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Habitat fragmentation and land use intensification are major threats to biodiversity worldwide, affecting both species (SD) and genetic (GD) diversity. It remains unclear whether SD and GD respond to the same components of landscape changes and to what extent they correlate in fragmented systems. We explore the role of current and historical patch and landscape features on SD and GD, in and between forest fragments, along a gradient of landscape matrix permeability. We seek the circumstances under which SD and GD correlate. Within three contrasted agricultural landscapes of northern France, we assessed vascular plant SD and the GD of two plant species with contrasted life history traits in all forest fragments. Species richness and expected heterozygosity were taken as proxies for SD and GD respectively. Using regression and correlation analyses, we explored relationships between SD/GD and local, landscape and historical factors; and between SD and GD. When landscape permeability is above a certain threshold, SD and GD appear to be patterned by the same processes, which results in a positive SD-GD correlation. This permeability threshold is species-specific, depending upon species’ dispersal traits and niche width. The SD-GD correlation depends upon current and past landscape permeability, so that the lack of correlation emerges as the rule in weakly permeable landscape matrices, especially when fragments are small. Landscape matrix permeability and patch features drive SD and GD of vascular plants within and between forest fragments. A generalist, fast-colonizing species better reflects diversity patterns in fragmented forests.

International audience; The invasive pest Drosophila suzukii is a fruit fly native to Asia that infests a wide variety of fruits. Wild plant species are major reservoirs for D. suzukii populations but their infestation rates vary greatly among geographical areas. We aimed at disentangling the relative roles of macroclimatic, landscape and local factors in the rate of D. suzukii infestation of elderberry fruits (Sambucus nigra), a major wild host plant in Europe. We collected elderberry fruits across 215 sites distributed in 13 regions from North to South of France. We counted the number of emerging D. suzukii adults and tested for the effect of macroclimatic, landscape, local biotic and abiotic variables, as well as plant traits using linear mixed models. Site latitude and mean daily maximum temperature since the beginning of the year had respectively the strongest positive and negative effects on mean infestation rates across regions. Infestation rates also increased with forest cover in a 100 m radius around sampling sites. This study shows the importance of taking into account multiple scales and factors, from the fruit characteristics (i.e. maturity) to landscape composition and macroclimatic variables, when studying the interaction between D. suzukii and its host plants.

© 2019 The Authors. Diversity and Distributions Published by John Wiley & Sons Ltd Aim: Forests are highly fragmented across Western Europe, making forest edges important features in many agricultural landscapes. Forest edges are subject to strong abiotic gradients altering the forest environment and resulting in strong biotic gradients. This has the potential to change the forest's capacity to provide multiple ecosystem services such as nutrient cycling, carbon sequestration and natural pest control. Soil organisms play a key role in this perspective; however, these taxa are rarely considered in forest edge research. Location: A latitudinal gradient of 2,000 km across Western Europe. Methods: We sampled six dominant taxa of litter-dwelling macro-arthropods (carabid beetles, spiders, harvestmen, centipedes, millipedes and woodlice) in forest edges and interiors of 192 forest fragments in 12 agricultural landscapes. We related their abundance and community composition to distance from the edge and the interaction with forest age, edge orientation and edge contrast (contrast between land use types at either side of the edge). Results: Three out of six macro-arthropod taxa have higher activity-density in forest edges compared to forest interiors. The abundance patterns along forest edge-to-interior gradients interacted with forest age. Forest age and edge orientation also influenced within-fragment compositional variation along the forest edge-to-interior gradient. Edge contrast influenced abundance gradients of generalist predators. In general, older forest fragments, south-oriented edges and edges along structurally more continuous land use (lower contrast between forest and adjacent land use) resulted in stronger edge-to-interior gradients while recent forests, north-oriented edges and sharp land use edges induced similarity between forest edge and interior along the forest edge-to-interior gradients in terms of species activity-density and composition. Main conclusions: Edge effects on litter-dwelling macro-arthropods are anticipated to feedback on important ecosystem services such as nutrient cycling, carbon sequestration and natural pest control from small forest fragments. ispartof: DIVERSITY AND DISTRIBUTIONS vol:25 issue:6 pages:963-974 status: published

Le site d’étude de 180 hectares, communément appelé la « Cote 108 » se trouvait à l’interface des fronts français et allemand durant la Première Guerre mondiale. Il a été impacté par une guerre des mines dans sa partie ouest et par un intense pilonnage dans sa partie est. A la fin de la guerre, le site n’avait quasiment plus aucune végétation et était marqué par de nombreux entonnoirs. Notre étude s’est intéressée à la recolonisation de la végétation sur cette zone dévastée par la Première Guerre mondiale. Pour cela, six séries de photographies aériennes (IGN) allant de 1929 à 2016 ont été étudiées afin de reconstituer la dynamique de recolonisation de la végétation dans le temps. Parallèlement, une étude du sol a été menée. Son but a été de décrire le sol de la zone d’étude et de quantifier les macro-restes métalliques subsistant encore aujourd’hui. Cette étude a ainsi montré deux situations de recolonisation bien différentes : l’une spontanée, l’autre plantée et gérée par l’ONF. Malgré les plantations, la végétation a eu du mal à reprendre ses droits. Il a fallu 50 ans pour que la zone en recolonisation spontanée soit entièrement recouverte de végétation herbacée et arbustive et finalement un siècle pour assister à une recolonisation quasi-totale de la zone. Grâce aux descriptions de sol menées, nous avons pu proposer un ensemble de facteurs liés au sol et à la végétation pouvant expliquer cette lente recolonisation du site par la végétation. The 180-hectare study site, commonly known as « Hill 108 », was at the interface of the French and German fronts during the First World War. It has been impacted by a mine war in its western part and by intense shelling in its eastern part. At the end of the war the site had almost no vegetation and is marked by many funnels. Our study focused on the re-colonization of vegetation in this region devastated by the First World War. To this end, six series of aerial photographs (IGN) from 1929 to 2016 were studied in order to reconstruct the dynamics of vegetation recolonization over time. At the same time, a soil survey was carried out. Its purpose was to describe the soil in the study area and to quantify the metal macro-remains that still exist today. This study highlighted two very different recolonization situations: one spontaneous, the other planted and managed by the ONF. Despite the plantations, the vegetation had difficulty recovering its rights. It took 50 years for the area under spontaneous recolonization to be completely covered with herbaceous and shrub vegetation and finally a century to attend almost complete recolonization of the area. Thanks to the soil descriptions conducted, we were able to propose a set of soil and vegetation factors that could explain this slow recolonization of the site by vegetation.

The invasive pest Drosophila suzukii (Matsumura, 1931) is a fruit fly native to Asia that infests a wide variety of cultivated and wild fruits, causing important damages on agricultural production. Wild plant species are major reservoirs for D. suzukii populations but their infestation rates varies greatly among geographical areas. This heterogeneity could partly be caused by a heterogeneity of environmental conditions acting across different spatial scales. This study aimed to disentangle the relative roles of macroclimatic, landscape and local factors that could affect the success of D. suzukii infestation of elderberry fruits (Sambucus nigra), a major and widespread host plant along climatic gradients. We collected elderberry fruits and measured vegetative and reproductive life traits of the plants in 215 sites distributed in 13 regions from North to South France during summer 2020. We counted the number of D. suzukii emerging from sampled fruits and tested for an effect of macroclimatic, landscape and local abiotic and biotic variables, as well as plant traits using linear mixed models with region as random factor. Latitude and mean maximum temperature had respectively the strongest positive and negative effects on mean infestation rates across regions (R = 0.761, p = 0.003 and R = −0.758, p = 0.004). Mixed models also showed that fruit infestation rate increased with the number of mature fruits within corymb and with forest cover in a 100 m radius around sampling sites and decreased with mean maximum temperature. The latitudinal and climatic clines in infestation rates suggests that D. suzukii population size might vary greatly among geographic regions. Our results also suggest that population sizes are larger in the presence of semi-natural habitats such as forest patches in the surrounding landscape. Our work contributes to enhancing our understanding of D. suzukii ecology, which is important to predict how infestation rates might change in the context of global climatic changes.

International audience; Aim The spatio-temporal connectivity of forest patches in lowland agricultural landscapes and their age matter to explain current biodiversity patterns across regional as well as biogeographical extents, to the point that their effect exceeds the one of macroclimate for plant diversity in the understorey of temperate forests. Whether this remains true for other taxonomic groups is still largely unknown. Yet, this relative influence has important consequences for ecosystem functioning and the delivery of ecosystem services. Focusing on carabid beetle assemblages, we assessed the relative importance of macroclimatic, landscape and patch attributes in driving local species richness (alpha-diversity) and species dissimilarity between patches (beta-diversity).Location Deciduous forest patches in seven regions along a 2,100-km-long latitudinal gradient across the European temperate forest biome, from southern France to central Sweden.Methods We sampled 221 forest patches in two 5-km x 5-km landscape windows with contrasting management intensities. Carabid beetles were classified into four habitat-preference guilds: forest-specialist, forest-generalist, eurytopic and open-habitat species. We quantified the multi-level environmental influence using mixed-effects models and variation partitioning analysis.Results We found that both alpha- and beta-diversity were primarily determined by macroclimate, acting as a large-scale ecological filter on carabid assemblages among regions. Forest-patch conditions, including biotic and abiotic heterogeneity as well as patch age (but not patch size), increased alpha-diversity of forest species. Landscape management intensity weakly influenced alpha-diversity of forest species, but increased the number of non-forest species in forest patches. Beta diversity of non-forest species increased with patch heterogeneity and decreased with landscape management intensity.Main conclusions Our results highlight the leading role of broad macroclimatic gradients over local and landscape factors in determining the composition of local carabid communities, thereby shedding light on macroecological patterns of arthropod assemblages. This study emphasizes the urgent need for preserving ancient forest patches embedded in agricultural landscapes, even the small and weakly connected ones.

International audience; Questions. Are hedgerows efficient corridors for forest-dwelling species within agricultural landscapes? Do time and space interact synergistically to enhance forest plant species accumulation in hedgerows (i.e. the species–time–area relationship)? Does the distribution profile of forest herbs along hedgerows differ between specialist and generalist species?Location. Agricultural landscapes in northern France.Methods. We assembled a chronosequence of 99 dated (1725–2008) hedgerows, which were surveyed for forest plant species and a number of local-proximal descriptors. A subset of 29 hedgerows were further sampled for species occurrence data in 5-m segments. We used generalized linear models to test the interaction between time (hedgerow age) and space on species richness. Space was characterized by both habitat size (hedgerow length, width and height) and spatial connectedness: i.e. whether a hedgerow is attached to a woodland and how much woodland habitat is available in the surroundings. We used generalized linear mixed-effects models to test whether the probability of occurrence of forest herbs along hedgerows differ between specialists and generalists. Results. Hedgerow age and length interacted synergistically to increase forest plant species richness. Hedgerows attached to woodlands hosted systematically more species. Taller and wider hedgerows with a lower intensity of adjacent land uses hosted more forest plant species. Increasing the spatial connectedness of hedgerows had a positive effect on the probability of occurrence of dispersal-limited forest specialists in the understorey, which was not the case for generalists.Conclusion. As predicted by the species–time–area relationship, ancient and long hedgerows attached to woodlands host more species and are more effective corridors. Creating new hedgerows to connect isolated woodlands can be a suitable strategy to restore functional connectivity, but it will be effective only in the longer term. The conservation of the most ancient hedgerows within intensively managed agricultural landscapes, especially those attached to ancient woodlands, should therefore be a priority.

Questions: Forest fragmentation affects biodiversity locally (alpha diversity) and beyond - at relatively larger scales (gamma diversity) - by increasing dispersal and recruitment limitations. Yet, does an increase in fragmentation affect the relationship between alpha and gamma diversity and what can we learn from it? Location: Northern France. Methods: We surveyed 116 forest patches across three fragmentation levels: none (continuous forest); intermediate (forest patches connected by hedgerows); and high (isolated forest patches). Plant species richness of both forest specialists and generalists was surveyed at five nested spatial resolutions across each forest patch: 1 m(2); 10 m(2); 100 m(2); 1,000 m(2); and total forest patch area. First, we ran log-ratio models to quantify the alpha-gamma relationship. We did that separately for all possible combinations of fragmentation level (none vs intermediate vs high) x spatial scale (e.g., alpha-1 m(2) vs gamma-10 m(2)) x species type (e.g., alpha-specialists vs gamma-specialists). We then used linear mixed-effects models to analyze the effect of fragmentation level, spatial scale, species type and all two-way interaction terms on the slope coefficient extracted from all log-ratio models. Results: We found an interaction effect between fragmentation level and species type, such that forest specialists shifted from a linear (i.e., proportional sampling) to a curvilinear plateau (i.e., community saturation) relationship at low and high fragmentation, respectively, while generalists shifted from a curvilinear to a linear pattern. Conclusions: The impact of forest fragmentation on the alpha-gamma relationship supports generalist species persistence over forest specialists, with contrasting mechanisms for these two guilds. As fragmentation increases, forest specialists shift from proportional sampling towards community saturation, thus reducing alpha diversity likely due to dispersal limitation. Contrariwise, generalists shift from community saturation towards proportional sampling, thus increasing alpha diversity likely due to an increase in the edge:core ratio. To ensure long-term conservation of forest specialists, one single large forest patch should be preferred over several small ones.

International audience; Global forest loss and fragmentation have strongly increased the frequency of forest patches smaller than a few hectares. Little is known about the biodiversity and ecosystem service supply potential of such small woodlands in comparison to larger forests. As it is widely recognized that high biodiversity levels increase ecosystem functionality and the delivery of multiple ecosystem services, small, isolated woodlands are expected to have a lower potential for ecosystem service delivery than large forests hosting more species. We collected data on the diversity of six taxonomic groups covering invertebrates, plants and fungi, and on the supply potential of five ecosystem services and one disservice within 224 woodlands distributed across temperate Europe. We related their ability to simultaneously provide multiple ecosystem services (multiservice delivery potential) at different performance levels to biodiversity of all studied taxonomic groups (multidiversity), forest patch size and age, as well as habitat availability and connectivity within the landscape, while accounting for macroclimate, soil properties and forest structure. Unexpectedly, despite their lower multidiversity, smaller woodlands had the potential to deliver multiple services at higher performance levels per area than larger woodlands of similar age, probably due to positive edge effects on the supply potential of several ecosystem services. Biodiversity only affected multiservice delivery potential at a low performance level as well as some individual ecosystem services. The importance of other drivers of ecosystem service supply potential by small woodlands in agricultural landscapes also depended on the level of performance and varied with the individual ecosystem service considered. Synthesis and applications. Large, ancient woodlands host high levels of biodiversity and can therefore deliver a number of ecosystem services. In contrast, smaller woodlands in agricultural landscapes, especially ancient woodlands, have a higher potential to deliver multiple ecosystem services on a per area basis. Despite their important contribution to agricultural landscape multifunctionality, small woodlands are not currently considered by public policies. There is thus an urgent need for targeted policy instruments to ensure their adequate management and future conservation in order to either achieve multiservice delivery at high levels or to maximize the delivery of specific ecosystem services.

International audience; Purpose Most of the agricultural landscape in Europe, and elsewhere, consists of mosaics with scattered fragments of semi-natural habitat like small forest fragments. Mutual interactions between forest fragments and agricultural areas influence ecosystem processes such as nutrient cycling, a process strongly mediated by the macrodetritivore community, which is however, poorly studied. We investigated macrodetritivore distribution patterns at local and landscape level and used a key functional trait (desiccation resistance) to gain mechanistic insights of the putative drivers. Methods Macrodetritivores were sampled in forest edges-centres of 224 European forest fragments across 14 landscapes opposing in land use intensity. We used a multilevel analysis of variance to assess the relative contribution of different spatial scales in explaining activity-density and Shannon-diversity of woodlice and millipedes, together with a model-based analysis of the multivariate activity-density data testing the effect on species composition. Secondly, we tested if desiccation resistance of macrodetritivores varied across communities at different spatial scales using linear mixed effect models. Results Forest edge-centre and landscape use intensity determined activity-density and community composition of macrodetritivores in forest fragments, while fragment characteristics like size and continuity were relatively unimportant. Forest edges and higher intensity landscapes supported higher activity-density of macrodetritivores and determined species composition. Forest edges sustained woodlouse communities dominated by more drought tolerant species. Conclusions Landscape use intensity and forest edges are main drivers in macrodetritivore distribution in forest fragments with desiccation resistance a good predictor of macrodetritivore distribution. Key functional traits can help us to predict changes in community structure in changing landscapes.

International audience; Forest edges show strong abiotic and biotic gradients potentially altering community composition and ecosystem processes such as nutrient cycling. While abiotic gradients are well studied, short-scale biotic gradients, like detritivore species composition and their associated trait distribution remains a poorly explored research-field. We sampled woodlice in 160 forest patches across Europe at varying distances from the forest edge and discovered that species desiccation resistance determines distribution along forest edge-to-interior gradients. Forest edges are warmer and dryer compared to interiors and favour drought-tolerant species, while abundance and activity of drought-sensitive species is reduced at the edge. Key ecological factors for litter-dwelling detritivores (i.e. humidity) act as environmental filter, because of species-specific differences in desiccation resistance. Future research should focus on quantifying the consequences of a changing detritivore community and their associated functional traits for nutrient cycling.

Soil compaction, which results from the skidding of heavy machines used in forest operations, can seriously damage forest productivity. Indeed, it alters soil structure, disturbs its physical features and consequently affects gas exchange and biological activities. The impact of compaction on soil health has been widely studied, but less is known about the recovery of soil properties over time. In this study, soil compaction was examined by measuring soil penetration resistance. In order to detect the soil recovery on a multi-decadal scale, a space-for-time substitution approach was implemented. Two soil types from the Compiegne forest (Northern France) were investigated (i.e. Luvisol and Podzol). Heavy machine trails of compaction were selected and dated using LIDAR outcomes (Light Detection and Ranging), management documents and aerial photographs. A chronosequence for each soil type was created: 0, 10, 24 and 45 years for the Luvisol and 0, 2, 8, 13 and 23 years for the Podzol. A total of 432 penetration resistance profiles of 30 cm depth were performed in the ruts, as compacted soil, and beside the ruts in undisturbed soils, as control. Penetration resistance was significantly higher in compacted soils in comparison to control soils; it was also higher in the Luvisol than in the Podzol. A linear model with second-order polynomial relationship was used to test the interactions between the penetration resistance, the depth, the situation (compacted versus undisturbed) and the age of compaction. Variance partitioning showed that penetration resistance was mainly controlled by depth, followed by compaction and compaction age, and finally by soil type. The model showed a recovery trend over time as a decrease of the penetration resistance, and a recovery dynamic from the surface toward the deeper layers. The predicted duration of the complete recovery was about 54 and 70 years for the Luvisol and Podzol, respectively. This work also infers that sandy neutral soils could recover in less than 20 years, favored by soil biological activities.

International audience; Soil profiles keep records of the legacies of historical land uses on soil physicochemical properties with deep‐soil (3‐m depth) profiles providing information on centuries‐old dynamics. By combining geohistorical archives on past land uses and management practices together with soil pH data from 19 plots scattered across five study areas in North France, we analyzed the effect of two contrasting historical land‐use change trajectories (afforestation of former arable land vs. cultivation after deforestation) on the acidification and alkalinization dynamics along 3‐m‐depth loessic Luvisols profiles. An analysis of covariance and a generalized additive model were used to test the interaction effect between depth and the two studied chronosequences levels on soil pH. Results show two contrasting alkalinization dynamics for formerly acidic forest soils converted to arable land depending on past management practices. One century of liming practices based on hydrated lime is enough for a complete deprotonation, whereas alkalinization dynamic was much slower (two to four centuries are necessary to neutralize the relictual acidity below 2 m) under liming based on chalk‐blocks supply. Per contra, afforestation of former arable land cultivated and limed during at least 2–4 centuries keep an alkaline ‘memory’ effect over more than a millennium. The acidification process is progressive through time from the surface to deeper soil horizons. This suggests that soil pH profiles can be used to estimate time since afforestation of former arable land. Linking deep‐soil pH profiles with chronosequences is a powerful tool to understand the potential impact of future land‐use change trajectories on soil physicochemical properties.

International audience; Questions How does plant community diversity influence variation in plant biomass? There are two competing hypotheses: the ‘biomass‐ratio hypothesis’, where biomass is influenced by the abundance and traits of the most dominant species, and the ‘diversity hypothesis’, where the diversity of organisms influences biomass through mechanisms such as niche complementarity. However, no studies have tested which one of these two hypotheses better explains the variation in plant biomass in the forest understorey. Location Temperate deciduous forests in Northern France. Methods For the forest understorey, we assessed species diversity and biomass as well as soil and light conditions in 133 forest plots of 100m² each. Using mixed‐effect models and after controlling for 2 Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site. potential confounding factors, we tested the ‘biomass‐ratio hypothesis’ by relating the relative abundance of the most dominant species across our study sites and the community‐weighted mean values (CWM) of plant traits (leaf area and plant height) to biomass. The ‘diversity hypothesis’ was tested by relating biomass to various measures of taxonomic, functional and phylogenetic diversity. Results Biomass of the forest understorey was mainly related to the relative abundance and the trait values of the most dominant species, supporting the ‘biomass‐ratio hypothesis’. In contrast with the ‘diversity hypothesis’, functional diversity indices had a negative impact on biomass. We found no contribution of taxonomic or phylogenetic diversity indices. Conclusion The abundance and traits of the most dominant species matter more than taxonomic, functional or phylogenetic diversity of the forest understorey in explaining its biomass. Thus, there is a need for experiments that aim to fully understand keystone species’ responses to ongoing changing biotic and abiotic conditions and to predict their effects on ecosystem functioning and processes.

Aim Macroclimate is a major determinant of large-scale diversity patterns. However, the influence of smaller-scale factors on local diversity across large spatial extents is not well documented. Here, we quantify the relative importance of local (patch-scale), landscape-scale and macroclimatic drivers of herbaceous species diversity in small forest patches in agricultural landscapes across Europe. Location Deciduous forest patches in eight regions along a macroclimatic gradient from southern France to central Sweden and Estonia. Methods The diversity of forest specialists and generalists at three levels (whole forest patch, sampling plots within patches and between scales) was related to patch-scale (forest area, age, abiotic and biotic heterogeneity), landscape-scale (amount of forest, grasslands and hedgerows around the patch, patch isolation) and macroclimatic variables (temperature and precipitation) using generalized linear mixed models and variation partitioning for each group of variables. Results The total amount of explained variation in diversity ranged from 8% for plot-scale diversity of generalists to 54% for patch-scale diversity of forest specialists. Patch-scale variables always explained more than 60% of the explained variation in diversity, mainly due to the positive effect of within-patch heterogeneity on patch-scale and between-scale diversities and to the positive effect of patch age on plot-scale diversity of forest specialists. Landscape-scale variables mainly contributed to the amount of explained variation in plot-scale diversity, being more important for forest specialists (21%) than for generalists (18%). Macroclimatic variables contributed a maximum of 11% to the plot-scale diversity of generalists. Main conclusions Macroclimate poorly predicts local diversity across Europe, and herbaceous diversity is mainly explained by habitat features, less so by landscape structure. We show the importance of conserving old forest patches as refugia for typical forest species, and of enhancing the landscape context around the patches by reducing the degree of disturbance caused by agriculture.

© 2017 John Wiley & Sons Ltd Aim: To propose a species distribution modelling framework and its companion “iSDM” R package for predicting the potential and realized distributions of invasive species within the invaded range. Location: Northern France. Methods: The non-equilibrium distribution of invasive species with the environment within the invaded range affects the environmental representativeness of species presence–absence data collected from the field and introduces uncertainty in observed absences as these may either reflect unsuitable sites or be incidental. To address these issues, we here propose an environmental systematic sampling design to collect presence–absence data from the field and a probability index to sort and subsequently separate environmental absences (EAs: reflecting environmentally unsuitable sites) from dispersal-limited absences (DLAs: reflecting sites out of dispersal reach). We first conducted a comprehensive test based on a virtual species to evaluate the performance of our framework. Then, we applied it on different life stages of a non-native tree species (Prunus serotina Ehrh.) invasive in Europe. Results: Regarding the potential distribution, we found higher model performances for both the virtual species (true skill statistics (TSS) > 0.75) and P. serotina (TSS ≥ 0.68) after carefully selecting absences with a low probability to be DLAs compared with classical models that incorporate both EAs and DLAs (e.g. TSS = 0.11 for P. serotina with 80% of DLAs). On the contrary, both EAs and DLAs as well as dispersal-related covariates were needed to capture the realized distribution of both the virtual species and P. serotina. Main Conclusions: Our framework helps overcoming the conceptual and methodological limitations of the disequilibrium in species’ distribution models inherent to invasive species and enables managers to robustly estimate both the realized and potential distributions of invasive species. Although more relevant for modelling the distribution of non-native species, this framework can also be applied to native species. ispartof: Diversity & Distributions vol:23 issue:7 pages:806-819 status: published

Background and aims Salt marsh plant communities will be among the first to be exposed to the predicted increase in sea level and to the associated environmental changes. The objectives of this study

Summary 1. The maintenance, restoration or construction of corridors are among the most important conservation strategies world-wide in the face of global changes such as habitat fragmentation and climate change, although their effectiveness still remains an open question. Metacommunity ecology provides a useful framework to answer this question but so far relatively few studies have concerned plant species. 2. Here, we evaluate the connectivity effect of small streams originating in a large forest for plant communities of forest patches within an agricultural landscape. We compared a- and b-diversity of patches connected to a large forest with isolated patches whilst controlling for habitat effects and patch area. Species composition of each patch type was examined with a nonparametric MANOVA and an indicator species analysis. 3. We found that forest patches connected to the main forest through streams were not more species rich after accounting for habitat effects but were more similar than isolated patches, be the latter crossed or not by a stream. Connected patches exhibited a different species composition with more forest habitat specialists and more hydrochores than nonconnected patches. 4. Many forest herb species well known for being dispersal-limited appeared to be efficiently transported by water as incidental hydrochores over long distances and relatively short-time scales. Using streams as ‘high-speed corridors’, these species increased their colonization speed by at least 15 times compared with conventional dispersal. 5. Synthesis and applications. This study demonstrates that streams can act as efficient corridors for plant species across agricultural landscapes and contribute to the dynamics of forest metacommunities. From a management perspective, preserving the longitudinal integrity of streams is likely to increase the connectivity within and between forest metacommunities and can assist dispersal-limited species to be resilient to projected climate warming by increasing their migration speed. Restoring not only wooded elements but watercourse networks is thus a suitable strategy to manage landscapes efficiently for the forest flora conservation.

Aim In response to environmental changes and to avoid extinction, species may either track suitable environmental conditions or adapt to the modified environment. However, whether and how species adapt to environmental changes remains unclear. By focusing on the realized niche (i.e. the actual space that a species inhabits and the resources it can access as a result of limiting biotic factors present in its habitat), we here examine shifts in the realized-niche width (i.e. ecological amplitude) and position (i.e. ecological optimum) of 26 common and widespread forest understorey plants across their distributional ranges. Location Temperate forests along a ca. 1800-km-long latitudinal gradient from northern France to central Sweden and Estonia. Methods We derived species' realized-niche width from a β-diversity metric, which increases if the focal species co-occurs with more species. Based on the concept that species' scores in a detrended correspondence analysis (DCA) represent the locations of their realized-niche positions, we developed a novel approach to run species-specific DCAs allowing the focal species to shift its realized-niche position along the studied latitudinal gradient while the realized-niche positions of other species were held constant. Results None of the 26 species maintained both their realized-niche width and position along the latitudinal gradient. Few species (9 of 26: 35%) shifted their realized-niche width, but all shifted their realized-niche position. With increasing latitude, most species (22 of 26: 85%) shifted their realized-niche position for soil nutrients and pH towards nutrient-poorer and more acidic soils. Main conclusions Forest understorey plants shifted their realized niche along the latitudinal gradient, suggesting local adaptation and/or plasticity. This macroecological pattern casts doubt on the idea that the realized niche is stable in space and time, which is a key assumption of species distribution models used to predict the future of biodiversity, hence raising concern about predicted extinction rates.

Summary1. Al th o ug h h ab itat frag me n tatio n is reco gn ized as a ma jor th reat to bio dive rsity, few stu dies h av eex am ined th e relative imp o rtan ce o f loca l, land scap e an d histo rica l facto rs in co nt ro lling loca lsp ec ies as semb lage s, an d h o w th ese facto rs intera ct,in pa tchy ec o sy stem s. We q ua n tiÞe d th e directan d ind irec t effects o f pa tch size ,p atch h etero ge n eity,ag ricu ltu ra linten sity an d p atch ag e o n plan tsp ec ies rich n ess an d co mp o sitio n o ffo rest pa tche s em b ed d ed in ag ricu ltu ra lland scap es.2. In six 5 a 5 k m- sa mp ling lan ds ca pe wi n do ws , we su rv ey ed ea ch fo rest p atch fo r va scular p lantsp ec ies an d co llec ted th ree sets of ind ep en d en t va riab les, d escribing p atch size an d h etero ge n eity,lan ds ca pe co mp o sition an d h isto ry .T he six wi n do ws w ere ar ra ng ed alon g a gr ad ien t o f ag ricu ltu reint en sity in ru ra llan ds ca pe s of th e P icar d y region (N Fr an ce ).3. We u sed n on -m etric mu ltidim en sion al scaling (N MS ) to d etec t ma jor en viro n me n tal gr ad ient su n de rlying va riation in sp ec ies co mp o sition am on g pa tche s. We th en co n stru cted stru ctu ra l eq u a-tion mo de ls (S E M) to q ua nt ify th e direct an d ind irec t effects of th e th ree sets of va riab les o n loca lp lant d iversity,wh ich wa s su cc essive ly inco rp or ated as pa tch scor es alon g th e Þ rst th ree NM S ax es,w oo dy sp ec ies rich ne ss,fo rest he rb sp ec ies rich ne ss,an d no n- fo rest h erb sp ec ies rich ne ss.4. A ma jor insu en ce o f th e lan ds ca pe ma trix on loca l sp ec ies co mp os ition wa s reve aled b y NM San d su bs eq ue nt S EM ,ma inly th ro u gh no n -for esthe rb sp ec ies, w hich ex plain ed mo st of th e be tw ee np atch s or istic d issimi larity.S pe cies rich ne ss increa sed wi th pa tch he tero ge n eity,wh erea s pa tch ar ean ev er h ad a direct effect. Fo rest he rb s we re mo re resp o ns ive to pa tch ag e an d co nn ec tivity tha no th er sp ec ies, wh erea s n on -for est an d wo o d y sp ec ies we re mo re insu en ce d by ag ricu ltu re inten sityin th e su rro u nd ing ma trix.5. S ynthesis.We us ed o ne o f th e larg est da ta sets ev er co llec ted in temp erate frag me n ted fo rests tob u ild, fo r th e Þ rsttime ,a stru ctur al mo de linco rp or ating allsu sp ec ted dr ivers of loca lplan t co mm u -n ities. We sh o we d th at th e n u mb er an d iden tity of loca lsp ec ies co ex istin g in su cc essio na lfrag me n tso f a fo rest me taco mm un ity at a give n time is co nt ro lled by a u n iqu e co mb ination o f int erac tin gloc al, lan ds ca pe an d histo rica l factor s. Pr eservin g the larg est, old est frag me n ts an d fav o ur ing sp e-cies mo ve me n ts in th e su rro un d ing ma trix is th e be st wa y to co ns erve fo rest sp ec ialists in ch an gingru ra llan ds ca pe s.Key-wor ds: agricu ltural intens ity, disper sal lim itation, habita t fragm entat ion, he dgerow net-work, metacommun ity, plant communi ty divers ity, specie sÐarea relationshi p, specie sÐtimerelationshi p, struc tural equati on modellingIntroduc tion