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Responses to climate change have often been found to lag behind the rate of warming that has occurred. In addition to dispersal limitation potentially restricting spread at leading range margins, the persistence of species in new and unsuitable conditions is thought to be responsible for apparent time-lags.Soil seed banks can allow plant communities to temporarily buffer unsuitable environmental conditions, but their potential to slow responses to long-term climate change is largely unknown. As local forest cover can also buffer the effects of a warming climate, it is important to understand how seed banks might interact with land cover to mediate community responses to climate change.We first related species-level seed bank persistence and distribution-derived climatic niches for 840 plant species. We then used a database of plant community data from grasslands, forests and intermediate successional habitats from across Europe to investigate relationships between seed banks and their corresponding herb layers in 2763 plots in the context of climate and land cover.We found that species from warmer climates and with broader distributions are more likely to have a higher seed bank persistence, resulting in seed banks that are composed of species with warmer and broader climatic distributions than their corresponding herb layers. This was consistent across our climatic extent, with larger differences (seed banks from even warmer climates relative to vegetation) found in grasslands.Synthesis. Seed banks have been shown to buffer plant communities through periods of environmental variability, and in a period of climate change might be expected to contain species reflecting past, cooler conditions. Here, we show that persistent seed banks often contain species with relatively warm climatic niches and those with wide climatic ranges. Although these patterns may not be primarily driven by species' climatic adaptations, the prominence of such species in seed banks might still facilitate climate-driven community shifts. Additionally, seed banks may be related to ongoing trends regarding the spread of widespread generalist species into natural habitats, while cool-associated species may be at risk from both short- and long-term climatic variability and change. Responses to climate change have often been found to lag behind the rate of warming that has occurred. In addition to dispersal limitation potentially restricting spread at leading range margins, the persistence of species in new and unsuitable conditions is thought to be responsible for apparent time-lags. Soil seed banks can allow plant communities to temporarily buffer unsuitable environmental conditions, but their potential to slow responses to long-term climate change is largely unknown. As local forest cover can also buffer the effects of a warming climate, it is important to understand how seed banks might interact with land cover to mediate community responses to climate change. We first related species-level seed bank persistence and distribution-derived climatic niches for 840 plant species. We then used a database of plant community data from grasslands, forests and intermediate successional habitats from across Europe to investigate relationships between seed banks and their corresponding herb layers in 2763 plots in the context of climate and land cover. We found that species from warmer climates and with broader distributions are more likely to have a higher seed bank persistence, resulting in seed banks that are composed of species with warmer and broader climatic distributions than their corresponding herb layers. This was consistent across our climatic extent, with larger differences (seed banks from even warmer climates relative to vegetation) found in grasslands. Synthesis. Seed banks have been shown to buffer plant communities through periods of environmental variability, and in a period of climate change might be expected to contain species reflecting past, cooler conditions. Here, we show that persistent seed banks often contain species with relatively warm climatic niches and those with wide climatic ranges. Although these patterns may not be primarily driven by species' climatic adaptations, the prominence of such species in seed banks might still facilitate climate-driven community shifts. Additionally, seed banks may be related to ongoing trends regarding the spread of widespread generalist species into natural habitats, while cool-associated species may be at risk from both short- and long-term climatic variability and change.

Terrestrial landscapes surrounding aquatic habitat influence the persistence of amphibian spatially structured populations (SSPs) via their crucial role in providing estivation and overwintering sites, facilitating or hampering dispersal and colonisation, and consequently the maintenance or loss of genetic diversity. To highlight the landscape drivers of genetic variation, we investigated the relationship between the level of genetic variation measured within ponds of the great crested newt (Triturus cristatus), and the composition of the surrounding landscape at various spatial scales. Based on the sampling of 40 ponds in 13 SSPs, the influence of landscape features on several estimators of genetic variation was investigated via linear mixed models, with effects within and between SSPs incorporated. The best models depended on the spatial scale, with more significant associations within radii of 50 and 100 m of core ponds, particularly for allelic richness. Responses within and between SSPs were mostly similar. The availability of aquatic habitat in the landscape had a positive effect, while woodland, arable land and pasture had different effects depending on scale and response variable. Total length of roads within a 250 m radius influenced effective population size negatively. Our results stress the need to investigate the influence of environmental predictors at multiple spatial scales for an adequate understanding of ongoing processes. Generally, the landscape affected genetic variation similarly within and between SSPs. This allowed us to provide general guidelines for the persistence of great crested newt populations, with an emphasis on the importance of the aquatic habitat.

Aim\ud \ud Climate and land use are key determinants of biodiversity, with past and ongoing changes posing serious threats to global ecosystems. Unlike most other organism groups, plant species can possess dormant life‐history stages such as soil seed banks, which may help plant communities to resist or at least postpone the detrimental impact of global changes. This study investigates the potential for soil seed banks to achieve this.\ud \ud \ud \ud Location\ud \ud Europe.\ud \ud \ud \ud Time period\ud \ud 1978–2014.\ud \ud \ud \ud Major taxa studied\ud \ud Flowering plants.\ud \ud \ud \ud Methods\ud \ud Using a space‐for‐time/warming approach, we study plant species richness and composition in the herb layer and the soil seed bank in 2,796 community plots from 54 datasets in managed grasslands, forests and intermediate, successional habitats across a climate gradient.\ud \ud \ud \ud Results\ud \ud Soil seed banks held more species than the herb layer, being compositionally similar across habitats. Species richness was lower in forests and successional habitats compared to grasslands, with annual temperature range more important than mean annual temperature for determining richness. Climate and land‐use effects were generally less pronounced when plant community richness included seed bank species richness, while there was no clear effect of land use and climate on compositional similarity between the seed bank and the herb layer.\ud \ud \ud \ud Main conclusions\ud \ud High seed bank diversity and compositional similarity between the herb layer and seed bank plant communities may provide a potentially important functional buffer against the impact of ongoing environmental changes on plant communities. This capacity could, however, be threatened by climate warming. Dormant life‐history stages can therefore be important sources of diversity in changing environments, potentially underpinning already observed time‐lags in plant community responses to global change. However, as soil seed banks themselves appear, albeit less, vulnerable to the same changes, their potential to buffer change can only be temporary, and major community shifts may still be expected.

Aims: Historical land-use legacies and chemical soil characteristics both explain either directly or indirectly the habitat quality of Nardus grassland, which is protected under the European habitat directive. Yet the relative importance and complementarity of both sets of variables are generally unknown. This knowledge is also relevant for practical reasons, as historical land-use variables can be used in desktop spatial analyses, whereas soil characteristics require field surveys to collect samples for laboratory analyses. To this end, we aim to disentangle the relative importance of historical land-use legacies and soil chemistry for the Nardus grassland quality, and determine the potential of habitat suitability mapping for predicting potential restoration areas. Location: Natura 2000 grasslands in Flanders (northern Belgium). Methods: We compared the model performance of three generalized additive models (GAMs), using either land-use history metrics, soil chemistry, or both as explanatory variables, with the Nardus grassland indicator species count as response. Results: All three models were able to predict areas suitable for at least three Nardus grassland indicator species with high sensitivity and specificity. However, a minimum of four indicator species are required for a favorable conservation status of Natura 2000 Nardus grasslands in Flanders. Using this threshold to detect high-priority zones, the model based on historical land-use variables resulted in a lower sensitivity than models which included soil chemistry. Conclusions: We suggest a two-step approach, with an a priori desktop spatial analysis based on historical land-use variables subdivided in a high-priority zone and a lower-priority zone. If the targeted area for restoration or conservation can be found within the high-priority zone, additional soil analyses are only required to help guide conservation and restoration measures. If additional sites are considered within the lower-priority zone, a field survey to collect additional soil data is recommended.

International audience; Species turnover is ubiquitous. However, it remains unknown whether certain types of species are consistently gained or lost across different habitats. Here, we analysed the trajectories of 1827 plant species over time intervals of up to 78 years at 141 sites across mountain summits, forests, and lowland grasslands in Europe. We found, albeit with relatively small effect sizes, displacements of smaller- by larger-ranged species across habitats. Communities shifted in parallel towards more nutrient-demanding species, with species from nutrient-rich habitats having larger ranges. Because these species are typically strong competitors, declines of smaller-ranged species could reflect not only abiotic drivers of global change, but also biotic pressure from increased competition. The ubiquitous component of turnover based on species range size we found here may partially reconcile findings of no net loss in local diversity with global species loss, and link community-scale turnover to macroecological processes such as biotic homogenisation.

Bertrand et al . question our interpretation about warming effects on the thermophilization in forest plant communities and propose an alternative way to analyze climatic debt. We show that microclimate warming is a better predictor than macroclimate warming for studying forest plant community responses to warming. Their additional analyses do not affect or change our interpretations and conclusions.

Local factors restrain forest warming Microclimates are key to understanding how organisms and ecosystems respond to macroclimate change, yet they are frequently neglected when studying biotic responses to global change. Zellweger et al. provide a long-term, continental-scale assessment of the effects of micro- and macroclimate on the community composition of European forests (see the Perspective by Lembrechts and Nijs). They show that changes in forest canopy cover are fundamentally important for driving community responses to climate change. Closed canopies buffer against the effects of macroclimatic change through their cooling effect, slowing shifts in community composition, whereas open canopies tend to accelerate community change through local heating effects. Science , this issue p. 772 ; see also p. 711

The results from analyses of botanical remains (pollen, wood, charcoal, seeds) from several archaeological features excavated in Kluizen (northern Belgium) are presented. The region was largely uninhabited until the Iron Age and Roman period when a rural settlement was established, resulting in small-scale woodland clearance. The site was subsequently abandoned fromc.AD 270 till the High Middle Ages. The results of the archaeological and archaeobotanical analyses provide information on changes in land use and resulting dynamics of woodland cover and composition betweenc.600 BC and AD 1200, with a spatial and temporal resolution unrivalled in northern Belgium. Especially the long period of woodland regeneration following abandonment of the site around AD 270, covering the Late Roman and Early Medieval period, could be reconstructed in detail. Abandoned fields were first covered with pioneer woodland (Salix,CorylusandBetula), thenQuercus-dominated secondary forest and finally a late-successional forest withFagus sylvatica,Carpinus betulusandIlex aquifolium, an evolution that took over 300 years. The results also indicate that the observed increase ofFagusduring the Early Middle Ages, which was never an important element in the woodland vegetation in northern Belgium before, was related to climatic changes rather than anthropogenic factors.

Aims To introduce a new distance-based field method for (herbaceous, terrestrial) plant species that relates cover to relative shoot frequency as a continuous process of occurrence probabilities and explain how these data can be analyzed. Methods We propose to measure shortest distances from a sample of sampling points to the nearest aboveground part of plant species (up to a maximum search distance). We show how, after appropriate transformation of the point-to-plant distances to a 0-1 interval scale, cover as well as relative shoot frequency at any area up to the searched area can be read from the same curve. This leads to the notion of an integral occurrence probability, which we propose as a new species abundance measure. For estimation and regression modelling we make use of the zero-and-one inflated beta distribution. We supply all code required for these analyses. Results Simulations of plant distribution patterns showed that the integral occurrence probability is able to differentiate between plant abundance patterns that differed in terms of relative cover, density and type of spatial distribution pattern. It is more sensitive to these differences than either cover or relative shoot frequency alone. The method allows summing occurrence probabilities over species to predict expected species richness as a function of the area searched. Aggregation across species while accounting for overlap in species spatial distributions is a simple matter of taking the minimum among the point-to-plant distances at each sampling point. The latter was demonstrated with data from a field trial in Nardetea grassland. Conclusions The method may be a viable alternative for currently employed field methods, such as visual cover estimates, point-intercept sampling and recording the frequency of plant species in equal-area plots. Applications include, but are not limited to, conservation management monitoring and ground-truthing of remote sensing data. This article is protected by copyright. All rights reserved.

The loss of biodiversity at the global scale has been difficult to reconcile with observations of no net loss at local scales. Vegetation surveys across European temperate forests show that this may be explained by the replacement of small-ranged species with large-ranged ones, driven by nitrogen deposition. Biodiversity time series reveal global losses and accelerated redistributions of species, but no net loss in local species richness. To better understand how these patterns are linked, we quantify how individual species trajectories scale up to diversity changes using data from 68 vegetation resurvey studies of seminatural forests in Europe. Herb-layer species with small geographic ranges are being replaced by more widely distributed species, and our results suggest that this is due less to species abundances than to species nitrogen niches. Nitrogen deposition accelerates the extinctions of small-ranged, nitrogen-efficient plants and colonization by broadly distributed, nitrogen-demanding plants (including non-natives). Despite no net change in species richness at the spatial scale of a study site, the losses of small-ranged species reduce biome-scale (gamma) diversity. These results provide one mechanism to explain the directional replacement of small-ranged species within sites and thus explain patterns of biodiversity change across spatial scales.

A first comprehensive account on the dolichopodid fauna (Diptera: Dolichopodidae) of Portugal is presented as the result of multiple surveys by primarily Portuguese researchers between 2009 and 2016. All mainland Portuguese provinces and all districts but one (Évora) were investigated. A total of 761 dolichopodid samples were collected in 278 sampling sites distributed over 87 municipalities and 182 localities, with nearly ¾ of the samples gathered by sweep net. They contained 6,680 specimens of 200 different species, with 142 recognized (known), 40 new (undescribed) and 18 doubtful species. Medetera and Dolichopus were the most diverse among the recognized species, with 20 and 18 species respectively. Fourteen genera were represented by the new species, with Medetera as most diverse. The doubtful species included one species of Pelastoneurus, which is a first record of this genus for the Palaearctic realm. At present 208 dolichopodid species are known from Portugal. A checklist with 150 recognized species is presented, with first records of 116 species for Portugal. For nearly every species, information on its distribution, ecology and rarity in Portugal and northwestern Europe is given, as well as its seasonal activity in Portugal. Raw distribution data are available as dataset in GBIF. Seventy-five pictures of species in the field, and 15 habitat photos are also provided. Current data suggest that a higher proportion of Portuguese species are rare as compared to the Flemish fauna (northern Belgium). Both share 104 species, with 38 species only recorded from Portugal; only seven can be considered Iberian or Portuguese specialities. Though differences between the two Portuguese biomes cannot be substantiated at this moment, two very common and widespread European species, Campsicnemus scambus and Chrysotimus molliculus, seem to be restricted to the Eurosiberian biome in the northwest of the country. In terms of generic representation, the Portuguese dolichopodid fauna occupies an intermediate position between those of northwestern European and other Mediterranean countries. Despite the large amount of data gathered, the dolichopodid fauna of Portugal remains insufficiently known and a considerable number of additional known and new species can be expected with continued sampling.

Manipulating the overstorey is the key tool for forest managers to steer natural regeneration. Opening up the canopy does not only create favourable light conditions for tree seedling growth, but also for (competitive) understorey species. Therefore, a thorough understanding of how changes in the abundance of the overstorey and understorey influence tree regeneration is needed to attain successful regeneration. To this end, we used the regional Flemish Forest Inventories, which contain vegetation plots that were surveyed at two times and include large variation in species composition and abundance of both overstorey and understorey layers. These plots were classified into poor and rich forest types, which differ in overstorey and understorey species composition and soil fertility. For each forest type, we first investigated the effect of overstorey abundance and shade-casting ability on the understorey herbaceous vegetation cover and its competitive nature. Then, we modelled how both these strata influence the presence-absence as well as the cover of tree regeneration, using the zero-inflated beta distribution. Our results show that the understorey cover and its competitiveness mainly increase when the abundance and shade-casting ability of the overstorey is reduced. The shade-casting ability of the overstorey and competitiveness of the understorey were more important in determining tree regeneration, especially probability of presence, than the abundance of these layers per se. This was consistent for both forest types, although directions and magnitudes of the effects differed. In predictions mimicking several thinning scenarios we found that in the poor forests, reducing overstorey abundance could lead to an increase in seedling cover, whereas in rich forests, the opposite is true and seedling cover will potentially be reduced. Finally, in a single-species analysis focusing on Quercus, we found a trade-off between sufficiently reducing overstorey abundance, while at the same retaining parent trees as potential seed sources. These findings can be used to guide forest management decisions in order to attain successful forest regeneration in temperate forests.

During the “Our Planet Reviewed” French Guiana 2014-2015 expedition, Diptera were collected in seven habitat types over an approximately 1 km2 area in the Mitaraka Mountains of southwestern French Guiana. Sixteen collecting methods were used, seven of which yielded multiple samples containing Dolichopodidae. The survey produced a total of 4918 specimens of Dolichopodidae, belonging to 244 morphospecies, 31 genera including four new ones, and 10 recognized subfamilies. This is the highest dolichopodid species richness thus far recorded from a single location anywhere in the world. Three taxa could be identified to species level and all represent first records for French Guiana. Paraclius Loew, 1864, Chrysotus Meigen, 1824 and Medetera Fischer von Waldheim, 1819 were the most speciose genera. Paraclius represented by 50 species, exhibited an unprecedented species richness, mainly in the palm swamps. The three most productive methods in terms of numbers of specimens collected (68% of all specimens obtained using the three methods combined), SLAM traps, sweep nets, and a 6 m long Malaise trap, each yielded between 78 and 90 species, with approximately half of the species from each trap type unique to that method. Both blue, white or yellow pan traps, on the contrary, captured less than 20 species, and overall yellow traps were clearly the least efficient. Pan trap yields, however, were severely affected by repeated heavy rainfall. The highest species richness was recorded around the drop zone and in the base camp, on river banks and in river bank forests, with 40 to 60% of species unique to one of these habitat types. Forty-five species were collected on ‘savanes roches’, and 14 species on inselbergs, with four species shared by both types of rocky outcrops and uniquely found on them.

International audience; Understorey plant communities play a key role in the functioning of forest ecosystems. Under favourable environmental conditions, competitive understorey species may develop high abundances and influence important ecosystem processes such as tree regeneration. Thus, understanding and predicting the response of competitive understorey species as a function of changing environmental conditions is important for forest managers. In the absence of sufficient temporal data to quantify actual vegetation changes, space-for-time (SFT) substitution is often used, i.e. studies that use environmental gradients across space to infer vegetation responses to environmental change over time. Here we assess the validity of such SFT approaches and analysed 36 resurvey studies from ancient forests with low levels of recent disturbances across temperate Europe to assess how six competitive understorey plant species respond to gradients of overstorey cover, soil conditions, atmospheric N deposition and climatic conditions over space and time. The combination of historical and contemporary surveys allows (i) to test if observed contemporary patterns across space are consistent at the time of the historical survey, and, crucially, (ii) to assess whether changes in abundance over time given recorded environmental change match expectations from patterns recorded along environmental gradients in space. We found consistent spatial relationships at the two periods: local variation in soil variables and overstorey cover were the best predictors of individual species’ cover while interregional variation in coarse-scale variables, i.e. N deposition and climate, was less important. However, we found that our SFT approach could not accurately explain the large variation in abundance changes over time. We thus recommend to be cautious when using SFT substitution to infer species responses to temporal changes.

International audience; The contemporary state of functional traits and species richness in plant communities depends on legacy effects of past disturbances. Whether temporal responses of community properties to current environmental changes are altered by such legacies is, however, unknown. We expect global environmental changes to interact with land‐use legacies given different community trajectories initiated by prior management, and subsequent responses to altered resources and conditions. We tested this expectation for species richness and functional traits using 1814 survey‐resurvey plot pairs of understorey communities from 40 European temperate forest datasets, syntheses of management transitions since the year 1800, and a trait database. We also examined how plant community indicators of resources and conditions changed in response to management legacies and environmental change. Community trajectories were clearly influenced by interactions between management legacies from over 200 years ago and environmental change. Importantly, higher rates of nitrogen deposition led to increased species richness and plant height in forests managed less intensively in 1800 (i.e., high forests), and to decreases in forests with a more intensive historical management in 1800 (i.e., coppiced forests). There was evidence that these declines in community variables in formerly coppiced forests were ameliorated by increased rates of temperature change between surveys. Responses were generally apparent regardless of sites’ contemporary management classifications, although sometimes the management transition itself, rather than historic or contemporary management types, better explained understorey responses. Main effects of environmental change were rare, although higher rates of precipitation change increased plant height, accompanied by increases in fertility indicator values. Analysis of indicator values suggested the importance of directly characterising resources and conditions to better understand legacy and environmental change effects. Accounting for legacies of past disturbance can reconcile contradictory literature results and appears crucial to anticipating future responses to global environmental change.

Summary 1. Habitat patches that have been completely cleared of their original vegetation historically and subsequently recolonized naturally provide a useful study system to explore the importance of the processes involved in community assembly. Forests where the understorey vegetation is recovering from past agricultural land use form an iconic example of such a system. 2. The colonization capacity of forest plant species into post-agricultural forests has been related to dispersal traits in previous comparative analyses, demonstrating the significance of dispersal limitation. Yet, none of them has evaluated evidence for a phylogenetic signal in colonization capacity and, thus, explored the possibility that the dispersal traits are correlated with unmeasured establishment-related traits that are also shared through common ancestry. 3. Here, we analysed the colonization capacity of 330 species into post-agricultural forests across seven different landscapes in Europe and North America. With phylogenetic meta-analysis models, we quantified the phylogenetic signal in colonization capacity and tested whether the colonization – dispersal trait relationships are confounded by phylogenetic non-independence. 4. Closely related forest understorey species were more similar to one another in terms of their capacity to colonize post-agricultural forests than were more distantly related species. The correlations between dispersal traits and colonization were not independent from phylogeny. While we found some evidence of phylogenetic clustering of species’ frequencies in post-agricultural communities, this was apparently not a result of strong filtering on dispersal traits. 5. Synthesis. Given the phylogenetic signal in plant colonization capacity, a multitude of conserved species characteristics may explain community assembly in forests. Earlier trait-based syntheses strongly emphasised dispersal, but the factors limiting establishment and persistence of forest herbs in post-agricultural forests may be more nuanced than generally appreciated.

More and more ecologists have started to resurvey communities sampled in earlier decades to determine long-term shifts in community composition and infer the likely drivers of the ecological changes observed. However, to assess the relative importance of, and interactions among, multiple drivers joint analyses of resurvey data from many regions spanning large environmental gradients are needed. In this paper we illustrate how combining resurvey data from multiple regions can increase the likelihood of driver-orthogonality within the design and show that repeatedly surveying across multiple regions provides higher representativeness and comprehensiveness, allowing us to answer more completely a broader range of questions. We provide general guidelines to aid implementation of multi-region resurvey databases. In so doing, we aim to encourage resurvey database development across other community types and biomes to advance global environmental change research.

Dispersal is a crucial process in metapopulation persistence, both in terms of colonization-extinction dynamics and as a means to counter genetic drift and inbreeding in local demes. To investigate effective dispersal in a coastal dune metapopulation of Natterjack Toad (Epidalea calamita Laurenti), 256 larvae in four potential subpopulations were genotyped with 11 microsatellites. The grey dunes they inhabit are rare natural features on the Belgian coast. They are separated by urban areas and surrounded by agricultural fields. Because spatial landscape heterogeneity is expected to influence dispersal and genetic structure, we analyzed which landscape features affect functional connectivity and to what degree. Sixty landscape resistance scenarios were assessed using two different approaches. Our results revealed a genetic structure which was clearly not influenced by distance alone and source-sink dynamics among subpopulations. Urbanized areas seemed to hinder dispersal as well as surfaces with higher vegetation. On the other hand, distant subpopulations appeared functionally connected by the beach. Estimates of genetic diversity and effective population size further supported the landscape genetic results.

The restoration of forest ecosystems on former agricultural land faces numerous problems. Recolonisation of forest species is hampered by the modified habitat quality and by the isolation from source populations. Tree species are ecosystem engineers that can modify soil and light conditions and can therefore act as a possible catalyst for understory recovery. Therefore, we set out to study the effects of tree species on herb layer development. For this purpose, a chronosequence of post-agricultural oak (Quercus robur and Quercus petraea) and poplar (Populus x euramericana and Populus x interamericana) plantations on silt and sandy silt soils was selected. The selected tree species are frequently planted and have contrasting characteristics (e.g. in terms of litter quality, shade casting ability and growth rate). Under plantations of oak, soils acidified with increasing stand age and dropped into the aluminium buffer range after only 20–30 y, whereas soil pH hardly changed under poplar plantations. Carbon (C) and nitrogen (N) soil content increased with stand age, while C/N ratio depended on tree species but remained constant in time. Multivariate analysis revealed that vegetation development depended on tree species, isolation and stand age. Poplar stands were characterised by rough Arrhenaterion grassland species while oaks had low understory cover and consequently had no indicator herb species. No tree species effect was found on the cover of strict forest species and ancient forest species. Oak favoured acid tolerant forest species, while poplars favoured light demanding and acid intolerant forest species. Our results lead to the conclusion that tree species can be important drivers of vegetation development in post-agricultural forests, in particular through their impact on soil development and light availability for the understory. Therefore it is important that goals for soil development and understory restoration are taken into account when tree species are selected for afforestations. Acidifying tree species may have irreversible effects, permanently excluding acid intolerant species. This is especially important when aiming to safeguard acid intolerant forest species from acidification in ancient forest by creating post-agricultural forest as refugee zones. When a species rich herb layer with acid intolerant species are aimed at, selecting a tree species with a good decomposable litter like poplar is a necessity and suppressing competitors by a shady overstory of the tree or shrub layer. Soil acidifying species like oak might be more suitable to enlarge forest habitats that mainly contain acid and shade tolerant species.

1. Atmospheric nitrogen (N) deposition is expected to change forest understorey plant community composition and diversity, but results of experimental addition studies and observational studies are not yet conclusive. A shortcoming of observational studies, which are generally based on resurveys or sampling along large deposition gradients, is the occurrence of temporal or spatial confounding factors. 2. We were able to assess the contribution of N deposition versus other ecological drivers on forest understorey plant communities by combining a temporal and spatial approach. Data from 1205 (semi-)permanent vegetation plots taken from 23 rigorously selected understorey resurvey studies along a large deposition gradient across deciduous temperate forest in Europe were compiled and related to various local and regional driving factors, including the rate of atmospheric N deposition, the change in large herbivore densities and the change in canopy cover and composition. 3. Although no directional change in species richness occurred, there was considerable floristic turnover in the understorey plant community and a shift in species composition towards more shade-tolerant and nutrient-demanding species. However, atmospheric N deposition was not important in explaining the observed eutrophication signal. This signal seemed mainly related to a shift towards a denser canopy cover and a changed canopy species composition with a higher share of species with more easily decomposed litter. 4. Synthesis. Our multi-site approach clearly demonstrates that one should be cautious when drawing conclusions about the impact of atmospheric N deposition based on the interpretation of plant community shifts in single sites or regions due to other, concurrent, ecological changes. Even though the effects of chronically increased N deposition on the forest plant communities are apparently obscured by the effects of canopy changes, the accumulated N might still have a significant impact. However, more research is needed to assess whether this N time bomb will indeed explode when canopies will open up again.

While the influence of climate, vegetation, management and abiotic site factors on total carbon budgets and turn-over is intensively assessed, the influences of these ecosystem properties on the chemical complexity of soil organic matter (SOM) remains poorly understood. This study addresses the chemical composition of NaOH-extracted SOM from maritime temperate forest sites in Flanders (Belgium) by pyrolysis-GC/MS. The studied forests were chosen based on dominant tree species (Pinus sylvestris, Fagus sylvatica, Quercus robur and Populus spp.), soil texture and soil-moisture conditions. Differences in extractable-SOM pyrolysis products were correlated to site variables including dominant tree species, management of the woody biomass, site history, soil properties, total carbon stocks and indicators for microbial activity. Despite of a typical high intercorrelation between these site variables, the influence of the dominant tree species is prominent. The extractable-SOM composition is strongly correlated to litter quality and available nutrients. In nutrient-poor forests with low litter quality, the decomposition of relatively recalcitrant compounds (i.e. short and mid-chain alkanes/alkenes and aromatic compounds) appears hampered, causing a relative accumulation of these compounds in the soil. However, if substrate quality is favorable, no accumulations of recalcitrant compounds were observed, not even under high soil-moisture conditions. Former heathland vegetation still had a profound influence on extractable-SOM chemistry of young pine forests after a minimum of 60 years.

Question: Did the composition of the herb layer of adeciduous forest on loamy soils sensitive to soil acidifica-tion change between 1954 and 2000? How are thesechange related to the abandonment of traditional cop-pice-with-standards forest management and increased soilacidification?Location: Central Belgium (Europe).Methods: Twenty semi-permanent phytosociologicalquadrats from an ancient deciduous forest (Meerdaalforest) were carefully selected out of a total of 70 plotsdating from 1954 and were revisited in 2000. Speciescomposition and soil pH H 2 O were recorded using ananalogous methodology. The studied period coincideswith a period of forest conversion from coppice-with-standards towards a high forest structure and with anincrease in acidifying and eutrophying deposition.Results: Between 1954 and 2000, species composition ofthe herb layer changed significantly. Redundancy analysispointed to increased shade resulting from shifts in coverand species composition of the shrub and tree layer asthe main driving force. Soil acidity increased and themajority of plots entered the aluminium buffer range,which potentially affected herb layer composition. Obser-vations at the species level, especially a strong decrease incover of the vernal species Anemone nemorosa supportedthis hypothesis.Conclusions: Our results show significant shifts in theforest herb layer in less than five decades. These shiftswere related to an alteration in the traditional forestmanagement regime and increased soil acidity. Whereasthe effect of a changed management regime can bemitigated, soil acidification is less reversible. Testing thegenerality of these patterns on more extensive data sets iscertainly needed.Keywords: Forest conversion; Forest management; Highforest; Increased shade; Semi-permanent plots.Nomenclature: Lambinon et al. (1998)

Summary 1. Former land use has long-lasting effects on the distribution and abundance of forest herbs. Pre vious studies mainly focussed on limited dispersal capacities of forest herbs to explain these patterns and few studies have experimentally evaluated the relative importance of recruitment. Introduction experiments offer a direct test of recruitment limitation, but are generally only monitored until the germination stage. 2. We examined recruitment of 10 forest herbs during five growing seasons by means of a seed sowing experiment in two contrasting forest types (valley and plateau) established on former agricultural land. Effects of seed density and clearing of vegetation and litter (disturbed microsites) were tested in a factorial design. The data were analysed in two successive steps: germination 2 years after seed

Traditional coppice management creates a temporal release of resources. We determined how this affected three herbaceous species (Cardamine pratensis, Primula elatior and Geum urbanum) and if it was suitable for their conservation within woodland given their differing phenologies and habitat affinities for woodland.Reproductive adults were transplanted and their fate, i.e. survival and counts of leafs and flowers, plus the fate of their progeny, were monitored for three years following cutting of coppice shoots (three light levels) or yearly autumn mowing.Cardamine pratensis and P. elatior produced more flowers with increasing light availability. Mowing increased flower and leaf production with time for P. elatior. Seedling numbers followed a similar trend. Geum urbanum initially produced more flowers with increasing light and when mown, but the effect disappeared and did not increase seedling numbers. Its basal leaves showed the opposite pattern. Population growth rates (λ), calculated for P. elatior and G. urbanum, confirmed the strong treatment effects on the former and the absence of effects on the latter. Yet, decomposition of treatment effects, showed considerable flexibility in life history of G. urbanum, except for contributions of fecundity. The latter, however, contributed most to positive effects on λ for P. elatior.Early flowering species with an affinity for open habitats (C. pratensis > P. elatior) benefited more from temporal resource release than the later flowering, typical woodland species. Coppice management thereby maintains both typical forest herbs and herbs with affinity for more open habitats. This is an important conservation tool especially in intensively managed landscapes.

Conversion of historical to modern forest management regimes can have profound effects on understorey diversity and composition, because overstorey changes affect environmental conditions in the herbaceous layer. Management-driven changes (1957/1967–2005) in the overstorey of two temperate, deciduous forests generated nine conversion types in a set of 255 semi-permanent plots formerly managed as coppice-with-standards. Dominant canopy cover shifted from the shrub to the tree layer in all conversion types. Tree and shrub richness decreased significantly for most conversion types. Differences in forest structure (uneven-aged vs. even-aged), changes in litter quality and overstorey permeability for light characterised each conversion. We determined temporal changes in herb layer cover, species richness and Shannon–Wiener diversity for each conversion. We tested if herbaceous species composition for each conversion type changed between 1957/1967 and 2005 in terms of among plot variability in species composition (multivariate dispersion) and directional changes in average composition (composition shift). Differential changes in richness, cover, litter quality and shade casting ability of the overstorey were related to changes in herb layer species or ecological groups of species across conversions. Total herb layer cover increased (mainly related to Anemone nemorosa , Hyacinthoides non-scripta or Rubus fruticosus agg.), except where Beech was planted on poor soils. Richness increased where litter quality increased and decreased only on strongly shaded poor soils. Decreased/increased multivariate dispersion coincided with decreased/increased richness and Shannon–Wiener diversity. Furthermore, only conversions to even-aged stands, except for Oak on poor soils, had strong composition shifts which were reflected by an increase of indifferent/acidophilous species and species with wide amplitude. For gradual conversions to uneven-aged high forest, the edaphic changes caused by altered overstorey composition were reflected in the understorey. In the absence of incentives to reinitiate traditional management, conserving the understorey community is best achieved by a continuation of former overstorey species composition and uneven-aged high forest management. Beech plantations caused strong and negative effects, but as it is a climax species, Beech could still be used in spatiotemporal mixtures with soil improving species. Favouring or introducing the latter species can improve edaphic conditions of acid-sensitive poor soils due to their high-litter quality.

International audience; Global biodiversity is affected by numerous environmental drivers. Yet, the extent to which global environmental changes contribute to changes in local diversity is poorly understood. We investigated biodiversity changes in a meta-analysis of 39 resurvey studies in European temperate forests (3988 vegetation records in total, 17-75 years between the two surveys) by assessing the importance of (i) coarse-resolution (i.e., among sites) vs. fine-resolution (i.e., within sites) environmental differences and (ii) changing environmental conditions between surveys. Our results clarify the mechanisms underlying the direction and magnitude of local-scale biodiversity changes. While not detecting any net local diversity loss, we observed considerable among-site variation, partly explained by temporal changes in light availability (a local driver) and density of large herbivores (a regional driver). Furthermore, strong evidence was found that presurvey levels of nitrogen deposition determined subsequent diversity changes. We conclude that models forecasting future biodiversity changes should consider coarse-resolution environmental changes, account for differences in baseline environmental conditions and for local changes in fine-resolution environmental conditions.

In fragmented landscapes, habitat patches are often destroyed and created through time, though most metapopulation models treat patch networks as static. Here we present a generally applicable, modified version of Hanski's Incidence Function Model (IFM) that incorporates landscape dynamics (i.e., habitat patch turnover), and we param- eterize the model with data on patch occupancy patterns for forest plants in central Lin- colnshire, UK. The modified IFM provided a better, or equally good, fit to species' patch occupancy patterns than logistic regression. Estimated colonization and extinction rates, and the results of logistic regression analyses, varied significantly among species with different life history traits. For example, species with low seed production and predomi- nantly short-distance seed dispersal showed lower rates of colonization and extinction and were more likely to show effects of patch age and connectivity on patch-level presence than species with the opposite set of traits. Model simulations demonstrate a profound negative influence of habitat turnover rate on metapopulation dynamics and persistence, particularly for slow-colonizing species. The incorporation of temporal habitat dynamics into the metapopulation paradigm will permit its application to organisms in a much wider range of real landscapes.

We recently assessed plant community responses to macroclimate warming across European and North American temperate forests (1). To do so, we inferred the temperature preferences of understory species from distribution data by means of ecological niche, or species distribution models (SDMs). Harwood et al. (2) propose that subcanopy temperatures, instead of gridded climate data, should have been used in our analyses. Despite exciting ongoing advances in the downscaling of microclimates from macroclimatic data, Harwood et al.’s suggestion is, at present, simply not possible at the scale of our study: One would need to match the occurrence of every individual of each of 1,032 species with the microclimate in each location across two continents. More fundamentally, such downscaling is not necessary for our purpose: when applied correctly (3), SDMs can infer species’ climatic tolerances without the need of those detailed field data, based on mean field approximation (4). Nonetheless, as SDMs only approximate thermal tolerances, we went beyond common practice to propagate their uncertainties into thermophilization rates (1). Even if microclimates might bias the niche models of some species (2), no bias at the level of among-region comparisons is expected given that we quantified thermophilization as the relative temporal difference in floristic temperatures per unit time. Thus, presence of bias in species’ temperature preferences, as hypothesized by Harwood et al. (2), is not enough to cause bias in thermophilization rates. Our sensitivity analyses removing random subsets of species from the total pool (1) confirm that the reported thermophilization rates are robust.

1. Non-random species loss and gain in local communities change the compositional heterogeneity between communities over time, which is traditionally quantified with dissimilarity-based approaches. Yet, dissimilarities summarize the multivariate species data into a univariate index and obscure the species-level patterns of change, which are central to understand the causes and consequences of the community changes. 2. Here, we propose a model-based approach that looks for species-level effects of time period and construct a multiple-site metric as a sum across species to test the consistency of the individual species responses. Species fall into different response types, showing how they influence the changes in community heterogeneity. 3. In a comparison with other multiple-sitemetrics, we illustrate the properties of our method and the differences and similarities with other approaches. For instance, ourmetric estimates the total variation in a community data set based on species-level contributions, not the compositional dissimilarities between particular sites. Similar to some other approaches, we can distinguish between heterogeneity derived from turnover or richness differences. 4. Our approach was applied to a set of 23 forest understorey resurvey studies spread across Europe. We show the species gains and lossesmay as well decrease or increase levels of community heterogeneity. Although species occurrences and communities have not changed in a consistent way along continental-scale environmental gradients such as climatic conditions, several species shifted in a similar way across the different data sets. 5. Testing the significance of shifts in species prevalence over time to infer corresponding changes in the compositional heterogeneity among sites provides a very intuitive tool for community resurvey studies. The main strengths of our framework are the explicit consideration of the relative roles of species gains and losses and the straightforward generalization to different sets of hypotheses related to community changes. Key-words: biodiversity, community composition, biotic homogenization, binomial deviance, dissimilarity, beta diversity,multivariate analysis,meta-analysis, forest understorey

Recent global warming is acting across marine, freshwater, and terrestrial ecosystems to favor species adapted to warmer conditions and/or reduce the abundance of cold-adapted organisms (i.e., “thermophilization” of communities). Lack of community responses to increased temperature, however, has also been reported for several taxa and regions, suggesting that “climatic lags” may be frequent. Here we show that microclimatic effects brought about by forest canopy closure can buffer biotic responses to macroclimate warming, thus explaining an apparent climatic lag. Using data from 1,409 vegetation plots in European and North American temperate forests, each surveyed at least twice over an interval of 12–67 y, we document significant thermophilization of ground-layer plant communities. These changes reflect concurrent declines in species adapted to cooler conditions and increases in species adapted to warmer conditions. However, thermophilization, particularly the increase of warm-adapted species, is attenuated in forests whose canopies have become denser, probably reflecting cooler growing-season ground temperatures via increased shading. As standing stocks of trees have increased in many temperate forests in recent decades, local microclimatic effects may commonly be moderating the impacts of macroclimate warming on forest understories. Conversely, increases in harvesting woody biomass—e.g., for bioenergy—may open forest canopies and accelerate thermophilization of temperate forest biodiversity. ispartof: Proceedings of the National Academy of Sciences of the United States of America vol:110 issue:46 pages:18561-18565 ispartof: location:United States status: published

Questions: How do changes in forest management, i.e. in disturbance type and frequency, influence species diversity, abundance and composition of the seed bank? How does the relationship between seed bank and vegetation change? What are the implications for seed bank dynamics? Location: An ancient Quercus petraea - Carpinus betulus forest in conversion from coppice-with-standards to regular Quercus high forest near Montargis, France. Methods: Seed bank and vegetation were sampled in six replicated stand types, forming a chronosequence along the conversion pathway. The stand types represented mid-successional stages of stands in transition from coppice-with-standards (to high forest (16 plots) and early- and mid-successional high forest stands (32 plots). Results: Seed bank density and species richness decreased with time since last disturbance. Adjusting for seed density effects obscured species richness differences between stand types, but species of later seres were nested subsets of earlier seres, implying concomitant shifts in species richness and composition with time since disturbance. Later seres were characterized by species with low seed weight and high seed longevity. Seed banks of early seres were more similar to vegetation than to later seres. Conclusions: Abandonment of the coppice-with-standards regime altered the seed bank characteristics, as well as its relationship with vegetation. Longer management cycles under high forest yield impoverished seed banks. For their persistence, seed bank species will increasingly rely on management of permanently open areas in the forest landscape. Thus, revegetation at the beginning of new high-forest cycles may increasingly depend on inflow from seed sources., L'abandon du régime en taillis sous futaie a modifié les caractéristiques de la banque de graines, de même que sa relation avec la végétation. Les cycles sylvicoles plus longs qui caractérisent la futaie régulière appauvrissent la banque de graines. Les espèces qui misent sur la banque de graines pour persister dans le paysage vont dépendre de plus en plus des espaces ouverts permanents en forêt. Le retour de la végétation herbacée au début des cycles sylvicoles dépendra de plus en plus de des flux de graines des zones adjacentes, plus que sur l'activation localement de la banque de graines.