The pollination seesaw of Rhynchospora cephalotes (L.) Vahl (Cyperaceae): Influence of plant location on the role of wind and insects as pollen vectors

Ambophily (wind and insect pollination) has been reported for some genera of the typically wind-pollinated family Cyperaceae, including the genus Rhynchospora. The significance of wind and insect pollination can vary, depending on local microclimatic conditions. Rhynchospora cephalotes is an ambophilous species that can grow under different environmental conditions, either along forest edges or inside forest fragments. This study, therefore, tests the hypothesis that (a) there is greater contribution by wind than insects to fruit set of the individuals at the forest edge and (b) there is greater contribution by insects than wind to fruit set of the individuals inside the forest. Field work was carried out in a fragment of Atlantic Forest in northeastern Brazil. We quantified the number of visits by insects, wind velocity and the reproductive success (fruit set) of R. cephalotes provided by wind and insects through exclusion experiments performed at the edge of and inside the forest. We observed a greater number of visits per day by pollinating bees to individuals inside the forest (36.83 ± 7.46) than to individuals at the edge (16.66 ± 6.53). The wind speed was significantly higher at the edge (1.71 ± 0.46 m/s) than inside the forest (0.97 ± 0.18 m/s). Bees and wind are both pollen vectors of R. cephalotes, but bees were the pollen vector that contributed most to fruit set (63.3%) for individuals inside the forest, whereas wind was the primary vector for individuals at the forest edge (76.6%). This seesaw in importance of each pollen vector in the two different environments guarantees high fruit set in R. cephalotes under different microclimatic conditions.     

Foraging behaviour of bird pollinators on Embothrium coccineum (Proteaceae) trees in forest fragments and pastures in southern Chile

Abstract We investigated the effects of forest patch size on the behaviour of birds feeding on the flower nectar of the proteaceous tree Embothrium coccineum J. R. et G. Forster, which is typically restricted to forest edges in agricultural landscapes in southern Chile. We quantified reproductive parameters of trees (no. inflorescences per branch, total and open flowers per inflorescence) in forest fragments varying from 1 ha (small), to 20 ha (medium) and to >150 ha (large), and in remnant trees in pastures. Visits to flowers by nectar‐feeding birds were recorded during 30‐min observation periods, spread throughout the day during two flowering seasons, November 1992 and 1993 (n = 242 periods overall). Aggressive encounters among flower visitors were recorded in 1992. We expected less visits to trees in pastures and small forest patches because abundances of Embothrium's main pollinators, the flycatcher Elaenia albiceps and the hummingbird Sephanoides sephaniodes, decreased in smaller patches. We found, however, that pollinator visiting rates were negatively correlated with forest patch area and were highest for pasture trees. This trend was largely due a decline in the number of visits by E. albiceps, the main flower visitor, in larger patches. Hummingbird visits did not change with forest patch size. Lower visitation rates to flowering trees in larger forest fragments seemed to be a consequence of territorial defence by E. albiceps and were unrelated to differences in floral display.     

Floral Visitors and Pollination of Psychotria tenuinervis (Rubiaceae): Distance from the Anthropogenic and Natural Edges of an Atlantic Forest Fragment1

Pollinators, especially insects, could be influenced by forest fragmentation. The aim of this paper was to examine whether there were differences in 1) the communities of floral visitors; 2) the frequency of visits; and 3) the fruit and seed sets of individuals of Psychotria tenuinervis occurring at anthropogenic edges (AEs), natural edges (NEs), and in the forest interior (FI) in 2 yr of study. In 2002, the total number of flower visits was greater in NE and lower in AE, while no difference among habitats was found in 2003. There were differences among sample plots, within habitats, in both years. Bees were the most frequent visitors of P. tenuinervis flowers, and the introduced honeybee Apis mellifera was the most common species observed. There were no differences in the fruit and seed sets, or in the density of reproductive individuals of P. tenuinervis among habitats. However, in 2002, NE showed the greatest proportion of fruits per flower and AE the smallest. The similarity among the habitats was probably due to the marked variation or heterogeneity among the sample plots and among the plants within the habitats, which may have masked any interhabitat differences. The observed heterogeneity and the likely importance of other factors, such as gaps and the age of the edge, on the fragment studied, could be viewed as important issues for conservation programs.     

Edge responses are different in edges under natural versus anthropogenic influence: a meta‐analysis using ground beetles

Most edges are anthropogenic in origin, but are distinguishable by their maintaining processes (natural vs. continued anthropogenic interventions: forestry, agriculture, urbanization). We hypothesized that the dissimilar edge histories will be reflected in the diversity and assemblage composition of inhabitants. Testing this “history‐based edge effect” hypothesis, we evaluated published information on a common insect group, ground beetles (Coleoptera: Carabidae) in forest edges. A meta‐analysis showed that the diversity‐enhancing properties of edges significantly differed according to their history. Forest edges maintained by natural processes had significantly higher species richness than their interiors, while edges with continued anthropogenic influence did not. The filter function of edges was also essentially different depending on their history. For forest specialist species, edges maintained by natural processes were penetrable, allowing these species to move right through the edges, while edges still under anthropogenic interventions were impenetrable, preventing the dispersal of forest specialists out of the forest. For species inhabiting the surrounding matrix (open‐habitat and generalist species), edges created by forestry activities were penetrable, and such species also invaded the forest interior. However, natural forest edges constituted a barrier and prevented the invasion of matrix species into the forest interior. Preserving and protecting all edges maintained by natural processes, and preventing anthropogenic changes to their structure, composition, and characteristics are key factors to sustain biodiversity in forests. Moreover, the increasing presence of anthropogenic edges in a landscape is to be avoided, as they contribute to the loss of biodiversity. Simultaneously, edges under continued anthropogenic disturbance should be restored by increasing habitat heterogeneity.     

Seed rain of fleshy and dry propagules in different habitats in the temperate rainforests of Chiloé Island,Chile

In temperate rainforests on Chiloé Island in southern Chile (42°S), most canopy trees bear fleshy, avian‐dispersed propagules, whereas emergent tree species have dry, wind‐borne propagules. In the present study, the following hypothesis was tested: regardless of species, fleshy propagules are deposited in greater numbers in canopy gaps and in forest margins and hence have a more heterogeneous seed shadow than wind‐dispersed propagules. To test this hypothesis, the seed rains of these two types of propagules were compared in the following forest habitats: (i) tree‐fall gaps (edges and centre); (ii) forest margins with adjacent pastures; and (iii) under closed canopy (forest interior). Seed collectors (30‐cm diameter) were placed in two (15 and 100 ha) remnant forest patches (n = 60–100 seed collectors per patch) distributed in the four habitats. Seeds were retrieved monthly from each collector during two reproductive seasons (1996, 1997). In both years, the seed rain was numerically dominated by two species with dry propagules (Laureliopsis philippiana and Nothofagus nitida) and three species with fleshy fruits (Drimys winteri, Amomyrtus luma, and Amomyrtus meli). The seed shadows of the two species with dry, wind‐dispersed seeds differed markedly. Seeds of L. philippiana were deposited predominantly in canopy openings, whereas N. nitida seeds fell almost entirely in the forest interior. The fleshy‐fruited species, Drimys and Amomyrtus spp., had similar seed deposition patterns in the various habitats studied, but the between‐year differences in seed rain were greater in Drimys winteri than in Amomyrtus spp. Although no more than 10% of fleshy‐fruited propagules reached the margins of the patch, approximately 7% of these were carried there by birds. Every year, canopy gaps (pooling data from edges and centres) concentrated approximately 60% of the total seed rain of both propagule types in both forest patches. Forest margins received less than 20% of the total seed rain, which was largely dominated by fleshy‐fruited species. Seed shadows were a species‐specific attribute rather than a trait associated with propagule type and dispersal mode.     

片断化森林的边缘效应与自然保护区的设计管理

森林片断化引起了森林边缘物理环境与生物的变化。从森林边缘向林内,光辐射,温度、湿度、风等因素发生改变,这些反过 边缘上和边缘附近的生物产生极其重要的影响。有些研究表明,生物与非生物存在明显的边缘－核心的变化梯度,而有些则没有,除了影响边缘效应的客观因素（如边缘的取向、地势、年龄等）外,主观因素对这缘效应也有影响。边缘对生物与非生物的影响因片断化森林的面积、形状以及与其他森林片连接程度的不同而不同,     

Use of Forest Edges by Bats in a Managed Pine Forest Landscape

ABSTRACT Forest edges often have increased species richness and abundance (edge effect) and affect spatial behaviors of species and dynamics of species interactions. Landscapes of intensively managed pine (Pinus spp.) stands are characterized by a mosaic of patches and linear forest edges. Managed pine forests are a primary landscape feature of the southeastern United States, but the effects of intensive management on bat communities are poorly understood. Insectivorous bats are important top predators in nocturnal forest food webs. We examined bat foraging behavior along forest edges and in 4 structurally distinct stand types (open-canopy pine, prethinned pine, thinned pine, and unmanaged forest) within a managed pine forest in the coastal plain of North Carolina, USA. During May-August, 2006 and 2007, we recorded echolocation calls using Pettersson D240X bat detectors linked to digital recorders at 156 sites. We also sampled nocturnal flying insects at each site using Malaise insect traps. We used negative binomial count regression models to describe bat foraging behavior relative to forest edges, stand types, and prey availability. Although some species showed affinities for certain stand types and prey items, bat activity patterns were most strongly related to forest edges. Edges were used extensively by 6 aerial-hunting bat species, but avoided by Myotis species. Forest edges function similarly to natural forest gaps, by providing foraging opportunities for aerial-hunting bat species. Therefore, the maintenance of forest edges in managed pine landscapes may enhance foraging habitat for aerial-hunting bat species.     

Plant size,flowering synchrony and edge effects: What,how and where they affect the reproductive success of a Neotropical tree species

Plant reproductive success is supposedly influenced by phenology and individual size, which may be modified under edge effects. We tested if reproductive success, estimated by fruit set, in Senefeldera verticillata (Euphorbiaceae) is related to flowering synchrony and tree size, including plant height and circumference at breast height. The study was carried out in the interior and in edges of clearings for gas pipelines and electric lines of a lowland rainforest in south‐eastern Brazil. Monthly observations were performed during one reproductive season, of 19 individuals that grew at edges of electric lines and gas pipelines and at forest interior. Reproductive success was significantly higher at forest interior than at gas pipeline area; there was no significant difference between gas pipeline and electric line areas or between forest interior and electric line area. In the forest edges, only plant height was positively related to plant reproductive success. This is probably related to crown exposure to sunlight, which enhances flower production. At forest interior, reproductive success was positively influenced by the synchrony of flowering activity among neighbouring individuals. In contrast, flowering synchrony based on phenophase intensity negatively impacted reproductive success. Senefeldera verticillata shows temporal dioecy and is mainly pollinated by small social bees, and the high degree of flowering synchrony at low intensity may increase the number of mating partners and therefore enhance its reproductive success. Inside the forest fragments, individuals with thicker trunks showed lower reproductive success, which may be related to a loss of reproductive capacity of older individuals. Our results evidenced the complexity of responses experienced by tropical plants subjected to forest fragmentation because of linear clearings.     

Characterizing the spatial distribution of giant pandas (Ailuropoda melanoleuca) in fragmented forest landscapes

Aim To examine the effects of forest fragmentation on the distribution of the entire wild giant panda (Ailuropoda melanoleuca) population, and to propose a modelling approach for monitoring the spatial distribution and habitat of pandas at the landscape scale using Moderate Resolution Imaging Spectro‐radiometer (MODIS) enhanced vegetation index (EVI) time‐series data. Location Five mountain ranges in south‐western China (Qinling, Minshan, Qionglai, Xiangling and Liangshan). Methods Giant panda pseudo‐absence data were generated from data on panda occurrences obtained from the third national giant panda survey. To quantify the fragmentation of forests, 26 fragmentation metrics were derived from 16‐day composite MODIS 250‐m EVI multi‐temporal data and eight of these metrics were selected following factor analysis. The differences between panda presence and panda absence were examined by applying significance testing. A forward stepwise logistic regression was then applied to explore the relationship between panda distribution and forest fragmentation. Results Forest patch size, edge density and patch aggregation were found to have significant roles in determining the distribution of pandas. Patches of dense forest occupied by giant pandas were significantly larger, closer together and more contiguous than patches where giant pandas were not recorded. Forest fragmentation is least in the Qinling Mountains, while the Xiangling and Liangshan regions have most fragmentation. Using the selected landscape metrics, the logistic regression model predicted the distribution of giant pandas with an overall accuracy of 72.5% (κ = 0.45). However, when a knowledge‐based control for elevation and slope was applied to the regression, the overall accuracy of the model improved to 77.6% (κ = 0.55). Main conclusions Giant pandas appear sensitive to patch size and isolation effects associated with fragmentation of dense forest, implying that the design of effective conservation areas for wild giant pandas must include large and dense forest patches that are adjacent to other similar patches. The approach developed here is applicable for analysing the spatial distribution of the giant panda from multi‐temporal MODIS 250‐m EVI data and landscape metrics at the landscape scale.     

Assessing edge effect on the spatial distribution of selected forest biochemical properties derived using the Worldview data in Dukuduku forests,South Africa

This work explores the potential of the high‐resolution WorldView‐2 sensor in quantifying edge effects on the spatial distribution of selected forest biochemical properties in fragmented Dukuduku forest in KwaZulu‐Natal, South Africa. Specifically, we sought to map fragmented patches within forested areas in Dukuduku area, using very high spatial resolution WorldView‐2 remotely sensed data and to statistically determine the effect of these fragmented patches on the spatial distribution of selected forest biochemical properties. Edge effects on carbon, LAI and foliar nitrogen were quantified based on the models derived by Omer et al. (IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2015, 8, 4825). Edge effect statistical results on the spatial distribution of carbon, LAI and nitrogen showed significant (α = 0.05) variations with change in distance from fragmented patches (>150 m²). Forest foliar carbon concentrations significantly (p‐value = 0.016) increased from 44.8% to 45.3% with increasing distance (25–375 m) from fragmented patches. A similar trend was observed for LAI. Nevertheless, for nitrogen the results show that its concentration significantly (p = 0.016) decreased with increase in distance from the fragmented patches. Overall, the findings of this work underscore the invaluable potential and strength of WorldView‐2 data set in assessing edge effect on the spatial distribution of selected forest biochemical properties.     

Differential and delayed response of two ant species to habitat fragmentation via the introduction of a pine matrix

1. Ants are a ubiquitous and crucial component of Australian Eucalyptus forests, but responses to long‐term habitat fragmentation remain poorly understood. Two ant species were followed across a 21‐year history of pine plantation establishment and maturation in a southeast Australian Eucalyptus forest. 2. At Wog Wog in southeastern Australia, a Native Eucalyptus forest was clear‐cut to make way for plantation establishment and 12 remnant patches of forest were left intact and subsequently surrounded by a pine matrix. Pitfall traps were placed in the continuous native forest, remnant Eucalyptus patches, and the pine matrix between fragments, and were stratified based on proximity to remnant patch edges and habitat type. Two ant species are focused on that represent the only remaining data for the early years of the experiment. 3. While Leptomyrmex erythrocephalus (Fabricius), the rarer of the two species, was not affected by fragmentation in the short term, 21 years after fragmentation, it was less likely to occur in both the mature pine matrix and fragments than in continuous forest controls. Aphaenogaster longiceps (Smith F.) was equally likely to occur in the fragments, continuous forest, and pine matrix early in the experiment but by year 21 post‐fragmentation was less likely to occur in the pine matrix than fragments or controls. 4. Importantly, we only detected negative impacts of fragmentation on ant occurrence as the pine plantation matrix matured and isolated ant populations on fragments. 5. It is concluded that changes in matrix suitability and specific habitat characteristics influence ant persistence in Eucalyptus fragments.     

Edge effects reduce the nesting success of Acadian Flycatchers in a moderately fragmented forest

ABSTRACT.   Forest fragmentation can create negative edge effects that reduce the reproductive success of birds nesting near the forest/nonforest interface, and threaten bird populations deeper in remnant forest habitats. Negative edge effects may be more pronounced in landscapes that are moderately fragmented, particularly where agriculture is the primary land-use fragmenting forests. Information about the extent and strength of edge effects at a site can help guide conservation actions, and determine their effectiveness. We examined edge effects for birds breeding in a nearly contiguous forest fragmented by relatively narrow agricultural corridors in Illinois (USA). We measured rates of nest predation and brood parasitism for Acadian Flycatchers ( Empidonax virescens ) over a continuum of distances from the edge of an agricultural inholding. Nest predation and brood parasitism were highest near the edge and decreased with increasing distance from the edge. Given the cumulative effects of nest predation and brood parasitism on reproductive success, we determined that forest within 600 m of the inholding was sink habitat. We found, however, that deeper forest interior areas currently serve as source habitat, and that conversion of the entire 205 ha agricultural corridor to forest would add 1350 ha of source habitat for Acadian Flycatchers. Such results provide support for a local conservation strategy of forest consolidation and establish baseline measures necessary to determine the relative effectiveness of any subsequent reforestation efforts.     

Plant–frugivore networks are less specialized and more robust at forest–farmland edges than in the interior of a tropical forest

Forest fragmentation and local disturbance are prevailing threats to tropical forest ecosystems and affect frugivore communities and animal seed dispersal in different ways. However, very little is known about the effects of anthropogenic forest edges and of local disturbance on the structure and robustness of plant–frugivore networks. We carried out focal tree observations to record the frugivore species feeding on eight canopy tree species in the forest interior and at forest–farmland edges in a little and a highly disturbed part of a Kenyan rain forest. For each frugivore species, we recorded its body mass and its forest dependence. We examined how forest edge and local disturbance affected the abundance, the richness and the composition of the frugivore community and tested whether forest edge and local disturbance affected plant frugivore networks. Abundance and species richness of frugivores were higher at edges than in the forest interior. Forest visitors and small‐bodied frugivores increased, while forest specialists decreased in abundance at forest edges. The changes in frugivore community composition resulted in plant–frugivore networks that were more connected, more nested and more robust against species extinctions at forest–farmland edges than in the forest interior. Network specialization was lower at forest edges than in the forest interior because at the edges plant specialization on frugivores was very low in small‐fruited species. In contrast, small‐fruited plants were more specialized than large‐fruited plants in the forest interior. Our findings suggest that forest‐visiting birds may stabilize seed‐dispersal services for small‐fruited plant species at rain forest margins, while seed‐dispersal services for large‐fruited plant species may be disrupted at forest edges due to the decrease of large‐bodied frugviores. To assess the ultimate consequences of bird movements from farmland to forest edges for ecosystem functioning, future studies are required to investigate the seed‐dispersal qualities provided by forest‐visiting bird species in the tropics.     

Viability of ecological processes in small Afromontane forest patches in South Africa

Abstract The conservation of biodiversity is dependent on protecting ecosystem‐level processes. We investigated the effects of fragment size and habitat edge on the relative functioning of three ecological processes – decomposition, predation and regeneration of trees – in small Afromontane forests in KwaZulu‐Natal, South Africa. Ten sampling stations were placed in each of four forest categories: the interior of three large indigenous forest fragments (100 m from the edge), the edges of these large fragments, 10 small indigenous fragments (<1 ha) and 10 small exotic woodlands (<0.5 ha). Fragment size and edge effects did not affect the abundance of the amphipod Talitriator africana, a litter decomposer, and overall dung beetle abundance and species richness significantly. Bird egg predation was marginally greater at large patch edges compared with the other forest categories, while seed predation did not differ among forest categories. Tree seedling assemblage composition did not differ significantly among large patch interiors and edges, and small indigenous fragments. Sapling and canopy assemblage composition each differed significantly among these three indigenous forest categories. Thus, while tree recruitment was not negatively affected by patch size or distance from the edge, conditions in small fragments and at edges appear to affect the composition of advanced tree regeneration. These ecological processes in Afromontane forests appear to be resilient to fragmentation effects. We speculate that this is because the organisms in these forests have evolved under fragmented conditions. Repeated extreme changes in climate and vegetation over the Pleistocene have acted as significant distribution and ecological extinction filters on these southern hemisphere forest biota, resulting in fauna and flora that are potentially resilient to contemporary fragmentation effects. We argue that because small patches and habitat edges appear to be ecologically viable they should be included in future conservation decisions.     

Landscape‐level effects on aboveground biomass of tropical forests: A conceptual framework

Despite the general recognition that fragmentation can reduce forest biomass through edge effects, a systematic review of the literature does not reveal a clear role of edges in modulating biomass loss. Additionally, the edge effects appear to be constrained by matrix type, suggesting that landscape composition has an influence on biomass stocks. The lack of empirical evidence of pervasive edge‐related biomass losses across tropical forests highlights the necessity for a general framework linking landscape structure with aboveground biomass. Here, we propose a conceptual model in which landscape composition and configuration mediate the magnitude of edge effects and seed‐flux among forest patches, which ultimately has an influence on biomass. Our model hypothesizes that a rapid reduction of biomass can occur below a threshold of forest cover loss. Just below this threshold, we predict that changes in landscape configuration can strongly influence the patch's isolation, thus enhancing biomass loss. Moreover, we expect a synergism between landscape composition and patch attributes, where matrix type mediates the effects of edges on species decline, particularly for shade‐tolerant species. To test our conceptual framework, we propose a sampling protocol where the effects of edges, forest amount, forest isolation, fragment size, and matrix type on biomass stocks can be assessed both collectively and individually. The proposed model unifies the combined effects of landscape and patch structure on biomass into a single framework, providing a new set of main drivers of biomass loss in human‐modified landscapes. We argue that carbon trading agendas (e.g., REDD+) and carbon‐conservation initiatives must go beyond the effects of forest loss and edges on biomass, considering the whole set of effects on biomass related to changes in landscape composition and configuration.     

Forest cover,hunting pressure,and fruit availability influence seed dispersal in a forest‐savanna mosaic in the Congo Basin

Forest fragmentation, reduced forest cover, and hunting pressure are the main threats affecting animal‐mediated seed dispersal. However, their combined effects on seed dispersal rates have been simultaneously investigated only rarely, and never in Africa. We aimed to disentangle the effects of forest cover, hunting pressure, frugivore abundance, and fruit availability at the local and landscape scales on the seed dispersal rates of Staudtia kamerunensis (Myristicaceae). To estimate the percentages of seed dispersal failure (undispersed seeds), we quantitated fruit remains below fruiting trees distributed across five contrasting sites in a semi‐natural forest‐savanna mosaic in the Democratic Republic of Congo. We used statistical analyses accounting for spatial autocorrelation and found that forest cover in the surrounding landscape, hunting level, the associated abundance of dispersers, and fruit availability all had significant effects on the percentage of seed dispersal failure. The combination of high fruit availability and reduced abundance of seed dispersers could accelerate seed disperser satiation, causing the seed dispersal system to be saturated. Our study highlights how two major factors associated with anthropogenic activities, forest cover and hunting, affect seed dispersal by animals. These findings could have far‐reaching implications for our understanding of tree‐frugivore interactions and the conservation of tropical communities.     

Down by the riverside: Riparian edge effects on three monkey species in a fragmented Costa Rican forest

Rivers represent natural edges in forests, serving as transition zones between landscapes. Natural edge effects are important to study to understand how intrinsic habitat variations affect wildlife as well as the impact of human-induced forest fragmentation. We examined the influence of riparian and anthropogenic edge on mantled howler, white-faced capuchin, Central American spider monkeys, and vegetation structure at La Suerte Biological Research Station (abbreviated as LSBRS), Costa Rica. We predicted lower monkey encounter rate, tree species richness, and median dbh at both edge types compared to interior and that monkeys would show species-specific responses to edge based on size and diet. We expected large, folivorous–frugivorous howler monkeys and small, generalist capuchins would be found at increased density in forest edge, while large, frugivorous spider monkeys would be found at decreased density in forest edge. We conducted population and vegetation surveys along interior, riparian, and anthropogenic edge transects at LSBRS and used GLMM to compare vegetation and monkey encounter rate. Tree species richness and median dbh were higher in forest interior than anthropogenic edge zones. Although spider monkey encounter rate did not vary between forest edges and interior, howler monkeys were encountered at highest density in riparian edge, while capuchins were encountered at highest density in anthropogenic edge. Our results indicate that diverse forest edges have varying effects on biota. Vegetation was negatively affected by forest edges, while monkey species showed species-specific edge preferences. Our findings suggest that riparian zones should be prioritized for conservation in Neotropical forests.     

Edge and shape effects on ant (Hymenoptera: Formicidae) species richness and composition in forest fragments

In this paper, we tested four hypotheses relative to edge and shape effects on ant communities: (i) forest edges have lower species richness than the remnant core; (ii) species richness increases with distance from the edge; (iii) irregularly shaped remnants have lower species richness than more regular remnants; (iv) there is a higher similarity of species composition between edge and core in irregular than in regular remnants. We sampled litter ant communities on the edge and core of ten remnants, in Viçosa, Minas Gerais, Brazil. Species richness was larger at the forest core than at the edges, although did not increase with distance from the edge. Species richness did not vary with shape complexity. The similarity of species composition between edge and core showed a decreasing trend with remnant area, and did not vary with shape complexity. The observed differences of species richness between forest core and edge may be due to higher harshness of edges, caused by environmental changes. The absence of relationship between species richness and distance from the edge might indicate the range of edge effects, which would be smaller than the smallest distance of core sampled. Therefore, edges would affect litter-dwelling ant species richness in a distance smaller than 50 m. The observation of species composition allowed us to notice an effect of fragmentation that would not be noticed if we were considering only species richness. Edge may serve as step to generalist species, which may use it to colonise forest remnants. Furthermore, small remnants are more colonisation-prone by such species, and have a more homogeneous species composition than large remnants.     

Tree Regeneration and Understory Woody Plants Show Diverse Responses to Forest–Pasture Edges in Costa Rica

ABSTRACT Edge effects along tropical forest–pasture margins are thought to cause a shift toward early successional characteristics of the understory forest vegetation. We tested this idea by sampling vegetation at five forest sites in northeast Costa Rica each of which had edges that were established over 20 yr earlier. Four of these sites had been selectively logged. We sampled woody plants >0.2 and ≤1.3 m height in 54 m² within 0.2 ha plots at edges (N=14), and at 150 m (N=11) and 300 m from edges (N=9). Composition and diversity did not vary with edge distance. Abundance of tree regeneration, mainly of canopy and emergent species, increased at edges. Abundance of lianas and slow‐growing tree species did not differ significantly across the sampling locations. Weighted mean wood density varied little, with a reduction at edges for canopy species. Palms were less abundant at edges, but not less species rich. At edges, these plant assemblages maintain many of the characteristics of forest interior vegetation, though the changes observed may indicate ongoing functional change. Degradation of forest–pasture edges is not a universal feature of tropical forest fragmentation, and forests with high rates of natural turnover might have a high capacity to maintain themselves within forest edges alongside pasture.     

Understorey plant species richness and composition in metropolitan forest archipelagos: effects of forest size, adjacent land use and distance to the edge

Aim To address the relative role of adjacent land use, distance to forest edge, forest size and their interactions on understorey plant species richness and composition in perimetropolitan forests. Location The metropolitan area of Barcelona, north‐eastern Spain. Methods Twenty sampling sites were distributed in two forest size‐categories: small forest patches (8–90 ha) and large forest areas (> 18,000 ha). For each forest‐size category, five sites were placed adjacent to crops and five sites adjacent to urban areas. Vascular plant species were recorded and human frequentation was scored visually in 210 10 × 10 m plots placed at 10, 50 and 100 m from the forest edge, and additionally at 500 m in large forest areas. Plant species were grouped according to their ecology and rarity categories. A nonmetric multidimensional scaling (NMS) ordination was carried out to detect patterns of variation in species assemblage, and to explore the relationships between these patterns and the richness of the species groups and the studied factors. Factorial anovas were used to test the significance of the studied factors on the richness of species groups. Relationships between human frequentation and the studied variables were assessed through contingency tables. Results Forest‐size category was the main factor affecting synanthropic species (i.e. those thriving in man‐made or man‐disturbed habitats). Synanthropic species richness decreased with increasing distance from the forest edge and, when forests were adjacent to crops, it was higher in small forest patches than in large forest areas. Richness of rare forest species was lower in small forest patches than in large forest areas when forests were adjacent to urban areas. Richness of common forest species and of all forest species together were higher close to the forest edge than far from it when forests were adjacent to urban areas. Forests adjacent to urban areas were more likely to experience high human frequentation, particularly in those plots nearest to the forest edge. Main conclusions Forest‐size category and adjacent land use were the most important factors determining species richness and composition. The preservation of large forests adjacent to crops in peri‐urban areas is recommended, because they are less frequented by humans, are better buffered against the percolation of nonforest species and could favour the persistence of rare forest species.