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Abstract: Postfire tree species compositions are predicted to be the same prior to fire according to the direct regeneration hypothesis (DRH). We studied 94 upland boreal forest stands between 5 and 18 years after fire in Ontario, Canada. Postfire species-specific regeneration density was positively related to prefire stand basal area for Pinus banksiana, Populus spp., Betula papyrifera and Picea mariana, but not for Picea glauca and Abies balsamea. In addition, seedling density of Populus spp., B. papyrifera, P. mariana, P. glauca and A. balsamea were positively affected by build up index and, except Populus spp., their density increased with age of burn. To facilitate testing the DRH, we introduced a term called compositional difference (CD) that is the difference in a species relative percentage between the postfire and prefire stand. The testable null hypothesis is CD=0 for a given species. CD was not different from 0 for P. banksiana, was 19.8% for Populus spp., 10.4% for B. papyrifera, −17.9% for P. mariana, −14.6% for P. glauca, and −14.9% for A. balsamea, indicating fire increases broadleaves at the expenses of mid- and late-successional coniferous species. Compositional increases of Populus spp. and B. papyrifera in postfire stands occurred mostly where these species were a minor component prior to fire. In conclusion, the DRH was supported by the specific positive relationships between postfire regeneration densities and prefire basal area for P. banksiana, Populus spp., B. papyrifera and P. mariana. However, if the DRH is used for predicting postfire composition, P. banksiana is the only species that had the same composition between postfire and prefire stands. Nevertheless, CD for P. banksiana was negatively related to its prefire composition. Similarly, CD for other species was negatively related to their prefire compositions with varying effects of build up index and age of burn. Our results suggest, if fire occurrences increase with global change, the boreal landscape will be more dominated by hardwoods and mixtures of conifers and hardwoods. [Copyright &y& Elsevier]

Background: Protected areas (PA) are central to biodiversity, but their efficiency is challenged by human-induced habitat loss and fragmentation. In the Fennoscandian boreal region, forestry with clearcutting is a threat to biodiversity causing the loss of mature forest elements and deterioration of ecological processes in forest landscapes, ultimately affecting PAs via declined structural connectivity. This paper aims to (1) determine PAs with high, red-listed species concentrations; (2) estimate the change in forest habitat around these PAs on different spatial scales; and (3) determine if forest management intensity is higher around biologically most valuable PAs. Occurrences of red-listed forest-dwelling species in Finland were used to identify PAs harbouring these species and to produce site-specific importance indices. CORINE landcover data was used as a baseline for the distribution of forests to assess the cover of clear-cuttings from 2001 to 2019 with the Global Forest Change (GFC) data set in three buffer areas around the PAs with occurrences of red-listed species. Results: The largest proportion of clear-cuts occurred in 1 km and 10 km buffers around the PAs in the southern and middle boreal zones, being ca. 20%. This indicates that the forest habitat is degrading fast at regional and landscape levels. On the positive side, the change in forest cover was lower around the biologically most important PAs compared to other PAs with red-listed species. Conclusions: Open and free satellite-data based assessments of the cover and change of forests provide reliable estimates about the rates at which mature and old-growth forests are being converted into young managed ones in Finland mainly via clear-cuts on different scales around PAs. The rate of clear-cuts was lowest in adjacent buffer areas next to the most species-rich PAs, which provides opportunities for biodiversity conservation efforts to be targeted to the remaining mature and old-growth forests found in the vicinity of these areas. [ABSTRACT FROM AUTHOR]

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

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

Isle Royale National Park (IRNP) is an archipelago in west central Lake Superior. In 2010, the National Park Service Great Lakes Inventory and Monitoring Network initiated a long-term monitoring program at IRNP with the goals being to: ( 1 ) determine the current forest structure, (2) assess how succession and climate change will impact species assemblages, and (3) develop realistic management targets related to climate change impacts on IRNP forests. Five forest types were identified, with three of these (sugar maple {Acer saccharum Marsh.)/birch, eastern white cedar {Thuja occidentalis L), and balsam fir {Abies balsamea (L.) Mill.)) being climax types with little likelihood of succeeding into any other type over the next two to three decades. Two forest types (white spruce {Picea glauca (Moench) Voss),/trembling aspen {Populus tremuloides Michx.), and paper birch {Betula papyrifera Marsh.)) were in a state of transition. The long-term (> 50 year) successional pathways of all five forest types will be influenced by climate change, species' migration abilities, and disease. Many dominant species currently on the island, including balsam fir, black spruce {Picea mariana (Mill.) Britton, Sterns & Poggenb.), and white spruce, are expected to become extirpated, while the abundance of other common species, including paper birch and trembling aspen, is expected to decline. The 21 km distance between the mainland and the islands will prohibit timely immigration of new species onto the island in the face of climate change. Immigration will likely be led by avian-dispersed species {Prunus spp., exotic Lonicera spp., and Rhamnus cathartica, another exotic species) with dispersal of other taxa relying on stochastic events or human transport. Managers should consider assisted migration to ensure that species assemblages remain congruent; otherwise, stable ecosystems dominated by a few non-native taxa may result. This is especially relevant on the eastern side of the island where balsam fir forests dominate in shallow, bedrock-derived soils. [ABSTRACT FROM AUTHOR]

Forecasts of future resource states are central to resource management planning. Many simulation models and planning tools are used to produce such forecasts and apply knowledge of resource change dynamics as key input. Consistency among knowledge sources is therefore important to avoid knowledge ambiguity and uncertainty in resource forecasts and management plan outcomes. Using Ontario's boreal forest landscape as a case study, this paper examined two knowledge sources of forest resource change, practitioner expertise and research studies, commonly applied in plans and policies for large forest landscapes. The two knowledge sources were quantitatively compared by constructing networks of forest cover change for both sources and determining their agreement in structure and transition times. Some networks agreed well, indicating little knowledge ambiguity and comparatively low uncertainty if they were used to forecast forest landscapes. Other networks showed low agreement, thus indicating higher knowledge ambiguity and a dilemma of choice for forest landscape planners who may have to select from these knowledge sets. It is suggested that knowledge disagreements may be widespread in knowledge-driven management planning of many natural resource types and their causes similar. These disagreements signal areas of knowledge uncertainty, where resource planners must address resulting uncertainty of management outcomes and research should focus on improving resource change knowledge. [ABSTRACT FROM AUTHOR]

Recent interest in sustainable forest management planning in the Yukon has coincided with growing public awareness of climate change, providing an opportunity to explore how forestry plans are incorporating climate change. In this paper, the Strategic Forest Management Plans for the Champagne and Aishihik First Nations Traditional Territory (CATT) and the Teslin Tlingit Traditional Territory (TTTT) are examined for evidence of adaptation to climate change. For each plan, management policies and practices that are also recognized as ways to adapt to climate change are identified to provide information on the incremental costs and benefits of additional adaptation efforts. A typology for classifying sustainable forest management plans according to how they address climate change is proposed and applied to the CATT and TTTT plans. This typology, which may be useful to any future retrospective assessments on how successful these or other sustainable forest management plans have been in addressing and managing the risks posed by climate change, consists of a matrix that categorizes plans into one of four types; (1) proactive-direct, (2) proactive-indirect, (3) reactive-direct, and (4) reactive-indirect. Neither of the plans available for the southern Yukon explicitly identifies climate change vulnerabilities and actions that will be taken to reduce those vulnerabilities and manage risks. However, both plans have incorporated some examples of 'best management practices' for sustainable forest management that are also consistent with appropriate climate adaptation responses. Even in a jurisdiction facing rapid ecological changes driven by climate change, where there is a relatively high level of awareness of climate change and its implications, forestry planning processes have yet to grapple directly with the risks that climate change may pose to the ability of forest managers to achieve the stated goals and objectives of sustainable forest management plans. [ABSTRACT FROM AUTHOR]

Balsam fir (Abies balsamea) and black spruce (Picea mariana) forests are the main conifer forest types in the North American boreal zone. The coexistence of the two species as well as their respective canopy dominance in distinct stands raises questions about the long-term evolution from one forest type to the other in relation to environmental factors including climate and stand disturbance. We tested the hypothesis that repetitive fire events promote the succession of balsam fir forest to black spruce forest and vice versa. Postfire chronosequences of one black spruce (BSP) and one balsam fir (BFI) sites were reconstructed based on the botanical composition and 14C-dated soil macrocharcoals. The results support the hypothesis of a successional dynamics. The BSP site has been affected by fires for the last 7600 years, whereas the BFI site, after having been impacted by several fires during the first half of the Holocene, evolved in a fire-free environment for the last 4400 years. Periods of fire activity facilitated the dominance of black spruce forests. The cessation of fires around 4400 cal. years BP on BFI site marks the beginning of the transition from black spruce to balsam fir stands. This succession is a long process, due to the ability of black spruce to regenerate by layering in the absence of fire. The resulting balsam fir stands are ancient and precarious ecosystems, since fire generally leads to the return of black spruce. The increase in balsam fir to the detriment of black spruce in boreal forests is a response to a decrease in fire frequency. [ABSTRACT FROM AUTHOR]

The rotation forestry system provides high biomass production, but could also have a negative impact on species sensitive to disturbance. Continuous cover forestry (CCF) could contribute to solving these conflicting goals, but its feasibility in nutrient limited boreal forests is yet unresolved. In a unique experiment, we simultaneously assessed the short-term effect of single-tree selection on both biomass production and biodiversity (vascular plants, bryophytes, wood-inhabiting fungi), and tested fertilization as a way to mediate growth-biodiversity trade-offs. We found that unharvested stands and stands subjected to single-tree selection had a similar species assemblage of vascular plants, bryophytes, and wood-inhabiting fungi. Fertilization increased growth by 37% and induced shifts in two understory species (favoring the grass Avenella flexuosa and disfavoring the bryophyte Hylocomium splendens). We conclude that single-tree selection may become a useful tool to enhance biodiversity in managed forests. [ABSTRACT FROM AUTHOR]

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

Much of Canada's terrestrial biodiversity is supported by boreal forests. Natural resource development in boreal forests poses risks to this biodiversity. This paper reviews the scientific literature to assess the effects of natural resource development on terrestrial biodiversity in Canadian boreal forests. We address four questions: (1) To what extent have Canadian boreal forests changed due to natural resource development? (2) How has biodiversity responded to these changes? (3) Will the biodiversity of second-growth forests converge with that of primary boreal forests? (4) Are we losing species from boreal forests? We focus on trees, understory plants, insects, fungi, selected mammals, and songbirds because these groups have been most studied. We review more than 600 studies and found that changes in community composition are prevalent in response to large-scale conversion of forest types, changes in stand structures and age distributions, and altered landscape structure resulting from forest management and habitat loss associated with other developments such as oil and gas, hydroelectric, and mining. The southern boreal forest has been more highly impacted than the north due to more extensive forest management and the cumulative effects of multiple forms of development. There is abundant evidence that most species are not in danger of being extirpated from the boreal forest due to these anthropogenic changes. A few species, including woodland caribou ( Rangifer tarandus) and grizzly bear ( Ursus arctos), have, however, undergone long-term range contractions. Significant gaps in our ability to assess the effects of natural resource development on biodiversity in the boreal zone are the lack of long-term spatial and population data to monitor the impact of forest changes on ecosystems and species. [ABSTRACT FROM AUTHOR]

Climate change is affecting Canada's boreal zone, which includes most of the country's managed forests. The impacts of climate change in this zone are expected to be pervasive and will require adaptation of Canada's forest management system. This paper reviews potential climate change adaptation actions and strategies for the forest management system, considering current and projected climate change impacts and their related vulnerabilities. These impacts and vulnerabilities include regional increases in disturbance rates, regional changes in forest productivity, increased variability in timber supply, decreased socioeconomic resilience, and increased severity of safety and health issues for forest communities. Potential climate change adaptation actions of the forest management system are categorized as those that reduce nonclimatic stressors, those that reduce sensitivity to climate change, or those that maintain or enhance adaptive capacity in the biophysical and human subsystems of the forest management system. Efficient adaptation of the forest management system will revolve around the inclusion of risk management in planning processes, the selection of robust, diversified, and no-regret adaptation actions, and the adoption of an adaptive management framework. Monitoring is highlighted as a no-regret action that is central to the implementation of adaptive forest management. [ABSTRACT FROM AUTHOR]

Across forest ecosystems worldwide, alternative silvicultural practices such as partial or “structural retention” harvesting are gaining increasing use as means to balance economic and ecological management goals. Recent studies have documented highly elevated rates of residual-tree mortality and growth, both of which are likely to influence post-harvest stand development. Explicit consideration of residual-tree responses to partial harvest is therefore required to make accurate growth and yield predictions. In this paper we incorporate empirically based, spatially explicit tree growth and mortality predictors into a forest simulation model in order to quantify stand dynamics following a range of simulated partial harvests. We consider lowland black spruce boreal forests and use a common strip-cutting technique, Harvest with Advance Regeneration Protection, as a reference against which to compare alternative scenarios. Predicted stand development proceeded most rapidly in scenarios with reduced skidding impacts and relatively high levels of retention, since these treatments were associated with lower residual-tree mortality rates and larger growing stocks respectively. Stand development was also influenced on a proportional basis by residual-tree growth rates, which increased with declining neighbourhood competition. Across a range of harvest scenarios with equivalent retention levels (20%), differences in residual-tree responses among treatments led to a 35-year range in projected basal area return intervals (70–105 years). Our results demonstrate that short-term responses of residual trees affect stand development rates over long (>100-year) time scales, and show that post-harvest stand recovery rates are influenced not only by the retention level but also by the specific parameters of partial harvest prescriptions, including the layout of skid trails and the spatial arrangement of residual trees. Results from this study provide essential information for evaluating partial harvests in the black spruce boreal forest and supply modelling tools for assessing alternative silvicultural treatments in other forest ecosystems. [Copyright &y& Elsevier]

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

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

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

Statistical models relating habitat characteristics to species occurrences are increasingly used to evaluate the consequences of forest management activities and conservation plans over large spatial and temporal scales. In practice, such models do not always generalize to other locations, hence, they should be validated using independent data. In this paper, we assess the predictive ability of 16 songbird habitat models developed in the Calling Lake region of the boreal mixedwood forest of Alberta using both internal and external validation approaches. Internal validation relied on the same dataset used to develop the models while external validation utilised independent data collected within four validation landscapes in the same ecological region. Two aspects of predictive accuracy were evaluated: the agreement between observations and predicted values (calibration) and the models’ ability to classify locations into those in which species are present or absent (discrimination). Calibration was assessed using the Hosmer–Lemeshow (H–L) statistic and plots showing predicted versus observed probabilities of occurrence. Discrimination was assessed using receiver operating characteristic (ROC) curves and the associated area under the ROC curve. With internal validation, the calibration plots were reasonable for all species, however the H–L statistic indicated a good fit for only eight species. Model discrimination between occupied and unoccupied sites, on the other hand, was reasonable for 14 of 16 models. With external validation, both the calibration plots and the H–L statistic identified only three species with a reasonable fit. The remaining models generally over- or under-predicted probability of occurrence. External model discrimination was reasonable for 10 of 16 species. When we re-estimated the models using all available data, the calibration plots were again reasonable for all species, with the H–L statistic indicating good fit for 12 species. Similarly, model discrimination was reasonable for 14 of 16 species. Several factors may help to explain why model performance using external data was generally poorer and more variable than when using internal data. These include differences in landscape structure and disturbance history as well as differences in the frequency of occurrence of individual species. Overall, our analyses identified several species whose habitat models degraded considerably, especially as measured by calibration. By re-estimating the models, we increased the range of variation in our covariates which likely led to an improvement in model calibration. We discuss the importance of ongoing evaluation and refinement of habitat models that will be used in conservation planning or to evaluate management scenarios at large spatial and temporal scales. [Copyright &y& Elsevier]

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

The article focuses on lichen colonization. Branches are well suited for studying lichen colonization as new substrate is added to the branch each year. However, few papers have focused on ecology and dynamics of lichen colonization, and no earlier publications have focused on how environmental changes, caused by logging, influence diaspore attachment and establishment in boreal spruce forests. Increased knowledge about how forestry influences lichen colonization is a prerequisite for developing appropriate forestry methods aimed to maintain species diversity. The survival of a lichen population is influenced by the species' ability to reproduce, to colonize new substratum, and to grow under changing environmental conditions. Foliose and fruticose epiphytic lichens in boreal spruce forest reproduce mainly asexually by dispersal of vegetative diaspores. Vegetative diaspores, such as soredia and isidia, are generally considered advantageous for rapid colonization on the substratum. However, poor dispersal of diaspores has often been postulated as limiting for development of populations of different epiphytic species.

Greater fibre yields may be possible in commercial forests through an increased application of post-harvest silvicultural techniques. In Canadian boreal forests, while basic silvicultural regeneration techniques such as planting, seeding, scarifying, and tending, have been employed since the 1940’s, more intensive techniques (intensive forest management (IFM)) such as increased area planted, pre-commercial and commercial thinning, extra tending events, fertilizing, and short rotations may soon be used. There may be effects of basic and more intensive silviculture on biodiversity in the long-term, compared to natural regeneration following logging or especially stand development following natural disturbances. We reviewed approximately 50 papers that reported studies of the long-term effects of post-harvest silviculture on vertebrate wildlife. In particular, large impacts to biodiversity universally occur when native forest types are replaced by rapidly-growing exotic tree species. However, in boreal forests, native tree species are usually planted, and so any effects on associated wildlife communities may be considerably less than in non-native species plantations. Limited long-term information is available, but published studies of effects of basic silviculture and IFM suggested that loss of structures in forest stands was an important common impact that resulted in vertebrate species responses. Fewer structural features in managed forests compared to in natural forests likely results in reduced numbers of animal species dependent on those structures, such as cavity-using species and species for which large decaying woody debris is important. Simplifying stand structures and species composition may result in systems with low connectivity, making them vulnerable to insect and mammalian herbivory. Concentration of IFM in stands on highly productive sites could exacerbate effects (positive or negative), owing to the positive relationship between forest productivity and animal and plant diversity. Species such as black-backed woodpeckers (Picoides arcticus) may be reduced over large areas by stand conversion to mixedwoods, stand structural changes and especially age-class truncation. On the other hand, IFM may contribute increased habitats to species favoring young to mature coniferous-dominated forests, that normally decline across a landscape following clearcutting in boreal mixed and upland conifer stands. An aspatial model, based on published and local information and expert opinion, suggested that IFM and post-harvest silviculture in Ontario’s boreal forests would produce positive and negative species-specific effects on the vertebrates that we modeled. However, IFM appeared to result in little increased effect over basic post-harvest silviculture. We also expect that stand-level effects of IFM on species would accumulate through time over landscapes, as more stands come under intensive management and the level of effects will be cumulative. [Copyright &y& Elsevier]

Summary: This paper presents a synthesis of the dendroecological work conducted in the area of Lake Duparquet in the southern boreal forest of northwestern Quebec (Canada) during the last 15 years. The topics of these syn- and autecological studies encompassed forest dynamics and tree growth related to natural disturbances such as forest fires, insect outbreaks, and flooding, as well as the effects of climate change. Seven major fire events occurred around Lake Duparquet since 1720: 1760, 1797, 1823, 1847, 1870, 1916, and 1944. Post-fire stand dynamics, established by a chronosequence of over 200 years, are characterized by the gradual transition from broadleaf dominated stands towards mixed and finally almost pure conifer stands. After fire, insect outbreaks are the second most important disturbance type in the southern boreal forest. Spruce budworm, the predominating defoliating insect, but also forest tent caterpillar and larch sawfly have major impacts on growth and stand dynamics of their respective host species. Global warming since the end of Little Ice Age around 1850 coincided with increasing precipitation and, hence, decreasing droughts in the southeastern boreal area of North America. The accelerated radial growth of eastern white-cedar and black ash at Lake Duparquet is a direct effect of these wetter climatic conditions. Population dynamics and forest composition, however, are rather indirectly affected by climate change through the alteration of the natural disturbance regimes, i. e., the decreased frequency and size of the forest fires and the increased frequency and amplitude of the spring floods. Potential consequences of future global warming on disturbance dynamics and forest composition are briefly discussed. The results of the dendroecological studies contributed to the elaboration of a natural-disturbance based forest management model for the southern boreal forest of Quebec. [Copyright &y& Elsevier]

There is ample evidence that intensive management of ecosystems causes declines in biodiversity as well as in multiple ecosystem services, i.e., in multifunctionality. However, less is known about the permanence and reversibility of these responses. To gain insight into whether multifunctionality can be sustained under intensive management, we developed a framework building on the concept of resilience: a system's ability to avoid displacement and to return or transform to a desired state. We applied it to test the ability of forest multifunctionality to persist during and recover from intensive management for timber production in a boreal forest. Using forest growth simulations and multiobjective optimization, we created alternative future paths where the forest was managed for maximal timber production, for forest multifunctionality, or first maximal timber production and then multifunctionality. We show that forest multifunctionality is substantially diminished under intensive forestry and recovers the slower, the longer intensive forestry has been continued. Intensive forestry thus not only reduces forest multifunctionality but hinders its recovery should management goals change, i.e., weakens its resilience. The results suggest a need to adjust ecosystem management according to long-term sustainability goals already today. [ABSTRACT FROM AUTHOR]

The microclimate of streamside habitats are protected from the effects of logging with buffer strips of retained trees. However, these buffer strips are often narrow due to their financial loss. Wider, selectively logged buffers might protect the microclimate while providing the same economic return. This study investigates the effects of logging on the microclimate and the growth of the bryophyte Hylocomium splendens on two streamside buffers: a standard unlogged narrow buffer (∼15 m) and a wider buffer (∼30 m) selectively logged with decreasing intensity towards the stream. The study was conducted in Central Finland on eight sites where the two buffers were logged next to each other. The near-stream change in air temperature and relative humidity was measured from pre-logging to post-logging. Additionally, post-logging microclimate gradients and the growth of H. splendens was measured on a 30 m transect away from the stream. The results showed no significant differences in the ability of the two kinds of buffers in maintaining streamside microclimate, and neither buffer seems to protect the microclimate from the negative effects of logging. The growth of H. splendens also decreased in both buffers. We conclude that wider, unlogged buffer strips are required to protect riparian forest microclimate. [ABSTRACT FROM AUTHOR]

Retention harvests are preferred over traditional clear‐cuts for sustainable forest management because maintenance and re‐establishment of native forest biodiversity is a priority. However, few studies have examined long‐term responses of biotic assemblages to retention harvest at particular sites.We studied the effects of decreasing initial harvest intensities (clear‐cut, 10%, 20%, 50% and 75% dispersed green‐tree retention) on carabid beetle assemblages relative to assemblage changes in un‐harvested control stands in four successionally ordered cover‐types of boreal mixedwood forest. We also studied temporal effects by comparing assemblages over a 16‐year pre‐ and post‐harvest period, using data collected through monitoring of the EMEND (Ecosystem Management Emulating Natural Disturbance) experiment in NW Alberta, Canada.Retention harvests affected assemblages differently across cover‐types. Assemblages in compartments harvested in the earlier forest successional stages of 'deciduous' or 'deciduous with spruce understorey' converged towards the pre‐harvest structure of corresponding controls over time. In contrast, beetle assemblages in 'mixed' or 'conifer' compartments, that represent later successional forest, moved steadily away from their pre‐harvest structures during the first post‐harvest decade. These latter assemblages became strikingly more similar to those under deciduous canopies by 15‐year post‐harvest.Synthesis and applications. Variable retention harvests will promote and maintain biodiversity better than clear‐cutting. Higher retention levels promote faster recovery, but towards fauna typical of early successional forest in all cover‐types. Carabids associated with conifer habitats are less resistant to impact from harvesting than are those from broadleaf deciduous forest. Therefore, conifer‐dominated stands present the most significant management challenge and higher retention levels are required to promote rapid and effective faunal recovery in such late successional stands. [ABSTRACT FROM AUTHOR]

Key message: Forest owners who maximize profitability with a low discount rate or whose management goals are related to conservation and recreation, rarely sell timber. These owners make it difficult to achieve the high harvesting targets of the growing bioeconomy sector of Finland. To increase timber supply, these landowners should be informed about alternative silvicultural methods. Context: The round wood harvests from Finnish forests are increasing and approaching to the level of maximum sustainable cut. Cutting budget calculations assume that forests are harvested in an optimal way for national timber supply. The calculations ignore the variability of landowners' forest management preferences. Aims: This study analyzed the effect of variation in the management objectives and silvicultural preferences of forest landowners on the forecasted timber supply from Finnish forests. Methods: Forest owners were divided into savers (net present value maximized with a 1% discount rate), average owners (3% discount rate), and investors (5% discount rate). The owners of each group were further divided into three groups: those who allow only continuous cover management (12%), owners who use only rotation forest management (10%), and indifferent landowners who may use both silvicultural systems (78%). Scenarios were composed of management prescriptions that were optimized separately for the different groups of forest landowners. Results: Compared to the even-flow timber drain scenario for rotation forest management (calculated without acknowledging the varying preferences of landowners), the scenario where the owners' preferences varied decreased harvested volume by 15–19% during a 100-year calculation period. The main reason for the difference was the saver type of landowners who rarely sell timber. Conclusion: It was concluded that variation of the preferences of forest landowners may make it challenging to meet the increasing harvesting targets of the growing bioeconomy of Finland. [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]

Managing competing vegetation is crucial in stand establishment strategies; forecasting the abundance, composition, and impact of competing vegetation after harvesting is needed to optimize silviculture scenarios and maintain long-term site productivity. Our main objective was to identify factors influencing the short-term abundance and composition of competing vegetation over a large area of the Canadian boreal forest. Our second objective was to better understand the mid-term evolution of the regeneration/competing vegetation complex in cases of marginal regeneration conditions. We used operational regeneration surveys of 4471 transects sampled ≈5 years after harvesting that contained data on regeneration, competing vegetation, elevation, ecological classification, soil attributes, and pre-harvest forest stands. We performed a redundancy analysis to identify the relationships between competing vegetation, harvesting and biophysical variables. We then estimated the probability of observing a given competing species cover based on these variables. In 2015, we re-sampled a portion of the sites, where conifer regeneration was marginal early after harvesting, to assess the temporal impact of different competing levels and species groups on the free-to-grow stocking, vigour and basal area of softwood regeneration. Results from the first inventory showed that, after careful logging around advance growth, ericaceous shrubs and hardwoods were not associated with the same sets of site attributes. Ericaceous shrubs were mainly found on low fertility sites associated with black spruce (Picea mariana (Mill.) BSP) or jack pine (Pinus banksiana Lamb.). The distinction between suitable environments for commercial shade-intolerant hardwoods and non-commercial hardwoods was less clear, as they responded similarly to many variables. Analysis of data from the second inventory showed a significant improvement in conifer free-to-grow stocking when commercial shade-intolerant hardwood competing levels were low (stocking 0%–40%) and when ericaceous shrubs competing levels were moderate (percent cover 26%–75%). In these conditions of marginal regeneration, the different types and intensities of competition did not affect the vigour or basal area of softwood regeneration, 9–14 years after harvesting. [ABSTRACT FROM AUTHOR]

Aim: Information on the amount of carbon stored in the living tissue of tree stems (sapwood) is crucial for carbon and water cycle applications. Here, we aim to investigate sapwood‐to‐stem proportions and differences therein between tree genera and derive a sapwood biomass map. Location: Northern Hemisphere boreal and temperate forests. Time period: 2010. Major taxa studied: Twenty‐five common tree genera. Methods: First, we develop a theoretical framework to estimate sapwood biomass for a given stem biomass by applying relationships between sapwood cross‐sectional area (CSA) and stem CSA and between stem CSA and stem biomass. These measurements are extracted from a biomass and allometry database (BAAD), an extensive literature review and our own studies. The established allometric relationships are applied to a remote sensing‐based stem biomass product in order to derive a spatially continuous sapwood biomass map. The application of new products on the distribution of stand density and tree genera facilitates the synergy of satellite and forest inventory data. Results: Sapwood‐to‐stem CSA relationships can be modelled with moderate to very high modelling efficiency for different genera. The total estimated sapwood biomass equals 12.87 ± 6.56 petagrams of carbon (PgC) in boreal (mean carbon density: 1.13 ± 0.58 kgC m−2) and 15.80 ± 9.10 PgC in temperate (2.03 ± 1.17 kgC m−2) forests. Spatial patterns of sapwood‐to‐stem biomass proportions are crucially driven by the distribution of genera (spanning from 20–30% in Larix to > 70% in Pinus and Betula forests). Main conclusions: The presented sapwood biomass map will be the basis for large‐scale estimates of plant respiration and transpiration. The enormous spatial differences in sapwood biomass proportions reveal the need to consider the functionally more important sapwood instead of the entire stem biomass in global carbon and water cycle studies. Alterations in tree species distribution, induced by forest management or climate change, can strongly affect the available sapwood biomass even if stem biomass remains unchanged. [ABSTRACT FROM AUTHOR]

The climate of the circumpolar Boreal forest is changing rapidly, resulting in a growing frequency of wildfires and changing precipitation patterns. These climate-related stressors may influence the cycling of nutrients within, and overall ecosystem condition of, Boreal watersheds. However, long-term perspectives of concurrent climate-related impacts on the cycling of nutrients in watersheds are rare. We present multi-decadal terrestrial and lake mass budgets of nitrogen, phosphorus and carbon within a headwater Boreal Shield watershed that was recovering from an extensive wildfire while experiencing measureable increases in annual precipitation. We used these budgets to quantify associations between nutrient retention in each ecosystem and changes in metrics defining landscape recovery after wildfire or precipitation. The terrestrial watershed retained over half of all nitrogen and phosphorus delivered to it by the atmosphere. Strong nutrient retention occurred despite ongoing landscape recovery from wildfire, measurable increases in precipitation, a forest tent caterpillar defoliation and rising atmospheric deposition. A downstream headwater lake was also a strong and consistent sink of nitrogen and phosphorus, highlighting a whole-watershed resistance to environmental disturbances. However, carbon was strongly lost downstream from the terrestrial ecosystem in close and positive association with precipitation, resulting in a darkening of the headwater lake over time with implications for the functioning of its ecosystem. Long-term mass budget monitoring of a Boreal catchment has provided insight into the resistances and dynamic changes within a northern watershed exposed to concurrent wildfire and increasing precipitation conditions. [ABSTRACT FROM AUTHOR]

The importance to consider changes in surface albedo and go beyond simple carbon accounting when assessing climate change impacts of forestry and land use activities is increasingly recognized. However, representation of albedo changes in climate models is complex and highly parameterized, thereby limiting their applications in climate impact studies. The availability of simple yet reliable albedo models can enhance consideration of albedo changes in land use studies. We propose a set of simplified models for estimating surface albedo in a boreal forest. We process and harmonize datasets of remotely‐sensed albedo estimates, forest structure parameters, and meteorological records for different forest locations in Norway. By combining linear unmixing with nonlinear programming, we simultaneously produce albedo estimates at the same resolution of the land cover dataset (16 m, notably higher than satellite retrievals) and a variety of flexible models for albedo predictions. We test different combinations of functional forms, variables, and constraints, including variants specific for snow‐free conditions. We find that models capture the seasonal pattern of surface albedo and the interactive effect of forest structures and meteorological parameters, and many of them show good statistical scores. The cross‐validation exercise shows that the models derived from one area perform reasonably well when applied to other forested areas in Norway, regardless of the temporal and spatial scales. By incorporating changes in forest structure and climate conditions as explicit variables, these models are simple to be used in different applications aiming at estimating albedo changes from forest management and climate change. Plain Language Summary: Surface albedo is the fraction of solar radiation reflected back into the atmosphere by a surface, and it determines how much energy is re‐distributed in the biosphere. It is one of the most important physical properties of land cover and a key mechanism for climate control. By combining satellite retrievals of Norwegian boreal forest with high resolution land cover data and meteorological records, our study produces a range of relatively simple models to estimate surface albedo using the forest structure parameters and climate data. The models require simple variables of forest structure information (age and/or volume) and temperature and/or snow water equivalents. These models are relatively easy and fast to be used for quantifying effects of forest management and climate change on surface albedo. Key Points: Availability of models for simulating surface albedo changes in climate impact assessment studies of forest management is limitedA set of flexible models based on forest and climate variables can predict albedo changes from forest management and climate changeThe models capture the seasonal pattern of surface albedo and the interactive effects of forest structure and meteorological parameters [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]

The boreal forest plays a critical role in regulating global atmospheric carbon dioxide and is highly influenced by wildfire. However, the long-term recovery of forest carbon (C) storage following wildfire remains unclear, especially during late succession. Uncertainty surrounding C storage in old forests largely stems from both a lack of repeated measurements in forest stands older than the longevity of the pioneer cohort and a lack of consideration of multiple succession pathways. In this study, we constructed a replicated chronosequence, which covered a wide range of forest stand age classes (up to 210 years old) following fire in the boreal forest of central Canada. We selected stands of different overstorey types (that is, broadleaf, conifer, or mixedwood) and age classes to account for multiple succession pathways known to occur in our study area. Our results show a strong relationship between total ecosystem C storage and stand age following fire. Broadleaf stands had on average higher total ecosystem C; however, the inferred temporal dynamics of total ecosystem C were similar among all three overstorey types. Importantly, we found that total ecosystem C storage declined from canopy transition to late-succession stages, irrespective of succession pathway, contradicting views that old forests continually accumulate C as they age. Our findings emphasize that further study of stands older than the longevity of the pioneer cohort is critical to better understand the contribution of old forests to the global C cycle. [ABSTRACT FROM AUTHOR]

Globally, intensive forestry has led to habitat degradation and fragmentation of the forest landscape. Taking Sweden as an example, this development is contradictory to international commitments, EU obligations, and to the fulfillment of the Parliament's environmental quality objective "Living Forests", which according to Naturvårdsverket (The Swedish Environmental Protection Agency) will not be achieved in 2020 as stipulated. One important reason for the implementation deficit is the fragmented forestry management. In a forest landscape, felling and other measures are conducted at different times on separate forest stands (often relatively small units) by different operators. Consequently, the authorities take case by case decisions on felling restrictions for conservation purposes. In contrast, conservation biology research indicates a need for a broad geographical and strategical approach in order to, in good time, select the most appropriate habitats for conservation and to provide for a functioning connectivity between different habitats. In line with the EU Commission, we argue that landscape forestry planning could be a useful instrument to achieve ecological functionality in a large area. Landscape planning may also contribute to the fulfilment of Sweden's climate and energy policy, by indicating forest areas with insignificant conservation values, where intensive forestry may be performed for biomass production etc. Forest owners should be involved in the planning and would, under certain circumstances, be entitled to compensation. As state resources for providing compensation are scarce, an alternative could be to introduce a tax-fund system within the forestry sector. Such a system may open for voluntary agreements between forest owners for the protection of habitats within a large area. [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]

Key message: Selective logging affects climate sensitivity of Larix sibirica in the Mongolian forest-steppe mediated by changes in age and stand structure. Abstract: Climate warming increasingly limits the productivity of boreal forests via increased drought stress, especially at the southern fringe of the biome. The southernmost boreal forests are exposed to more intensive human disturbance than most forests at more northern latitudes. We asked the question of how forest use through logging and moderate forest grazing interferes with the climate response of the annual radial stem increment. We conducted a case study in Larix sibirica stands of the Mongolian forest-steppe involving two neighboring forest regions (20 km distance) differing in logging and grazing intensity. One site was subjected to heavy logging until 25 years ago and low intensity of livestock grazing; another site was exposed to moderate selective logging and higher, but still moderate livestock numbers. While the differences in grazing had no detectable effect, former heavy logging led to younger and more even-aged forest stands. Forests at both sites showed recent increases in missing-ring frequency, which probably indicated increased drought vulnerability. Climate-response analysis indicated that heavy logging 25 years ago was associated with high sensitivity of stemwood formation to high summer (especially June) temperatures. These findings suggest that: (1) recent logging under the conditions of climate warming has increased the sensitivity of tree growth to temperature in these southern boreal forests; (2) high replication at the stand level is needed to avoid bias in dendrochronological analyses in regions exposed to spatially heterogeneous logging intensities. [ABSTRACT FROM AUTHOR]

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

The reduction of competition through thinning increases radial growth in the stem and roots of many conifer species. However, not much is known about the effect of thinning on the dynamics of wood formation and intra-annual development of the growth ring, especially in the roots, which are an essential part of the tree for stability and resource acquisition. The aim of this study was to evaluate the effect of an experimental thinning on the dynamics and phenology of xylogenesis in the stem and roots of black spruce and balsam fir. Experimental and control trees were selected in two mature even-aged stands, one black spruce (Picea mariana (Mill.) BSP) and one balsam fir (Abies balsamea (L.) Mill.). Wood microcores were collected weekly in the stem and roots from May to October for a period of 4 years. The onset and ending of each cell differentiation phase were computed, as well as growth rate and total cell production. Results show that thinning increased the cell production rate of stem and roots of black spruce and balsam fir. This higher daily growth rate caused an increase in the total number of cells produced by the cambium. The intensity of the treatment was sufficient to significantly increase light availability for residual trees, but insufficient to modify soil temperature and water content to a point at which a significant change in the timing or duration of xylogenesis would be induced. Thus, thinning increased cell production rate and total number of cells produced in both stem and roots, but did not result in a change in the phenology of wood formation that could lead to increased risks of frost damage in the spring or autumn. [ABSTRACT FROM AUTHOR]

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

Background: After their death, Scots pine trees can remain standing for decades and sometimes up to 200 years, forming long-lasting and ecologically important structures in boreal forest landscapes. Standing dead pines decay very slowly and with time develop into 'kelo' trees, which are characterized by hard wood with silvery-colored appearance. These kelo trees represent an ecologically important, long lasting and visually striking element of the structure of natural pine-dominated forests in boreal Fennoscandia that is nowadays virtually absent from managed forest landscapes. Methods: We examined and mapped the amount, structural features, site characteristics and spatial distribution of dead standing pine trees over a ten hectare area in an unmanaged boreal forest landscape in the Kalevala National Park in Russian Viena Karelia. Results: The mean basal area of dead standing pine trees in the forested part of the landscape was 1.7 m∙ha and the estimated volume 12.7 m∙ha. From the total number of standing dead pine trees 65% were kelo trees, with a basal area of 1.1 m∙ha and volume of 8.0 m∙ha, the remainder consisting of standing dead pines along the continuum between a recently dead tree and a kelo tree. Overall, standing dead pines were distributed throughout the study area, but there was a tendency towards spatial clustering up to <100 m distances. Standing dead pines were most commonly situated on flat ground or in the mid slope in the local topography. In addition, standing dead pines contributed to substrate diversity also by commonly having charred wood and broken tops. Based on the presence of dead pine snags in different stage of transition from a recently dead pine to a kelo with silvery surface, it seems evident that the process of kelo recruitment was continuously in action in the studied landscape. Conclusions: Kelo trees are an omnipresent feature in natural pine-dominated forest landscapes with important contribution to forest structural and substrate diversity. Because of their longevity and extremely slow turnover dynamics and importance for biodiversity, protection of vulnerable kelo tree populations, and ensuring their continuous recruitment, should be of high priority in forest restoration and sustainable management. [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]

Knowing the historical variation in fire regimes is instrumental in managing forests today and in predicting what may happen in the future. By cross-dating 745 fire scars in 378 samples of remnant Scots pines, we delineated 254 individual forest fires during the past 700 years in a 74-km2 section of Trillemarka-Rollagsfjell Nature Reserve in south-central Norway. Fire sizes, numbers, burn rates, and frequencies were compared with historical climate proxies, vegetation maps, and written sources. The results revealed patterns consistent with a predominantly climate-driven fire regime up to 1625, followed by periods of strong anthropogenic influence that increased fire frequency during 1600-1700s and diminished fires during 1800-1900s. This was documented by an abrupt increase in number of small fires from the early 1600s that markedly shortened fire intervals from a median of 73 to 37 yr. This shift in fire frequency coincided with a sudden appearance of early-season fires from 1625 and onward. Whereas late-season burn rate increased with summer temperature, no such relationship was found for early-season fires. These results were corroborated by written sources that describe anthropogenic forest fires and slash-and-burn cultivation expanding with the increasing population from the late 1500s and subsequently diminishing due to increasing timber values during 1700-1800s. Whereas human activity strongly influenced the fire regime at multidecadal to centennial scales, it was the interannual variability in climate that triggered large fire events, especially during the pre-1625 period. Prior to 1625, the percentage of years with fire tripled from 7% during cold summers (10-12°C) to 21% during warm summers (14-16°C). Burn rate increased even more, from 0.01% to 1.3% for the same temperature intervals. Ecologically, the post-1625 period is remarkable in such a way that human activity, first by greatly increasing fire frequency and subsequently almost eradicating fires, possibly influenced the fire regime to such an extent that it may be unprecedented for millennia. [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]

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

Human activities have exerted a powerful influence on the biogeochemical cycles of nitrogen (N) and carbon (C) and drive changes that can be a challenge to predict given the influence of multiple environmental stressors. This study focused on understanding how land management and climate change have together influenced terrestrial N storage and watershed inorganic N export across boreal and sub-arctic landscapes in northern Sweden. Using long-term discharge and nutrient concentration data that have been collected continuously for over three decades, we calculated the hydrologic inorganic N export from nine watersheds in this region. We found a consistent decline in inorganic N export from 1985 to 2011 over the entire region from both small and large watersheds, despite the absence of any long-term trend in river discharge during this period. The steepest declines in inorganic N export were observed during the growing season, consistent with the hypothesis that observed changes are biologically mediated and are not the result of changes in long-term hydrology. Concurrent with the decrease in inorganic N export, we report sustained increases in terrestrial N accumulation in forest biomass and soils across northern Sweden. Given the close communication of nutrient and energy stores between plants, soils, and waters, our results indicate a regional tightening of the N cycle in an already N-limited environment as a result of changes in forest management and climate-mediated growth increases. Our results are consistent with declining inorganic N efflux previously reported from small headwater streams in other ecosystems and shed new light on the mechanisms controlling these patterns by identifying corresponding shifts in the terrestrial N balance, which have been altered by a combination of management activities and climate change. [ABSTRACT FROM AUTHOR]

Inputs of anthropogenic mercury (Hg) to the environment have led to accumulation of Hg in terrestrial and aquatic ecosystems, contributing to fish Hg concentrations well above the European Union standards in large parts of Fennoscandia. Forestry operations have been reported to increase the concentrations and loads of Hg to surface waters by mobilizing Hg from the soil. This summary of available forestry effect studies reveals considerable variation in treatment effects on total Hg (THg) and methylmercury (MeHg) at different sites, varying from no effect up to manifold concentration increases, especially for the bioavailable MeHg fraction. Since Hg biomagnification depends on trophic structures, forestry impacts on nutrient flows will also influence the Hg in fish. From this, we conclude that recommendations for best management practices in Swedish forestry operations are appropriate from the perspective of mercury contamination. However, the complexity of defining effective policies needs to be recognized. [ABSTRACT FROM AUTHOR]

Intensive management of boreal forests has replaced natural disturbances, leading to losses of residual deadwood and saproxylic biodiversity. Declining population sizes have been well documented for insect groups such as bark and wood-boring beetles, whilst other groups such as flat bugs (Heteroptera: Aradidae) are less well-studied and little is known about their response to forest restoration. We conducted two restoration experiments addressing this lack of knowledge. We predicted the following responses to restoration: (1) artificial gap-creation and prescribed burning will attract more flat bugs than control stands, (2) increasing pre-burning fuel loads will have a positive influence on flat bug response to fire restoration. To test these predictions we conducted two field experiments; in Sweden we compared prescribed burning of standing forest with artificial gap-creation and in Finland we compared differing levels of fuel-load prior to burning. We found partial support for our first prediction, total numbers of flat bugs collected was higher in burned forest stands compared to controls in both countries. By contrast, gap-cutting only resulted in a marginal increase in the numbers and species of flat bugs collected. We found no support for our second hypothesis. The red-listed Aradus angularis and A. laeviusculus were primarily found in burned stands. Aradus betulae, A. betulinus and A. lugubris were more frequent in burned stands than gap-cuttings and untreated controls. Our study therefore suggests that ecological restoration, especially burning, is an efficient way of attracting flat bugs to suitable habitat, we therefore recommend ecological restoration to be incorporated in boreal forest management. [ABSTRACT FROM AUTHOR]

Retention forestry and prescribed burning aim to alleviate the negative effects of forestry on biodiversity by maintaining the structural elements of natural forests in managed forests. We present the long-term effects of these methods on polypore fungi, a taxonomic group that has been severely affected by forestry., Using a 10-year, large-scale field experiment, we studied how prescribed burning and two different tree retention levels (10 and 50 m3 ha−1) affect polypore fungi. We monitored polypore sporocarps on 2767 individually marked trees four times over the study period: in the first autumn after the treatments, and again 2, 4 and 10 years after the treatments., The number of polypore species and records initially increased rather slowly but showed a marked increasing trend towards the end of the 10-year monitoring period. After 2 years, the higher retention sites had an average 8·5 species and the low retention sites 4·5 species per site. After 4 years, the difference was 14 vs. 9 species and after 10 years 26 vs. 19 species. Red-listed species were not found often on the trunks earlier than 10 years after the treatments., Prescribed burning increased the number of polypore species and records along with time. Furthermore, 13 species favoured burned sites, while only six species favoured unburned sites, and the differences in the composition of species assemblages between burned and unburned sites were evident 10 years after the treatments., Synthesis and applications. We show, for the first time, that retention trees can host rich polypore assemblages, and even some red-listed species, and, thus, be useful in conservation of forest biodiversity outside protected areas. Higher retention levels maintain more diverse polypore assemblages. Prescribed burning increases the positive effects of retention forestry by creating substrates that are typical in the early-successional natural forests. [ABSTRACT FROM AUTHOR]