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Intensive forest management has drastically reduced the amount and diversity of dead wood resulting in population decline of saproxylic species. Forestry practices can also disrupt spatiotemporal continuity of dead wood habitats. We studied the effects of stand- and landscape-level densities of host trees on the incidence (proportion of occupied trees) of saproxylic beetles inhabiting recently dead standing Scots pines, a common host-tree type both in natural and managed boreal forests. We compared the occurrence patterns of eight rare specialist and eight common generalist species. Saproxylic beetles were collected from a total of 315 trees in 67 forest stands, including both managed and natural forests, located in three regions which form a gradient in forest-use intensity. Species richness of the entire community at tree and stand level did not respond to the stand- and landscape-level host-tree density. The incidence of six common generalist species did not depend on the stand-level host-tree density, whereas the incidences of four rare specialist species increased with increasing host-tree density. Five out of eight rare specialist species were either significantly less common or absent from the region with the lowest landscape-level density of host trees. We conclude that rare specialist species living in recently dead pines are susceptible to changes in spatiotemporal dynamics of their host trees. To conserve rare early-successional species, it is necessary to ensure continuous input of dying trees by prolonging rotation times in mature forests, regenerating stands using seed-tree cutting and leaving as many permanent retention trees as possible. [ABSTRACT FROM AUTHOR]

We investigated how compositional differences in riparian leaf litter derived from burned and undisturbed forests influenced leaf breakdown and macroinvertebrate communities using experimental mixed‐species leaf packs in boreal headwater streams. Leaf pack mixtures simulating leaf litter from dominant riparian woody‐stem species in burned and undisturbed riparian zones were incubated in two references and two fire‐disturbed streams for 5 weeks prior to measuring temperature‐corrected breakdown rates and macroinvertebrate community composition, richness, and functional metrics associated with decomposers such as shredder abundance and % shredders.Leaf litter breakdown rates were higher and had greater variability in streams bordered by reference riparian forests than in streams where riparian forests had been burned during a wildfire. Streams bordered by fire disturbance showed significant effects of litter mixture on decomposition rates, observed as significantly higher decomposition rates of a fire‐simulated leaf mixture compared to all other mixtures.Variation among sites was higher than variation among litter mixtures, especially for macroinvertebrate community composition. In general, fire‐simulated leaf mixtures had greater shredder abundances and proportions, but lower overall macroinvertebrate abundance; however, the shredder abundance trend was not consistent across all leaf mixtures at each stream.These results show that disturbance‐driven riparian forest condition and resulting composition of leaf subsidies to streams can influence aquatic invertebrate community composition and their function as decomposers. Therefore, if one of the primary goals of modern forest management is to emulate natural disturbance patterns, boreal forest managers should adapt silvicultural practices to promote leaf litter input that would arise post‐fire, thereby supporting stream invertebrate communities and their function. [ABSTRACT FROM AUTHOR]

Aim: Climate change is expected to influence boreal bird communities significantly, notably through changes in forest habitat (composition and age structure), in the coming decades. How these changes will accumulate and interact with anthropogenic disturbances remains an open question for most species. Location: Northeastern Alberta, Canada. Methods: We used the LANDIS‐II forest landscape model to project changes in forest landscapes, and associated bird populations (72 passerine species), according to three climatic scenarios (baseline, RCP 4.5 and RCP 8.5) and three forest harvesting scenarios of differing intensity. Results: Both forest harvesting and climate‐related drivers were projected to have large impacts on bird communities in this region. As a result of climate‐induced increases in fire activity as well as decreased conifer productivity, our simulations projected that an important proportion of Alberta's boreal forests would transition to treeless habitat (i.e. grass‐ or shrub‐dominated vegetation) while many conifer‐dominated stands would likely be replaced by broadleaf tree cover. Consequently, the abundance of bird species associated with open and deciduous habitats were projected to increase. With a strong anthropogenic climate‐forcing scenario (RCP 8.5), sharp declines in abundance of coniferous trees were also projected, particularly in mature and old forest stands, triggering major declines for bird species associated with coniferous and mixedwood forest types. Main conclusions: As the most comprehensive simulation of climate change and harvesting impacts on avian habitats in the North American boreal region to date, our study stresses the importance of considering key habitat characteristics like forest age structure and composition through forest landscape modelling and identifies 18 bird species particularly sensitive to climate change. Our simulations suggest that a change in forest management practices could play an important role in the conservation of boreal bird species vulnerable to climate change. The intensive forest harvesting simulated accelerated declines in bird abundance compared to a "no harvesting" scenario. [ABSTRACT FROM AUTHOR]

Forest ecosystems are already responding to changing environmental conditions that are driven by increased atmospheric CO2 concentrations. These developments affect how societies can utilise and benefit from the woodland areas in the future, be it for example climate change mitigation as carbon sinks, lumber for wood industry, or preserved for nature tourism and recreational activities. We assess the effect and the relative magnitude of different uncertainty sources in ecosystem model simulations from the year 1980 to 2100 for two Finnish boreal forest sites. The models used in this study are the land ecosystem model JSBACH and the forest growth model PREBAS. The considered uncertainty sources for both models are model parameters and four prescribed climates with two RCP (representative concentration pathway) scenarios. Usually, model parameter uncertainty is not included in these types of uncertainty studies. PREBAS simulations also include two forest management scenarios. We assess the effect of these sources of variation at four different points in time on several ecosystem indicators, e.g. gross primary production (GPP), ecosystem respiration, soil moisture, recurrence of drought, length of the vegetation active period (VAP), length of the snow melting period and the stand volume. The uncertainty induced by the climate models remains roughly the same throughout the simulations and is overtaken by the RCP scenario impact halfway through the experiment. The management actions are the most dominant uncertainty factors for Hyytiälä and as important as RCP scenarios at the end of the simulations, but they contribute only half as much for Sodankylä. The parameter uncertainty is the least influential of the examined uncertainty sources, but it is also the most elusive to estimate due to non-linear and adverse effects on the simulated ecosystem indicators. Our analysis underlines the importance of carefully considering the implementation of forest use when simulating future ecosystem conditions, as human impact is evident and even increasing in boreal forested regions. [ABSTRACT FROM AUTHOR]

Bats utilize forests as roosting sites and feeding areas. However, it has not been documented how bats utilize these habitats in the boreal zone with methods afforded by recent technological advances. Forest structure and management practices can create a variety of three‐dimensional habitats for organisms capable of flight, such as bats. Here, we study the presence of boreal bats in a forest forming a mosaic of different age classes, dominant tree species, canopy cover, soil fertility, and other environmental variables, throughout their active season in the summer using passive ultrasound detectors. Our results indicate a preference for mature forest by Eptesicus nilssonii and a pooled set of Myotis bats. Both groups of bats also showed temporal changes in their habitat use regarding forest age. In June and July, both groups occurred more often in mature than young forests, but from August onwards, the difference in occurrence became less evident in Myotis and disappeared completely in E. nilssonii. In addition, E. nilssonii was more often present in forests with low canopy cover, and its occurrence shifted from coniferous forests to deciduous forests during the season. The results reflect the within‐season dynamics of bat communities and their ability to utilize different types of forest as environmental conditions change. Yet, the results most importantly emphasize the importance of mature forests to bat diversity and the need to conserve such environments in the boreal zone. [ABSTRACT FROM AUTHOR]

The ability to expand the use of predictive Airborne Laser Scanning (ALS)-derived Forest Resource Inventory (FRI) models to broader regional scales is crucial for supporting large scale sustainable forest management. This research examined the transferability of ALS-based FRI attributes between two forest estates located in the eastern and western boreal forest regions of Canada. The sites were structurally diverse due to a strong east-to-west gradient in climate conditions and disturbance regimes. We first examined the ALS–FRI attribute relationships between the sites. Second, we applied Ordinary Least Squares regressions and Random Forest, to predict four FRI attributes. Third, we tested if the inclusion of calibration data from the target location improved the performance of the transferred models. As the sites were located on opposing sides of a bioclimatic gradient, inclusion of target calibration data improved transferred model performance. However, attribute prediction accuracy varied with modeling approach, attribute, and site. The best transferability models fell within a ± 5% relative RMSE of the local predictive models but increased up to 10% in relative bias. These results have implications for forest researchers and managers on both the number, and location, of FRI plots when considering undertaking forest inventories over large disparate areas. [ABSTRACT FROM AUTHOR]

Comparisons between field data and available maps show that 64% of wet areas in the boreal landscape are missing on current maps. Primarily forested wetlands and wet soils near streams and lakes are missing, making them difficult to manage. One solution is to model missing wet areas from high-resolution digital elevation models, using indices such as topographical wetness index and depth to water. However, when working across large areas with gradients in topography, soils and climate, it is not possible to find one method or one threshold that works everywhere. By using soil moisture data from the National Forest Inventory of Sweden as a training dataset, we show that it is possible to combine information from several indices and thresholds, using machine learners, thereby improving the mapping of wet soils (kappa = 0.65). The new maps can be used to better plan roads and generate riparian buffer zones near surface waters. [ABSTRACT FROM AUTHOR]

In sustainable forestry, forests should produce multiple ecosystem services for society, such as timber, carbon sequestration and biodiversity. Therefore, in the evaluation of forest management strategies, we have to consider the impacts of management on several ecosystem services. In this study, we compared the effects of five different forest management strategies on timber drain, carbon stocks, carbon balance and biodiversity indicators, while maximizing economic revenues from timber production. The assessment was carried out in a boreal landscape of 43 000 ha over a 100-year calculation period. The five management strategies were rotation forest management (with thinning from below or above), continuous cover forestry, a combination of rotation forest management and continuous cover forestry and any-aged forestry. Rotation forest management with thinning from below was less profitable than the other strategies, which were close to each other in economic profitability. Rotation forest management with thinning from below was also the poorest in terms of carbon stocks, carbon balance and biodiversity indicators. Any-aged and continuous cover forestry were the best in terms of carbon sequestration and biodiversity indicators. In general, management strategies that used thinning from above and that were not restricted to rotation forest management as the only option provided more ecosystem services and were also economically profitable. Such management strategies may help to satisfy the increasing demand for diverse uses of forests. [ABSTRACT FROM AUTHOR]

Research Highlights: We show the difference in the long-term effects on economic and ecological forest values between four forest management scenarios of a large representative forest landscape. The scenarios were largely formulated by stakeholders representing the main views on how to manage north-European forests. Background and Objectives: Views on how to balance forest management between wood production and biodiversity differ widely between different stakeholder groups. We aim to show the long-term consequences of stakeholder-defined management scenarios, in terms of ecological and economic forest values. Materials and Methods: We simulated management scenarios for a forest landscape in Sweden, based on the management objectives and strategies of key stakeholders. We specifically investigated the difference in economic forest values coupled to wood supply and ecological indicators coupled to structural biodiversity between the scenarios over a 100-year period. The indicators were net present value, harvest, growing stock and increment, along with deadwood volume, the density of large trees, area of old forests and mature broad leaf-rich forests. Results: We show that the scenarios have widely different outcomes in terms of the studied indicators, and that differences in indicator outcome were largely due to different distributions in management regimes, i.e., the proportion of forest left unmanaged or under even-aged management or continuous cover forest, as well as specific retention practices. Retention and continuous cover forestry mitigate the negative effects that clear-cut forestry has upon biodiversity. Conclusions: We found that an increase in the forest area under the continuous cover forestry regime could be a cost-efficient way to increase structural diversity in managed boreal forests. On the other hand, no single management regime performed best with respect to all indicators, which means that a mixture of several management regimes is needed to balance conflicting objectives. We also show that the trade-off between economic and ecological indicators was not directly proportional, meaning that an increase in structural biodiversity may be obtained at a proportionally low cost with appropriate management planning. [ABSTRACT FROM AUTHOR]

Surface albedo is one of the most important processes governing climate forcing in the boreal forest and is directly affected by management activities such as harvesting and natural disturbances such as forest fires. Empirical data on the effects of these disturbances on boreal forest albedo are sparse. We conducted ground-based measurements of surface albedo from a series of instrument towers over 4 years in a replicated chronosequence of mixedwood boreal forest sites differing in stand age (to 19 years since disturbance) in both post-harvest and post-fire stands. We investigated the effects of stand age, canopy height, tree species composition, and ground vegetation cover on surface albedo through stand development. Our results indicate that winter and spring albedo values were 63 % and 24 % higher, respectively, in post-harvest stands than in post-fire stands. Summer and fall albedo values were similar between disturbance types, with summer albedo showing a transient peak at ∼10 years stand age. The proportion of deciduous broadleaf species showed a strong positive relationship with seasonal averages of albedo in both post-harvest and post-fire stands. Given that stand composition in mixedwood boreal forests generally shows a gradual replacement of deciduous trees by conifers, our results suggest that successional changes in species composition are likely a key driver of age-related patterns in albedo. Our findings also suggest the efficacy of increasing the proportion of deciduous broadleaf species as a silvicultural option for climate-friendly management of the boreal forest. [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]

• Increasing harvesting intensity rapidly increases the total species richness of beetles. • In the short term, most beetle species in mature managed forests seem to tolerate cutting disturbances. • Irrespective of treatment, species richness of saproxylic beetles increased with the volume of dead wood. • Species richness of non-saproxylic beetles increased with gap size. • Community recovery may be faster in the less intensive treatments. Even-aged management based on clear cutting has simplified the structure of boreal forests, which has adversely affected ecosystem services, including biodiversity. A potential way of combining economic, ecological and social sustainability in forest management is emulation of natural disturbance dynamics. However, ecological effects of alternative cutting methods have been little studied in northern Europe. We studied the responses of beetles (Coleoptera) to four cutting treatments – selection, gap, patch and clear cutting – compared to uncut control stands. We collected beetles one year before, and one and three years after cutting using flight-intercept window traps to assess the effects of treatment, proportion of removed trees, size of harvested gaps, and the volume of dead wood on the species richness and composition of beetles. The total number of species increased sharply in the first year after cutting in all the four treatments. Three years after cutting, the difference in species richness between controls and treatments had decreased. Both species richness and community structure formed a continuum according to treatment intensity. Selection cuts were most similar to the controls, while clear cuts differed from all the other treatments. Irrespective of the treatment, species richness of saproxylic beetles increased with the volume of dead wood, while the number of non-saproxylic species increased with gap size. Contrary to expectation, the proportion of species that were found both before and after cutting did not differ significantly between the treatments. According to an indicator species analysis, two species were associated with controls, 11 with a combination of controls and selection, gap or patch cuts, 17 with patch and clear cuts, and 38 with clear cuts. Our findings suggest that increasing harvesting intensity rapidly increases the total species richness of beetles in the studied spruce forests, but that community recovery may be faster in the less intensive treatments. In the short term, most beetle species inhabiting mature managed forests seem to tolerate cutting disturbances creating open conditions. Clear cuts hosted a large number of species, including species of conservation concern, which were missing from other cutting treatments. Even a moderate increase in the level of dead wood in managed forests is likely to enhance saproxylic diversity. If the aim of management is to preserve mature-forest beetle communities, selection or gap cutting should be used instead of clear cutting. [ABSTRACT FROM AUTHOR]

Vegetation is known to have strong influence on evapotranspiration (ET), a major component of terrestrial water balance. Yet hydrological models often describe ET by methods unable to include the variability of vegetation characteristics in their predictions. To take advantage of the increasing availability of high-resolution open GIS data on land use, vegetation and soil characteristics in the boreal zone, a modular, spatially distributed model for predicting ET and other hydrological processes from grid cell to catchment level is presented and validated. An improved approach to upscale stomatal conductance to canopy scale using information on plant type (conifer/deciduous) and stand leaf-area index (LAI) is proposed by coupling a common leaf-scale stomatal conductance model with a simple canopy radiation transfer scheme. Further, a generic parametrization for vegetation-related hydrological processes for Nordic boreal forests is derived based on literature and data from a boreal FluxNet site. With the generic parametrization, the model was shown to reproduce daily ET measured using an eddy-covariance technique well at 10 conifer-dominated Nordic forests whose LAI ranged from 0.2 to 6.8 m 2 m -2. Topography, soil and vegetation properties at 21 small boreal headwater catchments in Finland were derived from open GIS data at 16 m × 16 m grid size to upscale water balance from stand to catchment level. The predictions of annual ET and specific discharge were successful in all catchments, located from 60 to 68 ∘ N, and daily discharge was also reasonably well predicted by calibrating only one parameter against discharge measurements. The role of vegetation heterogeneity in soil moisture and partitioning of ET was demonstrated. The proposed framework can support, for example, forest trafficability forecasting and predicting impacts of climate change and forest management on stand and catchment water balance. With appropriate parametrization it can be generalized outside the boreal coniferous forests. [ABSTRACT FROM AUTHOR]

Abstract Uncertainties in estimation of albedo-related radiative forcing cause ambiguity in evaluation of net climate effects of forests and forest management. Numerous studies have reported local relations between forest structure and albedo in the boreal zone. However, more research is needed to establish these relations for geographically extensive areas, and to examine seasonal courses of albedo to understand the effects of forest structure on mean annual shortwave energy balance. Remote sensing is a viable option for accomplishing these goals, but there are many challenges related to e.g. long periods of cloud cover and low solar elevations in high latitudes. We used the new MODIS Collection 6 (MCD43A3) daily albedo product, and analyzed MODIS albedo dependence on airborne LiDAR-based forest structure in 22 study sites in Estonia, Finland, Sweden, and Russia (57°–69° N, 12°–57° E). Wall-to-wall LiDAR data allowed us to take into account the effective spatial resolution of MODIS, which notably improved correlations between albedo and forest structure. Use of the best quality backup algorithm (magnitude inversion) together with main algorithm results in the MODIS albedo product did not reduce the correlations compared to using main algorithm only. We quantified the effects of landscape-level forest structure (forest height, canopy cover, fraction of young forest) and fraction of broadleaved deciduous forest on mean annual albedo. We showed that because the forest structure-albedo relations are the strongest in snow-covered periods, and because the snow-covered period is longest in the north, the effect of forest structure on mean annual albedo increases towards the north. On the other hand, the effect of broadleaved fraction did not show such latitudinal trend. Our results indicate that even within a single climatic zone the optimal forest management solution to mitigate climate change depends on geographic location. Highlights • Linking daily MODIS albedo and forest structure in a large geographic area • Airborne LiDAR used for deriving forest structure wall-to-wall for each MODIS pixel • Accounting for MODIS effective resolution strengthened albedo-structure relations • Albedo-forest structure relations stronger in snow covered than snow-free seasons • Effects of snow and forest structure on mean annual albedo increased towards north [ABSTRACT FROM AUTHOR]

Highlights • Common species and mid-successional forests can tolerate moderate timber harvesting. • There is time delay in responses of understorey vegetation communities. • Forest logging has legacy effects on understorey communities and accumulation of coarse woody debris. Abstract We followed how forest thinning, repeated twice during a period of 93 years, altered understorey plant community composition, affected the succession of forest understorey vegetation and the accumulation of logs in the long-term. The study was carried out in northern Finland by resampling 20 permanent experimental plots, established after a wildfire in 1920. Understorey vegetation was inventoried in 1961, 1986 and 2013 with forest thinning treatments done in 1953 and 1987, using four and three different harvesting intensities, respectively. We found succession to override the effects of forest logging until the latest study period (2013). We observed negligible long-term effects of logging on understorey communities during the two mid-successional stages (1961, 1986), when the forest was 41 and 66 years old respectively. The impacts of logging on understorey vegetation were strongest in the latest successional stage (2013), the forest being at the age of 93 years. In the latest successional stage (2013) logged plots had less coarse woody debris than unlogged plots. Forest management thus influenced the key feature for forest biodiversity and potential habitats for endangered species. These findings are of major interest since the studies of long-term impacts of less intensive forest management practices are scarce. Our results suggest that in addition to possible immediate impacts, harvesting treatments have legacy effects (subtle or delayed inherited effects of forestry in the past) that influence the forest understorey vegetation community composition and the amount of coarse woody debris. This finding deserves special attention when planning of species conservation, multiple use of forests and sustainable forestry. [ABSTRACT FROM AUTHOR]

Highlights • The timing of bud phenology is the result of internal and external cues. • Bud burst and bud set mirror the temperature of their provenance. • Ecotypes with later growth in spring could be sensitive to autumn frosts. • Ecotypes selection can aim to avoid early or late frosts, but not both. Abstract Forest managers use artificial regeneration to influence tree species composition and productivity. The selection of plant material could assume a leading role in forest planning, mainly when aiming to increase the adaptation of stands within a context of climate change. In this study, we investigated the timing of bud burst and bud set in five black spruce [ Picea mariana (Mill.) B.S.P.] ecotypes growing in a common garden and originating from a latitudinal range in the boreal forest of Québec, Canada. Bud phenology was monitored weekly during the 2015, 2017 and 2018 growing seasons. On average, the bud burst process lasted 23 days, occurring 1.2 days later for each degree Celsius of increase in mean annual temperature at the provenance site. Bud set duration was 55 days and occurred 1.8 days later for each degree Celsius of increase in mean annual temperature at the provenance site. We demonstrated that both bud burst and bud set occurred earlier in individuals from colder sites, which resulted in similar lengths of the growing season among provenances. This clinal variation in the timings of growth resumption and cessation confirms the ecotypic differentiation of black spruce populations and reflects a long-lasting adaptation to the local temperatures in the sites of origin. The findings of this study demonstrate that ecotype selection in black spruce can aim to avoid damage from either early or late frosts, but not both. [ABSTRACT FROM AUTHOR]

The branch xylem of six important Inner Asian southern boreal forest trees was studied for wood-anatomical and hydraulic traits in order to infer the species' drought tolerance from embolism resistance, potential hydraulic conductivity, mean conduit diameters and conduit density. The only studied angiosperm tree, Betula pendula Roth, was much more sensitive to cavitation than all five conifers (evergreen or summer-green), even when using 88% loss of conductivity (P 88) in birch, but 50% (P 50) in the conifers as critical thresholds. This suggests that pioneer birch forests, which have widely replaced the conifer climax forests after anthropogenic disturbance (e.g. logging, man-made fire), are more vulnerable to climate warming-induced drought than the original conifer forests. In contrast to expectation, the generally more drought-exposed light taiga species (Larix sibirica Ledeb. Pinus sylvestris L.) did not have consistently lower P 50 and P 88 values than the dark taiga conifers, suggesting that other drought survival traits are equally important. Among the dark-taiga species, only Pinus sibirica Du Tour, but not Abies sibirica Ledeb. and Picea obovata Ledeb. had relatively high P 50 values indicating higher vulnerability. In the light-taiga forest, P. sylvestris revealed lower embolism resistance than L. sibirica. In the face of rapid climate warming and drying in Inner Asia, the drought survival strategies of southern boreal tree species deserve further intensive study, which should include other drought survival traits. [ABSTRACT FROM AUTHOR]

Abstract Boreal forests are an important carbon (C) sink and fire is the main natural disturbance, directly affecting the C-cycle via emissions from combustion of biomass and organic matter and indirectly through long-term changes in C-dynamics including soil respiration. Carbon dioxide (CO 2) emission from soil (soil respiration) is one of the largest fluxes in the global C-cycle. Recovery of vegetation, organic matter and soil respiration may be influenced by the intensity of post-fire management such as salvage logging. To study the impact of forest fire, fire and salvage, and recovery time on soil respiration and soil C and N content, we sampled two permanent research areas in north-western Estonia that were damaged by fire: Vihterpalu (59°13′ N 23°49′ E) in 1992 and Nõva (59°10′ N 23°45′ E) in 2008. Three types of sample plots were established: 1) unburned control with no harvesting (CO); 2) burned and uncleared (BU); and 3) burned and cleared (BC). Measurements were made in 2013, 21 years after wildfire in Vihterpalu and 5 years after wildfire in Nõva. Soil respiration ranged from 0.00 to 1.38 g CO 2 m−2 h−1. Soil respiration in the burned and cleared areas (BC) was not reduced compared to burned and uncleared (BU) areas but the average soil respiration in unburned control areas was more than twice the value in burned areas (average soil respiration in CO areas was 0.34 CO 2 m−2 h−1, versus 0.16 CO 2 m−2 h−1, the average soil respiration of BC and BU combined). Recovery over 20 years was mixed; respiration was insignificantly lower on younger than older burned sites (when BC and BU values were combined, the average values were 0.15 vs. 0.17 g CO 2 m−2 h−1, respectively); soil-C was greater in the older burned plots than the younger (when BC and BU values were combined, the average values were 9.71 vs. 5.99 kg m−2, respectively); but root biomass in older and recently burned areas was essentially the same (average 2.23 and 2.11 kg m−2, respectively); soil-N was highest on burned areas 20 years after fire. Twenty years post-fire may be insufficient time for carbon dynamics to fully recover on these low productivity sandy sites. Highlights • 20 years post-burning was insufficient for soil respiration recovery on sandy soils. • Soil respiration in burned areas was not reduced further by salvage logging. • Soil carbon may be restored to unburned levels in 20 years. • Salvage logging on burned areas decreases the rate of recovery of soil carbon. • Soil nitrogen recovered in 20 years but was not correlated with respiration. [ABSTRACT FROM AUTHOR]

Highlights • Species traits are linked to species complementarity and competitive ability. • The intraspecific component of functional diversity is high in European forests. • Conspecific trees adjust leaf traits in response to canopy species richness. • Conspecific trees have architectures more variable in richer communities. • Species respond to canopy species richness promoting species complementarity. Abstract Functional diversity informs about biodiversity-ecosystem functioning relationships. The intraspecific component of functional diversity (i.e. the phenotypic space of each species) depicts individual differences in the resource use and fitness among conspecifics, and gives valuable information about the functional similarity (competition) or dissimilarity (complementarity) of coexisting species. Here, we quantified trait differences within tree species along local diversity gradients to shed light on the role that this intraspecific variability exerts on functional complementarity of tree species. We measured architectural traits in 5,036 individuals and leaf traits in 1,403 individuals from nine dominant tree species, surveyed in 92 plots located in three major European forest types (Mediterranean, temperate and boreal forests). In each forest type, plots were positioned along a canopy richness gradient, with every study species present in different species richness levels, including monocultures. Our results showed that the relative magnitude of intraspecific trait variability to community-level variability is high in these forests. At the species level, we found adjustments of species leaf traits (mean shifts) in response to neighbouring trees, suggesting the existence of processes that limit niche overlap. We also found higher variability in architectural traits of conspecific individuals in more diverse canopies, suggesting greater niche packing and a more efficient use of available space as the number of species in the canopy increases. Altogether, our results support the hypothesis that differential responses of individuals within a species promote species complementarity, suggesting that biodiversity-ecosystem functioning relationships cannot be properly estimated without accounting for the intraspecific level of functional variation. [ABSTRACT FROM AUTHOR]

Despite the insignificant contribution to the total forest phytomass, fine roots form 30% of the production of forest ecosystems, playing a crucial role in biogeochemical cycles. However, estimates of the biomass, annual production, dieback, and age of fine roots remain understudied, especially in Russian forests, due to technical difficulties. There are only a few estimates of nitrogen consumption for the annual production of fine roots. It is believed that they comprise up to 75 kg N ha-1 in mature forests. This is up to 60% of the total consumption of nitrogen for annual yield and is comparable with mineralized soil nitrogen. However, these values are approximate because the methods of measuring fine roots production are debatable. [ABSTRACT FROM AUTHOR]

Abstract Boreal forests subject to low fire activity are complex ecosystems in terms of structure and dynamics. They have a high ecological value as they contain important proportions of old forests that play a crucial role in preserving biodiversity and ecological functions. They also sequester important amounts of carbon at the landscape level. However, the role of time since fire in controlling the different processes and attributes of those forests is still poorly understood. The Romaine River area experiences a fire regime characterized by very rare but large fires and has recently been opened to economic development for energy and timber production. In this study, we aimed to characterize this region in terms of live aboveground biomass, merchantable volume, stand structure and composition, and to establish relations between these attributes and the time since the last fire. Mean live aboveground biomass and merchantable volume showed values similar to those of commercial boreal coniferous forests. They were both found to increase up to around 150 years after a fire before declining. However, no significant relation was found between time since fire and stand structure and composition. Instead, they seemed to mostly depend on stand productivity and non-fire disturbances. At the landscape level, this region contains large amounts of biomass and carbon stored resulting from the long fire cycles it experiences. Although in terms of merchantable volume these forests seemed profitable for the forest industry, a large proportion were old forests or presented structures of old forests. Therefore, if forest management was to be undertaken in this region, particular attention should be given to these old forests in order to protect biodiversity and ecological functions. Partial cutting with variable levels of retention would be an appropriate management strategy as it reproduces the structural complexity of old forests. Highlights • In low fire activity boreal forests, aboveground biomass can reach commercial values. • At the landscape level, these forests store large amounts of carbon. • Live aboveground biomass and merchantable volume peak 150 years after a fire. • Stand structure is driven by site productivity rather than time since fire. • Management strategies should be adapted to complex and irregular stand structures. [ABSTRACT FROM AUTHOR]

Understorey vegetation hosts the most species diversity in temperate and boreal forests and contributes substantially to ecosystem functions. Despite its ecological importance, the dynamics of understorey biomass, production and turnover rates following stand-replacing disturbance and throughout forest succession remain poorly understood. Using a replicated chronosequence spanning 8, 16, 34, 98, 146 and 210 years following fire, we examined the dynamics of understorey biomass, production and turnover associated with stand development and overstorey types (broadleaf, mixedwood, and conifer) in the central boreal forest of Canada. Across all ages and overstorey types, biomass, production and turnover rates of woody plants, herbs, and bryophytes were on average 2.71, 0.10, and 0.13 Mg ha −1 ; 0.24, 0.13, and 0.08 Mg ha −1 year −1 and 9.7%, 127.3%, and 67.6% year −1 , respectively. Total understorey biomass and production increased continuously with stand age and reached the maximum in 146-year-old stands. Herbaceous biomass and production, peaked in 16-year-old stands, and remained stable thereafter with a slight increase in 146-year-old stands; in contrast, woody plant and bryophyte biomass and production peaked in 98- and 146-year-old stands. Herbaceous and woody vegetation turnover rates were higher in young stands, and those of bryophytes were higher in older stands. Total, woody and herbaceous biomass, production and turnover rates were higher under deciduous broadleaf overstorey, while values for bryophytes were higher in conifer stands, with mixedwood being intermediate. Overstorey mixture had no overall effect on total, woody, herbaceous biomass and production other than the expected from the averages of their broadleaf and conifer stands, but reduced bryophyte biomass and woody turnover. Our findings suggest that understorey biomass, production and turnover rates in the boreal forest are mainly driven by time since colonization and the resource availability and heterogeneity mediated via overstorey composition. Our results highlight the roles of stand development and overstorey composition in understorey biomass, production and turnover and their importance for modeling total forest ecosystem contribution to the global forest carbon. [ABSTRACT FROM AUTHOR]

Abstract: The accumulation of soil carbon (C) is regulated by a complex interplay between abiotic and biotic factors. Our study aimed to identify the main drivers of soil C accumulation in the boreal forest of eastern North America. Ecosystem C pools were measured in 72 sites of fire origin that burned 2–314 years ago over a vast region with a range of ∆ mean annual temperature of 3°C and one of ∆ 500 mm total precipitation. We used a set of multivariate a priori causal hypotheses to test the influence of time since fire (TSF), climate, soil physico‐chemistry and bryophyte dominance on forest soil organic C accumulation. Integrating the direct and indirect effects among abiotic and biotic variables explained as much as 50% of the full model variability. The main direct drivers of soil C stocks were: TSF >bryophyte dominance of the FH layer and metal oxide content >pH of the mineral soil. Only climate parameters related to water availability contributed significantly to explaining soil C stock variation. Importantly, climate was found to affect FH layer and mineral soil C stocks indirectly through its effects on bryophyte dominance and organo‐metal complexation, respectively. Soil texture had no influence on soil C stocks. Soil C stocks increased both in the FH layer and mineral soil with TSF and this effect was linked to a decrease in pH with TSF in mineral soil. TSF thus appears to be an important factor of soil development and of C sequestration in mineral soil through its influence on soil chemistry. Overall, this work highlights that integrating the complex interplay between the main drivers of soil C stocks into mechanistic models of C dynamics could improve our ability to assess C stocks and better anticipate the response of the boreal forest to global change. [ABSTRACT FROM AUTHOR]

Loss of global forest, and in particular forest that has little human disturbance, is a standard against which we measure progress to conserve Earth's forests. The value of intact forest landscapes has taken hold in the global psyche. We provide a brief history of the intact forest landscape concept and discuss how this has moved to an operational definition used as a global and regional metric of forest conservation. We distinguish between a conceptual intact forest landscape and an operational definition. For the purposes of this paper we will use the term IFL to mean the operational definition and intact forest landscapes to mean the conceptual idea. We provide an overview of the science that supports the value of intact forest landscapes in a Canadian boreal context and analyse issues with using a standard operationalized IFL definition to both measure and promote conservation of forests at global and regional scales. We found many arguments for protecting large, intact forest landscapes that are relevant to the Canadian boreal forest, including conservation of biodiversity, ecological processes and ecosystem services, existence values, application of the precautionary principle, and the need for scientific benchmarks. But it is clear that the standard operational IFL size threshold of 50 000 ha in the boreal forest is inadequate to meet these broad conservation objectives. However, the concept of intact forest being large enough to allow for all natural processes and biodiversity is likely not logistically feasible in Canada's managed boreal forest. The scale at which the most extensive processes (e.g., fire and insects) occur and species (e.g., woodland caribou) function is likely too large. Management options incorporating local knowledge of conservation needs and the specifics of ecosystem function and composition are more likely to be effective in conservation than rigid IFL requirements. A standardized approach is useful for global tracking of IFLs but it is not the best approach to meet more regional forest conservation goals. Intact forest landscapes have exceptional value but should be managed in the context of integrated land use planning that includes protected areas, sustainable forest management, species at risk management, and ecosystem restoration. [ABSTRACT FROM AUTHOR]

Intensive forest management activities that maximize economic gains could have a negative impact on the ecosystems and generate environmental conflicts, which may in turn translate to poor delivery of ecosystems services. Although plant diversity is positively associated with multiple ecosystem functions, it remains unclear how economic gains influence plant diversity across vegetation strata. We analyzed the relationships between economic gains, assessed as profit, and plant species richness following forest management alternatives (managing rotation age and overstorey composition) for the boreal forests of Canada. We found a hump-shaped relationship between total plant richness and profit, with total plant richness increasing initially, reaching a peak, and then declining with increasing profits. The relationship between profit and plant diversity differed among vegetation strata. Understorey plant richness followed similar trends to total plant richness, but overstorey tree richness increased linearly. The results of path analysis presented management alternatives as major drivers determining profit and plant diversity across vegetation strata. Our analysis indicated that maximum profit ($5000/ha) could lead to 20% loss of total plant species richness. Among the alternatives we compared, we conclude that managing for mixedwood with approximately a rotation of 100 years is an optimal compromise between economic and plant diversity objectives. [ABSTRACT FROM AUTHOR]

The growth of high-latitude temperature-limited boreal forest ecosystems is projected to become more constrained by soil water availability with continued warming. The purpose of this study was to document ongoing shifts in tree growth sensitivity to the evolving local climate in unmanaged black spruce (Picea mariana (Miller) B.S.P.) forests of eastern boreal North America (49°N-52°N, 58°W-82°W) using a comparative study of field and modeled data. We investigated growth relationships to climate (gridded monthly data) from observed (50 site tree-ring width chronologies) and simulated growth data (stand-level forest growth model) over 1908-2013. No clear strengthening of moisture control over tree growth in recent decades was detected. Despite climate warming, photosynthesis (main driver of the forest growth model) and xylem production (main driver of radial growth) have remained temperature-limited. Analyses revealed, however, a weakening of the influence of growing season temperature on growth during the mid- to late twentieth century in the observed data, particularly in high-latitude (> 51.5°N) mountainous sites. This shift was absent from simulated data, which resulted in clear model-data desynchronization. Thorough investigations revealed that desynchronization was mostly linked to the quality of climate data, with precipitation data being of particular concern. The scarce network of weather stations over eastern boreal North America (> 51.5°N) affects the accuracy of estimated local climate variability and critically limits our ability to detect climate change effects on high-latitude ecosystems, especially at high altitudinal sites. Climate estimates from remote sensing could help address some of these issues in the future. [ABSTRACT FROM AUTHOR]

Reindeer husbandry in northern Sweden, Norway, and Finland is an extensive agroforestry system, and the management of reindeer occurs alongside other land uses such as forestry, hunting, and tourism. The economic, social, and environmental impact of using GPS collars to track the reindeer was evaluated in the Sami village of Njaarke in boreal Sweden. A second objective was to evaluate how adapted forest management influenced reindeer husbandry. The results show that the use of GPS tracking enables the improved monitoring of the reindeer but the financial costs were greater than the financial benefits. The increased income did not cover the costs of depreciation and maintenance. Whilst the labour inputs associated with reindeer husbandry were high, 30-40% of the gross value added by village activities were related to hunting, tourism, and the renting of fishing rights. The use of adaptive forest management was assumed to increase the number of reindeer that could be reared through to slaughter and it was calculated to increase the gross value added by reindeer husbandry by more than 30%. [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]

Forestry practices generally result in an increased export of carbon and nitrogen to downstream aquatic systems. Although these losses affect the greenhouse gas budget of managed forests, it is unknown if they modify greenhouse gas emissions of recipient aquatic systems. To assess this question, we quantified atmospheric fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) of humic lakes and their inlet streams in four boreal catchments of which two were treated with forest clear-cuts followed by site preparation (18 % and 44 % of the catchment area) using a Before/After-Control/Impact-experiment. We measured atmospheric gas fluxes and hydrological and physicochemical water characteristics in hillslope groundwater, along stream transects and at multiple locations in lakes at 2-hourly to biweekly intervals throughout the summer season over a four year period. We found that the treatment did not significantly change greenhouse gas emissions from streams or lakes within three years of the treatment, despite significant increases of CO2 and CH4 concentrations in hillslope groundwater. Our results highlight the importance of the riparian zone-stream continuum as effective biogeochemical buffers and wind shelters to prevent greenhouse gases leaching from forest clear-cuts and evasion via downstream inland waters. These findings are representative for low productive forests located in relatively flat landscapes where forestry practices cause only a limited initial impact on catchment hydrology and biogeochemistry. [ABSTRACT FROM AUTHOR]

The boreal ecoregion supports about one-third of the world’s forest. Over 90% of boreal forest streams are found in headwaters, where terrestrial-aquatic interfaces are dominated by organic matter (OM)-rich riparian zones (RZs). Because these transition zones are key features controlling catchment biogeochemistry, appropriate RZ conceptualizations are needed to sustainably manage surface water quality in the face of a changing climate and increased demands for forest biomass. Here we present a simple, yet comprehensive, conceptualization of RZ function based on hydrological connectivity, biogeochemical processes, and spatial heterogeneity. We consider four dimensions of hydrological connectivity: (1) laterally along hillslopes, (2) longitudinally along the stream, (3) vertically down the riparian profile, and (4) temporally through event-based and seasonal changes in hydrology. Of particular importance is the vertical dimension, characterized by a ‘Dominant Source Layer’ that has the highest contribution to solute and water fluxes to streams. In addition to serving as the primary source of OM to boreal streams, RZs shape water chemistry through two sets of OM-dependent biogeochemical processes: (1) transport and retention of OM-associated material and (2) redox-mediated transformations controlled by RZ water residence time and availability of labile OM. These processes can lead to both retention and release of pollutants. Variations in width, hydrological connectivity, and OM storage drive spatial heterogeneity in RZ biogeochemical function. This conceptualization provides a useful theoretical framework for environmental scientists and ecologically sustainable and economically effective forest management in the boreal region and elsewhere, where forest headwaters are dominated by low-gradient, OM-rich RZs. [ABSTRACT FROM AUTHOR]

Abstract: Rapid warming and changes in water availability at high latitudes alter resource abundance, tree competition, and disturbance regimes. While these changes are expected to disrupt the functioning of boreal forests, their ultimate implications for forest composition are uncertain. In particular, recent site‐level studies of the Alaskan boreal forest have reported both increases and decreases in productivity over the past few decades. Here, we test the idea that variations in Alaskan forest growth and mortality rates are contingent on species composition. Using forest inventory measurements and climate data from plots located throughout interior and south‐central Alaska, we show significant growth and mortality responses associated with competition, midsummer vapor pressure deficit, and increased growing season length. The governing climate and competition processes differed substantially across species. Surprisingly, the most dramatic climate response occurred in the drought tolerant angiosperm species, trembling aspen, and linked high midsummer vapor pressure deficits to decreased growth and increased insect‐related mortality. Given that species composition in the Alaskan and western Canadian boreal forests is projected to shift toward early‐successional angiosperm species due to fire regime, these results underscore the potential for a reduction in boreal productivity stemming from increases in midsummer evaporative demand. [ABSTRACT FROM AUTHOR]

We analysed a dataset composed by the frequency of 79 epiphytic lichens recorded on 243 oaks distributed in 29 oak dominated stands of the Western Carpathians, representing areas with high environmental quality up to disturbed environments. Lichen diversity indices (based on total frequencies and on functional and morphological groups) were used as indicators of the response to air quality and forest management. The level of air quality in these categories was a function of NOx, SO2 and particulate matter. From management viewpoint the units were classified as managed (areas subjected to periodic logging) and semi-natural (which currently have the status of National Nature Reserve and where eventual management practices date back to the history). The results showed that higher environmental levels of pollution were associated to the decrease of fruticose and in general pollution sensitive species, while low environmental levels of pollution were associated to the diffusion of common nitrophilous lichens as well as to a higher share of fruticose and in general pollution sensitive species. As far as forest management is concerned, a higher share of fruticose and sensitive species was associated to semi-natural and natural stands, whereas a higher share of foliose (pioneer and tolerant) species was associated to the managed stands. [ABSTRACT FROM AUTHOR]

Post-harvest regeneration failure of white spruce ( Picea glauca Moench [Voss]), has led to concerns of “de-coniferization” on productive site in the Alaskan boreal forest. Forest management in the region sought historically to increase spruce composition after harvest through silvicultural practices such as site preparation and assisted regeneration; however, successful reforestation requires the effects of these practices to persist over time and control non-target tree species. In order to identify the enduring effects of silvicultural regeneration practices, we sampled a large (26.7 ha) white spruce regeneration trial established immediately following a stand-replacing wildfire and subsequent salvage harvest in a productive upland forest. The original regeneration treatments followed a split-split plot experimental design on two landform types (LF), four ground scarification treatments (GST) plus a non-scarified control, and five artificial white spruce regeneration treatments (WSRT) plus a natural seedfall control (Densmore et al., 1999). Here we analyze the total biomass, stand density, and basal area for all tree species within each of the regeneration treatments 28 years post-establishment, and calculate seed dispersal distances. Our results show that compared to natural seedfall control plots, white spruce basal area was six times greater in planted seedling plots, and white spruce stem density (dbh ≥ 1.0 cm) was nearly three times greater in broadcast seeding plots. White spruce stem density from natural seedfall averaged 944 stems ha −1 , but was dependent on both topographic position and distance to wind-dispersed seed sources. Our results also indicate that GST had few significant effects on white spruce basal area or stem density. However, scarification nearly doubled Alaska birch ( Betula neoalaskana Sarg.) stem density and basal area compared to non-scarified control plots. Planted white spruce plots supported 19% less birch basal area, except in the most intensive scarification treatments in which birch basal area did not differ. Intensive scarification reduced quaking aspen ( Populus tremuloides Michx.) basal area by half on slope plots. Our results demonstrate that early regeneration practices profoundly influence stand development beyond the stem initiation stage, but pre-fire stand type, post-fire configuration of unburned seed sources, and topographical variation play a mediating role in determining species assemblages and competitive relationships. A fire-killed stand must be considered within its ecological and landscape context to determine the probable success of a management action such as salvage and tree regeneration. [ABSTRACT FROM AUTHOR]

The supply of nitrogen commonly limits plant production in boreal forests and also affects species composition and ecosystem functions other than plant growth. These interrelations vary across the landscapes, with the highest N availability, plant growth and plant species richness in ground-water discharge areas (GDAs), typically in toe-slope positions, which receive solutes leaching from the much larger groundwater recharge areas (GRAs) uphill. Plant N sources include not only inorganic N, but, as heightened more recently, also organic N species. In general, also the ratio inorganic N over organic N sources increase down hillslopes. Here, we review recent evidence about the nature of the N limitation and its variations in Fennoscandian boreal forests and discuss its implications for forest ecology and management. The rate of litter decomposition has traditionally been seen as the determinant of the rate of N supply. However, while N-rich litter decomposes faster than N-poor litter initially, N-rich litter then decomposes more slowly, which means that the relation between N % of litter and its decomposability is complex. Moreover, in the lower part of the mor-layer, where the most superficial mycorrhizal roots first appear, and N availability matters for plants, the ratio of microbial N over total soil N is remarkably constant over the wide range in litter and soil C/N ratios of between 15 and 40 for N-rich and N-poor sites, respectively. Nitrogen-rich and -poor sites thus differ in the sizes of the total N pool and the microbial N pool, but not in the ratio between them. A more important difference is that the soil microbial N pool turns over faster in N-rich systems because the microbes are more limited by C, while microbes in N-poor systems are a stronger sink for available N. Furthermore, litter decomposition in the most superficial soil horizon (as studied by the so-called litter-bag method) is associated with a dominance of saprotrophic fungi, and absence of mycorrhizal fungi. The focal zone in the context of plant N supply in N-limited forests is further down the soil profile, where ectomycorrhizal (ECM) roots become abundant. Molecular evidence and stable isotope data indicate that in the typical N-poor boreal forests, nitrogen is retained in saprotrophic fungi, likely until they run out of energy (available C-compounds). Then, as heightened by recent research, ECM fungi, which are supplied by photosynthate from the trees, become the superior competitors for N. In N-poor boreal soils strong N retention by microorganisms keeps levels of available N very low. This is exacerbated by an increase in tree C allocation to mycorrhizal fungi (TCAM) relative to net primary production (NPP) with decreasing soil N supply, which causes ECM fungi to retain much of the available soil N for their own growth and transfer little to their tree hosts. The transfer of N through the ECM fungi, and not the rate of litter decomposition, is likely limiting the rate of tree N supply under such conditions. All but a few stress-tolerant less N-demanding plant species, like the ECM trees themselves and ericaceous dwarf shrubs, are excluded. With increasing N supply, a weakening of ECM symbiosis caused by the relative decline in TCAM contributes to shifts in soil microbial community composition from fungal dominance to bacterial dominance. Thus, bacteria, which are less C-demanding, but more likely to release N than fungi, take over. This, and the relatively high pH in GDA, allow autotrophic nitrifying bacteria to compete successfully for the NH 4 + released by C-limited organisms and causes the N cycle to open up with leaching of nitrate (NO 3 − ) and gaseous N losses through denitrification. These N-rich conditions allow species-rich communities of N-demanding plant species. Meanwhile, ECM fungi have a smaller biomass, are supplied with N in excess of their demand and will export more N to their host trees. Hence, the gradient from low to high N supply is characterized by profound variations in plant and soil microbial physiologies, especially their relations to the C-to-N supply ratio. We propose how interactions among functional groups can be understood and modelled (the plant-microbe carbon-nitrogen model). With regard to forest management these perspectives explain why the creation of larger tree-free gaps favors the regeneration of tree seedlings under N-limited conditions through reduced belowground competition for N, and why such gaps are less important under high N supply (but when light might be limiting). We also discuss perspectives on the relations between N supply, biodiversity, and eutrophication of boreal forests from N deposition or forest fertilization. [ABSTRACT FROM AUTHOR]

Boreal forests are an important source of timber and pulp wood, but provide also other products and services. Utilizing a simulation program and field data from a tree retention experiment in a Scots pine forest in central Sweden, we simulated the consequences during the following 100 years of various levels of retention on production of merchantable wood, dead wood input (as a proxy for biodiversity), and carbon stock changes. At the stand level, wood production decreased with increased retention levels, while dead wood input and carbon stock increased. We also compared 12 scenarios representing a land sharing/land sparing gradient. In each scenario, a constant volume of wood was harvested with a specific level of retention in a 100-ha landscape. The area not needed to reach the defined volume was set-aside during a 100-year rotation period, leading to decreasing area of set-asides with increasing level of retention across the 12 scenarios. Dead wood input was positively affected by the level of tree retention whereas the average carbon stock decreased slightly with increasing level of tree retention. The scenarios will probably vary in how they favor species preferring different substrates. Therefore, we conclude that a larger variation of landscape-level conservation strategies, also including active creation of dead wood, may be an attractive complement to the existing management. [ABSTRACT FROM AUTHOR]

The article reports that boreal forest is a defining feature of nation, a giant swath of terrestrial biodiversity pulsing with life which covers several percentage of landmass, sweeping across the central and near-northern portions of all provinces and territories except the Maritimes. Topics include examines the boreal forest wraps the entire global northern hemisphere, making it the largest forest ecosystem on the planet, and one of the most threatened.

Landscape context is known to affect species diversity patterns and can even influence the effectiveness of local conservation management in agricultural landscapes. For other land uses, like forestry, landscape effects are poorly known. We aimed to determine whether landscape composition modifies the response of saproxylic beetle species to local habitat and conservation management, with focus on dead wood and prescribed fire, in managed boreal forest landscapes. We surveyed beetles on 32 clearcuts in central Sweden. We measured local (fire, dead wood, flower resources, patch size) and landscape factors (fire, dead wood within 1–2 km radius), and analysed interactions between these in mixed models. The response was species richness of beetles with different habitat specialization – conifer specialists, deciduous specialists, flower visitor and pyrophilous species, and abundance of a red-listed species, Tragosoma depsarium . Local and landscape factors, as well as interactions between them, affected species richness patterns. Prescribed fire and amount of dead wood, both on local and landscape scale, affected species richness and composition of several groups. There were interactions between local and landscape factors in five models out of six. Locally, we observed a positive response to flower richness for several groups, while the response to prescribed fire and dead wood amounts typically was affected by landscape factors. The results suggest that effectiveness of local conservation management is affected by landscape properties; the positive effects of local dead wood amounts and burning occurred on clearcuts in landscapes with large amounts of dead wood, but not in landscapes with small amounts of dead wood. [ABSTRACT FROM AUTHOR]

Clearcutting practices combined with the predicted increase in fire activity may induce post-fire regeneration failure in boreal forest landscapes. This study aims (1) to evaluate if recently managed landscape by clear cut logging is susceptible to be affected by post-fire regeneration failure; and (2) to explore the ecological drivers of black spruce ( Picea mariana (Mill.) BSP) post-fire regeneration. In 2014, we surveyed the regeneration of 36 stands in northwestern Quebec that had burned in a major fire in 2005. Fire severity was evaluated for each site with the differenced Normalized Burn Ratio. Using linear models, we explored the relationship between environmental variables (fire severity, pre-fire stand maturity, nature of the seedbed, and physiographic variables) and black spruce post-fire regeneration. Black spruce post-fire seedling density was highly variable (range: 25–16 000 seedlings/ha; mean ± standard deviation: 4549 seedlings/ha ± 4752) within the studied fire, but did not significantly differ between stands that had been logged 50 years prior to fire and those that were mature prior to the 2005 fire. However, post-fire regeneration failure (defined as <40% stocking that corresponds in our study region to a regeneration density <1750 seedlings/ha) was observed in 48% of the stands that had been logged, but only in 29% of the stands that were mature prior to the fire. The presence of residual trees left after clearcutting may explain why regeneration level was relatively good (>50%) in stands affected by past logging activities. Our study illustrates how biological legacies, environmental conditions and fire severity determine post-fire recovery and resilience of black spruce-dominated ecosystems of eastern Canada. By identifying the drivers of post-fire regeneration success, our study will help forest managers allocating resources where restoration of productive forest are truly needed. [ABSTRACT FROM AUTHOR]

Forest managers across the Canadian boreal require detailed fire pattern information to support disturbance-based management. However, there are no consistent classifications of post-fire patterns, and those that exist rely on field-data that is both expensive and lacking in spatial representation. As a result, across the managed boreal forest there is limited fire pattern information, no standardized protocols to derive the quantitative fire pattern information nor agreement on the most appropriate metrics needed to implement management planning based on emulating natural disturbances. In this paper we first derived three classes of tree mortality based on Landsat spectral data and aerially photo-interpreted (API) polygons. Next we used these derived classes to compute seven fire pattern metrics over 14 fires that occurred from 1984 to 2006 in the Canadian provinces of Alberta and Saskatchewan, Canada. We then compared the metrics derived from the Landsat data to those computed from the API coverage. Lastly, we assessed the influence of a suite of environmental and fire pattern variables on the Landsat-derived indices. Overall we found very close correspondence for the two event-scale indices: the total area affected by fire and the complexity of the perimeter. The more detailed within-fire event metrics presented more varied results and were somewhat less precise. For example, the total amount of residuals or the largest disturbed patch were accurately captured. Other indices such as the number of disturbed patches or total amount of island remnants presented moderate systematic biases, but still might be serviceable given that the biases were predictable in direction. Fire size and seasonal drought variables were the most correlated with the Landsat derived pattern indices and their inclusion as model variables is likely to increase overall prediction accuracy. A pan-boreal geospatial database of detailed fire pattern metrics would be an invaluable tool to support the implementation of disturbance-based management approaches. Here we demonstrate that a cost-effective Landsat methods produces comparable fire pattern information to conventional approaches based on manual interpretation of aerial photographs. Building upon the standardized methods proposed here hundreds of fires could be mapped, to potentially, create a comprehensive national fire pattern database. [ABSTRACT FROM AUTHOR]

Indicator species are widely used biodiversity surrogates that allow the assessment of biodiversity without the expensive and time-consuming construction of species inventories. The selection of indicator species often relies on species co-occurrence patterns, which may be altered by anthropogenic disturbance such as forest harvesting, imposing a unique challenge to their application in managed forest. Here, we studied boreal bird communities in natural forests originating from wildfire and managed forests originating from clearcutting. We aimed to (1) compare species co-occurrence patterns in natural and clearcut forest stands, (2) select indicator species based on species co-occurrence patterns to predict avian diversity, and (3) evaluate the predictive performance of indicator species under both natural and clearcutting disturbance regimes using the same training data set and an independent testing data set. We found that species co-occurrence patterns differ substantially between natural and clearcut stands, suggesting that forest harvesting alters species-environment relationships and/or interspecific interactions. Consequently, we selected different sets of species as indicators of avian diversity based on data from natural or clearcut stands. However, according to internal and external evaluation, selecting indicator species using data from both natural and clearcut stands produced surrogates that predicted avian diversity accurately and precisely in both types of forests. Our results suggest that, despite forest harvesting altering species co-occurrence patterns, a comprehensive understanding of species co-occurrence patterns across natural and managed forests can be used to develop robust biodiversity surrogates. Our study shows that small sets of indicator species can represent the biodiversity of a wide range of species in ecosystems undergoing anthropogenic disturbance, which has important implications for the application of biodiversity surrogates for conservation. [ABSTRACT FROM AUTHOR]

Context: Forest landscapes at the southern boreal forest transition zone are likely to undergo great alterations due to projected changes in regional climate. Objectives: We projected changes in forest landscapes resulting from four climate scenarios (baseline, RCP 2.6, RCP 4.5 and RCP 8.5), by simulating changes in tree growth and disturbances at the southern edge of Canada's boreal zone. Methods: Projections were performed for four regions located on an east-west gradient using a forest landscape model (LANDIS-II) parameterized using a forest patch model (PICUS). Results: Climate-induced changes in the competitiveness of dominant tree species due to changes in potential growth, and substantial intensification of the fire regime, appear likely to combine in driving major changes in boreal forest landscapes. Resulting cumulative impacts on forest ecosystems would be manifold but key changes would include (i) a strong decrease in the biomass of the dominant boreal species, especially mid- to late-successional conifers; (ii) increases in abundance of some temperate species able to colonize disturbed areas in a warmer climate; (iii) increases in the proportions of pioneer and fire-adapted species in these landscapes and (iv) an overall decrease in productivity and total biomass. The greatest changes would occur under the RCP 8.5 radiative forcing scenario, but some impacts can be expected even with RCP 2.6. Conclusions: Western boreal forests, i.e., those bordering the prairies, are the most vulnerable because of a lack of species adapted to warmer climates and major increases in areas burned. Conservation and forest management planning within the southern boreal transition zone should consider both disturbance- and climate-induced changes in forest communities. [ABSTRACT FROM AUTHOR]

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Terrestrial laser scanning has been widely used to analyze the 3D structure of a forest in detail and to generate data at the level of a reference plot for forest inventories without destructive measurements. Multi-scan terrestrial laser scanning is more commonly applied to collect plot-level data so that all of the stems can be detected and analyzed. However, it is necessary to match the point clouds of multiple scans to yield a point cloud with automated processing. Mismatches between datasets will lead to errors during the processing of multi-scan data. Classic registration methods based on flat surfaces cannot be directly applied in forest environments; therefore, artificial reference objects have conventionally been used to assist with scan matching. The use of artificial references requires additional labor and expertise, as well as greatly increasing the cost. In this study, we present an automated processing method for plot-level stem mapping that matches multiple scans without artificial references. In contrast to previous studies, the registration method developed in this study exploits the natural geometric characteristics among a set of tree stems in a plot and combines the point clouds of multiple scans into a unified coordinate system. Integrating multiple scans improves the overall performance of stem mapping in terms of the correctness of tree detection, as well as the bias and the root-mean-square errors of forest attributes such as diameter at breast height and tree height. In addition, the automated processing method makes stem mapping more reliable and consistent among plots, reduces the costs associated with plot-based stem mapping, and enhances the efficiency. [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]

Detailed understanding of forest disturbance interactions is needed for effective forecasting, modelling, and management. Insect outbreaks are a significant forest disturbance that alters forest structure as well as the distribution and connectivity of combustible fuels at broad spatial scales. The effect of insect outbreaks on fire activity is an important but contentious issue with significant policy consequences. The eastern spruce budworm ( Choristoneura fumiferana) is a native defoliating insect in eastern North America whose periodic outbreaks create large patches of dead fir and spruce trees. Of particular concern to fire and forest managers is whether these patches represent an increased fire risk, if so, for how long, and how the relationship between defoliation and fire risk varies through space and time. Previous work suggests a temporary increase in flammability in budworm-killed forests, but regional and seasonal variability in these relationships has not been examined. Using an extensive database on historical lightning-caused fire ignitions and spruce budworm defoliation between 1963 and 2000, we assess the relative importance of cumulative defoliation and fire weather on the probability of ignition in Ontario, Canada. We modeled fire ignition using a generalized additive logistic regression model that accounts for temporal autocorrelation in fire weather. We compared two ecoregions in eastern Ontario (Abitibi Plains) and western Ontario (Lake of the Woods) that differ in terms of climate, geomorphology, and forest composition. We found that defoliation has the potential to both increase and decrease the probability of ignition depending on the time scale, ecoregion, and season examined. Most importantly, we found that lagged spruce budworm defoliation (8-10 yr) increases the risk of fire ignition whereas recent defoliation (1 yr) can decrease this risk. We also found that historical defoliation has a greater influence on ignition risk during the spring than during the summer fire season. Given predicted increases in forest insect activity due to global change, these results represent important information for fire management agencies that can be used to refine existing models of fire risk. [ABSTRACT FROM AUTHOR]

The boreal biome, representing approximately one-third of remaining global forests, provides a number of crucial ecosystem services. A particular challenge in forest ecosystems is to reconcile demand for an increased timber production with provisioning of other ecosystem services and biodiversity. However, there is still little knowledge about how forest management could help solve this challenge. Hence, studies that investigate how to manage forests to reduce trade-offs between ecosystem services and biodiversity are urgently needed to help forest owners and policy makers take informed decisions., We applied seven alternative forest management regimes using a forest growth simulator in a large boreal forest production landscape. First, we estimated the potential of the landscape to provide harvest revenues, store carbon and maintain biodiversity across a 50-year time period. Then, we applied multiobjective optimization to identify the trade-offs between these three objectives and to identify the optimal combination of forest management regimes to achieve these objectives., It was not possible to achieve high levels of either carbon storage or biodiversity if the objective of forest management was to maximize timber harvest revenues. Moreover, conflicts between biodiversity and carbon storage became stronger when simultaneously targeting high levels of timber revenues. However, with small reductions in timber revenues, it was possible to greatly increase the multifunctionality of the landscape, especially the biodiversity indicators., Forest management actions, alternative to business-as-usual management, such as reducing thinnings, extending the rotation period and increasing the amount of area set aside from forestry may be necessary to safeguard biodiversity and non-timber ecosystem services in Fennoscandia., Synthesis and applications. Our results show that no forest management regime alone is able to maximize timber revenues, carbon storage and biodiversity individually or simultaneously and that a combination of different regimes is needed to resolve the conflicts among these objectives. We conclude that it is possible to reduce the trade-offs between different objectives by applying diversified forest management planning at the boreal landscape level and that we need to give up the all-encompassing objective of very intensive timber production, which is prevailing particularly in Fennoscandian countries. [ABSTRACT FROM AUTHOR]