six European forests, from Mediterranean to boreal regions., The modifying role of environmental factors, forest structure and tree diversity (species richness and composition) on ChlF signature was analysed., At the European level, conifers showed higher potential performance than broadleaf species. Forests in central Europe performed better than those in Mediterranean and boreal regions. At the site level, homogeneous clusters of tree species were identified by means of a principal component analysis (PCA) of ChlF parameters. The discrimination of the clusters of species was influenced by their taxonomic position and ecological characteristics. The species richness influenced the tree ChlF properties in different ways depending on tree species and site. Tree species and site also affected the relationships between ChlF parameters and other plant functional traits (specific leaf area, leaf nitrogen content, light-saturated photosynthesis, wood density, leaf carbon isotope composition)., The assessment of the photosynthetic properties of tree species, by means of ChlF parameters, in relation to their functional traits, is a relevant issue for studies in forest ecology. The connections of data from field surveys with remotely assessed parameters must be carefully explored. [ABSTRACT FROM AUTHOR]

Understanding variation in carbon (C) concentration of live trees is essential for quantifying forest C stocks and validating forest C accounting models. Previous studies in boreal forests have assumed 50% C concentration or focused on species-specific C concentration estimation based on samples taken mostly from stemwood tissue of large trees. Yet, little is known about differences in C concentration between woody tissues or among trees of different sizes nor about the effects of life-history traits, such as shade tolerance and the role of volatile C on total C concentration in live trees. In this study, we examined variation in total and volatile C concentration in bark and stemwood tissues for trees of different sizes for six major North American boreal tree species. We found that bark had significantly higher total C and volatile C concentrations than stemwood and that both total C and volatile C concentration significantly varied among tree species. The average total C concentrations were 56.2% in the bark and 50.5% in the stemwood, and the average volatile C concentration were 5.8% and 3.0% for bark and stemwood, respectively. Furthermore, total C and volatile C concentration in stemwood and bark of almost all shade-intolerant species increased with tree size, whereas those of shade-tolerant species showed negative or neutral size-associated change. Our results show that volatile C concentration is a key driver of variation in total C concentration and highlights the importance of considering variation in C concentration when quantifying forest C stocks, which has important consequences for predicting future global C emissions scenarios. [ABSTRACT FROM AUTHOR]

Understanding the development of landscape patterns over broad spatial and temporal scales is a major contribution to ecological sciences and is a critical area of research for forested land management. Boreal forests represent an excellent case study for such research because these forests have undergone significant changes over recent decades. We analyzed the temporal trends of four widely-used landscape pattern indices for boreal forests of Canada: forest cover, largest forest patch index, forest edge density, and core (interior) forest cover. The indices were computed over landscape extents ranging from 5,000 ha (n = 18,185) to 50,000 ha (n = 1,662) and across nine major ecozones of Canada. We used 26 years of Landsat satellite imagery to derive annualized trends of the landscape pattern indices. The largest declines in forest cover, largest forest patch index, and core forest cover were observed in the Boreal Shield, Boreal Plain, and Boreal Cordillera ecozones. Forest edge density increased at all landscape extents for all ecozones. Rapidly changing landscapes, defined as the 90th percentile of forest cover change, were among the most forested initially and were characterized by four times greater decrease in largest forest patch index, three times greater increase in forest edge density, and four times greater decrease in core forest cover compared with all 50,000 ha landscapes. Moreover, approximately 18% of all 50,000 ha landscapes did not change due to a lack of disturbance. The pattern database results provide important context for forest management agencies committed to implementing ecosystem-based management strategies. [ABSTRACT FROM AUTHOR]

The Canadian Drought Code (CDC) is an empirical soil-drying model adapted to high-latitude forests and commonly used by Canadian fire managers and researchers to predict the water content of the organic soil layer. Better knowledge of the capacity of the CDC to predict the effect of droughts on the water content of the mineral soil could improve our capacity to predict the future response of Canadian boreal forests to future changes in drought frequency and intensity. We tested the capacity of the CDC to predict mineral soil water content (SWC) and droughts against long-term (14-16 years) daily mineral SWC data from time domain reflectometry probes in multiple stations within three forest ecosystems of Eastern Canada respectively dominated by sugar maple, balsam fir and black spruce. Droughts were defined as SWC values lower than one standard deviation from their historical mean. The drought intensity and frequency of each growing season were computed as the sum of daily SWC departures from normal and the sum of days of drought, respectively. Our results show that the CDC is a reliable predictor of mineral SWC ( r = 0.6-0.8), drought frequency ( r = 0.5-0.9) and intensity ( r = 0.7-0.9) for high-latitude forest ecosystems of Eastern Canada. Lower correlations were due to the poor accuracy of the model at predicting mild droughts at the sugar maple stand due to the SWC values close to the drought threshold. We detected a higher susceptibility to droughts at the black spruce stand due to a 1-month-earlier occurrence of severe droughts. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Climate change is altering forests globally, some in ways that may promote further warming at the regional and even continental scales. In order to predict how forest ecosystems might adapt to a changing climate, it is important to understand the resilience and vulnerabilities that each species within that current ecosystem might have to a modified future environment. Complex systems that occupy large spatial domains and change slowly, on the order of decades to centuries, do not lend themselves easily to direct observation. A simulation model is often the more appropriate and attainable approach toward understanding the inner workings of large, slow-changing systems, and how they may change with imposed perturbations. We report on a new, spatially-explicit dynamic vegetation model SIBBORK developed for the purpose of investigating the effects of climatological changes on the long-term dynamics, structure and composition of the Siberian boreal forest. [ABSTRACT FROM AUTHOR]

Butterfly conservation in Europe is mainly focused on well-defined grassland habitat patches. Such an approach ignores the impact of the surrounding landscape, which may contain complementary resources and facilitate dispersal. Here, we investigated butterfly species richness and abundance in a habitat normally regarded as unsuitable matrix: production forestry clear-cuts. Butterflies were recorded in 48 clear-cuts in southern Sweden differing with regards to the time since clear-cutting and land-use history (meadow or forest based on historical maps from the 1870s). All clear-cuts had been managed as production forests for at least 80–120 years. A total of 39 species were found in clear-cuts of both land-use histories, but clear-cuts with a history as meadow had on average 34% higher species richness and 19% higher abundance than did clear-cuts with a history as forest. No effect of the time since clear-cutting was found, irrespective of land-use history, which was likely due to the narrow timespan sampled (<8 years). The absence of temporal effect suggests that clear-cuts may provide butterflies with valuable resources for 10–15 years. Assuming a 100 year forest rotational cycle, this means that 10–15% of the total forested area are made up by clear-cuts valuable to butterflies, which corresponds to an area about four times as large as that of species-rich semi-natural grasslands. The study illustrates the importance of considering land-use legacies in ecological research and question the landscape-ecological view that clear-cuts make up an unsuitable matrix for butterflies. Moreover, forest conservation management with special attention to land-use history may increase the quality of the landscape, thus facilitating butterfly metapopulation persistence. Given their large area and assets of nectar and host plant resources, clear-cuts must be considered as a butterfly habitat in its own right. Being a man-made environment with short history, we might call it a neo-habitat. [ABSTRACT FROM AUTHOR]

This article concerns the spatial distribution patterns of small-leaved forests in the Kuznetsk Depression, where these communities are the forest components of zonal vegetation. Two levels of spatial forest heterogeneity are described. Depending on mesorelief, forest communities are organized into topo-ecological series, which differ in sets of components and area covered by different elements. On a larger scale, depending on climatic features in different parts of the depression, the spatial pattern of communities and topo-ecological series reflect the zonal structures. In general, the spatial forest distribution is considered as follows: the central part of the depression is covered by Artemisio – Betuletum communities in combination with Calamagrostio – Betuletum forests; approaching the eastern border of the depression, they change to Trollio – Populetum and Campanulo – Betuletum combinations; the southern part is occupied by communities of Campanulo – Betuletum, together with Saussureo – Populetum forests; in the north-western part the only forest association is Primulo – Betuletum. Throughout the entire region, in places with bad drainage occur communities of Carici – Betuletum. Based on climatic parameters, forest-steppe and sub-taiga sub-belts can be distinguished. Forest-steppe in its turn can be divided into an original fragment of plain forest-steppe and typical forest-steppe. In the eastern part of the depression, a sub-taiga sub-belt developed but in the western part, it exists outside the depression. [ABSTRACT FROM AUTHOR]

ABSTRACT Understanding fire regime dynamics is central to predicting forest structure and the compositional dynamics of boreal forests. Spatial and temporal variations in fire frequency in central Canadian boreal forests over the last 10 000 years were examined to evaluate the influence of bottom-up controls on the regional fire regime. We analysed macroscopic charcoal larger than 160 μm from sediment cores from six lakes to reconstruct fire history and performed GIS analysis of regional landscape features to investigate how fire frequency has changed temporally and how non-climatic factors may have affected long-term fire frequency. Our generalized linear mixed model revealed that temporal changes in fire return intervals (FRIs) were highly dependent on landscape connectivity as inferred through the abundance of natural firebreaks in the form of open water lakes and wetlands. FRIs did not change significantly among highly connected landscapes throughout the Holocene; in contrast, FRIs were significantly longer among poorly connected landscapes in the early Holocene (10-5 cal ka BP), suggesting that the abundant regional firebreaks limited fire spread. All sites had similar FRIs in the late Holocene. The diminishing influence of firebreaks suggests that the regional climate during the late Holocene has overshadowed the influences of the bottom-up controls on fire activities. [ABSTRACT FROM AUTHOR]

Wildfire size, frequency, and severity are increasing in the Alaskan boreal forest in response to climate warming. One of the potential impacts of this changing fire regime is the alteration of successional trajectories, from black spruce to mixed stands dominated by aspen, a vegetation composition not experienced since the early Holocene. Such changes in vegetation composition may consequently alter the intensity of fires, influencing fire feedbacks to the ecosystem. Paleorecords document past wildfire-vegetation dynamics and as such, are imperative for our understanding of how these ecosystems will respond to future climate warming. For the first time, we have used reflectance measurements of macroscopic charcoal particles (>180μm) from an Alaskan lake-sediment record to estimate ancient charring temperatures (termed pyrolysis intensity). We demonstrate that pyrolysis intensity increased markedly from an interval of birch tundra 11 ky ago (mean 1.52%Ro; 485°C), to the expansion of trees on the landscape ∼10.5 ky ago, remaining high to the present (mean 3.54%Ro; 640°C) irrespective of stand composition. Despite differing flammabilities and adaptations to fire, the highest pyrolysis intensities derive from two intervals with distinct vegetation compositions. 1) the expansion of mixed aspen and spruce woodland at 10 cal. kyr BP, and 2) the establishment of black spruce, and the modern boreal forest at 4 cal. kyr BP. Based on our analysis, we infer that predicted expansion of deciduous trees into the boreal forest in the future could lead to high intensity, but low severity fires, potentially moderating future climate-fire feedbacks. [ABSTRACT FROM AUTHOR]

In the southern boreal forest of Québec, jack pine ( Pinus banksiana Lamb.) stands occur in two habitat units, mainland and island. These two habitats have historically experienced different fire regimes. Infrequent lethal fires characterize the mainland, while frequent non-lethal and infrequent lethal fires characterize the islands. Previous studies have shown that highly serotinous jack pine trees tend to dominate on the mainland, while intermediate and non-serotinous trees are more abundant on the islands. A comparison of morphological characters describing tree form, cone morphology and reproductive output was made on 14 mainland and 10 island stands in an effort to determine if they exhibited variation consistent with variation in fire regime and serotiny. Generally, mean values of the morphological and reproductive characters measured did not vary between the two habitats, nor did bark allometry. Live crown height to tree height ratio, as a function of tree age, and cone number as a function of tree height varied between the habitats. Relatively old mainland trees had a shorter crown in relation to tree height than their island counterparts. Cone number increased faster with tree height for island versus mainland trees. Island trees exhibited earlier reproduction than did mainland trees: in the island habitat the percentage of cone bearing trees (55 %) in the youngest age class (<21 years) was significantly greater than in the mainland habitat (34 %). Mainland populations were fire-resilient with a high degree of serotiny. Island populations behave like fire-resistant/fire-surviving species with a low degree of serotiny and earlier reproductive investment. [ABSTRACT FROM AUTHOR]

Boreal forests are sensitive to climatic warming, because low temperatures hold back ecosystem processes, such as the mobilization of nitrogen in soils. A greening of the boreal landscape has been observed using remote sensing, and the seasonal amplitude of CO2 in the northern hemisphere has increased, indicating warming effects on ecosystem productivity. However, field observations on responses of ecosystem productivity have been lacking on a large sub-biome scale. Here we report a significant increase in the annual growth of boreal forests in Finland in response to climatic warming, especially since 1990. This finding is obtained by linking meteorological records and forest inventory data on an area between 60° and 70° northern latitude. An additional increase in growth has occurred in response to changes in other drivers, such as forest management, nitrogen deposition and/or CO2 concentration. A similar warming impact can be expected in the entire boreal zone, where warming takes place. Given the large size of the boreal biome – more than ten million km2– important climate feedbacks are at stake, such as the future carbon balance, transpiration and albedo. [ABSTRACT FROM AUTHOR]

Northern Canadian boreal forest has a considerable ecological and economic importance, with the black spruce forest type occupying a large extent of this ecosystem. Organic layer thickness and its relationship to topography are two key factors affecting tree growth and productivity of black spruce boreal forests of the Canadian Clay Belt region. This study linked multi-scale models of organic layer thickness and topography to improve our understanding of how these variables influence forest productivity and its distribution at different spatial scales within the Clay Belt region, northwestern Quebec. Field data were used to calculate site indices, which were used as estimators of forest productivity. Organic layer thickness was determined from field measurements obtained by manual probing, whereas topographic variables were extracted from multi-scale LiDAR-derived digital terrain models (DTM) at four resolutions, i.e., 5-, 10-, 15- and 20-m. Correlations between individual predictors and site index were found to be weak; however, few were significant, viz., organic layer thickness. Regression tree-based models were fitted using two different sets of explanatory variables at the four scales: organic layer thickness and topography (model 1); and topographic variables only (model 2). Organic layer thickness, aspect, and slope were the most important variables explaining forest productivity (63% and 31% total variance explained for models 1 and 2, respectively). Model 1 was found to be scale-independent, since the total explained variance was similar under the four resolutions, whereas with model 2, effects of topography on productivity were greater for coarser scales (highest R 2 at 20-m resolution). Both models indicated higher forest productivity on southwest-facing slopes (i.e., >2.2%) with shallow organic layers (<35 cm), so then where organic horizons are the deepest the tree productivity is low. In contrast, lowest site indices (expressing low productivity) were found in areas with very deep organic layers (>85 cm). The resulting models could be applied at operational scales to predict site index at locations for which organic layer thickness information and DTM exist. Such information could be used to help forest managers in predicting how forest growth will respond to various harvesting activities. [ABSTRACT FROM AUTHOR]

Landscapes undergo changes in structure and function at multiple temporal and spatial levels. As a consequence of natural and anthropogenic drivers, these changes affect options for land use. We describe winter land use by reindeer husbandry in the boreal forest in Northern Sweden. The landscape changes in its suitability for husbandry practices due to environmental stochasticity and transformations due to other forms of land use. This creates structures that can either (i) promote flexibility in the form of mobility or (ii) create fragmentation that restricts adaptation to changes. As these drivers are interdependent in their influence on land use practices by reindeer herders, different choices regarding husbandry strategies have to be made within a season and between years. To allow such choices and ensure pastoral resilience to change, boreal forests should be regulated to provide continuity of grazing resources at multiple temporal and spatial levels. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Red wood ants of the Formica rufa group, as well as their nests, form a vital part of the ecosystems of both European and Siberian boreal and temperate forests. It has been well documented that the nests of red wood ants in clear-cuts do not perform as well as those deeper in the forest. However, clear-cuts may not be a homogeneously poor habitat for such forest-dwelling ants because the distance of the nest site to the edge of the remaining forest may be a significant factor affecting the nest performance. In this study, I compared the probability of nest survival and sexual offspring production between the nests of Formica aquilonia (Yarrow, 1955) in a forest edge zone (distance to the forest edge <9.2 m) and a clear-cut centre zone in 18 different clear-cut areas. Although the nests were generally smaller, the probability of sexual offspring production and nest survival was higher among those nests in the edge compared to the centre zone. Since the proximity to the forest edge increased the performance of a nest, selective logging and smaller scale clear-cuts may not be as harmful to red wood ants as clear-cutting over a large area. [ABSTRACT FROM AUTHOR]

Introduction: Rising temperatures may force boreal forests in central Siberia to transition to alternative ecological states, affecting species composition and carbon storage dynamics. A full understanding of how forests of different ages respond to warming remains elusive, despite being fundamental for proper forest management in the region. Aims: To document the sensitivity of Siberian forests of different successional stages to rising temperatures. Methods: We use the FAREAST forest gap model to investigate the variation in biophysical response of boreal forests of different stand ages as temperatures rise and question whether there is varying sensitivity at different successional states. Results: Our model predicts that mid-successional forests are more resistant to warming temperatures in low-level warming scenarios and resist biophysical changes more so than forests over 200 years old. This response diminished in more intense warming scenarios. Specifically, forest biomass increased with temperature; however, dieback of Siberian larch and replacement by Siberian Silver birch and by Siberian pine in early-successional stands yielded a net decrease in carbon storage. Mid-succession and old growth forests did not transition to pine forests, however, and may serve as a location for refugia of northern boreal species. [ABSTRACT FROM AUTHOR]

The manner in which organisms adapt to climate change informs a broader understanding of the evolution of biodiversity as well as conservation and mitigation plans. We apply common garden and association mapping approaches to quantify genetic variance and identify loci affecting bud flush and bud set, traits that define a tree's season for height growth, in the boreal forest tree Populus balsamifera L. (balsam poplar). Using data from 478 genotypes grown in each of two common gardens, one near the southern edge and another near the northern edge of P. balsamifera's range, we found that broad-sense heritability for bud flush and bud set was generally high ( H2 > 0.5 in most cases), suggesting that abundant genetic variation exists for phenological response to changes in the length of the growing season. To identify the molecular genetic basis of this variation, we genotyped trees for 346 candidate single nucleotide polymorphisms ( SNPs) from 27 candidate genes for the CO/ FT pathway in poplar. Mixed-model analyses of variance identified SNPs in 10 genes to be associated with variation in either bud flush or bud set. Multiple SNPs within FRIGIDA were associated with bud flush, whereas multiple SNPs in LEAFY and GIGANTEA 5 were associated with bud set. Although there was strong population structure in stem phenology, the geographic distribution of multilocus association SNP genotypes was widespread except at the most northern populations, indicating that geographic regions may harbour sufficient diversity in functional genes to facilitate adaption to future climatic conditions in many sites. [ABSTRACT FROM AUTHOR]

The effects on birch (Betula spp.) of elevated carbon dioxide (CO2) and ozone (O3), which are both increasing in the troposphere, are surveyed in detail based on the literature. Birches establish themselves in the open field after disturbances, and then become dominant trees in temperate or boreal forests. Ecophysiological approaches include the measurement of photosynthesis, biomass, growth, and survival of seedlings and trees. Elevated CO2 levels give rise to a net enhancement of the growth of birch trees, whereas high O3 generally reduces growth. Although the effects of the two are opposed, there is also an interactive effect. Basic physiological responses of the single genus Betula to CO2 and O3 are set out, and some data are summarized regarding ecological interactions between trees, or between trees and other organisms. [ABSTRACT FROM AUTHOR]

Copyright of Études Inuit Studies is the property of Centre interuniversitaire d'etudes et de recherches autochtones (CIERA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article discusses a study that examines the spatial distribution and species co-occurrence in soil invertebrate and plant communities on northern taiga islands. The study describes the patterns of species association across taxa and trophic groups using a data set on arctic plant and animal species obtained from arctic islands of the Kandalasha Bay. It reveals high frequency of significantly segregated taxa on the relatively stable forested island.

Abstract: Dead wood such as stumps and logs found on the forest floor is a key structural element that is used by a broad spectrum of organisms and contributes to soil nutrient cycling. The complexity of the forest floor in the boreal forest is largely dependent on coarse woody debris (CWD), but actual forestry practices may compromise the future recruitment of this resource. The main goal of our study was to determine the effects of CWD on small mammals in stands of varying green-tree retention levels. Since small mammals are associated with microhabitat components at multiple spatial scales, our secondary goal was to assess the effects of scale on small mammal relationship with CWD. Five trapping sessions were conducted in the boreal forest of western Québec, Canada during the summers of 2009 and 2010 in four managed forest blocks. Each block was composed of 12 independent trapping grids equally distributed in three treatments: clearcuts (0% green-tree retention), partial cuts (30% green-tree retention) and controls (undisturbed). We live-trapped small rodents and used pitfall traps for shrews in trapping sub-grids (fine-scale; 50m) nested in larger grids (stand-scale; 300m). Southern red-backed vole (Myodes gapperi) and deer mouse (Peromyscus maniculatus) abundances were positively associated with sites with high volumes of well decayed CWD in all treatments, at the fine-scale. Southern bog lemming (Synaptomys cooperi) abundance was positively associated with well decayed CWD, at both scales, but mainly in clearcut areas. Masked shrew (Sorex cinereus) abundance increased with high volumes of well decayed CWD in clearcuts but only at the stand-scale. In contrast, meadow voles were more abundant in sites with high volumes of well decayed CWD in controls than in sites with small volumes at the stand-scale. Patches of partial cuts with high volumes of well decayed CWD were characterized by high abundances of red-backed voles and this clearly indicates that volume and decay of CWD are important drivers that can mitigate the impacts of tree removal. We found different scale-dependent responses of small mammals to volumes of well decayed CWD, which indicates that associations were found at the individual as well as at the population level. We suggest that partial cuts composed of regularly distributed patches of high volumes of CWD (⩾11.4m3 in patches of 0.03ha) might have a high potential to maintain red-backed voles, a species associated with mature forests. [Copyright &y& Elsevier]

We investigated landscape resistance to movements of American marten (Martes americana) based on snow-tracking data. We generated movement cost maps of the study area with different grain size, thematic resolution, and habitat-specific resistance to movements. We compared simulated tracks obtained from resistance maps to real tracks plotted along transects that we surveyed in winters 2004 to 2008 at the Montmorency Forest, Quebec, Canada. Simulated tracks were located at the intersection between least-cost paths simulated across the study area and transects. We used nearest-neighbour distances between simulated and real tracks to assess the performance of resistance maps and estimate landscape resistance parameters. Simulations with specified costs to movement for open areas, young forest, and mature forest performed better than simpler resistance scenarios, suggesting that resistance to marten movements differed among those landscape attributes that were considered. Simulations with a map grain size of 100m performed significantly better than 5, 25, and 300 m, possibly because of gap crossing avoidance. Model performance (compared to null model) was maximal when resistance to movement in open habitat was set to 20 times higher than in mature forest, but uncertainty around this estimate was large. This research demonstrates that presence-only (point) data can be used to parameterize movements using spatially explicit modelling. [ABSTRACT FROM AUTHOR]

This study investigated public aesthetic preferences regarding naturally occurring dead and downed wood in Norwegian boreal forests. In an Internet-based survey conducted in cooperation with a commercial polling company, 1082 respondents from south-eastern and middle Norway were asked to rate 24 photos of forest settings. All photos had been taken at a stand level in primary or lightly altered semi-natural forests, although this was not disclosed to the respondents. Survey participants showed a clearly greater preference for images of forests settings containing little or no visible dead or downed wood. Participants also rated photos of forest settings with the dead wood elements removed through digital manipulation substantially higher than otherwise identical non-manipulated photos. However, public aesthetic perception of dead wood in forest setting did appear to be influenced by their understanding of the ecological benefits dead wood provides to forest biodiversity. Photos shown with an accompanying text describing the ecology or natural history of forest scenes containing dead wood received significantly higher ratings than identical photos without accompanying text. Our results suggest that those involved in maintaining or increasing forest biodiversity by retaining standing and fallen dead wood also need to incorporate outreach efforts that educate the public about the ecological benefits of these forest elements. [ABSTRACT FROM AUTHOR]

1. Mixed-wood boreal forests are often considered to undergo directional succession from shade-intolerant to shade-tolerant species. It is thus expected that overstorey gaps should lead to the recruitment of shade-tolerant conifers into the canopy in all stand development stages and that the recruitment of shade-intolerant hardwoods would be minimal except in the largest gaps. 2. We analysed short-term gap dynamics over a large 6-km2 spatial area of mixed-wood boreal forest across a gradient of stands in different developmental stages with different times of origin since fire (expressed as stand ‘age’) that were affected differentially by the last spruce budworm (SBW) outbreak. Structural measurements of the canopy from lidar data were combined with spectral classification of broad species groups to characterize the gap disturbance regime and to evaluate the effect of gap openings on forest dynamics. 3. Estimated annual gap opening rates increased from 0.16% for 84-year-old stands to 0.88% for 248-year-old stands. Trees on gap peripheries in all stands were more vulnerable to mortality than interior canopy trees. 4. Due to recovery from the last SBW outbreak 16 years previously, gap closure rates were higher than opening rates, ranging from 0.44% to 2.05% annually, but did not show any relationship with stand age. There was, however, a continuing legacy of the last SBW outbreak in old-conifer stands in terms of a continued high mortality of conifers. In all stands, the majority of the openings were filled from below, although a smaller but significant proportion filled from lateral growth of gap edge trees. 5. Synthesis. The forest response to moderate- to small-scale disturbances in old-growth boreal forest counters the earlier assumption that the transition from one forest state to the next is slow and directional with time since the last fire. Overall, a small 6% increase in hardwoods was observed over 5 years, largely due to regeneration in-filling of hardwoods in gaps instead of successional transition to more shade-tolerant conifers. Gaps are vital for hardwood maintenance while transition to softwoods can occur without perceived gap-formation as overstorey trees die, releasing understorey trees. [ABSTRACT FROM AUTHOR]

Boreal forests are under strong influences from climate change, and alterations in forest dynamics will have significant impacts on global climate-biosphere feedback as well as local to regional conservation and resource management. To understand the mechanisms of forest dynamics and to assess the fate of boreal forests, simulation studies should be based on plant ecophysiological responses onto environmental conditions. In central Canadian boreal forests, local geomorphology created by past glacial activities often generates a mosaic of very distinctive forest types. On sandy hilltop of a glacial till, due to limitations in moisture availability and short fire return intervals, drought-tolerant and fire-adapted jack pine usually becomes the dominant species. On mesic and nutrient-rich slopes, fast-growing and resource-demanding trembling aspen forms mixed forests with coniferous species. In bottomland, black spruce, slowly growing but tolerant species, is often the only species that can survive to the adult stage. These three very distinctive forest types often occur within a scale of 10 m. Simulation models of boreal forests should be able to reproduce this heterogeneity in forest structure and composition as an emergent property of plant ecophysiological responses to varying environmental properties. In this study, a process-based forest dynamics model, ecosystem demography model version 1.0, is used to mechanically reproduce the landscape heterogeneity due to edaphic variations. First, boreal tree species of northern Manitoba, Canada, are parameterized according to field observations, and, to explicitly capture interactions among tree saplings, allometric equations based on diameter at height of 0.15 m, instead of the conventional breast height of 1.37 m, is parameterized. Then, soil moisture regime and nutrient concentrations are statistically incorporated from a dataset. The resultant simulation successfully reproduces the distinctive forest dynamics influenced by the edaphic heterogeneity. The sequences of succession and the trajectories of forest development are generally consistent with the field observations. The differences in resource availability are the essential control on equilibrium values of total forest leaf area index. Next, to show the effect of anthropogenic atmospheric changes, changes in temperature and CO2 concentrations are studied by a set of factorial experiments. The magnitude of CO2 fertilization is largely affected by soil fertility. The temperature rise will increase the length of growing season, but can have a negative impact on forest growth by increasing aridity and autotrophic respiration. Overall, the boreal forest responses to climate change are complex due to the inherent edaphic variations and ecophysiological responses. [ABSTRACT FROM AUTHOR]

Morphometric parameters of mature leaves (area, venation density, and shape coefficient) and trunks (size and biomass) of two edificatory birch species, Betula pendula Roth and B. pubescens Ehrh., were characterized. These species inhabit a 1600-km transect of the Urals, from forest-tundra to forest-steppe. In both species, the highest trunk biomass was observed in the subzone of south taiga. Trunk parameters and leaf sizes of B. pendula varied in a narrower range than in B. pubescens. As distinct from leaf shape, leaf size was correlated with the average multiyear climate characteristics but not with the weather during a given growth season. In B. pubescens, which range extends wide from its climatic optimum, leaf area was positively correlated with trunk biomass. In B. pendula, growing mainly within the area of its climatic optimum, such correlation was not observed. We concluded that such parameter as mature leaf size could be used for prediction of tree productivity growing outside of the zone of their climatic optimum. [ABSTRACT FROM AUTHOR]

Abstract: Effects of clear-cutting on biodiversity have mainly been studied in the short-term, although knowledge of longer term effects are often more important for managers of forest biodiversity. We assessed relatively long-term effects of clear-cutting on litter dwelling land snails, a group with slow active dispersal and considered to be intolerant to microclimate changes. In a pair wise design we compared snail abundance, species density, and species composition between 13 old seminatural stream-side stands and 13 matched young stands developed 40–60years after clear-cutting. Using a standardized semi-quantitative method, we identified all snail specimens in a 1.5l subsample of a pooled litter sample collected from small patches within a 20×5m plot in each stream-side stand. From the young stands a mean of 135 shells and 9.5 species was extracted which was significantly higher than the 58.1 shells and 6.9 species found in old forests. Only two of the 16 species encountered showed a stronger affinity to old than to young forests. In short-term studies of boreal stream-side forests land snail abundance is reduced by clear-cutting. Our results indicate that this decline is transient for most species and within a few decades replaced by an increase. We suggest that local survival in moist stream-side refugia makes the land snails able to benefit from the higher pH and more abundant non-conifer litter in young than in old boreal forests. Our results highlight the importance of longer term studies as a basis for management guidelines for biodiversity conservation. [Copyright &y& Elsevier]

The article presents a study which examines the influence of weather and fuel type on the fuel composition of the area burned by forest fires in Ontario from 1996-2006. The relative importance of fuels and weather in the boreal forest was examined using the compositional analysis. The fuel composition of area burned by 594 large fires that occurred in boreal forest region was evaluated using the providence of Ontario's Provincial Fuels Database and fire records provided by the Ontario Ministry of Natural Resources.

Abstract: Decomposer microorganisms contribute to carbon loss from the forest floor as they metabolize organic substances and respire CO2. In temperate and boreal forest ecosystems, the temperature of the forest floor can fluctuate significantly on a day-to-night or day-to-day basis. In order to estimate total respiratory CO2 loss over even relatively short durations, therefore, we need to know the temperature sensitivity (Q 10) of microbial respiration. Temperature sensitivity has been calculated for microbes in different soil horizons, soil fractions, and at different depths, but we would suggest that for some forests, other ecologically relative soil portions should be considered to accurately predict the contribution of soil to respiration under warming. The floor of many forests is heterogeneous, consisting of an organic horizon comprising a few more-or-less distinct layers varying in decomposition status. We therefore determined at various measurement temperatures the respiration rates of litter, F-layer, and H-layer collected from a Pinus resinosa plantation, and calculated Q 10 values for each layer. Q 10 depended on measurement temperature, and was significantly greater in H-layer than in litter or F-layer between 5 and 17°C. Our results indicate, therefore, that as the temperature of the forest floor rises, the increase in respiration by the H-layer will be disproportionate to the increase by other layers. However, change in respiration by the H-layer associated with change in temperature may contribute minimally or significantly to changes of total forest floor respiration in response to changes in temperature depending on the depth and thickness of the layer in different forest ecosystems. [Copyright &y& Elsevier]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)