Forest edge contrasts have a predictable effect on the spatial distribution of carabid beetles in urban forests

Fragmented urban forest remnants are characterised by sharp edges and are bordered by various land-use types, which may have a considerable effect on the fauna and flora at forest edges, and into forest interiors. To investigate the effects of differentially contrasting edges (low vs. intermediate vs. high) on carabid beetle assemblages in urban boreal forests, we placed pitfall traps along a gradient from 6?m into three matrix types (secondary forest vs. grassland vs. asphalt) up to 60?m into urban forest patches in the cities of Vantaa and Helsinki, southern Finland. Individual species and carabid beetle assemblages were strongly affected by edge contrasts and distance from the forest edge. The strongest effect on individual species was caused by high contrasting edges: generalist and open-habitat species were favoured or not affected while forest specialists were affected negatively. Effects of the abundances of potential prey and competitors on the carabid beetles were also evaluated. Forest and moisture-associated carabid species were negatively to neutrally associated with springtail abundances while generalist and open habitat, and dryness associated species were more positively related to springtail abundances (a potential food source). In terms of potential competitors, forest and moisture-associated carabid species were negatively and/or neutrally affected by ant and wood ant numbers, while generalist and open-habitat species were neutrally to positively associated with these taxa. It appears that carabid beetle habitat associations are more important in the responses of these beetles across edges of different contrast than are the prey and competitor numbers collected there. We recommend the creation of “soft” or low-contrast urban edges if the aim of urban management is to protect forest carabids in cities.     

Forest–farm edge effects on communities of ground beetles (Coleoptera: Carabidae) under different landscape structures

In fragmented landscapes, ecological processes may be significantly influenced by edge effects, but few data are available for edge effects across forest–farmland edges. We investigated patterns of species richness, abundance, and species composition in ground beetles across forest–farm edges in two different agro-forest landscapes in Korea. Nine and five sites were selected from Hwaseong, a fragmented landscape, in 2011 and 2012, respectively, while eight sites were selected from Hoengseong, a relatively well-protected landscape, in 2012. Ground beetles were collected by pitfall trapping. Species richness was higher in the surrounding habitat than in the forest interior or edge in both Hwaseong and Hoengseong. However, in Hwaseong, species richness of the forest edge was similar to that of the forest interior, while in Hoengseong forest edge species richness was intermediate between that of the forest interior and surrounding areas. In addition, non-metric multidimensional scaling based on the combined data of both locations showed that the species composition of ground beetles in the forest edge was more similar to that of the forest interior than the surrounding areas, although some open-habitat species occurred at the forest edges. Three characteristic groups (forest specialists, edge-associated species, and open-habitat species) of ground beetle species were detected by indicator value analysis. In our study, ground beetle assemblages differed in the forest edges of two agro-forest landscapes, suggesting that the edge effect on biota can be influenced by landscape structure.     

Forest edge and diversity: carabids along forest-grassland transects

Diversity relationships of carabids in forest edges and the neighbouring forest interior and the surrounding grassland are studied. Samples were taken along three replicated forest-grassland transects using pitfall traps in the Aggtelek National Park in Hungary during 2 years. The study revealed significant edge effect on the carabids. The Shannon diversity of carabids were significantly higher in the forest edge and the grassland than in the forest interior. Carabids of the forest interior, forest edge and grassland can be separated from each other by ordinations, both on the species composition and abundance, suggesting that all three habitats have a distinct species assemblage. Moreover, indicator species analysis detected significant edge associated species; based on the specificity and fidelity of the carabids we have distinguished five groups of species: habitat generalists, grassland-associated species, forest generalists, forest specialists, and edge-associated species. Multiple linear regression analyses showed that relative air moisture, temperature of the ground and cover of the herbs are the most important factors determining the diversity of carabids along the transects. Our results show that the high diversity of carabids in forest edges is due to the edge-associated species and the presence of species characteristic to the adjacent habitats. The significance of forest edges in nature conservation, serving as a source habitat for dispersal processes, contributing to the recolonization of carabids after habitat destruction or other disturbance is emphasized.     

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.     

Bioindicators of edge effects within Atlantic Forest remnants: Conservation implications in a threatened biodiversity hotspot

Aim

Deforestation of the Atlantic Forest of eastern Paraguay has been recent but extensive, resulting in a fragmented landscape highly influenced by forest edges. We examined edge effects on multiple dimensions of small mammalian diversity.

Location

Forest fragments of eastern Paraguayan Atlantic Forest.

Methods

We trapped small mammal species at different distances from the forest edge (DTE) in reserves and estimated multiple dimensions of diversity per site. Similarity analysis identified species clusters that best described the patterns of diversity across reserves. Multivariate ordination and linear mixed models were used to determine the influence of DTE on various dimensions of small mammal diversity.

Results

There was an increase in richness and abundance along a DTE gradient, and remnants with higher edge:area ratios showed higher richness and abundance, independent of remnant size. Species at edges were generalists, open-habitat species or exotic species (spillover effect). We found higher phylogenetic diversity and functional richness and divergence towards forest edges. Spillover of non-forest and invasive species best explained richness, generalist forest species best explained total abundance, abundance of Hylaeamys megacephalus best explained diversity and evenness metrics and the presence of Marmosa paraguayana best explained various phylogenetic diversity models. None of the models that included megafauna or social factors were shown to be important in explaining patterns as a function of DTE.

Main Conclusions

We found strong support for a spillover effect and mixed support for complementary resource use and enhanced habitat resources associated with ecotones. Generalists characterized edge assemblages but not all generalists were equivalent. Edges showed more phylogenetically and functionally distinct assemblages than the interior of remnants. There was a conservation of functional diversity; however, open-habitat species, habitat generalists and exotic species boosted diversity near forest edges. Mechanisms governing diversity along forest edges are complex; disentangling those mechanisms necessitates the use of multiple dimensions of diversity.     

Boreal carabid-beetle (Coleoptera, Carabidae) assemblages along the clear-cut originated succession gradient

We examined the occurrence of carabid beetles along a forest successiongradient in central Finland (forest age classes: 5, 10, 20, 30 and 60years since clear-cutting). Species richness of carabids was higherin the two youngest age classes, while no clear differences were detected incarabid abundance. The high species richness in the young, open sites was due toinvasion of open-habitat species. Many forest species were absent from or scarcein the young sites and became gradually more abundant towards the older forestage classes. The catches indicated a drastic decrease and assemblage-levelchange in concert with canopy closure, i.e. 20–30 years afterclear-cutting. Some forest specialists with poor dispersal ability may facelocal extinction, if the proportion of mature forest decreases further and theremaining mature stands become more isolated. We recommend that, whileharvesting timber, connectivity between mature stands is ensured, mature standsare maintained close (a few tens of metres) to each other and the matrix qualityis improved for forest species by green tree retention.     

Regeneration pattern of primary forest species across forest-field gradients in the subtropical Mountains of Southwestern China

Evergreen broad-leaved forest is now gradually degraded and fragmented, and there is an increase in the amount of habitat edges as a result of long-term human activity. However, the role of edges in the regeneration of primary forest species is poorly understood. After 20 years of the edge creation, we analyzed primary forest species distribution and abundance, and changes in floristic composition, vegetation structure across forest-field gradients in Ailao Mountain, SW China. Our results revealed that there was a higher abundance and richness of primary species, late secondary species and thorny lianas at the distances 0–50 m than at the distances more than 50 m from the edge into the forest exterior. At the distances >50 m, no individuals of dominant canopy trees Lithocarpus xylocarpus, Castanopsis wattii, and L. jingdongensis were found, whereas the abundance of early pioneer shrub species and herbaceous cover was significantly greater. The richness of primary species showed a decrease with increasing distances from the forest edge to the exterior, particularly of medium-seeded primary species showing a drastic decrease. Moreover, no large-seeded primary species occurred at the distances >60 m. This study indicates that the forest edge as a buffer zone may be in favor of primary species regeneration. A dense shrub and herb layer, and seed dispersal may be the major factors limiting the forest regeneration farther from the forest edge. Therefore, to facilitate forest recovery processes, management should give priority to the protection of buffer zones of this forest edge.     

Habitat Islands,Forest Edge and Spring-active Invertebrate Assemblages

Forest management results in forest patches of varying sizes within a clearcut matrix. The result is a large amount of edge habitat and many small patches across the landscape. Here we describe the spring-active epigeal spider and carabid fauna found at the forest-clearcut edge of spruce forest in northern Ontario, Canada. We include two types of edge: the forest-clearcut interface and the small habitat patches formed by forest residuals within the clearcut. Spring-active forest spiders and carabids appear little affected by adjacent clearcutting activity, and some forest species, such as Agyneta olivacea (Emetron), Diplocentria bidentata (Emetron) and Microneta viaria (Blackwall), are more prevalent at the forested edge. Common and abundant spider species were equally recorded in forest interior and forest edge. Generally, no invasion of open-habitat species was observed within the forest, although smaller forest patches may be at higher risk.     

The effects of forestry on carabid beetles (Coleoptera: Carabidae) in boreal forests

As compared to natural forests, managed boreal forests are younger, more homogeneous in terms of tree age and species composition, and consist of smaller fragments. Here we examine the effects of such characteristics caused by forestry on carabid beetles (Coleoptera, Carabidae) in the boreal region. The main results are the following. (1) Fragmentation of forests and the size of a fragment appear not to be crucial for the survival of the majority of forest carabids, as they tend to be distributed over various successional stages, but species requiring old-growth habitats suffer. (2) For carabids there appear to be no or very few edge specialist species, and forest-open land edges appear to be effective barriers for species associated with forest or open habitat. However, generalist species easily cross the edge, and edges of forest fragments may be invaded by species from the surrounding open habitat. (3) Habitat change following clear-cutting dramatically changes the composition of carabid assemblages: species restricted to mature forests disappear and open-habitat species invade, while habitat generalists survive at least in the short term. Carabid diversity can probably best be maintained if forest management mimics natural processes, maintains natural structures and includes the natural composition of vegetation and other structural elements (such as dead wood) within the stands, provided that these forest features can be maintained and recreated through forest management practices. At a larger scale, the whole spectrum of forest types and ages (especially old-growth forests), and different successional processes (especially fire) should be maintained. These require the development and use of innovative logging methods, and the planning, implementation, and assessment of landscape-scale ecological management strategies.     

Adjacent woodlands rather than habitat connectivity influence grassland plant,carabid and bird assemblages in farmland landscapes

One response to biodiversity decline is the definition of ecological networks that extend beyond protected areas and promote connectivity in human-dominated landscapes. In farmland, landscape ecological research has focused more on wooded than open habitat networks. In our study, we assessed the influence of permanent grassland connectivity, described by grassland amount and spatial configuration, on grassland biodiversity. We selected permanent grasslands in livestock farming areas of north-western France, which were sampled for plants, carabids and birds. At two spatial scales we tested the effects of amount and configuration of grasslands, wooded habitats and crops on richness and abundance of total assemblages and species ecological groups. Grassland connectivity had no significant effects on total richness or abundance of any taxonomic group, regardless of habitat affinity or dispersal ability. The amount of wooded habitat and length of wooded edges at the 200 m scale positively influenced forest and generalist animal groups as well as grassland plant species, in particular animal-dispersed species. However, for animal groups such as open habitat carabids or farmland bird specialists, the same wooded habitats negatively influenced richness and abundance at the 500 m scale. The scale and direction of biodiversity responses to landscape context were therefore similar among taxonomic groups, but opposite for habitat affinity groups. We conclude that while grassland connectivity is unlikely to contribute positively to biodiversity, increasing or maintaining wooded elements near grasslands would be a worthwhile conservation goal. However, the requirements of open farmland animal species groups must be considered, for which such action may be deleterious.     

Carabid Beetle and Spider Assemblages along a Forested Urban–Rural Gradient in Southern Finland

To investigate the effects of urbanization on carabid beetles (Carabidae) and ground dwelling spiders (Araneae) a study was completed along a 20km urban–rural forest gradient in the Helsinki–Espoo area of southern Finland. To study changes in assemblage structure, abundance and species richness, these taxa were collected in the year 2000 using pitfall traps, which had been placed in four forest sites within each of the urban, suburban and rural zones. We expected to find changes in the abundances and species richnesses in the two taxa across the urban–rural gradient, but did not find any. Our second and third hypotheses, stating that generalist species and small-bodied species should gain dominance along the gradient from rural to urban sites, were partly supported as carabid specialists were more characteristic of suburban and rural environments whereas generalists were more likely to be collected from rural areas compared to suburban or urban sites. Furthermore, medium to large-sized carabid individuals were more likely to be collected in the rural sites compared to urban forests. We found no evidence for significant changes in spider abundance or species richness across the urban–rural gradient in relation to body size or habitat specialization. We suggest that urbanization does not have significant effects on the total abundances and species richnesses in these two taxa. However, individual species responded differently to urbanization, and there were significant differences in the specialization and body sizes of carabids across the gradient.     

No general edge effects for invertebrates at Afromontane forest/grassland ecotones

The Afromontane region of South Africa is characterised by numerous small, remnant forests in a grassland matrix. The edges, or ecotones between forests and grasslands are usually sharp (typically just over a few metres) and are mainly maintained by both natural and, more recently, anthropogenic fires. We investigated epigaeic amphipod, carabid and ant distribution patterns across Afromontane forest/grassland ecotones and found little evidence to support the biological edge effect. Five of the fifty-two sampled species however, did increase significantly in abundance at the ecotone. Among these was a very distinct edge species, the amphipod Talistroides africana. Overall, carabids were more abundant and species rich in forests while for ants it was in the grasslands. Ants and carabids were both more abundant and species rich in spring and summer than in autumn and winter. More interestingly, the abundance and species richness patterns across the ecotone did not change with the passing of the seasons. We argue that a conservation strategy for the Afromontane forest patches must also incorporate the surrounding grassland. The grassland habitat is often perceived as less valuable than forest and, as a consequence, is subject to many anthropogenic disturbances such as fragmentation, cattle grazing and afforestation. Protecting grasslands around forest patches not only conserves the rich ant diversity, but also conserves the biota in the forests and at the edges, and would therefore be more meaningful in terms of the overall conservation of Afromontane biodiversity.     

哀牢山中山湿性常绿阔叶林木质藤本对边缘效应的响应

全球范围内森林片断化现象日益严重。与其他木本植物(乔木和灌木)相比, 木质藤本更趋向于分布在片断化森林的边缘, 因而了解木质藤本对边缘效应的响应对于进一步了解其对森林动态的影响极其必要。本文对哀牢山中山湿性常绿阔叶林林缘到林内环境梯度上木质藤本的变化进行了调查。在形成年龄分别为13年、35年和53年的3种类型的林缘, 设置从林缘向林内连续延伸的长方形样地(20 m × 50 m)各10个(总面积3 ha), 每个样地再划分为5个20 m × 10 m的样方。在每个样方内对胸径≥ 0.2 cm且长度≥ 2.0 m的木质藤本进行了每木调查。在3 ha的林缘样地中共记录到木质藤本植物2,426株, 隶属于14科19属31种。木质藤本的物种丰富度和多度均随距林缘距离的增加而降低, 边缘效应深度在35年林缘的边缘为30 m, 13和53年林缘的边缘则为20 m; 它们的胸高断面积在53年林缘的边缘效应深度为20 m, 但在13和35年林缘的不同距离上差异不显著。木质藤本对边缘效应的响应在物种水平上存在显著差异, 主要呈现正向和中性的响应格局, 包括只分布于林缘的物种, 和从林缘到林内环境梯度上密度逐渐降低的物种; 也有对边缘效应不敏感的物种。典范对应分析(CCA)表明, 林冠开度、边缘形成年龄和土壤水分是决定木质藤本在片断化森林边缘分布的重要影响因子。     

Distributions of lizard species across edges delimiting open‐forest and sand‐mined areas

Abstract The distributions of lizards across habitat edges delimiting open‐forest and regenerating sand‐mined areas as a function of distance from the edge were studied at Tomago, New South Wales, Australia. Pitfall‐trapping was used to survey lizards across the northern edges of four forest fragments, to determine if lizards displayed characteristic responses across the edge, and whether these could be explained by the different habitat conditions. At each site, 11 equally spaced drift fences (each parallel to the edge) were arranged in a transect running perpendicular to the edge, and stretching 50 m into each habitat type. Captures of Amphibolurus muricatus (Agamidae) decreased substantially across the edge from the mine‐path to the forest so that it was identified as a mine‐path specialist lizard species. Captures of two skink species decreased across the mine‐path before reaching the edge, and were not caught (Ctenotus taeniolatus) or were seldom caught (Ctenotus robustus) in the forest, so they were identified as mine‐path specialist, edge avoiding, lizard species. Captures of Lampropholis delicata (Scincidae) increased across edges into the forest, consistent with the expectation for a forest specialist. Regression analyses indicated the responses to edges of three lizard species (A. muricatus, C. robustus and C. taeniolatus) were negatively correlated with canopy cover (probably due to its influence on temperature, as captures of A. muricatus and C. robustus were also correlated positively with mean daily temperature). In addition, the response of C. robustus correlated negatively with a vegetation factor (dense, even vegetation in the first 50 cm from ground level). The response of L. delicata correlated positively with understorey height. We have identified edge response strategies for four species of lizards across edges delimiting temperate open‐forest and mined areas, and identified habitat and microclimate variables that may have driven these responses.     

Urbanization Impacts on Mammals across Urban-Forest Edges and a Predictive Model of Edge Effects

With accelerating rates of urbanization worldwide, a better understanding of ecological processes at the wildland-urban interface is critical to conserve biodiversity. We explored the effects of high and low-density housing developments on forest-dwelling mammals. Based on habitat characteristics, we expected a gradual decline in species abundance across forest-urban edges and an increased decline rate in higher contrast edges. We surveyed arboreal mammals in sites of high and low housing density along 600 m transects that spanned urban areas and areas turn on adjacent native forest. We also surveyed forest controls to test whether edge effects extended beyond our edge transects. We fitted models describing richness, total abundance and individual species abundance. Low-density housing developments provided suitable habitat for most arboreal mammals. In contrast, high-density housing developments had lower species richness, total abundance and individual species abundance, but supported the highest abundances of an urban adapter (Trichosurus vulpecula). We did not find the predicted gradual decline in species abundance. Of four species analysed, three exhibited no response to the proximity of urban boundaries, but spilled over into adjacent urban habitat to differing extents. One species (Petaurus australis) had an extended negative response to urban boundaries, suggesting that urban development has impacts beyond 300 m into adjacent forest. Our empirical work demonstrates that high-density housing developments have negative effects on both community and species level responses, except for one urban adapter. We developed a new predictive model of edge effects based on our results and the literature. To predict animal responses across edges, our framework integrates for first time: (1) habitat quality/preference, (2) species response with the proximity to the adjacent habitat, and (3) spillover extent/sensitivity to adjacent habitat boundaries. This framework will allow scientists, managers and planners better understand and predict both species responses across edges and impacts of development in mosaic landscapes.     

Forest edges have high conservation value for bird communities in mosaic landscapes

A major conservation challenge in mosaic landscapes is to understand how trait‐specific responses to habitat edges affect bird communities, including potential cascading effects on bird functions providing ecosystem services to forests, such as pest control. Here, we examined how bird species richness, abundance and community composition varied from interior forest habitats and their edges into adjacent open habitats, within a multi‐regional sampling scheme. We further analyzed variations in Conservation Value Index (CVI), Community Specialization Index (CSI) and functional traits across the forest‐edge‐open habitat gradient. Bird species richness, total abundance and CVI were significantly higher at forest edges while CSI peaked at interior open habitats, i.e., furthest from forest edge. In addition, there were important variations in trait‐ and species‐specific responses to forest edges among bird communities. Positive responses to forest edges were found for several forest bird species with unfavorable conservation status. These species were in general insectivores, understorey gleaners, cavity nesters and long‐distance migrants, all traits that displayed higher abundance at forest edges than in forest interiors or adjacent open habitats. Furthermore, consistently with predictions, negative edge effects were recorded in some forest specialist birds and in most open‐habitat birds, showing increasing densities from edges to interior habitats. We thus suggest that increasing landscape‐scale habitat complexity would be beneficial to declining species living in mosaic landscapes combining small woodlands and open habitats. Edge effects between forests and adjacent open habitats may also favor bird functional guilds providing valuable ecosystem services to forests in longstanding fragmented landscapes.     

Species richness and composition of Neuroptera in the forests fregments of the Taurus Mountains Range,Turkey

In this study, diversity, species richness and composition of Neuroptera has been studied in the forest edges and fragments in the Taurus Mountain Range, southern Turkey. Sampling for species collection was carried out from April 2017 to September 2018 at different distances from the forest center, i.e., (0–500 m), forest mid-interior (501–1000 m), and forest edge (1001–3000 m). A total of 975 adults were collected frequently belonging to the families Ascalaphidae, Coniopterygidae, and Hemerobiidae from the forest edges while Chrysopidae and Myrmeleontidae were most common along the mid-interior regions of the forest. Majority of adutls caught from the mid-interior region comprised of female adults while the males of most species were abundant along the forest edges. Although the forest center shows the largest value for the Dominance species-diversity index and the smallest value for the Shannon index, forest edge was found highest for the Simpson index. The abundance of Neuroptera decreased with wind speed but increased with the temperature in the edge regions. Principal Component Analysis (PCA) indicated that some environmental and habitat variables, e.g. wind speed, temperature, and distance to the forest center, mid-interior and edge, accounted for species distribution patterns in Neuroptera. In the forest center, a linear correlation between wind speed, temperature and specimen abundance was recorded, while these factors were found negatively correlated with specimens abundance in the mid-interior regions of the forest.     

Positive edge effects on forest-interior cryptogams in clear-cuts

Biological edge effects are often assessed in high quality focal habitats that are negatively influenced by human-modified low quality matrix habitats. A deeper understanding of the possibilities for positive edge effects in matrix habitats bordering focal habitats (e.g. spillover effects) is, however, essential for enhancing landscape-level resilience to human alterations. We surveyed epixylic (dead wood inhabiting) forest-interior cryptogams (lichens, bryophytes, and fungi) associated with mature old-growth forests in 30 young managed Swedish boreal forest stands bordering a mature forest of high conservation value. In each young stand we registered species occurrences on coarse dead wood in transects 0-50 m from the border between stand types. We quantified the effect of distance from the mature forest on the occurrence of forest-interior species in the young stands, while accounting for local environment and propagule sources. For comparison we also surveyed epixylic open-habitat (associated with open forests) and generalist cryptogams. Species composition of epixylic cryptogams in young stands differed with distance from the mature forest: the frequency of occurrence of forest-interior species decreased with increasing distance whereas it increased for open-habitat species. Generalists were unaffected by distance. Epixylic, boreal forest-interior cryptogams do occur in matrix habitats such as clear-cuts. In addition, they are associated with the matrix edge because of a favourable microclimate closer to the mature forest on southern matrix edges. Retention and creation of dead wood in clear-cuts along the edges to focal habitats is a feasible way to enhance the long-term persistence of epixylic habitat specialists in fragmented landscapes. The proposed management measures should be performed in the whole stand as it matures, since microclimatic edge effects diminish as the matrix habitat matures. We argue that management that aims to increase habitat quality in matrix habitats bordering focal habitats should increase the probability of long-term persistence of habitat specialists.     

Species traits and the response of open‐habitat species to forest edge in landscape mosaics

Human driven changes in land‐use have increased the need to understand how landscape structure affects species distribution. We studied how forest edges affected the distribution of birds in grasslands recently encroached by forest patches. We investigated how species’ biological traits influenced their response to vegetation change near forest edges. We censured birds along 300‐m line transects run into the open habitat perpendicularly to forest edges. We recorded habitat variables and landscape context along each transect and characterized edges and forest patches. We recorded 33 bird species in 153 transects for a total of 654 individuals. We analyzed species response to edges with generalized linear mixed models. Habitat preference was prevalent to explain species response to forest edges. The abundance of open‐habitat birds such as skylark Alauda arvensis decreased significantly in the vicinity of edges. This negative response extended within 150 m from the edge. The effect was disproportionately higher in open‐habitat species with high conservation concern. The abundance of species feeding or/and breeding in both forest and open habitat, such as woodlarks Lullula arborea, sharply increased near edges (positive edge response). Abundance of shrub and non‐shrub dependent species increased with distance to edge. The two species groups did no differ in abundance/distance to edge relationship. Intensity of species response to forest edges varied among transects in relation to transect vegetation characteristics. Edge length or aspect, diet and nest height had no direct effect. We discuss the possible role of variation in resources and nest predation risk to explain observed patterns.     

Abundance of breeding farmland birds on arable and set-aside fields at forest edges

The aim with this study was to investigate whether abundance of farmland birds on fields at forest edges were associated with (I) type of field (young set-aside vs arable fields), (n) the length and structure of the field-forest edge zone, and/or (m) with residual habitats such as habitat islands, ditches, roads etc Twenty-eight farmland bird species (all nesting and/or foraging on open fields) were censused during the breeding season on 48 plots (open fields with adjoining forest edges) in the central parts of Sweden, covering a total area of 595 ha Skylark Alauda arvensis , linnet Carduelis cannabina , whitethroat Sylvia communis and whinchat Saxicola rubetra were found in significantly higher numbers in set-aside-plots than cereal ones However, the most important factor explaining variation in the abundance of most species was the structure of the field-forest ecotone, with the length of shrubby southern deciduous forest edges being the most important factor in 7 of the species Mixed forest edges seemed to be of some importance for the abundance of 3 species, while associations between abundance and length of the other deciduous and coniferous field-forest ecotones only were significant for one species each Skylarks, white wagtails Motaalla alba and whinchats were positively associated to ditches and yellowhammers Emberiza citrinella and linnets were significantly associated to habitat islands The observed preferences for set-asides and shrubby field forest edges are suggested to be results of reduced predation risk and increased food abundance