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We examine how levels of multiple ecosystem services (ESs) change with succession in forests with different tree species composition. More specifically we ask how ecosystem age interacts with environmental conditions to regulate ES delivery. Using the nationwide Swedish forest inventory, comprising boreal and temperate regions, we investigated how levels of six provisioning, regulating, recreational, and/or cultural forest ESs changed with forest age (10-185 years) in stands of different tree species composition. We also tested whether the number of ESs delivered (i.e. multifunctionality) changed substantially with stand age, using different threshold levels for ES delivery. Accounting for environmental conditions and stand properties, we found that levels of single ESs changed with stand age. Tree biomass production usually peaked in young to medium aged stands. In contrast, production of berries and game, and services related to biodiversity, were typically highest in old stands (120-185 years). Consistent with this strong temporal tradeoff, multifunctionality at lower threshold levels increased with stand age in most monocultures and mixtures, with the highest multifunctionality being reached somewhere between 100 and 185 years, depending on tree species composition. This was not evident for the highest threshold ES level (the top-20%), however. Moreover, multifunctionality usually decreased with warmer climatic conditions, with the exception of spruce-pine-birch mixtures. Taken together, our results show that a reduced forest age, e.g. due to forestry targeting early harvest of stands, most likely would limit the delivery of several ESs valued by society and result in less multifunctional forests. To maintain the capacity of forests to deliver high levels of multiple ESs, the role of stand age and tree species composition should be considered in decisions on how to manage future forests.

Global and local ecosystem change resulting in diversity loss has motivated efforts to understand relationships between species diversity and ecosystem services. However, it is unclear how such a general understanding can inform policies for the management of ecosystem services in production systems, because these systems are primarily used for food or fibre, and are rarely managed for the conservation of species diversity. Here, using data from a nationwide forest inventory covering an area of 230,000 km 2 , we show that relative abundances of commercial tree species in mixed stands strongly influence the potential to provide ecosystem services. The mixes provided higher levels of ecosystem services compared to respective plant monocultures (overyielding or transgressive overyielding) in 35% of the investigated cases, and lower (underyielding) in 9% of the cases. We further show that relative abundances, not just species richness per se, of specific tree-species mixtures affect the potential of forests to provide multiple ecosystem services, which is crucial information for policy and sustainable forest management. Ecosystem services from forests depend on the species therein, but the type of species diversity may also determine the level of services that the forest can provide. Swedish national forest data show that while mixed stands often provide more services than monoculture forests, it is the relative abundance of species within the mix that can be the key determinant, and necessary for understanding in forest management.

Migration is an important life-history event in a wide range of taxa, yet many migrations are influenced by anthropogenic change. Although migration dynamics are extensively studied, the potential effects of environmental contaminants on migratory physiology are poorly understood. In this study we show that an anxiolytic drug in water can promote downward migratory behaviour of Atlantic salmon ( Salmo salar ) in both laboratory setting and in a natural river tributary. Exposing salmon smolt to a dilute concentration of a GABA A receptor agonist (oxazepam) increased migration intensity compared with untreated smolt. These results implicate that salmon migration may be affected by human-induced changes in water chemical properties, such as acidification and pharmaceutical residues in wastewater effluent, via alterations in the GABA A receptor function. Fish migration is influenced by various environmental factors such as chemicals in water. Here, Hellstrom et al . show that an anxiolytic drug in the benzodiazepine family, oxazepam, can promote migratory behaviour of Atlantic salmon smolts in both laboratory setting and river tributary in Sweden.

Freshwater and terrestrial ecosystems are connected via reciprocal cross-boundary resource fluxes, where terrestrially derived (allochthonous) organic matter is a critical energy source to freshwater food webs. Therefore, some proportion of aquatic-to-terrestrial resource fluxes, which consist primarily of emergent aquatic insects, are of allochthonous origin (i.e., recycled terrestrial matter). Landuse activities modify basal resources and consumer community composition in aquatic systems and, thereby, aquatic resource fluxes to terrestrial systems. The origin of aquatic–terrestrial resource fluxes and alterations to them caused by land use should be considered to understand these fluxes better. Resource fluxes at the aquatic–terrestrial interface were measured at 10 streams along a forest-to-agriculture gradient. Autochthony in emergent aquatic insects ranged from 10 to 97%. Hence, aquatic fluxes to terrestrial systems drive the flux of matter of aquatic origin (true aquatic flux) and the recycling of terrestrial matter to the terrestrial environment. Land use indirectly affected autochthony of emergent aquatic insects via changes in water chemistry, high-quality resource availability, and in-stream consumer composition. Chironomidae diet shifts along the landuse gradient strengthened the aquatic flux to the land. For every 10% increase in agricultural land cover, aquatically derived matter deposited on land via emergent Chironomidae increased 0.005 g dry mass m−2 d−1. Plecoptera strengthened the aquatic flux and the recycling of terrestrial matter via changes in abundance across the landuse gradient. Aquatically derived matter deposited on land via emergent Plecoptera increased 0.002 g dry mass m−2 d−1 for every 10% increase in coniferous forest cover. Qualitative changes in resource fluxes across the aquatic–terrestrial interface may be driven indirectly by the influences of land use on diets and composition of emergent aquatic insects.

Extensive primary boreal forests within Europe are primarily located in Fennoscandia and northwestern Russia. These forests host numerous endemic and red-listed species but are rapidly being exploited and transformed to production forests that lack the habitat characteristics that are required for sustained biodiversity. Over the past 30 years, certain highly valuable areas within Swedish forests have been designated and registered as “woodland key habitats” (WKH) to be safeguarded from clear-cutting. However, despite their high conservation values, WKH lack proper legislative protection. Recently, many WKH were deregistered and thereby lost their potential protection against clear-cutting, jeopardizing biodiversity values in these forests. Moreover, the former way of classifying WKH has been criticized for being too lenient, making conventional forestry difficult. To assess the leniency of WKH registration and effect of WKH deregistration, we conducted a field inventory of WKH following a new inventory method proposed by the Swedish Forest Agency, featuring more stringent criteria for classification of WKH in north-western Sweden. The inventory was conducted in 9 still registered and 9 recently deregistered WKH to assess their conservation values. Our inventory results show that all 18 areas reach the criteria for WKH with the new method, despite higher, more stringent thresholds for conservation values. Hence, formerly registered WKH were not deregistered due to lower values. Moreover, analysis of recent harvest actions within deregistered WKH in Sweden showed that almost 1,200 hectares (~ 2%) of these areas were clear-cut or reported for clear-cutting 1–7 years post deregistration. As such, our results indicate that WKH contain high values, even using more stringent classification criteria, but also that deregistration of WKH does not consider these values and increases the risk of losing them to forest management. Given past and current declines in forest biodiversity, this is concerning, as conservation of areas containing high conservation values are needed, in order to preserve biodiversity in boreal forests.

Forest disturbances are expected to increase in severity with climate change and intensified land use, threatening future delivery of several ecosystem services, including the climate‐mitigating potential of forests. Alleviating these consequences through adaptive forest management demands a greater understanding of what drives the impacts of disturbances on forests, which, in turn, requires collection of high‐quality data through large‐scale and long‐term monitoring programs. The Swedish National Forest Inventory has been recording “damages” on living trees across a forest area of 230,000 km2, in addition to a wide range of stand characteristics and environmental conditions. Using 15 years of these data, we investigated the frequency of different types of tree damages and the causes of these damages and modeled damage risk among tree species and across gradients in stand attributes and environmental conditions. We found that 94% of all surveyed trees had some type of damage, but for 65% of these, the underlying cause was not identified. Nevertheless, for all damage types and causes, we found that damage risk varied considerably among tree species and across gradients in tree species richness, tree height, and stand age. For a few damages, stand age or tree species richness interacted with climate to influence risks. Among identified causes of damage, “wind and snow” was most common (11.9% of surveyed trees), followed by “forestry” (6.9%). Further, for most causes of damage where stand age was significant, the risk was highest in young or the youngest stands. As such, our results indicate that there is great potential for reducing the risk of tree damages via adaptive management, such as altered tree species composition and increased rotation length. However, for a greater understanding of what is driving the frequency and magnitude of forest damages, and to be able to provide specific, useful information to stakeholders, collection of higher‐quality data must be prioritized by monitoring programs.

1. Despite recent interest in linkages between above‐ and below‐ground communities and their consequences for ecosystem processes, much remains unknown about their responses to long‐term ecosystem change. We synthesize multiple lines of evidence from a long‐term ‘natural experiment’ to illustrate how ecosystem retrogression (the decline in ecosystem process rates due to long‐term absence of major disturbance) drives vegetation change, and thus above‐ground and below‐ground carbon (C) sequestration, and communities of consumer biota. 2. Our study system involves 30 islands in Swedish boreal forest that form a 5000‐year, fire‐driven retrogressive chronosequence. Here, retrogression leads to lower plant productivity and slower decomposition and a community shift from plants with traits associated with resource acquisition to those linked with resource conservation. 3. We present consistent evidence that above‐ground ecosystem C sequestration declines, while below‐ground and total C storage increases linearly for at least 5000 years following fire absence. This increase is driven primarily by changes in vegetation characteristics, impairment of decomposer organisms and absence of humus combustion. 4. Data from contrasting trophic groups show that during retrogression, biomass or abundance of plants and decomposer biota decreases, while that of above‐ground invertebrates and birds increases, due to different organisms accessing resources via distinct energy channels. Meanwhile, diversity measures of vascular plants and above‐ground (but not below‐ground) consumers respond positively to retrogression. 5. We show that taxonomic richness of plants and above‐ground consumers are positively correlated with total ecosystem C storage, suggesting that conserving old‐growth forests simultaneously maximizes biodiversity and C sequestration. However, we find little observational or experimental evidence that plant diversity is a major driver of ecosystem C storage on the islands relative to other biotic and abiotic factors. 6. Synthesis.Our study reveals that across contrasting islands differing in exposure to a key extrinsic driver (historical disturbance regime and resulting retrogression), there are coordinated responses of soil fertility, vegetation, consumer communities and ecosystem C sequestration, which all feed back to one another. It also highlights the value of well‐replicated natural experiments for tackling questions about above‐ground–below‐ground linkages over temporal and spatial scales that are otherwise unachievable.

Effective societal responses to rapid climate change in the Arctic rely on an accurate representation of region-specific ecosystem properties and processes. However, this is limited by the scarcity and patchy distribution of field measurements. Here, we use a comprehensive, geo-referenced database of primary field measurements in 1,840 published studies across the Arctic to identify statistically significant spatial biases in field sampling and study citation across this globally important region. We find that 31% of all study citations are derived from sites located within 50 km of just two research sites: Toolik Lake in the USA and Abisko in Sweden. Furthermore, relatively colder, more rapidly warming and sparsely vegetated sites are under-sampled and under-recognized in terms of citations, particularly among microbiology-related studies. The poorly sampled and cited areas, mainly in the Canadian high-Arctic archipelago and the Arctic coastline of Russia, constitute a large fraction of the Arctic ice-free land area. Our results suggest that the current pattern of sampling and citation may bias the scientific consensuses that underpin attempts to accurately predict and effectively mitigate climate change in the region. Further work is required to increase both the quality and quantity of sampling, and incorporate existing literature from poorly cited areas to generate a more representative picture of Arctic climate change and its environmental impacts. Analysing a database of >1,800 field studies in the terrestrial Arctic, the authors identify large spatial biases in sampling, with nearly one-third of all citations derived from sites located within 50 km of two research stations.

High‐resolution unoccupied aerial vehicle (UAVs) data have alleviated the mismatch between the scale of ecological processes and the scale of remotely sensed data, while machine learning and deep learning methods allow new avenues for quantification in ecology. Ant nests play key roles in ecosystem functioning, yet their distribution and effects on entire landscapes remain poorly understood, in part because they and their mounds are too small for satellite remote sensing. This research maps the distribution and impact of ant mounds in a 20 ha treeline ecotone. We evaluate the detectability from UAV imagery using a deep learning model for object detection and different combinations of RGB, thermal and multispectral sensor data. We were able to detect ant mounds in all imagery using manual detection and deep learning. However, the highest precision rates were achieved by deep learning using RGB data which has the highest spatial resolution (1.9 cm) at comparable UAV flight height. While multispectral data were outperformed for detection, it allows for novel insights into the ecology of ants and their spatial impact on vegetation productivity using the normalized difference vegetation index. Scaling up, this suggests that ant mounds quantifiably impact vegetation productivity for up to 4% of our study area and up to 8% of the Betula nana vegetation communities, the vegetation type with the highest abundance of ant mounds. Therefore, they could have an overlooked role in nutrient‐limited tundra vegetation, and on the shrubification of this habitat. Further, we show the powerful combination UAV multi‐sensor data and deep learning for efficient ecological tracking and monitoring of mound‐building ants and their spatial impact. We showed that we can efficiently detect ant mounds in unoccupied aerial vehicles data in heterogeneous environments and that deep learning models can efficiently automatize the detection. Multispectral data are valuable complementary data to detect and quantify the impact of ant mounds in the tundra ecotone. Ant mounds are visibly warmer and their surrounding show increased vegetation productivity. They are a potentially overlooked factor, among others, in the shrubification of the tundra.

There is much interest in understanding ecosystem responses to local‐scale soil fertility variation, which has often been studied using retrogressive chronosequences that span thousands of years and show declining fertility and plant productivity over time. There have been few attempts to experimentally test how plant nutrient limitation changes during retrogression. We studied a well‐characterized system of 30 forested lake islands in northern Sweden that collectively represent a 5350‐year post‐fire retrogressive chronosequence, with fertility and productivity decreasing as time since fire increases. For each island, we set up four plots on understorey vegetation, each subjected to a different fertilizer treatment over 6 years: no additions, nitrogen (N) only, phosphorus (P) only and N + P. We found that both N and P additions reduced feather moss and thus total plant biomass. Meanwhile, the three dominant vascular plant species showed contrasting biomass responses, but similar responses of foliar nutrient concentrations to nutrient additions. Fertilization reduced most microbial groups and altered CO₂ fluxes, most likely through feather moss reduction. Against expectations, the majority of interactive effects of N and P were antagonistic. Changes in effects of nutrient additions during retrogression were usually modest. Empetrum hermaphroditum biomass was increasingly promoted by P and N + P addition, while vascular plant N‐to‐P ratios were increasingly reduced by P addition, indicating increasing plant limitation by nutrients (notably P) during retrogression. Below‐ground, positive effects of N addition on soil mineral N increased, while negative effects of N addition on soil fungi decreased during retrogression; no other below‐ground effects of fertilization changed along the gradient. Synthesis. Our results show that forest understorey communities on islands of different fire history and thus stages of retrogression show relatively modest differences in how they respond to nutrient addition despite large changes in ecosystem productivity and soil fertility, probably because of high species turnover and adaptation of communities to infertile conditions. While increased nutrient availability (as expected through global change) may have important ecological consequences, these effects are likely, especially below‐ground, to be rather similar across ecosystems that differ greatly in nutrient availability and productivity.