Forest Edges as Nutrient and Pollutant Concentrators: Potential Synergisms between Fragmentation, Forest Canopies, and the Atmosphere

Abstract: Forest fragmentation leads to a dramatic increase in forest edge, and these edges may function as traps and concentrators for wind-borne nutrients and pollutants. We assessed the influence of forest edges on atmospheric deposition and subsequent inputs to the forest floor in deciduous-forest fragments in the eastern United States. To quantify these inputs, we collected throughfall—water that has passed through the forest canopy—from edge and interior zones of forests adjacent to open fields. During the 1995 growing season, atmospheric input (wet and dry deposition) of sulfur to forest edge zones was elevated compared with input to forest interiors. Throughfall fluxes of dissolved inorganic nitrogen and calcium were also greater at edges than interiors. The mean edge increases ranged from 17% to 56% for the nutrients and pollutants we measured. When we manipulated the structure of forest edges by removing all vegetation below half the canopy height, throughfall flux in the edge zone declined sharply and was less than that of the respective interior zone. Changing the vegetation structure of the edge also shifted the zone of highest throughfall flux farther into the interior of the forest. Our data suggest that forest edges can function both as significant traps for airborne nutrients and pollutants from adjoining agricultural or urban landscapes and effective concentrators of below-canopy chemical fluxes. These enhanced fluxes may have cascading effects on soil-nutrient cycling, microbial activity, seedling dominance, and other ecological processes near forest edges.     

Vegetation Responses along Edge-to-Interior Gradients in the Mixed Hardwood Forests of the Roanoke River Basin, North Carolina

Compared with forest interiors, forest edges typically have a different plant species composition and community structure, a phenomenon known as "edge effect." Edge effects make the functional interior area of a forest smaller than its actual area. The objective of this study was to estimate how far the effects of agriculturally maintained edges penetrate the mixed hardwood forests of the Roanoke River Basin, North Carolina. I determined percentage cover for all vascular plant species in 10-by-100-meter belt transects on north-facing or south-facing edges of four relatively undisturbed forests. Changes in the percentage cover of individual species, the relative cover of exotic species, and species richness all indicated that edge effects penetrate deeper on south-facing edges (to 60 meters) than on north-facing edges (to 20 meters). Analyses of species responses to the edge showed a number of species to be edge oriented, but no species was found to be interior oriented. The results of multivariate analyses (ordination and cluster analysis) suggested that edge effects could be detected to 50 meters on south-facing edges and 10–30 meters on north-facing edges. These results allow us to better understand the difference between a forest's actual area and its functional interior area.     

Effects of Pioneer Tree Species Hyperabundance on Forest Fragments in Northeastern Brazil

Abstract: Despite many studies on fragmentation of tropical forests, the extent to which plant and animal communities are altered in small, isolated forest fragments remains obscure if not controversial. We examined the hypothesis that fragmentation alters the relative abundance of tree species with different vegetative and reproductive traits. In a fragmented landscape (670 km²) of the Atlantic Forest of northeastern Brazil, we categorized 4056 trees of 182 species by leafing pattern, reproductive phenology, and morphology of seeds and fruit. We calculated relative abundance of traits in 50 1‐ha plots in three types of forest configurations: forest edges, small forest fragments (3.4–83.6 ha), and interior of the largest forest fragment (3500 ha, old growth). Although evergreen species were the most abundant across all configurations, forest edges and small fragments had more deciduous and semideciduous species than interior forest. Edges lacked supra‐annual flowering and fruiting species and had more species and stems with drupes and small seeds than small forest fragments and forest interior areas. In an ordination of species similarity and life‐history traits, the three types of configurations formed clearly segregated clusters. Furthermore, the differences in the taxonomic and functional (i.e., trait‐based) composition of tree assemblages we documented were driven primarily by the higher abundance of pioneer species in the forest edge and small forest fragments. Our work provides strong evidence that long‐term transitions in phenology and seed and fruit morphology of tree functional groups are occurring in fragmented tropical forests. Our results also suggest that edge‐induced shifts in tree assemblages of tropical forests can be larger than previously documented.     

Defining Forest Fragmentation by Corridor Width: The Influence of Narrow Forest-Dividing Corridors on Forest-Nesting Birds in Southern New Jersey

In studies of forest fragmentation, a fundamental inconsistency exists in the distance criterion used to define the discreteness of forest fragments. We examined three types of ubiquitous, narrow, forest-dividing corridors for effects that influence the relative abundance and community composition of forest-nesting birds. Fixed-radius (100-meter) point counts were conducted on 54 transects established along three width classes of corridors: unpaved roads (8 meters wide), paved roads (16 meters wide), and powerlines (23 meters wide). Transect locations were distributed equally among corridor edge, forest margin 100 meters from corridor edge, and forest interior 300 meters from corridor edge. Forest-interior species of Neotropical migrants had significantly reduced relative abundances on edge transects along 16- and 23-meter corridors, compared with 8-meter corridors and with forest interior points along all three corridor-width classes. At a landscape scale, the consequences of apparently small reductions in forest area by the presence of narrow forest-dividing corridors may be cumulatively significant for abundances of forest-interior species. Brown-headed Cowbirds were more abundant than 20 of 21 forest-interior Neotropical migrants. We found surprisingly high abundances of cowbirds associated with narrow forest-dividing corridors, especially those with mowed grass. Corridor widths as narrow as 8 meters produce forest fragmentation effects in part by attracting cowbirds and nest predators to corridors and adjacent forest interiors. The most serious implication of this study is that narrow forest-dividing corridors may function as ecological traps for forest-interior Neotropical migrants. We suggest that these widespread corridors may be inconspicuous but important contributors to declines of forest-interior nesting species in eastern North America.     

Use of polyvinyl chloride pipes (PVC) as potential artificial shelters for amphibians in a coastal plain forest of southeastern Brazil

We studied the use of polyvinil chloride pipes (PVC pipes) by frogs as artificial shelters in a Coastal Plain forest in the Vale Natural Reserve, north of Espírito Santo state, southeastern Brazil from June 2015 to May 2016. We used 14 plots distributed in the Coastal Plain Forest following the RAPELD methodology of sampling. The frogs were sampled in transects along the plots, using the active search method, with visual and auditory sampling. We recorded two species of frogs (Aparasphenodon brunoi and Scinax argyreornatus) using PVC pipes as shelters in the plots in the Forest. Of the 468 PVC pipes established along plots, 38 of them (8.1%) were used as shelter by the frogs. For both frog species, about 33% of microhabitats used in the forest were the interior of PVC pipes. We concluded that the PVC pipes might constitute artificial shelters for at least two of the frog species living in the community of the Coastal Plain Forest, potentially being of relevance in conservation programs. In altered areas and those in which there has been the loss of types of microhabitats, the addition of these PVC pipes as artificial shelters may represent additional and complementary microhabitats to keep or increase the population stocks of arboreal and semi-arboreal frog species and having a size that allow them entering the shelter. These artificial shelters can play an important role in conservation of these frogs in fragmented areas where the availability of the microhabitats of these frog species were locally reduced.     

Distribution of Carabid Beetles (Coleoptera, Carabidae) across a Boreal Forest–Clearcut Ecotone

Abstract: We studied the occurrence of carabid beetles (Coleoptera, Carabidae) in boreal forest fragments, their edges, and adjacent clearcuts in central Finland. Beetles were collected with pitfall traps along transects extending 60 m from the edge into clearcuts and 60 m into forest interior. Our main findings were that (1) species richness was significantly higher in the clearcut than in the forest fragments, (2) clearcuts hosted many open-habitat species, which increased overall species richness in these sites, (3) carabid assemblages in the edges were more similar to forest assemblages than to those found in the clearcuts, (4) no edge specialists were found, and (5) open-habitat species did not penetrate into the forest fragments from the clearcut. Because forest specialists occurred all the way to the edge on the forest side, it seems that edge effects per se do not adversely affect these species, at least in the short term. In the long term, however, habitat conditions in the edges may deteriorate for interior species because of trees falling over in strong winds, thereby reducing the size of the fragments and widening the edge zone.     

Edge Effects on the Understory Bird Community in a Logged Forest in Uganda

Abstract: Understanding how the fauna of logged tropical rainforests responds to fragmentation and the creation of edges is vital to ensure conservation of biodiversity. We studied the composition of the understory bird community from the edge of a 15-ha clearing toward the interior of the forest in a part of Budongo Forest Reserve, Uganda, that was selectively logged about 45 years ago. Mist netting was conducted along five transects from the edge and 500 m into the interior. The total number of individuals captured did not change with distance from the edge, but there was a significant increase in the number of species. We sampled fewer, but more common species near the edge, whereas the interior of the forest had more, and less common species. Guild composition also changed with distance from the edge. Frugivore-insectivores and nectarivores were most common close to the edge. Among insectivores, ground foragers, bark-gleaners, and leaf-gleaners were most common in the interior of the forest, whereas sallying insectivores favored the edge. Graminivores were unaffected by the edge. Analysis of common species showed that Ispidina picta , Andropadus curvirostris , A. latirostris , Camaroptera brachyura , Terpsiphone rufiventer , and Nectarinia olivacea were associated with the edge, but no species showed significant avoidance of the edge. This finding may be explained by the generally low sample sizes of interior species. Our results show that even bird communities in logged forests respond to edges. Estimates of edge effects suggested that changes in bird densities may have occurred several hundred meters from the edge. In conclusion, logged forests provide habitat for bird species avoiding forest edges, and this should be considered in the management of such forests for conservation.     

The distribution of lianas and their change in abundance in temperate forests over the past 45 years

Lianas (woody vines) are an important and dynamic component of many forests throughout the world, and increases in CO2, mean winter temperature, and forest fragmentation may promote their growth and proliferation in temperate forests. In this study, we used a 45-year data set to test the hypothesis that lianas have increased in abundance and basal area in the interiors of 14 deciduous temperate forests in Wisconsin (USA) since 1959. We also censused woody plants along a gradient from the forest edge to the interior in seven of these forests to test the hypothesis that the abundance of lianas declines significantly with increasing distance from the forest edge. We found that lianas did not increase in abundance within the interiors of temperate forests in Wisconsin over the last 45 years. However, relative and absolute liana abundance decreased sharply with increasing distance from forest edges. Our findings suggest that forest fragmentation, not climate change, may be increasing the abundance of lianas in northern deciduous temperate forests, and that lianas may further increase in abundance if the severity of forest fragmentation intensifies.     

Rain forest fragmentation and the proliferation of successional trees

The effects of habitat fragmentation on diverse tropical tree communities are poorly understood. Over a 20-year period we monitored the density of 52 tree species in nine predominantly successional genera (Annona, Bellucia, Cecropia, Croton, Goupia, Jacaranda, Miconia, Pourouma, Vismia) in fragmented and continuous Amazonian forests. We also evaluated the relative importance of soil, topographic, forest dynamic, and landscape variables in explaining the abundance and species composition of successional trees. Data were collected within 66 permanent 1-ha plots within a large (approximately 1000 km2) experimental landscape, with forest fragments ranging from 1 to 100 ha in area. Prior to forest fragmentation, successional trees were uncommon, typically comprising 2-3% of all trees (> or =10 cm diameter at breast height [1.3 m above the ground surface]) in each plot. Following fragmentation, the density and basal area of successional trees increased rapidly. By 13-17 years after fragmentation, successional trees had tripled in abundance in fragment and edge plots and constituted more than a quarter of all trees in some plots. Fragment age had strong, positive effects on the density and basal area of successional trees, with no indication of a plateau in these variables, suggesting that successional species could become even more abundant in fragments over time. Nonetheless, the 52 species differed greatly in their responses to fragmentation and forest edges. Some disturbance-favoring pioneers (e.g., Cecropia sciadophylla, Vismia guianensis, V. amazonica, V. bemerguii, Miconia cf. crassinervia) increased by >1000% in density on edge plots, whereas over a third (19 of 52) of all species remained constant or declined in numbers. Species responses to fragmentation were effectively predicted by their median growth rate in nearby intact forest, suggesting that faster-growing species have a strong advantage in forest fragments. An ordination analysis revealed three main gradients in successional-species composition across our study area. Species gradients were most strongly influenced by the standlevel rate of tree mortality on each plot and by the number of nearby forest edges. Species-composition also varied significantly among different cattle ranches, which differed in their surrounding matrices and disturbance histories. These same variables were also the best predictors of total successional-tree abundance and species richness. Successional-tree assemblages in fragment interior plots (>150 m from edge), which are subjected to fragment area effects but not edge effects, did not differ significantly from those in intact forest, indicating that area effects per se had little influence on successional trees. Soils and topography also had little discernable effect on these species. Collectively, our results indicate that successional-tree species proliferate rapidly in fragmented Amazonian forests, largely as a result of chronically elevated tree mortality near forest edges and possibly an increased seed rain from successional plants growing in nearby degraded habitats. The proliferation of fast-growing successional trees and correlated decline of old-growth trees will have important effects on species composition, forest dynamics, carbon storage, and nutrient cycling in fragmented forests.     

Edge-Related Variation in Medicinal and Other "Useful" Wild Plants of Bwindi Impenetrable National Park, Uganda

Abstract:  Harvesting of wild plants for nontimber uses is widespread in the tropics, but its impact is usually quantified only for one or a few species at a time. Thus, forest managers are never clear about how well their efforts are protecting such plants. We quantified abundance and edge-related variation in 91 species of useful wild plants commonly harvested by communities around Bwindi Impenetrable National Park (BINP), Uganda, to evaluate the effect of their harvest. Forty percent of these species were harvested exclusively for medicines, 22% for weaving, and 24% for other uses. Fourteen percent were harvested for combinations of uses. Plants were surveyed around the entire periphery of the park transects that extended out 1 km into the forest interior from the edge. Analyses of edge and interior distribution were controlled for effects of topography. Individually, nine (10%) species were very rare, occurring in <0.5% of the plots searched. Of the remaining 82 species, most (50%) decreased significantly away from the park boundary, whereas 4.9% increased and 45.1% showed no pronounced edge-related distributions. Rarer species were no more likely to be less abundant near the edge than commoner species. These results suggest that most plants used for nontimber purposes in BINP are not currently being harvested unsustainably. In this respect many of the species of useful wild plants we examined resembled animals commonly hunted in tropical forests for bushmeat because they increased in abundance in disturbed habitat. Conservation action should initially aim to understand what influences distributions of very rare species. Edge-based assessments of distributions may be valuable for revealing harvest impact on species of useful wild plants commonly harvested by people living around forest islands in the tropics.     

Are shrubland birds edge specialists?

In studies of forest fragmentation, birds of scrubby, early-successional habitats are considered edge specialists. Because these birds are assumed to thrive in fragmented, edge-dominated areas, their landscape ecology has received little attention from ecologists. With populations of shrubland birds declining throughout the eastern United States, the question of whether or not these birds really prefer edge habitats has important conservation implications. We used a meta-analysis to test how edges affect the abundance of shrubland birds in early-successional habitats. We analyzed data for 17 species from seven studies that compared the abundances of birds in the interiors and edges of regenerating clearcuts surrounded by mature forest. The meta-analysis clearly showed that shrubland birds avoid edges. All 17 species tested had higher abundances in patch centers than along edges, and edge effects were significant for 8 of 17 species. The key implication of this result is that small or irregular patches, dominated by edge, are unlikely to provide suitable habitat for shrubland birds. Thus, management for these declining species should involve providing large patches and minimizing edges. These findings demonstrate the importance of testing widely accepted ecological classifications and the need to view landscape ecology from the perspective of non-forest wildlife.     

Influence of Forest Fragmentation on Community Structure of Frogs and Lizards in Northeastern Costa Rica

Abstract:  To better understand responses of reptiles and amphibians to forest fragmentation in the lowland Neotropics, we examined community and population structure of frogs and lizards in the fragmented landscape surrounding La Selva Biological Station in the Sarapiquí region of northeastern Costa Rica. We used diurnal quadrats and nocturnal transects to sample frogs and lizards in nine forest fragments (1–7 ha each) and La Selva (1100 ha). Species richness in all fragments combined was 85% of that found in La Selva with comparable sampling effort. Richness varied from 10 to 24 species among forest fragments, compared with 36 species at La Selva. Lizard density was higher and frog density was lower in forest fragments than in La Selva. Community composition varied among sites and by fragment size class, and species occurrence was nested with respect to fragment area. Isolation and habitat variables did not significantly affect species richness, composition, or nestedness. We classified 34% of species as fragmentation sensitive because they were absent or occurred at low densities in fragments. Nevertheless, the relatively high diversity observed in the entire set of fragments indicates that preserving a network of small forest patches may be of considerable conservation value to the amphibians and reptiles of this region.     

Distribution and diversity of ground beetles in Başkonuş Mountain National Park of Turkey

This study was carried out in National Park Ba?konu? Mountain (Kahramanmara?, Turkey), in Mediterranean region from April to October of 2004 and 2005. A total 31 species of ground beetles (Coleoptera, Carabidae) were recorded in the pitfall traps. Among them, Carabus (Archicarabus) gotschi caramanus Fairmaire, 1886, Carabus (Procrustes) coriaceus mopsucrenae Peyron, 1858 and Nebria (Nebria) hemprichi Klug, 1832 were the most abundant species. Distribution, diversity and monthly distribution of species in steppes, forest edge and forest interior, and chorotypes and ecology of these species were separately given in this study. It was recorded that the diversity of ground beetles was significantly higher in the forest edge and steppes than in the forest interior. There was no significant difference in the diversity of ground beetles in the steppes and the forest edge.     

Changes in Wildlife Communities Near Edges

Abstract: Wildlife managers and land managers have traditionally considered edges as beneficial to wildlife because species diversity generally increases near habitat edges. Explanations for this edge effect include greater vegetative complexity at edges or the simultaneous availability of more than one landscape element. However, edges can have negative consequences for wildlife by modifying distribution and dispersal and by increasing incidence of nest predation and parasitism Edges also may be detrimental to species requiring large undisturbed areas because increases in edge generally result in concommitant reductions in size and possible isolation of patches and corridots. Thus, both wildlife and land managers should be cautious when describing the benefits of edges to wildlife: particularly when dealing with species that require forest interiors.
Changes in wildlife communities associated with habitat edges are not easily assessed because defining edge species and measuring edge dimensions can be difficult in field studies Also, there is no general consensus as to how edge effect is best measured. Well-designed long-term studies of edges in various landscapes are needed (1) to better understand the positive and negative impacts of edges on wildlife communities, guilds, or key species, and (2) to effectively quantify edge effect and thereby develop management recommendations to improve the quality of edges for wildlife. Additional studies of edge effect are timely because greater amounts of edge will continue to be created in future landscapes due to extensive agriculture and other land-use-practices, and because developing knowledge in conservation biology and landscape ecology will facilitate multidisciplinary approaches to edge and landscape management for the benefit of wildlife.     

Bryophyte responses to microclimatic edge effects across riparian buffers.

Although riparian buffers are an important aspect of forest management in the boreal forest of Canada, little is known about the habitat conditions within buffers, due in part to complex edge effects in response to both the upland clearcut and the stream. We investigated microclimatic conditions and bryophyte growth and vitality in seven locations between the stream edge and 60 m into the upland undisturbed conifer forests and at the clearcut sites with riparian buffer 30 km northwest of Thunder Bay, Ontario, Canada. We hypothesized that the growth and vitality of a pleurocarpous moss, Hylocomium splendens, and an acrocarpous moss, Polytrichum commune, would be directly related to the microclimatic gradients detected. We further hypothesized that sensitivity of the bryophytes to environmental factors will vary depending on their life form type, i.e., pleurocarpous moss will respond differently than the acrocarpous moss. Both bryophyte species were transplanted in pots and placed at 10-m intervals along 60-m transects perpendicular to the stream across the buffer and undisturbed sites. Bryophyte growth, cover, and vitality, as well as microclimatic parameters and plant cover, were measured over the summer in 2003. The riparian buffers were simultaneously affected by microclimatic gradients extending from both the clearcut edge and the riparian-upland ecotonal edge. Both bryophyte species responded to changes in the microclimatic conditions. However, vapor pressure deficit (VPD) was the most important factor influencing the growth of H. splendens, whereas for P. commune growth soil moisture was most important. Our study confirms earlier findings that interior forest bryophytes such as H. splendens can be used as indicators to monitor edge effects and biodiversity recovery following forest harvesting. We demonstrate that growth and vitality of these bryophytes reflect the prevailing near-ground microclimatic conditions at the forest edges. Abundance estimates of such bryophytes can be used to determine the depth of edge effects across both ecotonal edges (e.g., riparian-upland forest edge) and anthropogenically created edges (e.g., clearcut edge). Forest management practices must consider depth of edge in determining the appropriate width of riparian buffers that would be necessary to sustain biodiversity and associated values at the land/water interface.     

Edge effects on trophic cascades in tropical rainforests

The cascading effects of biodiversity loss on ecosystem functioning of forests have become more apparent. However, how edge effects shape these processes has yet to be established. We assessed how edge effects alter arthropod populations and the strength of any resultant trophic cascades on herbivory rate in tropical forests of Brazil. We established 7 paired forest edge and interior sites. Each site had a vertebrate-exclosure, procedural (exclosure framework with open walls), and control plot (total 42 plots). Forest patches were surrounded by pasture. Understory arthropods and leaf damage were sampled every 4 weeks for 11 months. We used path analysis to determine the strength of trophic cascades in the interior and edge sites. In forest interior exclosures, abundance of predaceous and herbivorous arthropods increased by 326% and 180%, respectively, compared with control plots, and there were significant cascading effects on herbivory. Edge-dwelling invertebrates responded weakly to exclusion and there was no evidence of trophic cascade. Our results suggest that the vertebrate community at forest edges controls invertebrate densities to a lesser extent than it does in the interior. Edge areas can support vertebrate communities with a smaller contingent of insectivores. This allows arthropods to flourish and indirectly accounts for higher levels of plant damage at these sites. Increased herbivory rates may have important consequences for floristic community composition and primary productivity, as well as cascading effects on nutrient cycling. By interspersing natural forest patches with agroforests, instead of pasture, abiotic edge effects can be softened and prevented from penetrating deep into the forest. This would ensure a greater proportion of forest remains habitable for sensitive species and could help retain ecosystem functions in edge zones.     

Edge Effects and Isolation: Red-Backed Voles Revisited

Abstract:  We examined demographic responses of California red-backed voles ( Clethrionomys californicus ) to forest fragmentation in southwestern Oregon at sites where this species has previously shown negative responses to fragmentation. Voles were captured in live traps and released. Voles were rarely caught in clearcuts surrounding 11 forest fragments, but relative vole density did not decrease from the forest-fragment interiors to edges. The first result agrees with previous findings at these sites 6 years earlier, but the latter result does not. There was no evidence that vole response to edge changes with fragment age. Two years of intensive mark-recapture efforts at two forest-fragment sites and two unfragmented (control) sites did not show negative effects of fragmentation on vole survival, an important demographic rate. Vole capture probabilities varied greatly across space and time on these four sites, which may explain the differences in vole responses to edge seen between this and the previous study. These results suggest that reliable appraisal of edge effects may be difficult for many species on small fragments because the data necessary to apply population estimators require great efforts to obtain and the use of indices leads to a confounding of detection probabilities with demographic change.     

Resilience of Southwestern Amazon Forests to Anthropogenic Edge Effects

Abstract:  Anthropogenic edge effects can compromise the conservation value of mature tropical forests. To date most edge-effect research in Amazonia has concentrated on forests in relatively seasonal locations or with poor soils in the east of the basin. We present the first evaluation from the relatively richer soils of far western Amazonia on the extent to which mature forest biomass, diversity, and composition are affected by edges. In a southwestern Amazonian landscape we surveyed woody plant diversity, species composition, and biomass in 88 × 0.1 ha samples of unflooded forest that spanned a wide range in soil properties and included samples as close as 50 m and as distant as >10 km from anthropogenic edges. We applied Mantel tests, multiple regression on distance matrices, and other multivariate techniques to identify anthropogenic effects before and after accounting for soil factors and spatial autocorrelation. The distance to the nearest edge, access point, and the geographical center of the nearest community ("anthropogenic-distance effects") all had no detectable effect on tree biomass or species diversity. Anthropogenic-distance effects on tree species composition were also below the limits of detection and were negligible in comparison with natural environmental and spatial factors. Analysis of the data set's capacity to detect anthropogenic effects confirmed that the forests were not severely affected by edges, although because our study had few plots within 100 m of forest edges, our confidence in patterns in the immediate vicinity of edges is limited. It therefore appears that the conservation value of most "edge" forests in this region has not yet been compromised substantially. We caution that because this is one case study it should not be overinterpreted, but one explanation for our findings may be that western Amazonian tree species are naturally faster growing and more disturbance adapted than those farther east.     

Neighboring groups and habitat edges modulate range use in Phayre’s leaf monkeys (<Emphasis Type="Italic">Trachypithecus phayrei crepusculus</Emphasis>)

An animal’s use of space may be strongly influenced by habitat edges and neighboring conspecifics encountered in and around its home range. Habitat edges are known to affect species density and distribution, but their impact on home range use is largely unknown. Additionally, among large animals, interactions with neighbors become particularly important as increasing home range size leads to decreasing exclusivity of resource use, but the effect of neighbors on home range use remains poorly understood. Here, we examine the influence of neighbors and habitat edges on the ranging patterns of three groups of Phayre’s leaf monkeys (Trachypithecus phayrei crepusculus) in northeast Thailand over a period of more than 2 years. The study animals occupied dry evergreen forest, and adjacent patches of dry dipterocarp forest created a habitat edge and formed barriers between some groups. We found that the use of home range interiors was 50–90% higher than the border areas, indicating concentrated use of resources within the home range. The use of peripheral areas was influenced by social organization, the presence of neighboring groups, and forest edges. While one multimale group showed no particular habitat preference, two single-male groups preferred areas bordering dry dipterocarp habitat and avoided areas bordering neighboring groups, suggesting that the threat of neighbors mediated border presence. Additionally, groups may have been attracted to the forest edge, where conspecific competitors are absent and increased sunlight may increase resource abundance and/or quality. This study revealed that the use of border areas can be modulated by neighboring groups and habitat edges, thereby adding to our understanding of home range use among territorial species in heterogeneous habitats.     

Effect of Edge Structure on the Flux of Species into Forest Interiors

Abstract: A key goal of conservation biology is to prevent the spread of exotic species. Previous work on exotic invasion has two limitations: (1) the lack of a spatially explicit approach and (2) a primary focus on the net effect of invasion by examining invasive species already present in the community. We address these limitations by focusing on the arrival of a potential invader into a community and use a spatially explicit approach to quantify the flow of seeds from the surrounding landscape into the interior of a forest. We hypothesize that the structure of forest-edge vegetation influences how the edge mediates seed flux. To test our hypothesis, we experimentally altered vegetation structure within 20 m of the edge to create two edge treatments: thinned and intact. We quantified the flux of seeds moving into the forest interior across the two treatments. We used seed traps randomly arrayed on transects from 5 to 50 m into the forest. More seeds crossed the thinned treatment than crossed the intact treatment to reach the forest interior. In addition, seeds that crossed the thinned treatment dispersed farther into the forest than those that crossed the intact treatment. These results were consistent throughout the period of maximum autumn dispersal, including periods before and after leaf drop. Our results show that the structure of vegetation on the edge interacts with the flux of wind-dispersed seed across the edge. We demonstrated that an edge with intact vegetation can function as a physical barrier to seed dispersal. Therefore, the structure of vegetation on edges can influence the function of edges as barriers to seed flux into the forest interior.