Distance Of Edge Influence Research Articles

Trends in studies of edge influence on vegetation at human-created and natural forest edges across time and space

Forest edges, or boundaries between adjacent ecosystems, play important ecological roles. Both anthropogenic and natural forest edges affect vegetation while contributing to landscape heterogeneity. The recent proliferation of studies on vegetation at edges suggests that a comprehensive review of global edge studies is timely. We reviewed the literature on forest edges to identify trends in edge studies over time, determine types and localities of studied edges, and compare findings on edge influence. We found 446 studies conducted in 55 different countries that considered edge influence on vegetation structure and (or) composition. Research on vegetation at anthropogenic edges has increased and expanded geographically, but studies are still scarce in some areas and at natural forest edges. Forest edges were generally characterized by greater species diversity and nonnative species abundance than interior forest. Distance of edge influence on vegetation extended furthest at tropical anthropogenic forest edges compared with other edge types and locations. Edge influence on responses caused by indirect effects of edges generally extended further into the forest than edge influence on responses related to forest structure. Our findings indicate that vegetation characteristics differ between edge and forest types and should be considered in the sustainable management of heterogeneous forested landscapes.

Edge influence on understorey plant communities depends on forest management

AbstractQuestionsDoes the influence of forest edges on plant species richness and composition depend on forest management? Do forest specialists and generalists show contrasting patterns?LocationMesic, deciduous forests across Europe.MethodsVegetation surveys were performed in forests with three management types (unthinned, thinned 5–10 years ago and recently thinned) along a macroclimatic gradient from Italy to Norway. In each of 45 forests, we established five vegetation plots along a south‐facing edge‐to‐interior gradient (n = 225). Forest specialist, generalist and total species richness, as well as evenness and proportion of specialists, were tested as a function of the management type and distance to the edge while accounting for several environmental variables (e.g. landscape composition and soil characteristics). Magnitude and distance of edge influence were estimated for species richness per management type.ResultsGreatest total species richness was found in thinned forests. Edge influence on generalist plant species richness was contingent on the management type, with the smallest decrease in species richness from the edge‐to‐interior in unthinned forests. In addition, generalist richness increased with the proportion of forests in the surrounding landscape and decreased in forests dominated by tree species that cast more shade. Forest specialist species richness, however, was not affected by management type or distance to the edge, and only increased with pH and increasing proportion of forests in the landscape.ConclusionsForest thinning affects the plant community composition along edge‐to‐interior transects of European forests, with richness of forest specialists and generalists responding differently. Therefore, future studies should take the forest management into account when interpreting edge‐to‐interior because both modify the microclimate, soil processes and deposition of polluting aerosols. This interaction is key to predict the effects of global change on forest plants in landscapes characterized by the mosaic of forest patches and agricultural land that is typical for Europe.

Edge influence on composition and structure of a Pinus palustris woodland following catastrophic wind disturbance

Forest edges are an important legacy of natural and anthropogenic disturbances. Edges of intact forest fragments are influenced by adjacent non-forested ecosystems, resulting in compositional and structural differences at the edge and into the intact forest. Edge influence (EI) is the altered biotic and abiotic interactions that occur along the edge-to-interior gradient in disturbed forests. Few studies have analyzed natural disturbance created edges, particularly in woodland structures, which contain fewer trees per hectare and are typically less light-limited than forests. The goal of our study was to examine the EI of a tornado-created edge in a Pinus palustris Mill. (longleaf pine) woodland in Alabama. In 2011, an EF-3 tornado impacted a restored P. palustris woodland, resulting in a distinct edge. We installed transects perpendicular to the edge to quantify biotic and abiotic response variables and calculate the distance of EI. Reduced structural forest complexity and basal area (negative EI) were evident 70 m into the interior woodland. Ground flora richness and diversity experienced a positive EI, with higher richness and diversity at the edge. Results of this study add to our understanding of EI on woodland composition and structure and naturally created edges and may help guide natural disturbance based silvicultural systems.

Negligible structural development and edge influence on the understorey at 16–17‐yr‐old clear‐cut edges in black spruce forest

AbstractQuestionsWhat is the distance of edge influence on the structure and understorey composition at 16–17‐yr‐old cut edges in black spruce boreal forest? How do these edges compare with more recent 2–5‐yr‐old cut edges in the same region?LocationNorthwestern Quebec, Canada.MethodsForest structure and understorey composition were sampled along transects perpendicular to ten 16–17‐yr‐old clear‐cut edges, and compared to published results from 2–5‐yr‐old cut edges. We used randomization tests to assess the magnitude and distance of edge influence, and to compare edge influence between different edge ages.ResultsBlack spruce forest next to the 16–17‐yr‐old cut edges was structurally and compositionally very similar to interior forest, with little edge influence from harvesting beyond 5 m into the forest. Edge influence on the understorey was weak (low magnitude) and not very extensive (short distance) at these edges, with no significant edge influence on the abundance of individual species. Logs peaked in abundance on the forest side of the edge, with values higher than in either adjacent ecosystem.ConclusionsOverall, 16–17‐yr‐old cut edges in black spruce forest showed little evidence of further structural change compared to the 2–5‐yr‐old cut edges. Structural development of these edges as well as regeneration of the disturbed areas also resulted in reduced edge influence on the understorey. Instead, clear‐cut edges in black spruce forest may experience more forest influence on the regenerating disturbed area.

Edge influence on vegetation at natural and anthropogenic edges of boreal forests in Canada and Fennoscandia

Summary Although anthropogenic edges are an important consequence of timber harvesting, edges due to natural disturbances or landscape heterogeneity are also common. Forest edges have been well studied in temperate and tropical forests, but less so in less productive, disturbance‐adapted boreal forests. We synthesized data on forest vegetation at edges of boreal forests and compared edge influence among edge types (fire, cut, lake/wetland; old vs. young), forest types (broadleaf vs. coniferous) and geographic regions. Our objectives were to quantify vegetation responses at edges of all types and to compare the strength and extent of edge influence among different types of edges and forests. Research was conducted using the same general sampling design in Alberta, Ontario and Quebec in Canada, and in Sweden and Finland. We conducted a meta‐analysis for a variety of response variables including forest structure, deadwood abundance, regeneration, understorey abundance and diversity, and non‐vascular plant cover. We also determined the magnitude and distance of edge influence (DEI) using randomization tests. Some edge responses (lower tree basal area, tree canopy and bryophyte cover; more logs; higher regeneration) were significant overall across studies. Edge influence on ground vegetation in boreal forests was generally weak, not very extensive (DEI usually < 20 m) and decreased with time. We found more extensive edge influence at natural edges, at younger edges and in broadleaf forests. The comparison among regions revealed weaker edge influence in Fennoscandian forests. Synthesis. Edges created by forest harvesting do not appear to have as strong, extensive or persistent influence on vegetation in boreal as in tropical or temperate forested ecosystems. We attribute this apparent resistance to shorter canopy heights, inherent heterogeneity in boreal forests and their adaptation to frequent natural disturbance. Nevertheless, notable differences between forest structure responses to natural (fire) and anthropogenic (cut) edges raise concerns about biodiversity implications of extensive creation of anthropogenic edges. By highlighting universal responses to edge influence in boreal forests that are significant irrespective of edge or forest type, and those which vary by edge type, we provide a context for the conservation of boreal forests.

The role of edge contrast and forest structure in edge influence: vegetation and microclimate at edges in the Brazilian cerrado

The effect of the adjacent non-forested environment on the forest near the edge, edge influence (EI), is an important impact in fragmented landscapes and is believed to vary with factors such as forest structure and edge contrast. In order to improve our understanding of the factors governing the variability in EI, we studied microclimate and vegetation at cerrado edges surrounded by variable land uses in southeastern Brazil, a system with both forest and savanna fragments. We determined the significance, magnitude and distance of EI on microclimate, vegetation structure and grass biomass which we measured along five transects perpendicular to fourteen edges in forest or savanna next to different land uses. We introduce a quantitative measure of edge contrast that considers land uses at different distances from the same edge (e.g., a firebreak between a forest edge and a plantation) and verified whether edge contrast is correlated with EI in this system. Notwithstanding the large variation in EI among variables and study sites, there were some similarities in the patterns of EI between forest and savanna edges. Edge contrast was successfully quantified by our measure but was only correlated with EI on moisture and grass biomass. Our results point to the high variability in EI within a region. Our quantitative measure of edge contrast may be useful in explaining variability in EI. However, much unexplained variation remains in the highly fragmented cerrado system which is affected by EI in both forest and savanna fragments.

The extent of edge effects increases during post-harvesting forest succession

As human activities increase landscape fragmentation, edge effects on ecosystem properties are growing at an unprecedented rate. The influence of logging-induced edges on biodiversity can ultimately jeopardize the long-term sustainability of forest management practices. These effects are difficult to quantify, however, because temporal changes in edge influence on residual forests remain poorly understood. We examined vegetation gradients along 17 transects crossing the boundary between stands harvested 5–66years ago and old-growth boreal forests. We estimated the magnitude and distance of edge influence (MEI and DEI, respectively) in uncut old-growth forests, and investigated how these attributes of edge influence changed during the regeneration of adjacent logged stands. Analyses indicated that three types of vegetation gradients were necessary to describe the temporal changes of edge influence on vegetation in uncut forests. No temporal changes were detected for MEI during 66years of forest succession. Conversely, DEI in uncut forests ranged from 0 to 70m, and increased as the adjacent logged stands regenerated. This edge expansion through time, together with persistent differences in vegetation between logged and old-growth forests for at least 66years, raise questions as to whether or not forest management involving fast rotations between logging events can maintain biodiversity. In forest ecosystems where edge habitat widens while vegetation has still not recovered to its typical characteristics, the planning of an adequate combination of rotation time, size and perimeter/area ratio of residual forests becomes critical to achieve the objectives of sustainable management, including regional biodiversity preservation.

Logging-Induced Edge and Configuration of Old-Growth Forest Remnants in the Eastern North American Boreal Forests

ABSTRACT: Worldwide, old-growth forest loss and fragmentation resulting from logging are considered major threats to biodiversity. In many regions of the boreal zone, remaining patches of old-growth forests left following logging are restricted to small areas exposed to edge effects. Our objectives were to evaluate, from a literature review, the distance of edge influence (DEI) induced by sharp logginginduced edges on adjacent old-growth residual forests and to compare, in order to exemplify edge effect influence, two contrasting scenarios of residual stand configurations (linear vs. agglomerated). Synthesis from studies conducted in boreal forests of Canada and Fennoscandia indicates a DEI of ∼50 meters for residual old-growth forests located along recently (≤ 20 years) cutover areas. Based on the comparison of two contrasted scenarios, we demonstrate the strong relationship between residual forest configuration and area under edge influence. For a similar area of residual old-growth forest, linear strip...

Spatial and temporal variations of soil moisture in three types of agroforestry boundaries in the Loess Plateau, China

Agroforestry is a ubiquitous landscape on the slopes in Loess Plateau, where soil moisture is a limiting factor for plant growth and development. The spatial and temporal characteristics of soil moisture were studied in three types of agroforestry boundaries: forest-grassland, forest-cropland and shelterbelt-cropland. The result shows that soil moisture content decreased with soil depth increasing from the surface to 110 cm. Soil moisture content differed significantly among the three boundaries all in the rainy season (July–September), dry season (May–June) and spring (March–April). The horizontal distribution of soil moisture in different soil layers in the three types of boundaries showed different patterns with line form, wave form, scoop form or “W” form. The distance of edge influence (DEI) of soil moisture in different types of landscape boundaries was estimated by variance analysis and multiple comparisons. In dry season the DEI in 0–10 cm soil layer was 0.4 H (H, average height of trees), which ranged from 0.2 H in grassland or in cropland to 0.2 H in forest field for both forest-grassland and forest- cropland boundaries, and 0.7 H (ranged from 0.2 H in cropland to 0.5 H in forest field) for shelterbelt-cropland boundary. In rainy season the DEI at soil depth of 0–110 cm was 0.7 H for the three boundaries. The results indicated that agroforestry type should be carefully selected to maintain soil moisture in land management, especially in restoring degraded land in Loess Plateau.

Edge Influence on Forest Structure and Composition in Fragmented Landscapes

Abstract: Although forest edges have been studied extensively as an important consequence of fragmentation, a unifying theory of edge influence has yet to be developed. Our objective was to take steps toward the development of such a theory by (1) synthesizing the current knowledge of patterns of forest structure and composition at anthropogenically created forest edges, (2) developing hypotheses about the magnitude and distance of edge influence that consider the ecological processes influencing these patterns, and (3) identifying needs for future research. We compiled data from 44 published studies on edge influence on forest structure and composition in boreal, temperate, and tropical forests. Abiotic and biotic gradients near created forest edges generate a set of primary responses to edge creation. Indirect effects from these primary responses and the original edge gradient perpetuate edge influence, leading to secondary responses. Further changes in vegetation affect the edge environment, resulting in ongoing edge dynamics. We suggest that the magnitude and distance of edge influence are a direct function of the contrast in structure and composition between adjacent communities on either side of the edge. Local factors such as climate, edge characteristics, stand attributes, and biotic factors affect patch contrast. Regional factors define the context within which to assess the ecological significance of edge influence (the degree to which the edge habitat differs from interior forest habitat). Our hypotheses will help predict edge influence on structure and composition in forested ecosystems, an important consideration for conservation. For future research on forest edges in fragmented landscapes, we encourage the testing of our hypotheses, the use of standardized methodology, complete descriptions of study sites, studies on other types of edges, synthesis of edge influence on different components of the ecosystem, and investigations of edges in a landscape context.

Multiple edge effects and their implications in fragmented landscapes

Summary Habitat edges are thought to explain much of the negative effects arising from habitat fragmentation; however, progress has been limited in extrapolating edge effects to different situations because ecologists still do not understand if and how multiple edges interact within fragments. It also remains controversial whether edge effects govern patch‐size effects, such as area sensitivity, observed in many migratory songbirds. I examined how multiple edges within fragments may intensify edge responses by investigating spatial distributions of an area‐sensitive songbird that breeds in temperate grasslands of North America, the bobolink (Dolichonyx oryzivorus Linnaeus). I tested whether bobolinks avoid edges and whether avoidance is stronger near two edges (double‐edge plots) than near only one edge (single‐edge plots). I subsequently linked bobolink distributions to landscape maps that vary in the amount of habitat and degree of fragmentation to explore some potential implications of multiple edges on patch‐ and landscape‐level distributions. Multiple edges appeared to influence the magnitude of observed edge effects, in which the probability of bobolink occurrence was four times lower in double‐edge plots and two times lower in single‐edge plots than in the interior of grasslands. Within single‐edge plots, the probability of occurrence increased with increasing distance from edge. Within double‐edge plots, the probability of occurrence increased as a function of the nearest and next‐nearest distances from edges. Multiple edges also appeared to increase the extent of edge effects, or distance of edge influence, which was estimated to be approximately 11–33% greater in double‐edge plots than in single‐edge plots, depending on the next‐nearest distance from edge. Extrapolating local bird distributions to landscape models suggests that edge effects can have strong influences on large‐scale distributions and that models incorporating multiple edge effects are different to simple nearest‐edge models only in highly fragmented landscapes, regardless of landscape composition. Furthermore, edge effects can lead to patch‐size effects similar to empirical patterns of area sensitivity observed in this species. I conclude that edge effects can be intensified when multiple edges collide, a feature that permeates many fragmented landscapes.

Structure and composition of edges next to regenerating clear‐cuts in mixed‐wood boreal forest

Abstract. We investigated the spatial and temporal pattern of edge influence on primary (forest structure) and secondary (understory structure and composition) responses at forest edges next to regenerating clear‐cuts in Populus‐dominated boreal forest in Alberta, Canada. We used before/after‐harvest comparisons to determine whether there were significant effects of edge creation in the first and second year after harvest. We also investigated 5‐ and 16‐yr‐old edges to determine whether their structure and composition were significantly different from interior forest. Distance of edge influence (20–60 m) was not extensive compared to findings from studies conducted in other forest types. In the first two years after harvest, there were significant primary responses to edge creation including increased tree mortality, snag breakage and amount of downed coarse woody debris; as well as secondary responses including prolific vegetative regeneration of Populus spp. and a decrease in total shrub cover. Significant edge effects were still detectable 5 and 16 yr after edge creation, despite the rapid regeneration of Populus‐ dominated forest in the adjacent clear‐cuts. These older edges showed evidence of past primary and secondary responses, including a more heterogeneous canopy, along with additional changes in under‐ story composition. At both younger and older edges the distance of edge influence was greater for secondary responses (up to 60 m) than for primary responses (10–20 m). We hypothesize that secondary responses to edge creation start later than primary responses and that the distance of edge influence is greater for secondary (vs. primary) responses.

Structure and composition of edges next to regenerating clear-cuts in mixed-wood boreal forest

Abstract. We investigated the spatial and temporal pattern of edge influence on primary (forest structure) and secondary (understory structure and composition) responses at forest edges next to regenerating clear-cuts in Populus-dominated boreal forest in Alberta, Canada. We used before/after-harvest comparisons to determine whether there were significant effects of edge creation in the first and second year after harvest. We also investigated 5- and 16-yr-old edges to determine whether their structure and composition were significantly different from interior forest. Distance of edge influence (20–60 m) was not extensive compared to findings from studies conducted in other forest types. In the first two years after harvest, there were significant primary responses to edge creation including increased tree mortality, snag breakage and amount of downed coarse woody debris; as well as secondary responses including prolific vegetative regeneration of Populus spp. and a decrease in total shrub cover. Significant edge effects were still detectable 5 and 16 yr after edge creation, despite the rapid regeneration of Populus- dominated forest in the adjacent clear-cuts. These older edges showed evidence of past primary and secondary responses, including a more heterogeneous canopy, along with additional changes in under- story composition. At both younger and older edges the distance of edge influence was greater for secondary responses (up to 60 m) than for primary responses (10–20 m). We hypothesize that secondary responses to edge creation start later than primary responses and that the distance of edge influence is greater for secondary (vs. primary) responses.

Identifying the Distance of Vegetative Edge Effects Using Landsat TM Data and Geostatistical Methods

The physical and biological changes that occur at the edges of forest clearings are increasingly well described. To date, however, estimates of the distances over which edge effects occur have generally resulted from intensive fieldwork. We present a method for estimating the distance of edge influence (DEI) – and thus the amount of forest affected by edge – from remote sensing data. We couple limited field‐based information with remote‐sensing classification techniques to locate clearings. We then develop and use a new geostatistical method – point‐based semivariogram analysis – to estimate DEI. We discuss methods of selecting inputs and methods for classification, and compare global, local, and point‐based methods of estimating DEI. We also demonstrate the use of idealized versions of actual landscapes to clarify complex behavior of semivariograms. Our technique can be generalized to edges in other forest types as well as to other approximately point‐based disturbances that produce an outwardly diminishing gradient of effects.