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  • 1.
    Berglund, Håkan
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Edman, Mattias
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Ericson, Lars
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Temporal variation of wood-fungi diversity in boreal old-growth forests: implications for monitoring2005In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 15, no 3, p. 970-982Article in journal (Refereed)
    Abstract [en]

    Monitoring programs that supply reliable and sufficient information on numbers and types of organisms are essential for following changes in biodiversity. In boreal Fennoscandia, forest-dwelling species are threatened in managed forest landscapes and, thus, are of particular concern for conservation strategies. Wood fungi represent key ecological components in the boreal forest that are sensitive to forestry and widely used as indicators in large-scale forest inventories for identifying valuable forest habitats. Knowledge of their natural dynamics is required for designing monitoring programs to assess the adequacy of conservation strategies. We studied the occurrence of corticoids (Corticiaceae) and polypores (Polyporaceae) over time at different spatial scales in unexploited boreal old-growth forests. Data from 70 downed logs followed during an eight-year period showed that the lifespan of fruit bodies of most species was shorter than four years. Even perennial species followed this pattern, although fruit bodies of some species (e.g., Phellinus spp.) remained vital throughout the eight years studied. Both species richness and species composition on individual logs changed markedly over the eight years due to deterministic succession of species paralleling the wood decay. By contrast, data from the stand scale, i.e., seven 0.1 -ha plots, showed that species richness and species composition of polypores did not undergo any major changes during a six-year period. A majority of all recorded polypore species (80%) were already present at the first inventory. However, although species richness remained constant at the stand scale, corticoid species composition differed between years, reflecting their short-lived, annual fruit bodies. This study suggests that monitoring should be performed at stand scale and focus on species with durable fruit bodies, e.g., polypores. This will provide data that can be used both to detect future changes in biodiversity in old-growth spruce forests and to evaluate conservation strategies.

  • 2.
    Deininger, Anne
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Norwegian Institute for Water Research (NIVA), Oslo, Norway; Department of Natural Sciences, University of Agder, Kristiansand, Norway.
    Jonsson, A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Karlsson, J.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Bergström, A-K.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Pelagic food webs of humic lakes show low short-term response to forest harvesting2019In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 29, no 1, article id UNSP e01813Article in journal (Refereed)
    Abstract [en]

    Forest harvest in the boreal zone can increase the input of terrestrial materials such as dissolved organic carbon (DOC) and nitrate (NO3-) into nearby aquatic ecosystems, with potential effects on phytoplankton growth through enhanced nutrient (i.e., positive) or reduced light availability (i.e., negative), which may affect ecosystem productivity and consumer resource use. Here, we conducted forest clear-cutting experiments in the catchments of four small, humic, and nitrogen-limited unproductive boreal lakes (two controls and two clear-cut, 18% and 44% of area cut) with one reference and two impact years. Our aim was to assess the effects of forest clear-cutting on pelagic biomass production and consumer resource use. We found that pelagic biomass production did not change after two years of forest clear-cutting: Pelagic primary and bacterial production (PP, BP), PP:BP ratio, chl a, and seston carbon (seston C) were unaffected by clear-cutting; neither did tree harvest affect seston stoichiometry (i.e., N:phosphorus [P], C:P) nor induce changes in zooplankton resource use, biomass, or community composition. In conclusion, our findings suggest that pelagic food webs of humic lakes (DOC > 15 mg/L) might be resilient to a moderate form of forest clear-cutting, at least two years after tree removal, before mechanical site preparation (e.g., mounding, plowing) and when leaving buffer strips along lakes and incoming streams. Thus, pelagic food web responses to forest clear-cutting might not be universal, but could depend on factors such as the time scale, share of catchment logged, and the forest practices involved, including the application of buffer strips and site preparation.

  • 3.
    Dynesius, Mats
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jansson, Roland
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Johansson, Mats E
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Intercontinental similarities in riparian-plant diversity and sensitivity to river regulation2004In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 14, p. 173-191Article in journal (Refereed)
    Abstract [en]

    We asked whether assemblages of species with separate evolutionary histories differed in their response to similar human interventions. We assessed this by comparing the response of riparian plant communities to river regulation on two different continents. We compared free-flowing and regulated rivers between boreal parts of North America (Alberta and British Columbia) and Europe (Sweden), using a standardized sampling protocol and the same field staff on both continents. Although the two regions shared few species, both riparian plant-species diversity along free-flowing rivers and the response to different kinds of flow regulation were similar between the continents. The number of riparian-plant species and their amount of cover differed among types of water-level regime, but the continental affiliation of a river-margin site did not statistically explain any of the variation. Within continents, the local flora of the regulated river-margin sites was largely similar in species composition to the free-flowing ones, but the sites along storage reservoirs were more species-poor. The similarity in the response to regulation between the continents suggests that general guidelines for rehabilitation of degraded boreal rivers are a realistic goal. The number of species and genera, plant cover, and species numbers in most trait groups (classified according to growth form and life span) were similar between free-flowing river margins in Europe and North America. Moreover, the regional native species pools of northern Sweden and Alberta were similar in size and composition of species groups, despite the fact that only 27% of the species in Alberta were found in northern Sweden. This is presumably because the floras share a common Tertiary origin and because the regions have had largely similar late-Tertiary and Quaternary histories. The most pronounced difference between the continents was that we found no exotic species on the 183 Swedish river-margin sites, whereas 9% of the species found in all 24 North American plots taken together were exotics. All North American exotics found have occurred in Europe since prehistoric times, and the difference in exotic richness most likely reflects a difference in the number of species humans have transferred from one continent to another, rather than a difference in invasibility between the regions.

  • 4.
    Hasselquist, Eliza Maher
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Hjalten, Joakim
    Jørgensen, Dolly
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Lind, Lovisa
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Polvi, Lina E.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Time for recovery of riparian plants in restored northern Swedish streams: a chronosequence study2015In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 25, no 5, p. 1373-1389Article in journal (Refereed)
    Abstract [en]

    A lack of ecological responses in stream restoration projects has been prevalent throughout recent literature with many studies reporting insufficient time for recovery. We assessed the relative importance of time, site variables, and landscape setting for understanding how plant species richness and understory productivity recover over time in riparian zones of northern Swedish streams. We used a space-for-time substitution consisting of 13 stream reaches restored 5-25 years ago, as well as five unrestored channelized reference reaches. We inventoried the riparian zone for all vascular plant species along 60-m study reaches and quantified cover and biomass in plots. We found that while species richness increased with time, understory biomass decreased. Forbs made up the majority of the species added, while the biomass of graminoids decreased the most over time, suggesting that the reduced dominance of graminoids favored less productive forbs. Species richness and density patterns could be attributed to dispersal limitation, with anemochorous species being more associated with time after restoration than hydrochorous, zoochorous, or vegetatively reproducing species. Using multiple linear regression, we found that time along with riparian slope and riparian buffer width (e.g., distance to logging activities) explained the most variability in species richness, but that variability in total understory biomass was explained primarily by time. The plant community composition of restored reaches differed from that of channelized references, but the difference did not increase over time. Rather, different time categories had different successional trajectories that seemed to converge on a unique climax community for that time period. Given our results, timelines for achieving species richness objectives should be extended to 25 years or longer if recovery is defined as a saturation of the accumulation of species over time. Other recommendations include making riparian slopes as gentle as possible given the landscape context and expanding riparian buffer width for restoration to have as much impact as possible.

  • 5.
    Hof, Anouschka R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, Wisconsin 53706 USA.
    Rodriguez-Castaneda, Genoveva
    Allen, Andrew M.
    Jansson, Roland
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Vulnerability of Subarctic and Arctic breeding birds2017In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 27, no 1, p. 219-234Article in journal (Refereed)
    Abstract [en]

    Recent research predicts that future climate change will result in substantial biodiversity loss associated with loss of habitat for species. However, the magnitude of the anticipated biodiversity impacts are less well known. Studies of species vulnerability to climate change through species distribution models are often limited to assessing the extent of species' exposure to the consequences of climate change to their local environment, neglecting species sensitivity to global change. The likelihood that species or populations will decline or go extinct due to climate change also depends on the general sensitivity and adaptive capacity of species. Hence, analyses should also obtain more accurate assessments of their vulnerability. We-addressed this by constructing a vulnerability matrix for 180 bird species currently breeding in Subarctic and Arctic Europe that integrates a climatic exposure-based vulnerability index and a natural-history trait-based vulnerability index. Species that may need extra conservation-attention based on our matrix include the Great Snipe (Gallinago media), the Rough-legged Buzzard (Buteo lagopus), the Red-throated Pipit (Anthus cervinus), the Common Swift (Apus apus), the Horned Lark (Eremophila alpestris), and the Bar-tailed Godwit (Limosa lapponica). Our vulnerability matrix stresses the importance of looking beyond exposure to climate change when species conservation is the aim. For the species that scored high in our matrix the future in the region looks grim and targeted conservation actions, incorporating macroecological and global perspectives, may be needed to alleviate severe population declines. We further demonstrate that climate change is predicted to significantly reduce the current breeding range of species adapted to cold climates in Subarctic and Arctic Europe. The number of incubation days and whether the species was a habitat specialist or not were also among the variables most strongly related to predicted contraction or expansion of species' breeding ranges. This-approach may aid the identification of vulnerable bird species worldwide.

  • 6.
    Hylander, Kristoffer
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Dynesius, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Jonsson, Bengt Gunnar
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Substrate form determines the fate of bryophytes in riparian buffer strips2005In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 15, no 2, p. 674-688Article in journal (Refereed)
  • 7.
    Hylander, Kristoffer
    et al.
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Jonsson, Bengt Gunnar
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Ecology and Environmental Science.
    Evaluating buffer strips along boreal streams using bryophtes as indicators2002In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 12, no 3, p. 797-806Article in journal (Refereed)
    Abstract [en]

    Buffer strips have recently become the main management practice for reducing logging impact on stream habitats in boreal and temperate regions. The habitat value of buffer strips, however, has not received much attention, although riparian forests belong to the systems with the highest biodiversity in these regions. We used plants as indicators of the ability of buffer strips to maintain an environment similar to intact riparian forests in a boreal forest landscape in northern Sweden. We measured the growth of three common bryophyte species (Hylocomiastrum umbratum, Calypogeia integristipula, and Tritomaria quinquedentata) transplanted to riparian habitat close to a stream in clear-cut logged sites 10-15 m wide buffer strips on each side of the stream, and intact (reference) sites. Each of the three site categories included six wet and six tnoist-mesic sites and the experiment was followed over three months in 1999. The species remained vital in the reference sites and grew substantially during the 3-mo-long experiment, but in the logged sites almost no growth was registered, and many shoots died (except for T. qninquedentata). The pattern was consistent irrespective of the ground moisture class. The performance of bryophytes in the moist-mesic buffer strips was almost as bad as in the logged sites, whereas in the wet buffer strips it was either intermediate between that in logged and reference sites (H. umbratum) or very similar to that in reference sites (C. integristipula and T. quinquedentata). The edge effect has previously been shown to vary depending on edge orientation, edge physiognomy, and weather conditions. We found that ground moisture can be of major importance as well. Although many buffer strips function better than no strips, 20-30 m wide strips (with a stream in the middle) through a logged area consist entirely of edge habitat. Increasing the buffer width and avoiding clear-cut logging on both sides of a watercourse would be the first steps to take for improving biodiversity conservation in riparian habitats. Our results also show that bryophytes are good indicators of habitat quality and efficient tools for assessing the ecological function of buffer strips.

  • 8.
    Jansson, Roland
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Applied Science, Mittuniversitetet Härnösand.
    Dynesius, Mats
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Andersson, Elisabet
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Effects of river regulation on river-margin vegetation: a comparison of eight boreal rivers2000In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 10, no 1, p. 203-224Article in journal (Refereed)
    Abstract [en]

    Regulation and fragmentation by dams belong to the most widespread deliberate impacts of humans on the world's rivers, especially in the Northern Hemisphere. We evaluated the effects of hydroelectric development by comparing the flora of vascular plants in 200-m-long reaches of river margin distributed along eight entire rivers in northern Sweden. Four of these rivers were free-flowing, and four were strongly regulated for hydroelectric purposes. First, we compared species diversity per site between entire free-flowing and regulated rivers. To reduce the effects of natural, between-river variation, we compared adjacent rivers. One regulated river had lower plant species richness and cover than two adjacent free-flowing ones, whereas two other parallel rivers, one regulated and another free-flowing, did not differ significantly. Second, river-margin vegetation responded differently to different types of regulated water-level regimes. Both along run-of-river impoundments, with small but daily water-level fluctuations, and along storage reservoirs, with large fluctuations between low water levels in spring and high levels in late summer and fall, the number of species and their cover per site were lower than along the free-flowing rivers. Regulated but unimpounded reaches were most similar to free-flowing rivers, having lower plant cover per site, but similar numbers of species. For reaches with reduced discharge, evidence was mixed; some variables were lower compared to free-flowing rivers whereas others were not. However, for the last two types of regulation, statistical power was low due to small sample sizes. Third, we classified all plant species according to their dispersal mechanisms and tested whether they respond differently to different types of regulated water-level regimes. Three out of four types of regulation had higher proportions of wind-dispersed species, and two out of four had lower proportions of species without specific mechanisms for dispersal, compared to free-flowing rivers, suggesting that dispersal ability is critical for persistence following regulation. Run-of-river impoundments had higher proportions of long-floating species and species with mechanisms for vegetative dispersal, suggesting that water dispersal may still be important despite fragmentation by dams. Fourth, plant species richness and cover varied with both local factors, such as water-level regime, and regional factors, such as length of the growing season. Presence of clay and silt in the river-margin soil, preregulation position of the contemporary river margin, non-reservoir sites, low altitudes, and long growing seasons were associated with high plant species richness and cover.

  • 9.
    Jansson, Roland
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Ström, Lotta
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Smaller future floods imply less habitat for riparian plants along a boreal river2019In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582Article in journal (Refereed)
    Abstract [en]

    Climate-change projections suggest large changes in riverine flow regime, which will likely alter riparian communities. In northern Europe, forecasts propose lower annual spring flood peaks and higher winter flows, resulting in narrower riparian zones. To estimate the impact of climate change on habitat extent of riparian plants, we developed a framework estimating the sensitivity and exposure of individual species to streamflow change, and surveyed five reaches along the free-flowing Vindel River in northern Sweden. We modeled the hydrologic niche of riparian plant species based on the probability of occurrence along gradients of flood frequency and duration and used predicted future water-level fluctuations (based on climate models and IPCC emission scenarios) to calculate changes in flow-related habitat availability of individual species. Despite projected increases in runoff, we predict most species to decrease in riparian elevational extent by on average 12-29% until the end of the century, depending on scenario. Species growing in the upper, spring-flood-controlled part of the riparian zone will likely lose most habitat, with the largest reductions in species with narrow ranges of inundation duration tolerance (decreases of up to 54%). In contrast, the elevational extent of most amphibious species is predicted to increase, but conditions creating isoetid vegetation will become rarer or disappear: isoetid vegetation is presently found in areas where ice formed in the fall settles on the riverbank during the winter as water levels subside. Higher winter flows will make these conditions rare. We argue that our framework is useful to project the effects of hydrologic change caused by climate change as well as other stressors such as flow regulation also in other regions. With few rivers remaining unaffected by dams and other human stressors, these results call for monitoring to detect species declines. Management to alleviate species losses might include mitigation of habitat degradation from land-use activities, more environmentally friendly flow schemes, and more intensive management options such as mowing riparian meadows no longer regularly maintained by recurrent floods.

  • 10. Lucas, Richard W.
    et al.
    Sponseller, Ryan A.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Gundale, Michael J.
    Stendahl, Johan
    Fridman, Jonas
    Hogberg, Peter
    Laudon, Hjalmar
    Long-term declines in stream and river inorganic nitrogen (N) export correspond to forest change2016In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 26, no 2, p. 545-556Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Pilotto, Francesca
    et al.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Nilsson, Christer
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Polvi, Lina E.
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    McKie, Brendan G.
    First signs of macroinvertebrate recovery following enhanced restoration of boreal streams used for timber floating2018In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 28, no 2, p. 587-597Article in journal (Refereed)
    Abstract [en]

    Although ecological restoration generally succeeds in increasing physical heterogeneity, many projects fail to enhance biota. Researchers have suggested several possible explanations, including insufficient restoration intensity, or time-lags in ecological responses that prevent detection of significant changes in short-term monitoring programs. This study aims to evaluate whether benthic macroinvertebrate communities responded to an expanded set of stream restoration measures within a study period of one to five years after completion of the restoration project. We studied 10 forest streams in northern Sweden that were channelized in the past for timber floating. Managers subjected six of these streams to habitat restoration, on each of these we selected two reaches, located in close proximity but differing in restoration intensity. In basic restored reaches, the restoration managers broke up the channelized banks and returned cobbles and small boulders to the main channel. In enhanced restoration reaches, they added additional large wood and boulders to reaches previously subjected to basic restoration, and rehabilitated gravel beds. The remaining four streams were not restored, and thus represent the baseline impacted (channelized) condition. We surveyed stream benthic assemblages before the enhanced restoration (year 2010) and three times afterward between 2011 and 2015. Five years after restoration, macroinvertebrate assemblages at the enhanced restored reaches were more differentiated from channelized conditions than those at basic-restored reaches. This reflected increased relative abundances of the insect orders Ephemeroptera and Trichoptera and the bivalve molluscs Sphaeriidae and decreased relative abundances of Chironomidae (Diptera). Analysis of functional traits provided further insights on the mechanistic explanations driving the recovery, e.g., indicating that the augmented channel retention capacity at enhanced restored reaches favored taxa adapted to slow flow conditions and more effectively retained passive aquatic dispersers. The increased restoration intensity in enhanced restored reaches has resulted in shifts in the composition of benthic macroinvertebrate assemblages, including increases in more sensitive taxa. These shifts became fully apparent five years after the enhanced restoration. Our results emphasize the value of longer-term monitoring to assess ecological responses following restoration, and of undertaking additional restoration as a valuable management option for previously restored sites that failed to achieve biotic recovery.

  • 12. Sitch, Sitch
    et al.
    Mcguire, David A.
    Kimball, John
    Gedney, Nicola
    Gamon, John
    Engström, Ryan
    Wolf, Annett
    Abisko Sci Res Stn, S-98107 Abisko, Sweden; Ecosystem Analysis, Lund University, 22362 Lund, Sweden.
    Zhuang, Qianlai
    Clein, Joy
    McDonald, Kyle C.
    Assessing the carbon balance of circumpolar Arctic tundra using remote sensing and process modeling2007In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 17, no 1, p. 213-234Article in journal (Refereed)
    Abstract [en]

    This paper reviews the current status of using remote sensing and process-based modeling approaches to assess the contemporary and future circumpolar carbon balance of Arctic tundra, including the exchange of both carbon dioxide and methane with the atmosphere. Analyses based on remote sensing approaches that use a 20-year data record of satellite data indicate that tundra is greening in the Arctic, suggesting an increase in photosynthetic activity and net primary production. Modeling studies generally simulate a small net carbon sink for the distribution of Arctic tundra, a result that is within the uncertainty range of field-based estimates of net carbon exchange. Applications of processbased approaches for scenarios of future climate change generally indicate net carbon sequestration in Arctic tundra as enhanced vegetation production exceeds simulated increases in decomposition. However, methane emissions are likely to increase dramatically, in response to rising soil temperatures, over the next century. Key uncertainties in the response of Arctic ecosystems to climate change include uncertainties in future fire regimes and uncertainties relating to changes in the soil environment. These include the response of soil decomposition and respiration to warming and deepening of the soil active layer, uncertainties in precipitation and potential soil drying, and distribution of wetlands. While there are numerous uncertainties in the projections of process-based models, they generally indicate that Arctic tundra will be a small sink for carbon over the next century and that methane emissions will increase considerably, which implies that exchange of greenhouse gases between the atmosphere and Arctic tundra ecosystems is likely to contribute to climate warming.

  • 13.
    Stenbacka, Fredrik
    et al.
    Vilt, fisk och miljö. Sveriges LantbruksUniversitet.
    Hjältén, Joakim
    Vilt, fisk och miljö. Sveriges LantbruksUniversitet.
    Hilszczanski, Jacek
    Vilt, fisk och miljö. Sveriges LantbruksUniversitet.
    Dynesius, Mats
    Vilt, fisk och miljö. Sveriges LantbruksUniversitet.
    Saproxylic and non-saproxylic beetle assemblages in boreal spruce forests of different age and forestry intensity2010In: Ecological Applications, ISSN 1051-0761, E-ISSN 1939-5582, Vol. 20, no 8, p. 2310-2321Article in journal (Refereed)
    Abstract [en]

    Current clear-cutting forestry practices affect many boreal organisms negatively, and those dependent on dead wood (saproxylics) are considered as particularly vulnerable. The succession of species assemblages in managed forest habitats regenerating after clearcutting is, however, poorly known. We compared beetle assemblages in three successional stages of managed boreal spruce forests established after clear-cutting and two types of olderspruce forests that had not been clear-cut. We also assessed whether saproxylic and nonsaproxylic beetle assemblages show similar biodiversity patterns among these forest types. Beetles were collected in window traps in nine study areas, each encompassing a protected oldgrowth forest (mean forest age ;160 years, mean dead wood volume 34 m3/ha), an unprotected mature forest (;120 years old, 15 m3/ha), a middle-aged commercially thinned forest (53 years old, 3 m3/ha), a young unthinned forest (30 years old, 4 m3/ha), and a clearcut (5–7 years after harvest, 11 m3/ha). Saproxylic beetles, in particular red-listed species, were more abundant and more species rich in older forest types, whereas no significant differences among forest types in these variables were detected for non-saproxylics. The saproxylic assemblages were clearly differentiated; with increasing forest age, assemblage compositions gradually became more similar to those of protected old-growth forests, but the assemblage composition in thinned forests could not be statistically distinguished from those of the two oldest forest types. Many saproxylic beetles adapted to late-successional stages were present in thinned middle-aged forests but absent from younger unthinned forests. In contrast, nonsaproxylics were generally more evenly distributed among the five forest types, and the assemblages were mainly differentiated between clearcuts and forested habitats. The saproxylic beetle assemblages of unprotected mature forests were very similar to those of protected old-growth forests. This indicates a relatively high conservation value of mature boreal forests currently subjected to clear-cutting and raises the question of whether future mature forests will have the same qualities. Our results suggest a high beetle conservation potential of developing managed forests, provided that sufficient amounts and qualities of dead wood are made available (e.g., during thinning operations). Confirming studies of beetle reproduction in dead wood introduced during thinning are, however, lacking.

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