The impact of hedge-forest connectivity and microhabitat conditions on spider and carabid beetle assemblages in agricultural landscapes

Agricultural intensification in terms of decreasing landscape complexity and connectivity has negatively affected biodiversity. Linear landscape elements composed of woody vegetation like hedges may counteract this negative trend by providing habitats and enhancing habitat connectivity for different organisms. Here, we tested the impacts of habitat type (forest edges vs. hedges) and hedges’ isolation (connected vs. isolated hedges) from forests as well as microhabitat conditions (percentage of bare ground and width) on trait-specific occurrence of ground-dwelling arthropods, namely spiders and carabids. Arthropods were grouped by habitat specialisation (forest vs. open-habitat species vs. generalists), hunting strategy (web-building or hunting spiders) and dispersal ability (wing morphology of carabids). Spider and carabid assemblage composition was strongly influenced by habitat type and isolation, but not by microhabitat conditions. Activity density of forest species and brachypterous carabids was higher in forest edges compared to hedges, whereas open-habitat species and macropterous carabids showed reverse patterns, with no effects of isolation. Occurrence of generalist carabids, but not spiders, was higher in hedges compared to forest edges. Habitat type and isolation did not affect spiders with different hunting strategy. Microhabitat conditions were less important for spider and carabid occurrence. Our study concludes that on a landscape scale, type of linear woody habitat is more important for arthropod occurrence than isolation effects and microhabitat conditions, depending on traits. Hedges provide refuges for species specialised to open habitats and species with high dispersal ability, such as macropterous carabids. Forest edges enhance persistence of species specialised to forests and species with low dispersal ability, such as brachypterous carabids.     

Impacts of Restored Patch Density and Distance from Natural Forests on Colonization Success

Abstract The reduction and fragmentation of forest habitats is expected to have profound effects on plant species diversity as a consequence of the decreased area and increased isolation of the remnant patches. To stop the ongoing process of forest fragmentation, much attention has been given recently to the restoration of forest habitat. The present study investigates restoration possibilities of recently established patches with respect to their geographical isolation. Because seed dispersal events over 100 m are considered to be of long distance, a threshold value of 100 m between recent and old woodland was chosen to define isolation. Total species richness, individual patch species richness, frequency distributions in species occurrences, and patch occupancy patterns of individual species were significantly different among isolated and nonisolated stands. In the short term no high species richness is to be expected in isolated stands. Establishing new forests adjacent to existing woodland ensures higher survival probabilities of existing populations. In the long term, however, the importance of long‐distance seed dispersal should not be underestimated because most species showed occasional long‐distance seed dispersal. A clear distinction should be made between populations colonizing adjacent patches and patches isolated from old woodland. The colonization of isolated stands may have important effects on the dynamics and diversity of forest networks, and more attention should be directed toward the genetic traits and viability of founding populations in isolated stands.     

Travelling to a former sea floor: colonization of forests by understorey plant species on land recently reclaimed from the sea

Questions: What are important forest characteristics determining colonization of forest patches by forest understorey species? Location: Planted forests on land recently reclaimed from the sea, the Netherlands. Methods: We related the distribution of forest specialist species in the understorey of 55 forests in Dutch IJsselmeer polders to the following forest characteristics: age, area, connectivity, distance to mainland (as a proxy for distance to seed source) and path density. We used species of the Fraxino‐Ulmetum association for the Netherlands as reference for species that could potentially occur in the study area. Results: Area and age of the surveyed forests explained a large part of the variation in overall species composition and species number of forest plant species. The importance of connectivity and distance to the mainland of forest habitats became apparent only at a more detailed level of dispersal groups and individual species. The importance of forest parameters differed between dispersal groups and also between individual species. After 60 years, 75% of the potential pool of wind‐dispersed species has reached the polders, whereas this was only 50% for species lacking specific adaptations to long‐distance dispersal. However, the average percentage of successful colonizing species present per forest was substantially lower, ranging from 15 to 37%. Conclusions: The data strongly suggest that the colonization process in polder forests is still in its initial phase, during which easily dispersed species dominate the vegetation. Colonization success of common species that lack adaptations to long‐distance dispersal is affected by spatial configuration of the forests, and most rare species that could potentially occur in these forests are still absent. Implications for conservation of rare species in fragmented landscapes are discussed.     

Effect of habitat area and isolation on plant trait distribution in European forests and grasslands

A number of studies show contrasting results in how plant species with specific life‐history strategies respond to fragmentation, but a general analysis on whether traits affect plant species occurrences in relation to habitat area and isolation has not been performed. We used published data from forests and grasslands in north‐central Europe to analyse if there are general patterns of sensitivity to isolation and dependency of area for species using three traits: life‐span, clonality, and seed weight. We show that a larger share of all forest species was affected by habitat isolation and area as compared to grassland species. Persistence‐related traits, life‐span and clonality, were associated to habitat area and the dispersal and recruitment related trait, seed weight, to isolation in both forest and grassland patches. Occurrence of clonal plant species decreased with habitat area, opposite to non‐clonal plant species, and long‐lived plant species decreased with grassland area. The directions of these responses partly challenge some earlier views, suggesting that further decrease in habitat area will lead to a change in plant species community composition, towards relatively fewer clonal and long‐lived plants with large seeds in small forest patches and fewer clonal plants with small seeds in small grassland patches. It is likely that this altered community has been reached in many fragmented European landscapes consisting of small and isolated natural and semi‐natural patches, where many non‐clonal and short‐lived species have already disappeared. Our study based on a large‐scale dataset reveals general and useful insights concerning area and isolation effects on plant species composition that can improve the outcome of conservation and restoration efforts of plant communities in rural landscapes.     

The role of landscape configuration in plant composition of floodplain forests across different physiographic areas

Questions: What is the relative importance of landscape variables compared to habitat quality variables in determining species composition in floodplain forests across different physiographic areas? How do species composition and species traits relate to effects of particular landscape variables? Do lowland and mountain areas differ in effects of landscape variables on species composition? Location: Southern Czech Republic. Methods: A total of 240 vegetation relevés of floodplain forests with measured site conditions were recorded across six physiographic areas. I tested how physiographic area, habitat quality variables and landscape variables such as current land‐cover categories, forest continuity, forest size and urbanization influenced plant species composition. I also compared how mountain and lowland areas differ in terms of the relative importance of these variables. To determine how landscape configuration affects the distribution of species traits, relationships of traits and species affinity with landscape variables were tested. Results: Among landscape variables, forest continuity, landscape forest cover and distance to nearest settlement altered the vegetation. These variables also influenced the distributions of species traits, i.e. life forms, life strategies, affinity to forest, dispersal modes, seed characteristics, flooding tolerance and Ellenberg indicator values for nitrogen, light, moisture and soil reaction. Nevertheless, physiographic area and habitat quality variables explained more variation in species composition. Landscape variables were more important in lowland areas. Forest continuity affected species composition only in lowlands. Conclusions: Although habitat quality and physiographic area explained more vegetation variability, landscape configuration was also a key factor influencing species composition and distribution of species traits. However, the results are dependent on forest geographical location, with lowland forests being more influenced by landscape variables compared to mountain forests.     

Plant dispersal strategies and the colonization of Araucaria forest patches in a grassland‐forest mosaic

Questions: In a natural grassland‐forest mosaic: What is the influence of phylogeny and diaspore traits related to disperser attraction (DAT) on (1) seed size/number trade‐off (SSNT) in woody species colonizing forest patches; (2) on the frequency of the species? 3. What is the influence of forest patch area on mean seed size and number. 4. Do phylogeny and DAT expressed at the species level affect this relationship? Location: Campos grassland and Araucaria forest in São Francisco de Paula, RS, Brazil, at ca. 29°28’ S; 50° 13’ W. Methods: Forest patches of different sizes in a grassland site recovering for ten years since human disturbances were surveyed by the relative abundance of vertebrate‐dispersed woody saplings. We described colonizer species according to taxonomic phylogenetic relationships and diaspore type, size and color. We analyzed with a variation partitioning method their influence on SSNT and on species frequency in the patches. At the community level we regressed mean seed size and number on forest patch area and evaluated how these relationships were affected by phylogeny and DAT at the species level. Results: 1. Phylogeny and DAT mostly explained seed size and seed number per diaspore variation. 2. By controlling phylogeny and DAT influence the frequency of species in forest patches was positively associated with their seed number in the diaspores, and negatively associated with their seed size. 3. Mean seed size and seed number at the community level were positively associated with patch area. 4. When phylogeny and DAT influences on seed size were removed this relationship was stronger for seed size and weaker for seed number. Conclusions: 1. Energy allocation to dispersal in detriment of offspring survival increased the successful establishment of colonizer species in forest patches, despite phylogenetic relationships and DAT variation in their diaspores. 2. Although patch area exerted a selective pressure on seed size, habitat preferences of dispersers may also influence patch colonization.     

Role of plant functional traits in determining vegetation composition of abandoned grazing land in north‐eastern Victoria,Australia

Question: In the Northern Hemisphere, species with dispersal limitations are typically absent from secondary forests. In Australia, little is known about dispersal mechanisms and other traits that drive species composition within post‐agricultural, secondary forest. We asked whether mode of seed dispersal, nutrient uptake strategy, fire response, and life form in extant vegetation differ according to land‐use history. We also asked whether functional traits of Australian species that confer tolerance to grazing and re‐colonisation potential differ from those in the Northern Hemisphere. Location: Delatite Peninsula, NE Victoria, Australia. Methods: The vegetation of primary and secondary forests was surveyed using a paired‐plot design. Eight traits were measured for all species recorded. ANOSIM tests and Non‐metric Multi‐dimensional Scaling were used to test differences in the abundance of plant attributes between land‐use types. Results: Land‐use history had a significant effect on vegetation composition. Specific leaf area (SLA) proved to be the best predictor of response to land‐use change. Primary forest species were typically myrmecochorous phanerophytes with low SLA. In the secondary forest, species were typically therophytes with epizoochorous dispersal and high SLA. Conclusions: The attributes of species in secondary forests provide tolerance to grazing suggesting that disturbance caused by past grazing activity determined the composition of these forests. Myrmecochores were rare in secondary forests, suggesting that species had failed to re‐colonise due to dispersal limitations. Functional traits that resulted in species loss through disturbance and prevented re‐colonisation were different to those in the Northern Hemisphere and were attributable to the sclerophyllous nature of the primary forest.     

Cyclic habitat displacements during Pleistocene glaciations have induced independent evolution of Tasimia palpata populations (Trichoptera: Tasimiidae) in isolated subtropical rain forest patches

Aim Mechanisms generating biodiversity and endemism are influenced by both historical and ecological patterns, and the relative roles of history vs. ecological interactions are still being debated. The phylogeography of one rain forest‐restricted caddisfly species, Tasimia palpata, thought to have good dispersal abilities, is used to address questions about shifts of highland rain forest habitat during Pleistocene glaciations and about their consequences for haplotype composition and distribution. Location Tasimia palpata occurs in highland subtropical rain forest patches, which are separated from one another by lowland dry bush, in south‐eastern Queensland, Australia. Methods We sequenced 375 base pairs of the mitochondrial cytochrome oxidase I gene from 169 individuals (20 populations) of T. palpata, mainly from three fragmented subtropical rain forest blocks, revealing 46 haplotypes. Analysis of molecular variance (amova ), genetic divergence between populations, nested clade analyses and tests based on coalescent theory were used to analyse phylogeographical relationships among T. palpata populations. Results amova indicates spatial genetic structure between isolated subtropical rain forest patches, with an isolation‐by‐distance effect. Tests based on coalescent theory suggest a repeated process of population reductions and divergence between isolated rain forests during Pleistocene glaciations as a consequence of habitat constrictions followed by population expansions during interglacial periods when subtropical rain forest expanded. In addition, these results suggest that, prior to the Pleistocene, rain forest and T. palpata had more widespread distributions in this region. Main conclusions Historical rain forest expansion and contraction during the Pleistocene resulted in changes in demography and genetic diversity of T. palpata, as well as in an increase in genetic divergence between populations from different patches of subtropical rain forest. Despite the fact that this caddisfly species was isolated in separate highland rain forest patches at various times during the Pleistocene, there is no evidence of allopatric speciation during the Quaternary, which contrasts with other examples of endemism and high diversity in rain forest highlands.     

Effects of age and distance on the composition of mixed deciduous forest fragments in an agricultural landscape

Abstract. Forest patches in central Belgium were inventoried twice for the presence or absence of forest plant species to study the effects of age and distance on species composition. All forests in the study area were subdivided based on their land use history. To avoid effects of autocorrelated environmental characteristics on species composition, habitat homogeneity was indirectly investigated using a TWINSPAN classification of the vegetation data. Two major habitats (alluvial and non‐alluvial forests) were distinguished and analysed separately. Patterns of species composition were investigated at the landscape level using Mantel tests. Species composition similarity measures were calculated between all pairs of fragments based on the floristic data. A highly significant correlation was found between species composition similarity and inter‐patch distance. Difference in age, which we used as a measure for habitat quality, was less important in explaining species composition patterns. The effects of spatial configuration became significant when difference in age was accounted for, and a partial correlation was calculated between inter‐patch distance and species composition similarity. Different results were found for alluvial and non‐alluvial forest types. Alluvial forests were more influenced by the spatial configuration than the non‐alluvial. For the non‐alluvial forest type effects measured with the difference in age between forest fragments obscured the effects of inter‐patch distance. Based on our findings we suggest that species composition is not only internally generated, but external processes such as differential colonization caused by varying degrees of isolation may be of overriding importance.     

Genetic evidence for landscape effects on dispersal in the army ant Eciton burchellii

Inhibited dispersal, leading to reduced gene flow, threatens populations with inbreeding depression and local extinction. Fragmentation may be especially detrimental to social insects because inhibited gene flow has important consequences for cooperation and competition within and among colonies. Army ants have winged males and permanently wingless queens; these traits imply male‐biased dispersal. However, army ant colonies are obligately nomadic and have the potential to traverse landscapes. Eciton burchellii, the most regularly nomadic army ant, is a forest interior species: colony raiding activities are limited in the absence of forest cover. To examine whether nomadism and landscape (forest clearing and elevation) affect population genetic structure in a montane E. burchellii population, we reconstructed queen and male genotypes from 25 colonies at seven polymorphic microsatellite loci. Pairwise genetic distances among individuals were compared to pairwise geographical and resistance distances using regressions with permutations, partial Mantel tests and random forests analyses. Although there was no significant spatial genetic structure in queens or males in montane forest, dispersal may be male‐biased. We found significant isolation by landscape resistance for queens based on land cover (forest clearing), but not on elevation. Summed colony emigrations over the lifetime of the queen may contribute to gene flow in this species and forest clearing impedes these movements and subsequent gene dispersal. Further forest cover removal may increasingly inhibit Eciton burchellii colony dispersal. We recommend maintaining habitat connectivity in tropical forests to promote population persistence for this keystone species.     

Effects of water regime and habitat continuity on the plant species composition of floodplain forests

Questions: 1. How big is the difference in the herbaceous layer composition between flooded and unflooded stands? 2. Are there species or species groups which have an affinity to ancient vs. recent forests in stands with different water regimes? 3. Are patterns of life history traits different between flooded and unflooded stands as well as between ancient and recent forests in stands with a different water regime? Location: Floodplain forests in the Middle Elbe region and district of Leipzig, Central Germany. Location: The herbaceous layer was studied in randomly selected quadrats of 9 m² in 2000 and 2001. Six ancient (n_plot=59) and six adjacent recent forests (n_plot=108) were investigated in flooded stands as well as three ancient (n_plot=41) and three recent forests (n_plot=70) in stands that have not been flooded for 50 years. The association of single species, species groups and life history traits were statistically tested for flooded vs. unflooded stands and for ancient vs. recent forests. Results: Interruption of flooding caused a complete species turnover in the herbaceous layer composition. Whereas in the still flooded stands typical alluvial species prevail, species composition in stands without flooding for 50 years showed a closed relation to the Stellario‐Carpinetum. Six herbaceous species in the flooded and five in the unflooded stands showed a preference for ancient forests. Only one species in the flooded and six herbaceous species in the unflooded stands are significantly associated with recent forests. Life history traits differ between flooded and unflooded stands but are similar in ancient and recently flooded stands, while unflooded ancient forests have more geophytes and myrmecochorous species than recent forests. Conclusions: The specificity of species composition in floodplain forests can only be maintained by regular flooding. Interruption of inundations lead to differences in the patterns of species composition and life history traits between ancient and recent forests.     

Effects of environment,habitat configuration and forest continuity on the distribution of forest plant species

In present day European landscapes many forest plant species are restricted to isolated remnants of a formerly more or less continuous forest cover. The two major objectives of this study were (1) to determine the relative importance of habitat quality (mainly in terms of soil parameters), habitat configuration (patch size and isolation) and habitat continuity for the distribution of herbaceous forest plant species in a highly fragmented landscape and (2) to examine if groups of species with different habitat requirements are affected differently. Deciduous forest patches in northwestern Germany were surveyed for the presence of a large set of forest species. For each patch, habitat quality, configuration and continuity were determined. Data were analysed by Redundancy Analysis with variation partitioning for effects on total species composition and multivariate logistic regression for effects on individual species, for two different data sets (base‐rich and base‐poor forest patches). Overall, we found strong effects of habitat quality (particularly of soil pH, water content and topographic heterogeneity in the base‐rich forest patches; and of calcium content and disturbance in the base‐poor patches), but only relatively weak effects of habitat configuration and habitat continuity. However, a number of species were positively affected by patch area and negatively affected by patch isolation. Furthermore, the relative importance of habitat configuration tended to be higher for species predominantly growing in closed forests compared to species occurring both in the forest and in the open landscape.     

Zero‐sum landscape effects on acorn predation associated with shifts in granivore insect community in new holm oak (Quercus ilex) forests

Aim

Landscape attributes can determine plant–animal interactions via effects on the identity and abundance of the involved species. As most studies have been conducted in a context of habitat loss and fragmentation, we know very little about interaction assembly in new habitats from a landscape approach. This study aimed to test the effect of forest age and connectivity on acorn predation by a guild of predator insects differing in dispersal ability and resilience mechanisms: two weevils (Curculio elephas and C. glandium) and one moth (Cydia fagiglandana) in expanding Quercus ilex forests.

Location

Barcelona, Spain.

Methods

We assessed the proportion of infested acorns and identified the predator at the species level in five patches of connected old forests, connected new forests and isolated new forests. Effects of habitat age and connectivity at three scales (tree, patch and landscape) were analysed using generalized linear mixed‐effects models.

Results

Predation by weevils was positively associated with old connected forests, while moths, with better dispersal ability, were able to predate upon all patches equally. Moreover, C. elephas, the weevil with lower dispersal ability, exhibited colonization credits in the new isolated patches. In spite of these changes in the guild of seed predators, the proportion of infested acorns was non‐significantly different among forests.

Main conclusions

The guild of seed predators may vary depending on forest age and connectivity. However, because those with higher dispersal ability may replace less mobile species, this resulted in zero‐sum effects of landscape attributes on acorn predation (i.e., similar predation rates in well‐connected old forests vs. isolated new forests).

     

The effect of landscape fragmentation and forest continuity on forest floor species in two regions of Denmark

Abstract. Forest species composition was recorded in 82 forests in the Himmerland and Hornsherred regions in Denmark and analysed with respect to isolation (distance to other forests and areas of forest), forest continuity (older or younger than 200 yr), soil pH, tree species composition and seed dispersal groups. Continuity and isolation measures were correlated with forest species richness in Hornsherred. Myrmecochorous, autochorous, anemoballistic and endozoochorous species were markedly fewer in recent than in ancient forests. In Himmerland, patterns were much weaker and few significant correlations were found between forest species richness or different seed dispersal groups and continuity or isolation of the forests. Differences between the two regions may result from less intensive land use, a more humid climate and a smaller species pool with less species with short distance dispersal in Himmerland. Landscape fragmentation therefore appears to limit forest species’recolonization more in Hornsherred than in Himmerland.     

Habitat fragmentation in forests affects relatedness and spatial genetic structure of a native rodent,Rattus lutreolus

Habitat fragmentation can have a range of negative demographic and genetic impacts on disturbed populations. Dispersal barriers can be created, reducing gene flow and increasing population differentiation and inbreeding in isolated habitat remnants. Aggregated retention is a form of forestry that retains patches of forests as isolated island or connected edge patches, with the aim of ‘lifeboating’ species and processes, retaining structural features and improving connectivity. Swamp rats (Rattus lutreolus) are a cover‐dependent species that are sensitive to habitat removal. We examined the effects of aggregated retention forestry and forestry roads in native wet Eucalyptus forests on swamp rat gene flow and population genetic structure. We characterized neighbourhood size in unlogged forest to provide a natural state for comparison, and examined population structure at a range of spatial scales, which provided context for our findings. Tests of pairwise relatedness indicated significant differentiation between island and edge populations in aggregated retention sites, and across roads in unlogged sites. Spatial autocorrelation suggested a neighbourhood size of 42–55 m and revealed male‐biased dispersal. We found no genetic isolation by geographical distance at larger (>2.3 km) scales and populations were all significantly differentiated. Our results suggest that removal of mature forest creates barriers for swamp rat dispersal. In particular, roads may have long‐term impacts, while harvesting of native forests is likely to create only short‐term dispersal barriers at the local scale, depending on the rate of regeneration.     

Functional community structure of African monodominant Gilbertiodendron dewevrei forest influenced by local environmental filtering

Monodominant patches of forest dominated by Gilbertiodendron dewevrei are commonly found in central African tropical forests, alongside forests with high species diversity. Although these forests are generally found sparsely distributed along rivers, their occurrence is not thought to be (clearly) driven by edaphic conditions but rather by trait combinations of G. dewevrei that aid in achieving monodominance. Functional community structure between these monodominant and mixed forests has, however, not yet been compared. Additionally, little is known about nondominant species in the monodominant forest community. These two topics are addressed in this study. We investigate the functional community structure of 10 one‐hectare plots of monodominant and mixed forests in a central region of the Congo basin, in DR Congo. Thirteen leaf and wood traits are measured, covering 95% (basal area weighted) of all species present in the plots, including leaf nutrient contents, leaf isotopic compositions, specific leaf area, wood density, and vessel anatomy. The trait‐based assessment of G. dewevrei shows an ensemble of traits related to water use and transport that could be favorable for its location near forest rivers. Moreover, indications have been found for N and P limitations in the monodominant forest, possibly related to ectomycorrhizal associations formed with G. dewevrei. Reduced leaf N and P contents are found at the community level for the monodominant forest and for different nondominant groups, as compared to those in the mixed forest. In summary, this work shows that environmental filtering does prevail in the monodominant G. dewevrei forest, leading to lower functional diversity in this forest type, with the dominant species showing beneficial traits related to its common riverine locations and with reduced soil N and P availability found in this environment, both coregulating the tree community assembly.     

Effects of habitat quality and landscape structure on saproxylic species dwelling in boreal spruce-swamp forests

Intensive forest management has caused loss and fragmentation of old‐growth forests and reduced the amount of dead wood throughout northwest Europe. Changes in habitat availability are reflected in occurrence patterns of habitat‐specialist species only after a certain time lag. Here we analyse the responses of wood‐decomposing fungi and saproxylic beetles inhabiting patches of spruce‐swamp forest to habitat quality, loss and isolation at three different spatial scales in eastern Finland and adjacent Russian Karelia, where forestry has been very marginal until recently. Both rare specialist species and common generalist species were included in the study to reveal whether their occurrence patterns differ. Variables describing habitat quality (density and continuity of host trees, patch area) turned out significant in explaining species' incidences (proportion of occupied host trees) in only a few cases, probably because of the relatively high quality of all study patches. Despite this fact, and consistent with our hypothesis, incidences of all the eight specialist species were higher in Russia than Finland, and the difference was significant in the two most strict habitat specialists, Pytho kolwensis and Phlebia centrifuga. In contrast, incidences of three out of four generalist species were higher in Finland than in Russia, and the difference was significant in Rhagium inquisitor. In a subset of 21 patches in Finland, we used a metapopulation model to predict the probability of each patch to be currently occupied by a species given the known spatiotemporal distribution of suitable forest stands during the last 50 years. The degree of isolation alone explained significantly the incidences of five species. However, including habitat variables into the models altered some of the effects. Moreover, inconsistent with our hypothesis, isolation appeared to also negatively affect some very common generalist species. Inclusion of these species in the study disclosed that apparently significant effects of spatiotemporal isolation should be interpreted cautiously.     

Differences in tree community among secondary deciduous oak forests in rural and residential areas in the Hokuriku District of Japan

Tree communities of secondary deciduous oak forests were surveyed in 13 forests (two in residential and 11 in rural areas) in the warm temperate Hokuriku District of Japan to understand the effects of fragmentation, location (residential or rural), and logging history. The rural forest logged most recently, where diameter at breast height was smallest, had a distinct canopy tree (>12 m) community due to an increase of trees from wind-dispersed seeds. The rural forest with gaps and the two residential forests also had different canopy tree communities from the other rural forests. In contrast, the tree community in the shrub layer (≤6 m) was not influenced by logging history and the existence of gaps but by location only. This was caused by an increase in evergreen trees (consequently causing poor light conditions on the forest floor) and a decrease in trees from wind-dispersed seeds in the residential forests. Among the rural forest patches, no negative effects of forest size and isolation on density of tree individuals were detected for any seed dispersal mode. This may be because many forest patches were arranged at distances of 10–50 m from neighboring patches in rural areas, which enables tree species with low dispersal ability to disperse their seeds to neighboring forests. However, as found in the residential forests, long-term abandonment and extensive fragmentation may gradually reduce tree diversity through loss of tree species with shade intolerance and low seed dispersal ability.     

Diaspore removal and potential dispersers of the rare and protected Paeonia officinalis L. (Paeoniaceae) in a changing landscape

Paeonia officinalis L., a rare and protected species, mostly occurs in open and semi‐open habitats and is often threatened by forest and shrubland spread. To explore the still undocumented dispersal features of this species, we address the following questions. What are the relative roles of ants, small rodents, and birds as diaspore removers in open habitat and woodland? Which animal groups constitute the potential disperser assemblage and how do they shape the spatial patterns of seed dispersal? Do diaspores fit the ornithochory syndrome or do they only mimic fleshy fruits? Two experiments were performed to quantify diaspore fall and diaspore removal by animal groups, above ground and on the ground. Ants did not contribute to dispersal. In open habitats, no seed removal was detected, either on follicles or once diaspores had fallen to the ground. In woodland, diaspores were weakly removed by vertebrates on follicles and were mainly removed by rodents on the ground. As a consequence, we suggest that long‐distance dispersal events are very rare, weakening the possible escape into space of populations subject to forest spread. Several traits indicate that diaspores fit the ornithochory syndrome, but other traits are strongly reminiscent of mimetic diaspores deceiving bird dispersers. © 2007 CNRS. Journal compilation © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 154 , 13–25.