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Predicting and mitigating impacts of climate change and development within the boreal biome requires a sound understanding of factors influencing the abundance, distribution, and population dynamics of species inhabiting this vast biome. Unfortunately, the limited accessibility of the boreal biome has resulted in sparse and spatially biased sampling, and thus our understanding of boreal bird population dynamics is limited. To implement effective conservation of boreal birds, a cost-effective approach to sampling the boreal biome will be needed. Our objective was to devise a sampling scheme for monitoring boreal birds that would improve our ability to model species-habitat relationships and monitor changes in population size and distribution. A statistically rigorous design to achieve these objectives would have to be spatially balanced and hierarchically structured with respect to ecozones, ecoregions and political jurisdictions. Therefore, we developed a multi-stage hierarchically structured sampling design known as the Boreal Optimal Sampling Strategy (BOSS) that included cost constraints, habitat stratification, and optimization to provide a cost-effective alternative to other common monitoring designs. Our design provided similar habitat and spatial representation to habitat stratification and equal-probability spatially balanced designs, respectively. Not only was our design able to achieve the desired habitat representation and spatial balance necessary to meet our objectives, it was also significantly less expensive (1.3−2.6 times less) than the alternative designs we considered. To further balance trade-offs between cost and representativeness prior to field implementation, we ran multiple iterations of the BOSS design and selected the one which minimized predicted costs while maximizing a multi-criteria evaluation of representativeness. Field implementation of the design in three vastly different regions over three field seasons showed that the approach can be implemented in a wide variety of logistical scenarios and ecological conditions. We provide worked examples and scripts to allow our approach to be implemented or adapted elsewhere. We also provide recommendations for possible future refinements to our approach, but recommend that our design now be implemented to provide unbiased information to assess the status of boreal birds and inform conservation and management actions. [ABSTRACT FROM AUTHOR]

Bird-window collisions are the second leading cause of human-related avian mortality for songbirds in Canada. Our ability to accurately estimate the number of fatalities caused by window collisions is affected by several biases, including the removal of carcasses by scavengers prior to those carcasses being detected during surveys. We investigated the role of scavenger behavior in modifying perceived carcass removal rate while describing habitat-specific differences for the scavengers present in a relatively scavenger-depauperate island ecosystem. We used motion activated cameras to monitor the fate of hatchling chicken carcasses placed at building (under both windows and windowless walls) and forest (open and closed canopy) sites in western Newfoundland, Canada. We recorded the identity of scavengers, timing of events, and frequency of repeat scavenging at sites. Using 2 treatments, we also assessed how scavenging varied with 2 levels of carcass availability (daily versus every third day). Scavenger activities differed substantially between forest and building sites. Only common ravens (Corvus corax) removed carcasses at building sites, with 25 of 26 removals occurring under windows. Burying beetles (Nicrophorus spp.) dominated scavenging at forest sites (14 of 18 removals), completely removing carcasses from sight in under 24 hours. Availability had no effect on removal rate. These findings suggest that ravens look for carcasses near building windows, where bird-window collision fatalities create predictable food sources, but that this learning preceded the study. Such behavior resulted in highly heterogeneous scavenging rates at fine spatial scales indicating the need for careful consideration of carcass and camera placement when monitoring scavenger activity. Our observations of burying beetle activity indicate that future studies investigating bird collision mortality near forested habitats and with infrequent surveys, should consider local invertebrate community composition during survey design. The high incidence of invertebrate scavenging may compensate for the reduced vertebrate scavenger community of insular Newfoundland. [ABSTRACT FROM AUTHOR]

A significant challenge of conservation biology is to preserve species in places where their critical habitat also attracts significant economic interest. The problem is compounded when species distributions occur across large spatial extents. Threatened boreal caribou (Rangifer tarandus caribou) epitomize this problem: their critical habitat encompasses a vast expanse of forest that also supplies much of Canada's merchantable timber. Boreal caribou were protected under the Canada Species at Risk Act in 2003. We investigated putative drivers of reduced disturbance for caribou habitat since then. Where the cumulative logging footprint slowed within caribou habitat, this has resulted neither from decreases in annual allowable cut of timber nor the creation or expansion of protected areas. Rather, it has fluctuated with the American economy relative to that of Canada. For each $0.05 US lost over the $CAD, 129 km2 of caribou habitat was not disturbed by logging in a given year. Recent population declines have been occurring even though logging typically remained at <70% of allowed levels. Our study raises concerns about how caribou are functionally being conserved under the current application of existing legislation. In this globalized world, the economy of foreign nations is increasingly likely to govern national conservation objectives. [ABSTRACT FROM AUTHOR]

The Adirondack Park in New York State contains a unique and limited distribution of boreal ecosystem types, providing habitat for a number of birds at the southern edge of their range. Species are projected to shift poleward in a warming climate, and the limited boreal forest of the Adirondacks is expected to undergo significant change in response to rising temperatures and changing precipitation patterns. Here we expand upon a previous analysis to examine changes in occupancy patterns for eight species of boreal birds over a decade (2007–2016), and we assess the relative contribution of climate and non-climate drivers in determining colonization and extinction rates. Our analysis identifies patterns of declining occupancy for six of eight species, including some declines which appear to have become more pronounced since a prior analysis. Although non-climate drivers such as wetland area, connectivity, and human footprint continue to influence colonization and extinction rates, we find that for most species, occupancy patterns are best described by climate drivers. We modeled both average and annual temperature and precipitation characteristics and find stronger support for species' responses to average climate conditions, rather than interannual climate variability. In general, boreal birds appear most likely to colonize sites that have lower levels of precipitation and a high degree of connectivity, and they tend to persist in sites that are warmer in the breeding season and have low and less variable precipitation in the winter. It is likely that these responses reflect interactions between broader habitat conditions and temperature and precipitation variables. Indirect climate influences as mediated through altered species interactions may also be important in this context. Given climate change predictions for both temperature and precipitation, it is likely that habitat structural changes over the long term may alter these relationships in the future. [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]

Climate change represents one of the most significant threats to human and wildlife communities on the planet. Populations at range margins or transitions between biomes can be particularly instructive for observing changes in biological communities that may be driven by climate change. Avian communities in lowland boreal habitats in the Adirondack Park, located at the North American boreal-temperate ecotone, have been the focus of long-term monitoring efforts since 2007. By documenting long-term changes in community structure and composition, such datasets provide an opportunity to understand how boreal species are responding differently to climate change, and which habitat characteristics may be best able to retain boreal avian communities. We examined three specific questions in order to address how well current biological communities in Adirondack boreal wetland habitats are being maintained in a changing climate: (1) how do trends in occupancy vary across species, and what guilds or characteristics are associated with increasing or decreasing occupancy? (2) how is avian community composition changing differently across sites, and (3) what distinguishes sites which are retaining boreal birds to a higher degree than other sites? Our analysis revealed that (1) boreal species appear to exhibit the largest changes in occupancy among our study locations as compared to the larger avian community, (2) dynamics of community change are not uniform across sites and habitat structure may play an important role in driving observed changes, and (3) the particular characteristics of large open peatlands may allow them to serve as refugia for boreal species in the context of climate change. [ABSTRACT FROM AUTHOR]

Freely-available satellite data streams and the ability to process these data on cloud-computing platforms such as Google Earth Engine have made frequent, large-scale landcover mapping at high resolution a real possibility. In this paper we apply these technologies, along with machine learning, to the mapping of peatlands–a landcover class that is critical for preserving biodiversity, helping to address climate change impacts, and providing ecosystem services, e.g., carbon storage–in the Boreal Forest Natural Region of Alberta, Canada. We outline a data-driven, scientific framework that: compiles large amounts of Earth observation data sets (radar, optical, and LiDAR); examines the extracted variables for suitability in peatland modelling; optimizes model parameterization; and finally, predicts peatland occurrence across a large boreal area (397, 958 km2) of Alberta at 10 m spatial resolution (equalling 3.9 billion pixels across Alberta). The resulting peatland occurrence model shows an accuracy of 87% and a kappa statistic of 0.57 when compared to our validation data set. Differentiating peatlands from mineral wetlands achieved an accuracy of 69% and kappa statistic of 0.37. This data-driven approach is applicable at large geopolitical scales (e.g., provincial, national) for wetland and landcover inventories that support long-term, responsible resource management. [ABSTRACT FROM AUTHOR]

While there is no denying that oil sands development in the Athabasca Oil Sands Region (AOSR) has large impacts upon the habitat it disturbs, developers are legally required to return this land to “an equivalent land capability.” While still early in the process of reclamation, land undergoing reclamation offers an opportunity to study factors influencing reclamation success, as well as how reclaimed ecosystems function. As such, an Early Successional Wildlife Dynamics (ESWD) program was created to study how wildlife return to and use reclaimed upland boreal habitat in the AOSR. Wildlife data comprising 182 taxa of mammals, birds, and amphibians, collected between 2011 and 2017 and from five oil sands leases, were compared from multiple habitat types (burned [BRN], cleared [CLR], compensation lakes [COMP], logged [LOG], mature forest [MF], and reclaimed sites [REC]). Overall, similarity of wildlife communities in REC and MF plots varied greatly, even at 33 years since reclamation (31–62% with an average of 52%). However, an average community similarity of 52% so early in the successional process suggests that current reclamation efforts are progressing towards increased similarity compared to mature forest plots. Conversely, our data suggest that REC plots are recovering differently than plots impacted by natural (BRN) or other anthropogenic disturbances (LOG), which is likely due to differences associated with soil reconstruction and development on reclaimed plots. Regardless of the developmental trajectory of reclaimed habitats, progression towards increased wildlife community similarity at REC and MF plots is apparent in our data. While there is no expectation that reclaimed upland habitats will resemble or function identically to naturally occurring boreal forest, the degree of similarity observed in our study suggests that comparable ecological functionality is possible, increasing the probability that oil sands operators will be able to fulfill their regulatory requirements and duty to reclaim regarding wildlife and wildlife habitat. [ABSTRACT FROM AUTHOR]

Agriculture is a primary driver of biodiversity loss worldwide, and several expensive schemes have been designed to make modern farming landscapes more hospitable for wildlife. One such market-based mechanisms is the agri-environment-climate schemes (AES) in the European Union (EU). AES compensate farmers for reducing land-use intensity and maintaining or introducing biodiversity-rich habitats. Despite their high costs, impacts of AES vary by measure, region and taxonomic group considered, and have rarely been studied over large areas covering an entire country. Here we assess the country-wide impact of several AES measures on bird abundance using citizen science data on birds and detailed information on AES take up from across Finland. We report a positive impact of organic animal farming on abundance of all farmland associated birds. This effect was particularly strong for insectivorous species, species that are associated to farmyards and long-distance species. None of the other AES measures considered for study did show any relationship with bird abundance. Overall, these findings highlight the potential positive impact that some compensatory measures, such as organic animal farming, may have on wildlife. Traditional animal husbandry is based on grazing of animals and restriction on external inputs, similarly to what is stipulated under organic production contract. As such, traditional animal husbandry may represent an effective landscape management tool for restoring or maintaining threatened species and ecosystems in rural areas of the EU. Ultimately, the apparent lack of a measurable effect of the other AES considered here supports the current move towards evidence-based regional targeting of compensatory measures, so as to concentrate scarce resources to where they can yield the highest ecological benefits. [ABSTRACT FROM AUTHOR]

Low-frequency mowing has been proposed to be an effective strategy for the restoration and management of boreal fens after abandonment of traditional haymaking. This study investigates how mowing affects long-term vegetation change in both oceanic and continental boreal rich-fen vegetation. This will allow evaluation of the effectiveness of mowing as a management and restoration tool in this ecosystem in the face of climate change. At two nature reserves in Central Norway (Tågdalen, 63° 03’ N, 9° 05 E, oceanic climate and Sølendet, 62° 40’ N, 11° 50’ E, continental climate), we used permanent plot data from the two sites to compare plant species composition from the late 1960s to the early 1980s with that recorded in 2012–2015 in abandoned and mown fens. Changes in species composition and frequency were analysed by multivariate and univariate methods in relation to environmental variables and modelled climate and groundwater data. Mowing resulted in a decline in shrub and Molinia caerulea cover at the continental and oceanic sites respectively, and the total cover of specialist fen species had increased to a significantly greater extent in the mown plots than the unmown at the continental site. However, mowing did not have an effect on the cover of specialist bryophyte species, and some specialist species declined regardless of mowing treatment. Temperature sums had increased at both sites, but precipitation had not changed significantly. Mowing was shown to be the most important determinant of plant community composition at both sites, with local environmental conditions being of secondary importance. In conclusion, the abandonment of traditional management practices results in the loss of characteristic fen species. In order to encourage the restoration of typical rich-fen vegetation, particularly in oceanic areas, additional management measures, such as more intensive mowing, may be required. [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]

Mammalian predators encounter unique hunting challenges during the winter as snow increases the cost of locomotion and influences predator-prey interactions. Winter precipitation may also affect predators’ ability to detect and pursue prey. We investigated the effects of snowfall events on grey wolves (Canis lupus) in a boreal forest ecosystem in northeastern Alberta, Canada. We predicted that wolves would respond to snowfall events by reducing their travel speed and the time they spent travelling. Over the course of two winters, we used remote cameras to identify localized snowfall events and estimate snow depth. We used telemetry data from 17 wolves to calculate travel speed and time spent travelling versus resting. Data were categorized by time of day (night versus day) and time since snowfall events, and analyzed using linear and logistic regression mixed-effects models. We found that wolves were less likely to travel on dates of snowfall events than any date prior to or after an event. Wolves also travelled slower during snowfall events, but only when compared to their travel speed 24 hours before. Effects were most pronounced at night, when movements appeared to be consistent with hunting behavior, and activity levels resumed within 24 hours of a snowfall event. Including snow depth as a variable did not improve model fit. Collectively, our findings suggest that wolves’ response is not driven by increased hunting success or by energetic considerations resulting from increased snow depth. Instead, we propose that wolves reduce their activity levels because precipitation dampens hunting success. Snowfall events may impact wolves’ ability to detect prey and changes in prey behavior could also lead to decreased encounter rates. We encourage scientists to further investigate the effects of short-term weather events on movement rates and predator-prey interactions. [ABSTRACT FROM AUTHOR]

At a multi-millennial scale, various disturbances shape boreal forest stand mosaics and the distribution of species. Despite the importance of such disturbances, there is a lack of studies focused on the long-term dynamics of spruce budworm (Choristoneura fumiferana (Clem.)) (SBW) outbreaks and the interaction of insect outbreaks and fire. Here, we combine macrocharcoal and plant macrofossils with a new proxy—lepidopteran scales—to describe the Holocene ecology around a boreal lake. Lepidopteran scales turned out to be a more robust proxy of insect outbreaks than the traditional proxies such as cephalic head capsules and feces. We identified 87 significant peaks in scale abundance over the last 10 000 years. These results indicate that SBW outbreaks were more frequent over the Holocene than suggested by previous studies. Charcoal accumulation rates match the established fire history in eastern Canada: a more fire-prone early and late Holocene and reduced fire frequency during the mid-Holocene. Although on occasion, both fire and insect outbreaks were coeval, our results show a generally inverse relationship between fire frequency and insect outbreaks over the Holocene. [ABSTRACT FROM AUTHOR]

Forest lands hold great potential for Populus plantations, but in native boreal forests, soils normally have low pH and thus higher levels of aluminum ions (Al3+ and hydroxides). Aluminum (Al) is one of the major factors limiting plant growth on these soils by inhibiting root growth, thus reducing water and nutrient uptake and slowing growth. There is a large variation in Al resistance both among and within species. In this study, growth responses of greenhouse-grown hybrid aspen (P. tremula × tremuloides) and poplar (P. trichocarpa hybrids) were monitored in relation to changes in Al concentrations. In quartz sand, hybrid aspen was more tolerant to exogenous application of Al than P. trichocarpa hybrids. This difference in Al-tolerance was further confirmed by hematoxylin staining of the roots, with hybrid aspen displaying less staining after Al treatment than poplar clones. When planted on forest land with low pH, hybrid aspen increased growth after planting and showed low mortality. This was not the case for poplar clones; plant height decreased after planting and mortality increased. Together, our results suggest that differences in initial growth and survival on forest land among hybrid aspen and the tested poplar clones may be connected to differences in Al tolerance. Our findings that staining with hematoxylin can identify Al-tolerant Populus genotypes may help identify Al-tolerant genotypes suitable for forest land. [ABSTRACT FROM AUTHOR]

Despite the prevalent use of nest-site selection studies to define habitat quality for birds, many studies relying on use-availability analysis have found poor correlations between selected vegetation and reproductive success. Using 3 years of data from northeastern British Columbia (2007–2009), we determined timing of breeding from hatching dates and contrasted the nest-site selection of earlier (n = 22) with later-nesting pairs (n = 36) of yellow-bellied sapsuckers (Sphyrapicus varius), because early breeders were expected to be more reproductively successful. We then compared these choices with those identified from use-availability analysis, and determined whether reproductive performance (fledgling production) was related to selected vegetation. None of the vegetation characteristics selected for nest sites from available vegetation predicted reproductive performance. Earlier-nesting pairs fledged more young on average than later breeders (4.41, SE = 0.18 versus 3.92, SE = 0.16), and chose less decayed aspen trees for nesting, that were surrounded on average by 3 times the number of food trees (paper birch, Betula papyrifera). Potential preference for birch trees was masked in the use-availability analysis, because the selection rate was dominated by the choices of the larger number of later-nesting pairs. Similarly, the majority (69%) of nest cavity entrances faced south, but earlier breeding pairs excavated northward-oriented cavities more frequently than did later breeding pairs, which strongly predicted their higher fledgling production. To our knowledge, our study is the first to compare the choices of early versus later breeders to test the efficacy of use-availability studies in defining habitat quality. We found that use-availability analysis was inadequate for determining vegetation characteristics related to reproductive performance. In contrast, measuring the distinct preferences of earlier breeders resulted in an improved ability to measure habitat quality and explain the spatial distribution of yellow-bellied sapsuckers, a keystone species of the mixedwood boreal forest. [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]

Over the long term, soil carbon (C) storage is partly determined by decomposition rate of carbon that is slow to decompose (i.e., recalcitrant C). According to thermodynamic theory, decomposition rates of recalcitrant C might differ from those of non-recalcitrant C in their sensitivities to global warming. We decomposed leaf litter in a warming experiment in Alaskan boreal forest, and measured mass loss of recalcitrant C (lignin) vs. non-recalcitrant C (cellulose, hemicellulose, and sugars) throughout 16 months. We found that these C fractions responded differently to warming. Specifically, after one year of decomposition, the ratio of recalcitrant C to non-recalcitrant C remaining in litter declined in the warmed plots compared to control. Consistent with this pattern, potential activities of enzymes targeting recalcitrant C increased with warming, relative to those targeting non-recalcitrant C. Even so, mass loss of individual C fractions showed that non-recalcitrant C is preferentially decomposed under control conditions whereas recalcitrant C losses remain unchanged between control and warmed plots. Moreover, overall mass loss was greater under control conditions. Our results imply that direct warming effects, as well as indirect warming effects (e.g. drying), may serve to maintain decomposition rates of recalcitrant C compared to non-recalcitrant C despite negative effects on overall decomposition. [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]

Climate change threatens natural landscapes through shifting distribution and abundance of species and attendant change in the structure and function of ecosystems. However, it remains unclear how climate-mediated variation in species’ environmental niche space may lead to large-scale fragmentation of species distributions, altered meta-population dynamics and gene flow, and disrupted ecosystem integrity. Such change may be especially relevant when species distributions are restricted either spatially or to a narrow environmental niche, or when environments are rapidly changing. Here, we use range-wide environmental niche models to posit that climate-mediated range fragmentation aggravates the direct effects of climate change on species in the boreal forest of North America. We show that climate change will directly alter environmental niche suitability for boreal-obligate species of trees, birds and mammals (n = 12), with most species ranges becoming smaller and shifting northward through time. Importantly, species distributions will become increasingly fragmented, as characterized by smaller mean size and greater isolation of environmentally-suitable landscape patches. This loss is especially pronounced along the Ontario-Québec border, where the boreal forest is narrowest and roughly 78% of suitable niche space could disappear by 2080. Despite the diversity of taxa surveyed, patterns of range fragmentation are remarkably consistent, with our models predicting that spruce grouse (Dendragapus canadensis), boreal chickadee (Poecile hudsonicus), moose (Alces americanus) and caribou (Rangifer tarandus) could have entirely disjunct east-west population segments in North America. These findings reveal potentially dire consequences of climate change on population continuity and species diversity in the boreal forest, highlighting the need to better understand: 1) extent and primary drivers of anticipated climate-mediated range loss and fragmentation; 2) diversity of species to be affected by such change; 3) potential for rapid adaptation in the most strongly-affected areas; and 4) potential for invasion by replacement species. [ABSTRACT FROM AUTHOR]

Ectomycorrhizal fungi (EMF) represent one of the major guilds of symbiotic fungi associated with roots of forest trees, where they function to improve plant nutrition and fitness in exchange for plant carbon. Many groups of EMF exhibit preference or specificity for different plant host genera; a good example is the genus Suillus, which grows in association with the conifer family Pinaceae. We investigated genetics of EMF host-specificity by cross-inoculating basidiospores of five species of Suillus onto ten species of Pinus, and screened them for their ability to form ectomycorrhizae. Several Suillus spp. including S. granulatus, S. spraguei, and S. americanus readily formed ectomycorrhizae (compatible reaction) with white pine hosts (subgenus Strobus), but were incompatible with other pine hosts (subgenus Pinus). Metatranscriptomic analysis of inoculated roots reveals that plant and fungus each express unique gene sets during incompatible vs. compatible pairings. The Suillus-Pinus metatranscriptomes utilize highly conserved gene regulatory pathways, including fungal G-protein signaling, secretory pathways, leucine-rich repeat and pathogen resistance proteins that are similar to those associated with host-pathogen interactions in other plant-fungal systems. Metatranscriptomic study of the combined Suillus-Pinus transcriptome has provided new insight into mechanisms of adaptation and coevolution of forest trees with their microbial community, and revealed that genetic regulation of ectomycorrhizal symbiosis utilizes universal gene regulatory pathways used by other types of fungal-plant interactions including pathogenic fungal-host interactions. [ABSTRACT FROM AUTHOR]

There is evidence that anthropogenic nitrogen (N) deposition enhances carbon (C) sequestration in boreal soils. However, key underlying mechanisms explaining this increase have not been resolved. Two potentially important mechanisms are that aboveground litter production increases, or that litter quality changes in response to N enrichment. As such, our aim was to quantify whether simulated chronic N deposition caused changes in aboveground litter production or quality in a boreal forest. We conducted a long-term (17 years) stand-scale (0.1 ha) forest experiment, consisting of three N addition levels (0, 12.5, and 50 kg N ha-1 yr-1) in northern Sweden, where background N deposition rates are very low. We measured the annual quantity of litter produced for 8 different litter categories, as well as their concentrations of C, N, phosphorus (P), lignin, cellulose and hemi-cellulose. Our results indicate that mosses were the only major litter component showing significant quantitative and qualitative alterations in response to the N additions, indicative of their ability to intercept a substantial portion of the N added. These effects were, however, offset by the other litter fractions where we found no changes in the total litter fluxes, or individual chemical constituents when all litter categories were summed. This study indicates that the current annual litter fluxes cannot explain the increase in soil C that has occurred in our study system in response to simulated chronic N application. These results suggest that other mechanisms are likely to explain the increased soil C accumulation rate we have observed, such as changes in soil microbial activity, or potentially transient changes in aboveground litter inputs that were no longer present at the time of our study. [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]

Tintinnids are planktonic ciliates that play an important role in marine ecosystem. According to their distribution in the world oceans, tintinnid genera were divided into several biogeographical types such as boreal, warm water, austral and neritic. Therefore, the oceanic tintinnid assemblage could be correspondingly divided into boreal assemblage, warm water assemblage and austral assemblage. The purpose of this study was to investigate the characteristics of boreal tintinnid assemblage in the Northwest Pacific and the Arctic, and to identify the connection between boreal tintinnid assemblage and neighboring assemblages. Surface water samples were collected along a transect from the East China Sea to the Chukchi Sea in summer 2014. According to the presence of boreal genera and warm water genera, three tintinnid assemblages (the East China Sea neritic assemblage, the Japan Sea warm water assemblage, and the boreal assemblage) were identified along the transect. The boreal assemblage extended from the Chukchi Sea to the waters north of the Sōya Strait. Densities peaks occurred at stations in the two branches of the Alaska Current and decreased both northward and southward. The densities were <10 ind./dm3 at most stations in Arctic region. The dominant genera (Acanthostomella, Codonellopsis, Parafavella, and Ptychocylis) accounted for 79.07±29.67% (n = 49) of the abundance in the boreal assemblage. The densities of the dominant genera covaried with strongly significant positive correlations. Tintinnids with lorica oral diameter of 22–26 μm and 38–42 μm were dominant and contributed 67.35% and 15.13%, respectively, to the total abundance in the boreal assemblage. The distribution and densities of tintinnids in the study area suggest that the Sōya Strait might be a geographical barrier for tintinnids expansion. [ABSTRACT FROM AUTHOR]

Boreal forests contain 30% of the global forest carbon with the majority residing in soils. While challenging to quantify, soil carbon changes comprise a significant, and potentially increasing, part of the terrestrial carbon cycle. Thus, their estimation is important when designing forest-based climate change mitigation strategies and soil carbon change estimates are required for the reporting of greenhouse gas emissions. Organic matter decomposition varies with climate in complex nonlinear ways, rendering data aggregation nontrivial. Here, we explored the effects of temporal and spatial aggregation of climatic and litter input data on regional estimates of soil organic carbon stocks and changes for upland forests. We used the soil carbon and decomposition model Yasso07 with input from the Norwegian National Forest Inventory (11275 plots, 1960–2012). Estimates were produced at three spatial and three temporal scales. Results showed that a national level average soil carbon stock estimate varied by 10% depending on the applied spatial and temporal scale of aggregation. Higher stocks were found when applying plot-level input compared to country-level input and when long-term climate was used as compared to annual or 5-year mean values. A national level estimate for soil carbon change was similar across spatial scales, but was considerably (60–70%) lower when applying annual or 5-year mean climate compared to long-term mean climate reflecting the recent climatic changes in Norway. This was particularly evident for the forest-dominated districts in the southeastern and central parts of Norway and in the far north. We concluded that the sensitivity of model estimates to spatial aggregation will depend on the region of interest. Further, that using long-term climate averages during periods with strong climatic trends results in large differences in soil carbon estimates. The largest differences in this study were observed in central and northern regions with strongly increasing temperatures. [ABSTRACT FROM AUTHOR]

Nitrogen (N2) fixation is a major source of available N in ecosystems that receive low amounts of atmospheric N deposition. In boreal forest and subarctic tundra, the feather moss Hylocomium splendens is colonized by N2 fixing cyanobacteria that could contribute fundamentally to increase the N pool in these ecosystems. However, N2 fixation in mosses is inhibited by N input. Although this has been shown previously, the ability of N2 fixation to grow less sensitive towards repeated, increased N inputs remains unknown. Here, we tested if N2 fixation in H. splendens can recover from increased N input depending on the N load (0, 5, 20, 80, 320 kg N ha-1 yr-1) after a period of N deprivation, and if sensitivity towards increased N input can decrease after repeated N additions. Nitrogen fixation in the moss was inhibited by the highest N addition, but was promoted by adding 5 kg N ha-1 yr-1, and increased in all treatments during a short period of N deprivation. The sensitivity of N2 fixation towards repeated N additions seem to decrease in the 20 and 80 kg N additions, but increased in the highest N addition (320 kg N ha-1 yr-1). Recovery of N in leachate samples increased with increasing N loads, suggesting low retention capabilities of mosses if N input is above 5 kg N ha-1 yr-1. Our results demonstrate that the sensitivity towards repeated N additions is likely to decrease if N input does not exceed a certain threshold. [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]

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]

Half of the world's forest is in boreal and sub-boreal ecozones, containing large carbon stores and fluxes. Carbon lost from headwater streams in these forests is underestimated. We apply a simple stable carbon isotope idea for quantifying the CO2 loss from these small streams; it is based only on in-stream samples and integrates over a significant distance upstream. We demonstrate that conventional methods of determining CO2 loss from streams necessarily underestimate the CO2 loss with results from two catchments. Dissolved carbon export from headwater catchments is similar to CO2 loss from stream surfaces. Most of the CO2 originating in high CO2 groundwaters has been lost before typical in-stream sampling occurs. In the Harp Lake catchment in Canada, headwater streams account for 10% of catchment net CO2 uptake. In the Krycklan catchment in Sweden, this more than doubles the CO2 loss from the catchment. Thus, even when corrected for aquatic CO2 loss measured by conventional methods, boreal and sub-boreal forest carbon budgets currently overestimate carbon sequestration on the landscape. [ABSTRACT FROM AUTHOR]

Boreal forests are characterized by spatially heterogeneous soils with low N availability. The decomposition of coniferous litter in these systems is primarily performed by basidiomycete fungi, which often form large mycelia with a well-developed capacity to reallocate resources spatially- an advantageous trait in heterogeneous environments. In axenic microcosm systems we tested whether fungi increase their biomass production by reallocating N between Pinus sylvestris (Scots pine) needles at different stages of decomposition. We estimated fungal biomass production by analysing the accumulation of the fungal cell wall compound chitin. Monospecific systems were compared with systems with interspecific interactions. We found that the fungi reallocated assimilated N and mycelial growth away from well-degraded litter towards fresh litter components. This redistribution was accompanied by reduced decomposition of older litter. Interconnection of substrates increased over-all fungal C use efficiency (i.e. the allocation of assimilated C to biomass rather than respiration), presumably by enabling fungal translocation of growth-limiting N to litter with higher C quality. Fungal connection between different substrates also restricted N-mineralization and production of dissolved organic N, suggesting that litter saprotrophs in boreal forest ecosystems primarily act to redistribute rather than release N. This spatial integration of different resource qualities was hindered by interspecific interactions, in which litters of contrasting quality were colonised by two different basidiomycete species. The experiments provide a detailed picture of how resource reallocation in two decomposer fungi leads to a more efficient utilisation of spatially separated resources under N-limitation. From an ecosystem point of view, such economic fungal behaviour could potentially contribute to organic matter accumulation in the litter layers of boreal forests. [ABSTRACT FROM AUTHOR]

The functional trait-based approach is increasingly used to predict responses of ecological communities to disturbances, but most studies target a single taxonomic group. Here, we assessed the resilience of a forest ecosystem to an overabundant herbivore population by assessing changes in 19 functional traits for plant, 13 traits for ground beetle and 16 traits for songbird communities after six years of controlled browsing on Anticosti Island (Quebec, Canada). Our results indicated that plants were more responsive to 6 years of reduced browsing pressure than ground beetles and songbirds. However, co-inertia analysis revealed that ground beetle communities responded in a similar way than plant communities with stronger relationships between plant and ground beetle traits at reduced deer density, a pattern not detected between plant and songbird. High deer density favored plants species that reproduce vegetatively and with abiotic pollination and seed dispersal, traits implying little interaction with animal. On the other hand, traits found at reduced deer density mostly involved trophic interaction. For example, plants in this treatment had fleshy fruits and large seeds dispersed by birds or other animals whereas ground beetle species were carnivorous. Overall, our results suggest that plant communities recovered some functional components to overabundant herbivore populations, since most traits associated with undisturbed forests were reestablished after six years of deer reduction. The re-establishment of functional plant communities with traits involving trophic interaction induces changes in the ground-beetle trait community, but forest structure remains likely insufficiently heterogeneous to shift the songbird trait community within six years. [ABSTRACT FROM AUTHOR]

Laboratory studies show that introduction of fresh and easily decomposable organic carbon (OC) into soil-water systems can stimulate the decomposition of soil OC (SOC) via priming effects in temperate forests, shrublands, grasslands, and agro-ecosystems. However, priming effects are still not well understood in the field setting for temperate ecosystems and virtually nothing is known about priming effects (e.g., existence, frequency, and magnitude) in boreal ecosystems. In this study, a coupled dissolved OC (DOC) transport and microbial biomass dynamics model was developed to simultaneously simulate co-occurring hydrological, physical, and biological processes and their interactions in soil pore-water systems. The developed model was then used to examine the importance of priming effects in two black spruce forest soils, with and without underlying permafrost. Our simulations showed that priming effects were strongly controlled by the frequency and intensity of DOC input, with greater priming effects associated with greater DOC inputs. Sensitivity analyses indicated that priming effects were most sensitive to variations in the quality of SOC, followed by variations in microbial biomass dynamics (i.e., microbial death and maintenance respiration), highlighting the urgent need to better discern these key parameters in future experiments and to consider these dynamics in existing ecosystem models. Water movement carries DOC to deep soil layers that have high SOC stocks in boreal soils. Thus, greater priming effects were predicted for the site with favorable water movement than for the site with limited water flow, suggesting that priming effects might be accelerated for sites where permafrost degradation leads to the formation of dry thermokarst. [ABSTRACT FROM AUTHOR]

Seed mass is an adaptive trait affecting species distribution, population dynamics and community structure. In widely distributed species, variation in seed mass may reflect both genetic adaptation to local environments and adaptive phenotypic plasticity. Acknowledging the difficulty in separating these two aspects, we examined the causal relationships determining seed mass variation to better understand adaptability and/or plasticity of selected tree species to spatial/climatic variation. A total of 504, 481 and 454 seed collections of black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb) across the Canadian Boreal Forest, respectively, were selected. Correlation analyses were used to determine how seed mass vary with latitude, longitude, and altitude. Structural Equation Modeling was used to examine how geographic and climatic variables influence seed mass. Climatic factors explained a large portion of the variation in seed mass (34, 14 and 29%, for black spruce, white spruce and jack pine, respectively), indicating species-specific adaptation to long term climate conditions. Higher annual mean temperature and winter precipitation caused greater seed mass in black spruce, but annual precipitation was the controlling factor for white spruce. The combination of factors such as growing season temperature and evapotranspiration, temperature seasonality and annual precipitation together determined seed mass of jack pine. Overall, sites with higher winter temperatures were correlated with larger seeds. Thus, long-term climatic conditions, at least in part, determined spatial variation in seed mass. Black spruce and Jack pine, species with relatively more specific habitat requirements and less plasticity, had more variation in seed mass explained by climate than did the more plastic species white spruce. As traits such as seed mass are related to seedling growth and survival, they potentially influence forest species composition in a changing climate and should be included in future modeling of vegetation shifts. [ABSTRACT FROM AUTHOR]

Disturbance can both initiate and shape patterns of secondary succession by affecting processes of community assembly. Thus, understanding assembly rules is a key element of predicting ecological responses to changing disturbance regimes. We measured the composition and trait characteristics of plant communities early after widespread wildfires in Alaska to assess how variations in disturbance characteristics influenced the relative success of different plant regeneration strategies. We compared patterns of post-fire community composition and abundance of regeneration traits across a range of fire severities within a single pre-fire forest type– black spruce forests of Interior Alaska. Patterns of community composition, as captured by multivariate ordination with nonmetric multidimensional scaling, were primarily related to gradients in fire severity (biomass combustion and residual vegetation) and secondarily to gradients in soil pH and regional climate. This pattern was apparent in both the full dataset (n = 87 sites) and for a reduced subset of sites (n = 49) that minimized the correlation between site moisture and fire severity. Changes in community composition across the fire-severity gradient in Alaska were strongly correlated to variations in plant regeneration strategy and rooting depth. The tight coupling of fire severity with regeneration traits and vegetation composition after fire supports the hypothesis that disturbance characteristics influence patterns of community assembly by affecting the relative success of different regeneration strategies. This study further demonstrated that variations in disturbance characteristics can dominate over environmental constraints in determining early patterns of community assembly. By affecting the success of regeneration traits, changes in fire regime directly shape the outcomes of community assembly, and thus may override the effects of slower environmental change on boreal forest composition. [ABSTRACT FROM AUTHOR]

The region of Churchill, Manitoba, contains a wide variety of habitats representative of both the boreal forest and arctic tundra and has been used as a model site for biodiversity studies for nearly seven decades within Canada. Much previous work has been done in Churchill to study the Daphnia pulex species complex in particular, but no study has completed a wide-scale survey on the crustacean species that inhabit Churchill's aquatic ecosystems using molecular markers. We have employed DNA barcoding to study the diversity of the Branchiopoda (Crustacea) in a wide variety of freshwater habitats and to determine the likely origins of the Churchill fauna following the last glaciation. The standard animal barcode marker (COI) was sequenced for 327 specimens, and a 3% divergence threshold was used to delineate potential species. We found 42 provisional and valid branchiopod species from this survey alone, including several cryptic lineages, in comparison with the 25 previously recorded from previous ecological works. Using published sequence data, we explored the phylogeographic affinities of Churchill's branchiopods, finding that the Churchill fauna apparently originated from all directions from multiple glacial refugia (including southern, Beringian, and high arctic regions). Overall, these microcrustaceans are very diverse in Churchill and contain multiple species complexes. The present study introduces among the first sequences for some understudied genera, for which further work is required to delineate species boundaries and develop a more complete understanding of branchiopod diversity over a larger spatial scale. [ABSTRACT FROM AUTHOR]