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River regulation may filter out riparian plants often resulting in reduced functional diversity, i.e., in the range of functions that organisms have in communities and ecosystems. There is, however, little empirical evidence about the magnitude of such reductions in different regions. We investigated the functional diversity patterns of riparian woody vegetation to streamflow regulation in boreal Sweden and Mediterranean Portugal using nine plant functional traits and field data from 109 sampling sites. We evaluated changes in mean plant functional traits as well as in indices of multidimensional functional traits, i.e., functional richness (FRic) and functional redundancy (FRed) within regions and between free-flowing and regulated river reaches. We found that regulation significantly reduced functional diversity in Sweden but not in Portugal. In Sweden, the increased magnitude of variations in water flow and water level in summer, the prolonged duration of extreme hydrological events, the increased frequency of high-water pulses, and the rate of change in water conditions were the likely main drivers of functional diversity change. Small riparian plant species with tiny leaves, poorly lignified stems, and shallow root systems were consistently associated with regulated sites in the boreal region. In Portugal, the similar functional diversity values for free-flowing and regulated rivers likely stem from the smaller streamflow alterations by regulation combined with the species legacy adaptations to the Mediterranean natural hydrological regimes. We conclude that streamflow regulation may reduce the functional diversity of riparian woody vegetation, but the magnitude of these effects will vary depending on the adaptations of the local flora and the patterns of streamflow disturbances. Our study provides insights into functional diversity patterns of riparian woody vegetation affected by regulation in contrasting biomes and encourages further studies of the functional diversity thresholds for maintaining ecosystems. [ABSTRACT FROM AUTHOR]

The boreal biome exchanges large amounts of carbon (C) and greenhouse gases (GHGs) with the atmosphere and thus significantly affects the global climate. A managed boreal landscape consists of various sinks and sources of carbon dioxide (CO2), methane (CH4), and dissolved organic and inorganic carbon (DOC and DIC) across forests, mires, lakes, and streams. Due to the spatial heterogeneity, large uncertainties exist regarding the net landscape carbon balance (NLCB). In this study, we compiled terrestrial and aquatic fluxes of CO2, CH4, DOC, DIC, and harvested C obtained from tall‐tower eddy covariance measurements, stream monitoring, and remote sensing of biomass stocks for an entire boreal catchment (~68 km2) in Sweden to estimate the NLCB across the land–water–atmosphere continuum. Our results showed that this managed boreal forest landscape was a net C sink (NLCB = 39 g C m−2 year−1) with the landscape–atmosphere CO2 exchange being the dominant component, followed by the C export via harvest and streams. Accounting for the global warming potential of CH4, the landscape was a GHG sink of 237 g CO2‐eq m−2 year−1, thus providing a climate‐cooling effect. The CH4 flux contribution to the annual GHG budget increased from 0.6% during spring to 3.2% during winter. The aquatic C loss was most significant during spring contributing 8% to the annual NLCB. We further found that abiotic controls (e.g., air temperature and incoming radiation) regulated the temporal variability of the NLCB whereas land cover types (e.g., mire vs. forest) and management practices (e.g., clear‐cutting) determined their spatial variability. Our study advocates the need for integrating terrestrial and aquatic fluxes at the landscape scale based on tall‐tower eddy covariance measurements combined with biomass stock and stream monitoring to develop a holistic understanding of the NLCB of managed boreal forest landscapes and to better evaluate their potential for mitigating climate change. [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]

Emulation of natural disturbances is often regarded as a key measure to make forestry biodiversity-oriented. Consequently, extraction of logging residues is assumed to have little negative effect in comparison to extraction of dead wood mainly formed at natural disturbances. This is consistent with the evolutionary species pool hypothesis, which suggests that most species are evolutionary adapted to the naturally most abundant habitats. We tested this hypothesis for dead-wood-dependent macrofungi, lichens, and beetles in a boreal forest landscape in central Sweden, assuming that species are adapted to conditions similar to today's unmanaged forest. No occurrence patterns, for the species groups which we investigated, were consistent with the hypothesis. Overall, stumps and snags had the highest habitat quality (measured as average population density with equal weight given to each species) and fine woody debris the lowest, which was unexpected, since stumps were the rarest dead-wood type in unmanaged forest. We conclude that the evolutionary species pool concept did not explain patterns of species' occurrences, and for two reasons, the concept is not reliable as a general rule of thumb: (1) what constitute habitats harbouring different species communities can only be understood from habitat-specific studies and (2) the suitability of habitats is affected by their biophysical characteristics. Thus, emulation of natural disturbances may promote biodiversity, but empirical studies are needed for each habitat to understand how natural disturbances should be emulated. We also conclude that stump extraction for bioenergy is associated with larger risks for biodiversity than fine woody debris extraction. [ABSTRACT FROM AUTHOR]

Variation in the distribution and abundance of animals in space and time are key concepts of population ecology. We studied these variations in a population of red foxes ( Vulpes vulpes) in the tundra and taiga of northern Sweden. We analysed 12 years (1974-1985) of snow tracking data from a large area of 65,375 km. Specifically, we evaluated to what extent the distribution of red foxes was explained by the presence of prey and how this interacted with snow depth and altitude. We also tested for temporal linear trends in the distribution and abundance of red foxes during the study period. The distribution of red foxes was explained by the presence of rodents, hares, tetraonid species, and ungulates (i.e. carcasses). Snow depth had a negative effect on the impact of small prey on the distribution of the red foxes, whereas it had a positive effect on the impact of ungulates. The influence of hares increased with altitude. Neither distribution nor abundance of red foxes showed a positive or negative linear trend, suggesting a stable population in northern Sweden during our study. This study showed that the distribution of red foxes was not only influenced by the presence of their main prey (rodents), but also by interactions between alternative prey, altitude, and snow depth. This study also emphasizes the importance of ungulate carcasses for red foxes and for wildlife management. [ABSTRACT FROM AUTHOR]

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

Human activities that involve land-use change often cause major transforma-tions to community and ecosystem properties both aboveground and belowground, and when land use is abandoned, these modifications can persist for extended periods. However, the mechanisms responsible for rapid recovery vs. long-term maintenance of ecosystem changes following abandonment remain poorly understood. Here, we examined the long-term ecological effects of two remote former settlements, regularly visited for --300 years by reindeer-herding Sami and abandoned ~100 years ago, within an old-growth boreal forest that is considered one of the most pristine regions in northern Scandinavia. These human legacies were assessed through measurements of abiotic and biotic soil properties and vegetation characteristics at the settlement sites and at varying distances from them. Low-intensity land use by Sami is characterized by the transfer of organic matter towards the settlements by humans and reindeer herds, compaction of soil through trampling, disappearance of understory vegetation, and selective cutting of pine trees for fuel and construction. As a consequence, we found a shift towards early successional plant species and a threefold increase in soil microbial activity and nutrient availability close to the settlements relative to away from them. These changes in soil fertility and vegetation contributed to 83% greater total vegetation productivity, 35% greater plant biomass, and 23% and 16% greater concentrations of foliar N and P nearer the settlements, leading to a greater quantity and quality of litter inputs. Because decomposer activity was also 40% greater towards the settlements, soil organic matter cycling and nutrient availability were further increased, leading to likely positive feedbacks between the aboveground and belowground components resulting from historic land use. Although not all of the activities typical of Sami have left visible residual traces on the ecosystem after 100 years, their low-intensity but long-term land use at settlement sites has triggered a rejuvenation of the ecosystem that is still present. Our data demonstrates that aboveground-belowground interactions strongly control ecosystem responses to historical human land use and that medium- to long-term consequences of even low-intensity human activities must be better accounted for if we are to predict and manage ecosystems succession following land-use abandonment. [ABSTRACT FROM AUTHOR]

Questions Do mortality rates of boreal bryophytes associated with leaf litter burial vary with degree of shelter on forest floor microsites in spruce-dominated forests? Do erect and prostrate species respond similarly? What is the relative importance of deciduous leaves (from aspen and birch) vs conifer needles as bryophyte mortality agents? Location Boreal spruce forests of central Sweden. Methods A transplant study examining mortality was set up with four different bryophyte species: two creeping, prostrate liverworts ( Calypogeia integristipula and Lepidozia reptans) and two more erect mosses ( Rhytidiadelphus triquetrus and Hylocomiastrum umbratum). We tested for differences in mortality rates associated with leaf litter burial in three microhabitats differing in degree of shelter on the forest floor, i.e. sheltered (large boulders, tree bases of spruce) and unsheltered (open forest floor). Results After two growing seasons, 12.7% of the bryophyte transplants (40 out of 316, of which 37 transplants were prostrate liverworts) were dead, presumably due to litter burial. These two prostrate liverworts displayed significantly higher mortality rates close to boulders and at tree bases compared to unsheltered forest floors. Furthermore, although only comprising a small portion of the canopy (<10%), deciduous litter accounted for 53% of all transplants that were buried by litter, compared to 47% for conifer needle litter. Conclusion We find fine-scale spatial patchiness in the responses of bryophytes to litter fall. Mortality of prostrate liverworts associated with litter burial varies among microhabitats on the forest floor, with significantly higher mortality at sheltered microsites (here exemplified by boulders and tree bases) compared to erect moss species. Bryophytes close to microtopographic structures (e.g. boulders and trees) are more strongly exposed to litter burial, but such structures can also function as refuges under disturbance events such as clear-cuts and windthrows. In addition, they may contain convex surfaces that accumulate less litter than flat or convex forest floor surfaces. The observed large effect of litter burial associated with bryophyte mortality, and the variation among microhabitats and species growth forms, suggest that incorporation of litter fall is of vital importance for our understanding of the dynamics of forest bryophyte communities. [ABSTRACT FROM AUTHOR]

We report experimentally determined first-order rate constants of MeHg photolysis in three waters along a Boreal lake-wetland gradient covering a range of pH (3.8-6.6), concentrations of total organic carbon (TOC 17.5-81 mg L-1), total Fe (0.8-2.1 mg L-1), specific UV254 nm absorption (3.3-4.2 L mg-1 m-1) and TOC/TON ratios (24-67 g g-1). Rate constants determined as a function of incident sunlight (measured as cumulative photon flux of photosynthetically active radiation, PAR) decreased in the order dystrophic lake > dystrophic lake/wetland > riparian wetland. After correction for light attenuation by dissolved natural organic matter (DOM), wavelength-specific (PAR: 400-700 nm, UVA: 320-400 nm and UVB: 280-320 nm) first-order photodegradation rate constants (kpd) determined at the three sites were indistinguishable, with average values (±SE) of 0.0023 ± 0.0002, 0.10 ± 0.024 and 7.2 ± 1.3 m² E-1 for kpdPAR, kpdUVA, and kpdUVB, respectively. The relative ratio of kpdPAR, kpdUVA, and kpdUVB was 1:43:3100. Experiments conducted at varying MeHg/TOC ratios confirm previous suggestions that complex formation with organic thiol groups enhances the rate of MeHg photodegradation, as compared to when O and N functional groups are involved in the speciation of MeHg. We suggest that if the photon fluxes of PAR, UVA, and UVB radiation are separately determined and the wavelength-specific light attenuation is corrected for, the first-order rate constants kpdPAR, kpdUVA, and kpdUVB will be universal to waters in which DOM (possibly in concert with Fe) controls the formation of ROS, and the chemical speciation of MeHg is controlled by the complexation with DOM associated thiols. [ABSTRACT FROM AUTHOR]

The article discusses a study of the carbon sequestration in island boreal forest soils in Sweden, focusing carbon isotope analysis and modeling of the contribution of belowground roots and rhizosphere microorganisms to organic matter sinks in soil chronosequences. The researchers identified soil fungi species and population distribution using DNA barcoding and looked at fungal biomass production and decomposition through biochemical markers. The results suggest that root-associated fungi play an important role in boreal forest carbon cycling. Other topics include organic matter dynamics during forest succession, nitrogen deposition and cycling in forest ecosystems, and global carbon cycle models.

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The initial establishment of Picea abies in Sweden and Norway on a landscape level, between 3000 and 1000 years ago, was often preceded by recurrent fire and thereafter the influence of fire decreased. However, in some swamp forests, the absence of fire over the last 3500 years has promoted the continuous presence of deciduous trees, i.e. Picea has not established although it has been present regionally for over 3000 years. Our objective was to study long-term vegetation development and fire history in a Picea swamp forest located close (c. 600 m) to a deciduous swamp forest with a documented fire-free history in northernmost Sweden. The study included analyses of charred particles, pollen and ignition residues. Principal component analysis was applied to identify major changes in the pollen spectra. Our results showed that the current Picea swamp forest has developed from a deciduous fen and that fires affected the fen between 6700 and 2300 cal. yr BP. Picea abies established on the fen around 2200 cal. yr BP, following the last local on-site fire. The main factors responsible for the local vegetation development have been: fire (6700 to 2300 cal. yr BP); autogenous processes and climate (2300 to 1000 cal. yr BP); autogenous processes or anthropogenic impact (1000 to 300 cal. yr BP); anthropogenic impact through selective cutting and grazing (300 to 100 cal. yr BP); and autogenous processes and grazing (100 cal. yr BP to present). We conclude that fire facilitated the initial Picea abies establishment. Once established, Picea abies created local conditions that in combination with a colder and wetter climate prevented fire and the establishment of other tree species. [ABSTRACT FROM AUTHOR]

Productivity in boreal ecosystems is primarily limited by available soil nitrogen (N), and there is substantial interest in understanding whether deposition of anthropogenically derived reactive nitrogen (Nr) results in greater N availability to woody vegetation, which could result in greater carbon (C) sequestration. One factor that may limit the acquisition of Nr by woody plants is the presence of bryophytes, which are a significant C and N pool, and a location where associative cyanobacterial N-fixation occurs. Using a replicated stand-scale N-addition experiment (five levels: 0, 3, 6, 12, and 50 kgNha-1 yr-1; n56) in the boreal zone of northern Sweden, we tested the hypothesis that sequestration of Nr into bryophyte tissues, and downregulation of N-fixation would attenuate Nr inputs, and thereby limit anthropogenic Nr acquisition by woody plants. Our data showed that N-fixation per unit moss mass and per unit area sharply decreased with increasing N addition. Additionally, the tissue N concentrations of Pleuorzium schreberi increased and its biomass decreased with increasing N addition. This response to increasing N addition caused the P. schreberi N pool to be stable at all but the highest N addition rate, where it significantly decreased. The combined effects of changed N-fixation and P. schreberi biomass N accounted for 56.7% of cumulative Nr additions at the lowest Nr addition rate, but only a minor fraction for all other treatments. This 'bryophyte effect' can in part explain why soil inorganic N availability and acquisition by woody plants (indicated by their δ15N signatures) remained unchanged up to N addition rates of 12 kg ha-1 yr-1 or greater. Finally, we demonstrate that approximately 71.8% of the boreal forest experiences Nr deposition rates at or below 3 kg ha-1 yr-1, suggesting that bryophytes likely limit woody plant acquisition of ambient anthropogenic Nr inputs throughout a majority of the boreal forest. [ABSTRACT FROM AUTHOR]

Abstract: Forest edges have numerous implications for structure and function of forest ecosystems. Previous studies on edge quantity have used broad classifications. However, edge influence is driven by the contrast in vegetation structure between adjoining ecosystems, and thus we need detailed site-specific data to assess the role of edges in forests. We studied the variability of sharp edges in 28 boreal landscapes (4km×4km) across an 830km gradient throughout northern Sweden. Our objectives were: (1) to compare the length of natural and created edges, (2) to classify edges in detail by edge origin, maintenance and forest attributes, and (3) to examine relationships between length of edge and landscape variables. Data were collected using stereo-interpretation of high spatial resolution colour infrared aerial photographs, in combination with line intersect sampling and plots. The length of edge varied from 12 to 102mha−1 among landscapes, with an overall mean of 54mha−1. Created edges dominated most landscapes (mean 33mha−1) and had greater variability than natural edges (mean 21mha−1). Maintained edges (e.g. roads, agricultural land) were more abundant than regenerating edges caused by logging. Thirty percent of total edges adjoined narrow linear features. Seventy percent adjoined wider patches and showed high variability (35 classes). Overall, high-contrast edges towards mature forest dominated, i.e. ones that may experience strong edge influence. The amount of edge increased with percent of landscape affected by disturbance, and decreased with latitude and elevation. This study shows that edges are both abundant and highly variable in boreal forests and that forestry is the main driver behind edge creation. Detailed classification of edges based on site-specific forest and patch attributes may help to estimate edge influence at landscape level, and can guide experimental design for examining the impact of edges on structure and function of forest ecosystems. [Copyright &y& Elsevier]

Knowledge of groundwater dynamics is important for the understanding of hydrological controls on chemical processes along the water flow pathways. To increase our knowledge of groundwater dynamics in areas with shallow groundwater, the groundwater dynamics along a hillslope were studied in a boreal catchment in Southern Sweden. The forested hillslope had a 1- to 2-m deep layer of sandy till above bedrock. The groundwater flow direction and slope were calculated under the assumption that the flow followed the slope of the groundwater table, which was computed for different triangles, each defined by three groundwater wells. The flow direction showed considerable variations over time, with a maximum variation of 75°. During periods of high groundwater levels the flow was almost perpendicular to the stream, but as the groundwater level fell, the flow direction became gradually more parallel to the stream, directed in the downstream direction. These findings are of importance for the interpretation of results from hillslope transects, where the flow direction usually is assumed to be invariable and always in the direction of the hillslope. The variations in the groundwater flow direction may also cause an apparent dispersion for groundwater-based transport. In contrast to findings in several other studies, the groundwater level was most responsive to rainfall and snowmelt in the upper part of the hillslope, while the lower parts of the slope reached their highest groundwater level up to 40 h after the upper parts. This can be explained by the topography with a wetter hollow area in the upper part. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The species richness of the scuttle fly (Diptera: Phoridae) genus Megaselia was estimated by various non-parametric estimators from EstimateS, Species Prediction And Diversity Estimation (SPADE) and Ws2m, based on material from a Swedish hemiboreal forest area recently affected by major wildfires, Tyresta National Park and Nature Reserve (TNPNR), south of Stockholm. A total of 21 249 individuals were collected in Malaise traps, of which males constituted 16 976 and females 4 273. The analysed dataset represents 37 samples containing 18 549 specimens sorted into 330 species (184 described, 146 are either undescribed or of unsettled taxonomic status). It was not possible to estimate the total species richness using all samples due to heterogeneity caused by inclusion of different communities and temporal incoherencies between samples within and between years. Even with material obtained from a sampling program that was not designed for species richness estimates, it was possible to obtain reliable results when sample heterogeneity was minimized. By dividing the data into community-specific datasets - for bog, forest and wildfire - it was possible to obtain asymptotic curves for the smaller of the two wildfire datasets. A total estimate of 357-439 (95% CI) was attained by using the smaller wildfire dataset and adding the 85 unique species from the samples not included in the estimation analysis. TNPNR has one of the richest known scuttle fly communities in Europe, consisting of almost 50% of the currently named Megaselia species; 48 of these species are reported as new records for Sweden in this study. [ABSTRACT FROM AUTHOR]

Osmium tetroxide (OsO) is one of the most toxic air contaminants but its environmental effects are poorly understood. Here, for the first time, we present evidence of osmium uptake in a common herbivore (bank vole, Myodes glareolus) in boreal forests of northern Sweden. Voles ( n = 22) and fruticose arboreal pendular lichens, the potential main winter food source of the vole, were collected along a spatial gradient to the west of a steelwork in Tornio, Finland at the Finnish-Swedish border. Os/Os isotope ratios increased and osmium concentrations decreased in lichens and voles along the gradient. Osmium concentrations in lichens were 10,000-fold higher than those in voles. Closest to the steelwork, concentrations were highest in kidneys rather than skin/fur that are directly exposed to airborne OsO. The kidney-to-body weight ratio was higher at the two localities close to the steelwork. Even though based on a small sample size, our results for the first time demonstrate that osmium is taken up, partitioned, and accumulated in mammal tissue, and indicate that high kidney-to-body weight ratios might be induced by anthropogenic osmium. [ABSTRACT FROM AUTHOR]

Lars Tiren was one of the leading forest researchers working in northern Sweden during the first half of the twentieth century. He studied forest regeneration and forest production but he was also interested in past land use and how it had affected the forests in northern Sweden. This paper is a review of Tiren's study, 'Forestry historical studies in the Degerfors district of the province of Vasterbotten', published in 1937. The specific aims of this review are to evaluate the main findings, the scientific quality and the possible bias of this study, as well as its value today. Tiren's study included an analysis of forest fire history, and studies of structural changes of old-growth and high-graded forests and of preindustrial forest utilization, and it is based on different methods and sources, including dendrochronology and historical records analyses. Many of Tiren's analyses on intensive uses of the boreal forest prior to commercial forestry are still valid today and his work has influenced research in many fields, for example in forest fire ecology. Tiren's conclusion is, however, somewhat biased since he had a strong objective to demonstrate the poor care of the forest before the twentieth century, and the need for a more production-oriented forest management. Nevertheless, an important value of his work lies in the thorough descriptions of a forest landscape that no longer exists but that he could observe at the beginning of the twentieth century. [ABSTRACT FROM AUTHOR]

Nitrogen leaching from boreal and temporal forests, where normally most of the nitrogen is retained, has the potential to increase acidification of soil and water and eutrophication of the Baltic Sea. In parts of Sweden, where the nitrogen deposition has been intermediate to high during recent decades, there are indications that the soils are close to nitrogen saturation. In this study, four different approaches were used to assess the risk of nitrogen leaching from forest soils in different parts of Sweden. Nitrate concentrations in soil water and C:N ratios in the humus layer where interpreted, together with model results from mass balance calculations and detailed dynamic modelling. All four approaches pointed at a risk of nitrogen leaching from forest soils in southern Sweden. However, there was a substantial variation on a local scale. Basing the assessment on four different approaches makes the assessment robust. [Copyright &y& Elsevier]

There is currently much interest in understanding how biodiversity loss affects the functioning of ecosystems, but few studies have evaluated how ecosystem processes change in response to one another following biodiversity loss. We focused on a well-described gradient of 30 forested lake islands in northern Sweden, where island size determines the occurrence of lightning-ignited wildfire, which in turn determines successional stage, plant species composition, and productivity. We investigated the effect of biodiversity loss on biological nitrogen fixation by feathermosses through an experiment consisting of factorial removals of three understory shrub species (Vaccinium myrtillis, Vaccinium vitis-idaea, and Empetrum hermaphroditum) and two plant functional groups (shrubs and tree roots). We tested the hypothesis that, following vascular plant species loss, N fixation rates would be impaired by changes in pools or processes that increase extractable soil N, because changes in the supply rate of N to feathermosses should influence their demand for newly fixed N. Further, we hypothesized that the effects of removals on N fixation would depend on environmental context (i.e., island size), because it has been previously demonstrated that the effect of vascular plant species removal on N recycling pools and processes was strongest on productive islands. The data demonstrated that removal of two shrub species (V. vitis-idaea and E. hermaphroditum) negatively affected the N fixation of Hylocomium splendens, but positively affected Pleurozium schreberi, resulting in unchanged areal N fixation rates. In the functional removal experiment, tree root removal resulted in a significant negative effect on N fixation. The effects of shrub and root removals on N fixation occurred only on small islands and thus were context dependent. This pattern did not correspond to the effect of shrub and root removal treatments on N-recycling pools or processes, which only occurred in response to specific vascular plant removals on large or medium islands. The data thus did not support our hypothesis that N fixation was directly responsive to changes in N-recycling pools or processes caused by vascular plant species removals, but instead highlighted the importance of species-specific interactions and environmental context in determining the manner in which biodiversity loss alters ecosystem processes. [ABSTRACT FROM AUTHOR]

The aim of this investigation was to determine the lateral export of dissolved inorganic carbon (DIC) from soils of a Swedish boreal forest to a first order stream and to estimate the partitioning of this DIC into CO2 evasion from the steam surface and the DIC pool exported down through the catchment by streamwater. The groundwater entering the stream was supersaturated with CO2 with values as high as 17 times equilibrium with the atmosphere. Up to 90% of the estimated daily soil DIC export to the stream was emitted to the atmosphere as CO2 within 200 m of the water entering the stream. The annual DIC export from the soil to the stream was estimated to be 3.2 (±0.1) g C m-2 yr-1 (normalized to catchment size). Ninety percent of the variation in soil DIC export could be explained by the variation in groundwater discharge and the DIC concentrations per se, were of minor importance. A significant correlation (R2 = 0.74, P < 0.01) between soil DIC export and CO2 emission from the stream surface suggests that emission dynamics were primarily driven by the export of terrestrial DIC and that in-stream processes were less important Our results reveal that current budget estimates of lateral DIC export from soils to aquatic conduits need to be revised because they do not account for conditions prevailing in headwater streams. Any quantification of lateral stream C export and CO2 emissions from freshwater systems must include headwater streams as well as the lower parts of the aquatic conduit. [ABSTRACT FROM AUTHOR]

Background: Saplings of mountain birch (Betula pubescens ssp. czerepanovii) have established in pockets of dwarf-shrub heath approximately 250 m above the treeline in the Latnjavagge Valley, northern Sweden. Aim: We examined if the establishment of these mountain birch outposts was related to favourable local microclimate, and if birch establishment has affected the surrounding vegetation, changing it from dwarf-shrub heath to more akin to birch forest floor. Methods: Daily mean and mean maximum temperatures were compared for two sites in the dwarf-shrub heath (990 m a.s.l., few birch saplings; 1060 m a.s.l., numerous birch saplings) between January 2005 and June 2006. The cover-abundance of vascular plants was estimated in sample plots in dwarf-shrub heath with mountain birch, dwarf-shrub heath without mountain birch, in heath between the upper limit of closed mountain birch forest and the treeline, and in closed mountain birch forest. Species composition and diversity were statistically compared. The presence in the dwarf-shrub heath of boreal montane species other than birch was also noted. Results: The higher elevation site, containing a higher density of birch, had a significantly higher growing season temperature than the lower elevation site. There was a significant difference in plant community composition between the alpine heath plots containing mountain birch saplings and plots without mountain birch, alpine heath with birch being more similar to the plots of the treeline ecotone and the birch forest than to alpine heath without birch. No significant difference in species diversity among plots in dwarf-shrub heath was found and species diversity increased with altitude. A number of montane species were observed in the dwarf-shrub heath, however, their distribution was not associated with that of the mountain birch. Conclusions: This study provides evidence for favourable microclimate being a key driver for the establishment of mountain birch above the treeline. In addition, the results imply that the composition of the dwarf-shrub heath changes after the establishment of mountain birch to a plant community whose composition points towards a birch forest. [ABSTRACT FROM AUTHOR]

The change of current pools of soil C in Norway spruce ecosystems in Sweden were studied using a process-based model (CoupModel). Simulations were conducted for four sites representing different regions covering most of the forested area in Sweden and representing annual mean temperatures from 0.7°C to 7.1°C. The development of both tree layer and field layer (understory) was simulated during a 100-year period using data on standing stock volumes from the Swedish Forest Inventory to calibrate tree growth using different assumptions regarding N supply to the plants. The model successfully described the general patterns of forest stand dynamics along the Swedish climatic transect, with decreasing tree growth rates and increasing field layer biomass from south to north. However, the current tree growth pattern for the northern parts of Sweden could not be explained without organic N uptake and/or enhanced mineralisation rates compared to the southern parts. Depending on the assumption made regarding N supply to the tree, different soil C sequestration rates were obtained. The approach to supply trees with both mineralised N and organic N, keeping the soil C:N ratio constant during the simulation period was found to be the most realistic alternative. With this approach the soils in the northern region of Sweden lost 5 g C m−2 year−1, the soils in the central region lost 2 g C m−2 year−1, and the soils in the two southern regions sequestered 9 and 23 g C m−2 year−1, respectively. In addition to climatic effects, the feedback between C and N turnover plays an important role that needs to be more clearly understood to improve estimates of C sequestration in boreal forest ecosystems. [ABSTRACT FROM AUTHOR]

Successful reconstruction of vegetation from fossil pollen data in the arctic and alpine tundra, and at the forest-tundra ecotone, is hampered by low pollen production of the major taxa in these environments and the likely dominance of the background pollen component. New approaches to the quantification of vegetation from pollen data (the REVEALS and LOVE models) rely on quantification of background and local pollen by applying models of pollen dispersal and deposition to modern pollen-vegetation survey work. To date, research within this emerging area has focused on lowland environments. This paper presents pollen productivity estimates (PPEs) from the forest-tundra ecotone derived from west central Sweden, discusses the relevant source area of pollen (RSAP) in this environment and estimates the background pollen contribution. The results suggest that the RSAP for moss polsters at the forest-tundra ecotone is c. 500 m, and that PPEs for the major forest tundra ecotone taxa show significant differences compared with previous studies from southern Sweden. Proximity to range limits (controlled by climatic factors) appears to be the main factor causing generally lower pollen production; however, individual taxa respond in different ways, depending on differences in growth behaviour, reproductive strategy and the species and subspecies that represent the pollen taxa. The background pollen component was dominated by arboreal taxa, and contributed c. 60% of the total pollen loading. Graminoids dominated the local component. The PPEs presented here are to date the most appropriate parameters to use for quantification of vegetation at the tundra treeline; however, the data demonstrate that caution needs to be exercised with regards to selection of appropriate PPEs for accurate quantification of taxa at their ecological range. [ABSTRACT FROM AUTHOR]

Detailed information from the Swedish National Forest Inventory was used to simulate the carbon balance for Sweden by the process-based model Biome-BGC. A few shortcomings of the model were identified and solutions to those are proposed and also used in the simulations. The model was calibrated against CO2 flux data from 3 forests in central Sweden and then applied to the whole country divided into 30 districts and 4 age classes. Gross primary production (GPP) ranged over districts and age classes from 0.20 to 1.71 kg C m−2 y−1 and net ecosystem production (NEP) ranged from −0.01 to 0.44. The 10- to 30-year age class was the strongest carbon sink because of its relatively low respiration rates. When the simulation results were scaled up to the whole country, GPP and NEP were 175 and 29 Mton C y−1, respectively, for the 22.7 Mha of forests in Sweden. A climate change scenario was simulated by assuming a 4°C increase in temperature and a doubling of the CO2 concentration; GPP and NEP then increased to 253 and 48 Mton C y−1, respectively. A sensitivity analysis showed that at present CO2 concentrations NEP would peak at an increase of 5°C for the mean annual temperature. At higher CO2 levels NEP showed a logarithmic increase. [ABSTRACT FROM AUTHOR]

For ecosystem modelling of the Boreal forest it is important to include processes associated with low soil temperature during spring-early summer, as these affect the tree water uptake. The COUP model, a physically based SVAT model, was tested with 2 years of soil and snow physical measurements and sap flow measurements in a 70-year-old Scots pine stand in the boreal zone of northern Sweden. During the first year the extent and duration of soil frost was manipulated in the field. The model was successful in reproducing the timing of the soil warming after the snowmelt and frost thaw. A delayed soil warming, into the growing season, severely reduced the transpiration. We demonstrated the potential for considerable overestimation of transpiration by the model if the reduction of the trees' capacity to transpire due to low soil temperatures is not taken into account. We also demonstrated that the accumulated effect of aboveground conditions could be included when simulating the relationship between soil temperature and tree water uptake. This improved the estimated transpiration for the control plot and when soil warming was delayed into the growing season. The study illustrates the need of including antecedent conditions on root growth in the model in order to catch these effects on transpiration. The COUP model is a promising tool for predicting transpiration in high-latitude stands. [ABSTRACT FROM AUTHOR]

Intensive forestry practises in the Swedish landscape have led to the loss and fragmentation of stable old-growth habitats. We investigated relationships between landscape composition at multiple scales and the composition of saproxylic beetle assemblages in nine clear-cut, mature managed and old-growth spruce-dominated forest stands in the central boreal zone of Sweden. We set out fresh spruce and birch logs and created spruce snags in 2001–2002 to experimentally test the effects of coarse woody debris (CWD) type and forest management on the composition of early and late successional, and red-listed saproxylic beetle assemblages. We examined effects of CWD availability at 100 m, and landscape composition at 1 and 10 km on saproxylic beetle abundances. Additionally, we tested whether assemblage similarity decreased with increasing distance between sites. We collected beetles from the experimental logs using eclector and window traps in four periods during 2003. CWD was measured and landscape composition data was obtained from maps of remotely sensed data. The composition of saproxylic beetles differed among different CWD substrates and between clear-cuts and the older stand types, however differences between mature managed and old-growth forests were significant only for red-listed species. Assemblage similarities for red-listed species on clear-cuts were more different at greater distances apart, indicating that they have more localised distributions. CWD availability within 100 m of the study sites was rarely important in determining the abundance of species, suggesting that early successional saproxylic beetles can disperse further than this distance. At a larger scale, a large area of suitable stand types within both 1 and 10 km resulted in greater abundances in the study sites for several common and habitat-specific species. The availability of suitable habitat at scales of 1–10 km is thus likely to be important in the survival of many saproxylic species in forestry-fragmented areas. [ABSTRACT FROM AUTHOR]

1. We conducted a new single-site study and a meta-analysis of pre-existing studies from multiple streams to assess whether intraspecific aggregation among leaf packs promotes coexistence among leaf-eating invertebrates (shredders) in Swedish streams. 2. In the single-site study, 48 standardised leaf bags were exposed for 1 month for shredder colonisation in a homogeneous glide of a forested stream. Current velocity, water depth and substratum composition were additionally assessed to investigate how these factors affected shredder distributions. 3. The meta-analysis included information on shredder colonisation of leaf packs from seven other studies of detritus decomposition to assess patterns of aggregation. Intra- and interspecific aggregation and their relative strength were assessed using indices ( J, C and A respectively) originally developed for terrestrial insects also dependent on patchy and ephemeral resources. 4. In both parts of the study, intraspecific aggregation was much stronger than interspecific aggregation, which was weak overall, indicating that the conditions under which aggregation is expected to facilitate coexistence were fulfilled in our shredder assemblages. 5. In the single-site study, shredder abundances were weakly associated with environmental variables suggesting that habitat heterogeneity only partly explains aggregation patterns. 6. Our results strongly suggest that shredder diversity in streams, particularly during periods of leaf limitation (such as might occur in spring), is promoted by the aggregation of individual species among patches of resource. [ABSTRACT FROM AUTHOR]

Leaching of dissolved organic carbon (DOC) from the forest floor and transport in soil solution into the mineral soil are important for carbon cycling in boreal forest ecosystems. We examined DOC concentrations in bulk deposition, throughfall and in soil solutions collected under the O and B horizons in three Norway spruce stands along a climatic gradient in Sweden. Mean annual temperature for the three sites was 5.5, 3.4 and 1.2 °C. At each site we also examined the effect of soil moisture on DOC dynamics along a moisture gradient (dry, mesic and moist plots). To obtain information about the fate of DOC leached from the O horizon into the mineral soil, 14C measurements were made on bulk organic matter and DOC. The concentration and fluxes of DOC in O horizon leachates were highest at the southern site and lowest at the northern. Average DOC concentrations at the southern, central and northern sites were 49, 39 and 30 mg l−1, respectively. We suggest that DOC leaching rates from O horizons were related to the net primary production of the ecosystem. Soil temperature probably governed the within-year variation in DOC concentration in O horizon leachates, but the peak in DOC was delayed relative to that of temperature, probably due to sorption processes. Neither soil moisture regime (dry, mesic or moist plots) nor seasonal variation in soil moisture seemed to be of any significance for the concentration of DOC leached from the O horizon. The 14C measurements showed that DOC in soil solution collected below the B horizon was derived mainly from the B horizon itself, rather than from the O horizon, indicating a substantial exchange (sorption–desorption reactions) between incoming DOC and soil organic carbon in the mineral soil. [ABSTRACT FROM AUTHOR]

1. The increased length of forest clear-cut edges is considered to be one of the main ecological consequences of silviculture. The effects vary over the landscape, and studies have shown that aspect is one important factor determining the extent of microclimatic edge effects across forest clear-cut boundaries. However, little is known about the relationship between contrasts in microclimate at edges and responses of ecological processes and biodiversity, such as growth, decomposition and species distributions.2. A field experiment was conducted in the boreal forest of northern Sweden to assess the effect of aspect at north- and south-facing edges using mosses as bioindicators. The growth of two species (Hylocomium splendensandHylocomiastrum umbratum) was evaluated during one growing season. Samples of each species were planted in pots at eight north- and eight south-facing forest clear-cut edges.3. Growth increased exponentially with distance from the edge to the interior, and there was a significant effect both in north- and south-facing edges. The percentage decline in growth at the edge was larger in the south- than in the north-facing edges.4. The spatial extent of the edge effect, when measured at the point of 90% of interior growth, was similar between north- and south-facing edges, although it differed between the two species evaluated.5. Synthesis and applications.The difference in exposure to sunlight between north- and south-facing edges was shown to modify the magnitude of the growth of a poikilohydric organism at the very edge, but not the depth of the edge influence. Aspect should be taken into account in management plans for conservation of boreal forests. In the northern hemisphere, wider buffers of uncut forest should be left at the south side than at the north side of retained forest patches. Those forest interior species that are most sensitive to alterations in microclimate will, however, need equal protection from edge effects at all aspects.Journal of Applied Ecology(2005)42, 518 –525doi: 10.1111/j.1365-2664.2005.01033.x [ABSTRACT FROM AUTHOR]

To analyze the effect of landscape structure (viz. amount of wetlands) on the past forest fire regime in boreal Sweden, we reconstructed detailed fire histories by cross-dating fire scars in living and dead Scots pine (Pinus sylvestris L.) in two different landscape types: mire-free landscapes with a low proportion (1%–2%) of mires and mire-rich landscapes with a high proportion (21%–33%) of mires. Two localities were selected and at each one, adjacent mire-free and mire-rich areas of 256–601 ha were sampled. Over the studied 650-year period, the two landscape types differed primarily in the fire intervals and sizes of fires. In the mire-rich landscapes, fires had frequently stopped against mire elements. The net effect was significantly longer fire intervals in the mire-rich than in the mire-free landscape (on average, 32 versus 56 years). The mire-rich areas also had a tail of very long fire intervals lacking in the mire-free areas (maximal interval 292 years). We conclude that mires can have a profound effect on both spatial and temporal patterns of forest fires in the boreal forest, but only when they are effective fuel breaks (i.e., they are wet enough) at the time the fires burn and if they truly dissect the nonmire portion of the forest landscape. [ABSTRACT FROM AUTHOR]

Concentrations of methyl mercury, CH3Hg (II), total mercury, Hgtot = CH3Hg (II) + Hg (II), and organic sulphur species were determined in soils, soil solutions and streams of a small (50 ha) boreal forest catchment in northern Sweden. The CH3Hg (II)/Hgtot ratio decreased from 1.2–17.2% in the peaty stream bank soils to 0.4–0.8% in mineral and peat soils 20 m away from the streams, indicating that conditions for net methylation of Hg (II) are most favourable in the riparian zone close to streams. Concentrations of CH3Hg (II) bound in soil and in soil solution were significantly, positively correlated to the concentration of Hgtot in soil solution. This, and the fact that the CH3Hg (II)/Hgtot ratio was higher in soil solution than in soil may indicate that Hg (II) in soil solution is more available for methylation processes than soil bound Hg (II). Reduced organic S functional groups (Org-SRED) in soil, soil extract and in samples of organic substances from streams were quantified using S K-edge X-ray absorption near-edge structure (XANES) spectroscopy. Org-SRED, likely representing RSH, RSSH, RSR and RSSR functionalities, made up 50 to 78% of total S in all samples examined. Inorganic sulphide [e.g. FeS2 (s)] was only detected in one soil sample out of 10, and in none of the stream samples. Model calculations showed that under oxic conditions nearly 100% of Hg (II) and CH3Hg (II) were complexed by thiol groups (RSH) in the soil, soil solution and in the stream water. Concentrations of free CH3Hg+ and Hg2+ ions in soil solution and stream were on the order of 10-18 and 10-32M, respectively, at pH 5. For CH3Hg (II), inorganic bi-sulphide complexes may contribute to an overall solubility at concentrations of inorganic sulphides higher than 10-9M, whereas considerably higher concentrations of inorganic sulphides (lower redox-potential) are required to increase the solubility of Hg (II). [ABSTRACT FROM AUTHOR]

Remaining deciduous forests in the Fennoscandian boreal landscape have high ecological value, and are considered as key components of the forest landscape as well as remnants of a former natural forest type. To improve our understanding of the formation of deciduous forests, we studied past disturbance regimes and vegetation dynamics in three deciduous forests in boreal Sweden using dendro-ecology, pollen analysis and charcoal analysis. We identified three stages in the development of the studied stands. Firstly, the coniferous period (pre 1800), a long-lasting period characterized by frequent fires, livestock grazing and extensive agriculture during which Pinus sylvestris was dominant. Secondly, the transformation period (1800-1900), when logging removed most pines from the sites while fire and grazing continued. At the time of the last fire, the sites lacked a local seed source of pines, resulting in a post-fire succession dominated by deciduous species with the capacity to disperse over long distances. Thirdly, the deciduous period (1900-present), with little or no disturbance from fire, grazing or logging. Thus, the present deciduous stands have their origins in a complex interaction between changes in fire regime, extensive land use patterns and logging, contrary to earlier simplified explanations. We conclude that the complexity of historical patterns of land use, vegetation dynamics and disturbance should be acknowledged in the future when selecting areas for nature conservation and developing models for ecologically oriented forestry. [ABSTRACT FROM AUTHOR]

Examines the importance of number of fire events per unit area and time as variables in the analysis of fire history in Swedish boreal landscape. Estimation of survivorship curves pre- and post-1650; Anthropogenic influence on fire regimens; Use of fire chronologies by cross-dating fire scars on Pinus sylvestris wood samples.

Studies swamp forests in the boreal part of Sweden. Forests dominated by Norway spruce; Stands of old-growth swamp forests; Forests functioning as fire-free refugia; Decreasing role of fire; Traits of young stands; Transformation of the boreal landscape; Such forests not usually studied; Biological diversity; Disturbance patterns; Stand structure, regeneration, and dead wood; Ecological role of swamp forests; Their future.

We present results from two years’ net ecosystem flux measurements above a boreal forest in central Sweden. Fluxes were measured with an eddy correlation system based on a sonic anemometer and a closed path CO2 and H2O gas analyser. The measurements show that the forest acted as a source during this period, and that the annual balance is highly sensitive to changes in temperature. The accumulated flux of carbon dioxide during the full two-year period was in the range 480–1600 g CO2 m–2. The broad range is caused by uncertainty regarding assessment of the night-time fluxes. Although annual mean temperature remained close to normal, the results are partly explained by higher than normal respiration, due to abnormal temperature distribution and reduced soil moisture during one growing season. The finding that a closed forest can be a source of carbon over such a long period as two years contrasts sharply with the common belief that forests are always carbon sinks. [ABSTRACT FROM AUTHOR]

Focuses on forest ecology while highlighting a study of the Fennoscandian boreal forests variation in forest productivity and controls of soil acidity along a short but extreme forest productivity gradient in northern Sweden. Demonstration of regional surveys; Length of the forest productivity gradient; Indication of the data; Examination of the fundamental differences.

Investigates the transformation of a large forest landscape in boreal Sweden from the end of the 19th century to the end of the 20th century. Use of historical documents to obtain quantitative data on fire influence, historical logging, development of forest management and ecological changes of the forest landscape; How the 19th century boreal forest landscape was shaped by recurrent forest fires and characterized by continuous multistoried old-growth forest; Indication that many interpretations of previous natural landscape properties used as base-line conditions in forest management must be seriously questioned; Discussion of historical records and their limitations when used for reconstruction of forest stand structure.

• Plots with lichen cover decreased by 36% within 30 years. • Forest management influences successional pathways of lichens. • Basal area of forests strongly affects the trajectories of lichen dynamics. • Forest management should be targeted at less dense forests with larger trees. The current decline of terrestrial lichens in Swedish boreal forests is a major challenge for reindeer husbandry, as lichens constitute essential grazing resources for reindeer during winter. Using a 30-year data set covering northern Sweden, we explore how the successional dynamics of lichen cover depend on several forest characteristics, as well as management strategies regarding both reindeer and forestry. We found a 36% reduction of plots with lichen cover, with a decrease in lichen cover becoming more likely in recent years. Year-round presence of reindeer in forests, compared to winter grazing only, had slightly negative impacts on lichens. We found increases in lichen cover in young forests following final harvest. However, increasing basal areas as forest grow older affected lichens negatively and supported dominance of mosses. Forest management that prioritizes less dense forests with larger trees would therefore improve the ability of lichens to persist as forage resource for reindeer. [ABSTRACT FROM AUTHOR]

The planned launch of a spaceborne P-band radar mission and the availability of C- and L-band data from several spaceborne missions suggest investigating the complementarity of C-, L-, and P-band backscatter with respect to the retrieval of forest above-ground biomass. Existing studies on the retrieval of biomass with multi-frequency backscatter relied on single observations of the backscatter and were thus not able to demonstrate the potential of multi-temporal C- and L-band data that are now available from spaceborne missions. Based on spaceborne C- and L-band and airborne P-band images acquired over a forest site in southern Sweden, we investigated whether C- and L-band backscatter may complement retrievals of above-ground biomass from P-band. To this end, a retrieval framework was adopted that utilizes a semi-empirical model for C- and L-bands and an empirical parametric model for P-band. Estimates of above-ground biomass were validated with the aid of 20 m-diameter plots and a LiDAR-derived biomass map with 100 m × 100 m pixel size. The highest retrieval accuracy when not combining frequencies was obtained for P-band with a relative root mean square error (RMSE) of 30% at the hectare scale. The retrieval with multi-temporal L- and C-bands produced errors of the order of 40% and 50%, respectively. The P-band retrieval could be improved for 4% when using P-, L-, and C-bands jointly. The combination of C- and L-bands allowed for retrieval accuracies close to those achieved with P-band. A crucial requirement for achieving an error of 30% with C- and L-bands was the use of multi-temporal observations, which was highlighted by the fact that the retrieval with the best individual L-band image was associated with an error of 61%. The results of this study reconfirmed that P-band is the most suited frequency for the retrieval of above-ground biomass of boreal forests based on backscatter, but also highlight the potential of multi-temporal C- and L-band imagery for mapping above-ground biomass, for instance in areas where the planned ESA BIOMASS P-band mission will not be allowed to acquire data. [ABSTRACT FROM AUTHOR]

Despite being one of the most extensive ecosystems at the global scale, our understanding of watershed transpiration (T, mm d-1) in boreal forests is limited compared to temperate or tropical forests. In northern Sweden, Pinus silvestris, and Picea abies are two of the most representative species in terms of timber production. These two species cover large areas of boreal forests, and contribute to most of the watershed T. However, despite the long history of forest management in Sweden, there are various questions that remain to be answered regarding the hydrological contributions of these species. For example, what is the relative importance of transpiration compared to other water loss pathways in boreal forests? Are both species contributing equally to the amount of water that is being lost back to the atmosphere? What are the environmental drivers influencing the amount of water loss via T and how do they change during the course of the growing season? With the increasing development of thermometric methods to estimate sap flow at the tree level, it is possible to answer some of these questions. However, sap flow methods are often limited by sample size and studies covering periods of time extensive enough to make reasonable inferences of the annual transpiration trends are thus rare. Additionally, scaling up from the tree to the watershed level is limited by site-specific effects that might override species effects. In this study, we deployed a total of 150 heat dissipation sensors, to monitor a total of 60 trees, 30 Pinus silvestris, and 30 Picea abies) in a boreal forest in northern Sweden. We monitored all trees during a three-year period 2015-2018, and recorded data every 30 minutes during the entire calendar year (365 days). Our main overarching goal was to explore the challenges associated in the scaling up process from the tree to the watershed level. Additionally, we set to answer some of the fundamental questions previously described, regarding the hydrology of these two dominant species, with the goal to incorporate their hydrological traits into forest management practices. [ABSTRACT FROM AUTHOR]

Summary 1. Forest management involving live tree retention and natural regeneration after cutting is currently increasing in boreal areas. This calls for further analysis of the optimal conditions for seedling establishment from seed following stand disturbances due to logging. 2. We studied post-dispersal predation on seeds and juvenile seedlings of Pinus sylvestris over 3 years in 32 north Swedish boreal forest stands with different levels of stand disturbance by logging. The aims were to identify the most important predator species and to quantify the damage inflicted upon seeds and seedlings in relation to disturbance. 3. In most stands and years, seed predation resulted in < 20% seed mortality, although occasionally it reached 60%. Predation on juvenile seedlings ranged from 5% to 100%, with > 70% mortality in 10 cases and < 30% in 44 cases (of a total of 79 observations). 4. The most important seed predators were the carabids Pterostichus oblongopunctatus and Calathus micropterus, and seed predation was correlated with the number of seed-eating carabids caught in pitfall traps. Microtine rodents caused high damage levels only on a single occasion. 5. Logging affected both catches of carabids and seed predation levels, but the relationship between tree stand density and predation was not linear and, generally, seed predation decreased in the order shelterwood > unlogged forest > clear-cut. 6. The most important predator on juvenile seedlings was the slug Arion subfuscus, which attacked seedlings during the first weeks after germination. Pitfall trap catches of Hylobius abietis, which commonly damage planted (1–3-year-old) conifer seedlings, were not related to the levels of seedling predation. 7. Seedling predation was negatively related to stand disturbance, with the highest predation levels by slugs in unlogged forests and the lowest in clear-cuts. Seedling predation was higher in wet than in dry summers, probably because slugs are moisture-limited. 8. There was a large between-site variation in both seed and seedling predation, but predation was not strongly related to forest site types. The fact that predation was strongly affected by logging operations indicates that there may be opportunities to reduce damage through modification of the silvicultural practices. [ABSTRACT FROM AUTHOR]