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© 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

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.

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.

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.

Questions (i) Do species richness and turnover across forest edges change with edge age and management intensity of adjacent lands? (ii) Does edge species composition respond to aging and landscape management and what are the environmental factors explaining this response? Location Agricultural landscapes of the Picardy region, N France. Methods We sampled forest edges differing in age (from a few decades to several centuries) and embedding landscape matrix (from slightly managed ‘bocages’ to intensively cultivated open fields). We recorded vascular plant species and a set of environment, landscape and historical variables along transects oriented perpendicularly to forest edges. We used mixed models to assess the impact of edge age and landscape type on edge species richness and turnover. We investigated the relationship between edge community composition and explanatory variables using redundancy analyses and a split-plot design. Results Species richness decreased with both increased edge age and increased landscape management intensity, while species turnover was not influenced by any of these factors. Edge maturation was characterized by a specialization of the flora over the entire transect, which is likely a response to increased shade, litter layer thickness and soil acidity. As landscape management was more intensive, true forest species were replaced by nitrophilous and/or calciphilous non-forest species, which might be more tolerant of agrochemical and lime drift and are able to disperse through a hostile matrix. Conclusion Although edge aging was associated with the progressive development of environmental gradients, especially light availability and litter thickness, plant communities poorly reflect these gradients under the constraint of neighbouring landscape management. On the contrary, the stronger the management intensity, the sharper the edge–interior gradient.

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