Towards a better mechanistic understanding of edge effects

Ruffell, Jay; Didham, Raphaël K.

doi:10.1007/s10980-016-0397-3

Cited by 27 publications

(18 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Third, researchers often assume that interdependent landscape factors are independently related to animals’ responses and ignore potential interactive and/or indirect effects (Didham et al., ; Wilson et al., ). If two landscape factors are causally related, an animal's response to one pattern is at least partially an indirect response to the other, and ignoring their interdependence can underestimate the importance of one or both factors (Didham et al., ; Ruffell & Didham, ). In our study, grasshopper sparrows favoured landscapes comprising not only large amounts of grassland but also unfragmented grassland with small proportions of habitat near cropland or woody edges.…”

Section: Discussionmentioning

confidence: 99%

The importance of core habitat for a threatened species in changing landscapes

Herse

With

Boyle

2018

Journal of Applied Ecology

View full text Add to dashboard Cite

Habitat loss, fragmentation, and alteration of the landscape matrix are interdependent processes, collectively responsible for most recent species extinctions. Thus, determining the extent to which these landscape processes affect animals is critical for conservation. However, researchers have often assumed that interdependent effects are independently related to animals’ responses, underestimating the importance of one or several landscape processes in driving species declines. We demonstrate how to disentangle the interdependent effects of habitat amount, fragmentation, and edge context on population size by assessing abundance of a rapidly declining grassland songbird species (grasshopper sparrow Ammodramus savannarum) in eastern Kansas (USA). We conducted >7,000 point count surveys at >2,000 sites over two breeding seasons, then modelled the direct, interactive, and indirect effects of landscape factors on abundance within spatial scales (200‐, 400‐, 800‐, and 1,600‐m radii) relevant to our focal species’ dispersal behaviour. Sparrow abundance correlated most strongly with landscape structure within 400‐m radii, increasing nonlinearly with grassland area and decreasing with the proportion of grassland near cropland or woody edges. Sparrows’ negative response to cropland edges was mostly an added, indirect consequence of reduced grassland area, whereas sparrows’ stronger negative response to woody edges was not attributable to variation in grassland area. Fragmentation and edge context mattered most in landscapes comprising c. 50%–80% grassland. Synthesis and applications. In our research, abundance of a threatened grassland songbird was influenced more by core grassland area (a function of total grassland area, fragmentation, and edge context) than total grassland area per se. Moreover, a local extinction threshold of c. 50% grassland indicated that small amounts of habitat were unsuitable for our focal species regardless of habitat configuration or matrix type. Local extinction thresholds in response to habitat area provide clear baseline targets for land managers; above those thresholds, configuration and the matrix can be modified to increase abundance of edge‐sensitive animals. Conflicting evidence in the literature regarding the importance of fragmentation and matrix features could be partially explained by species‐level traits, or methodological issues such as defining landscapes at ecologically arbitrary spatial scales, assessing landscape quality using species richness, and ignoring interactive and indirect effects.

show abstract

Section: Discussionmentioning

confidence: 99%

The importance of core habitat for a threatened species in changing landscapes

Herse

With

Boyle

2018

Journal of Applied Ecology

View full text Add to dashboard Cite

show abstract

“…The roles of habitat and landscape variables for species occupancy, abundance, and species richness have been actively examined during the past 20 years (Mazerolle and Villard / 31 1999;Yamaura et al 2008a;Ruffell and Didham 2016). Studies surveyed organisms within the sampling plots with equal areas, and examined the effects of environmental covariates on the plot-level (per area) abundance or species richness.…”

Section: 2community Responses To Environmental Covariatesmentioning

confidence: 99%

How much abandoned farmland is required to harbor comparable species richness and abundance of bird communities in wetland? Hierarchical community model suggests the importance of habitat structure and landscape context

et al. 2018

View full text Add to dashboard Cite

While wetlands have been converted into farmlands, large amounts of farmlands are now being abandoned, and this novel habitat is expected to be inhabited by species which depend on wetlands. Here we examined the effects of habitat and landscape variables on the densities of wetland bird species in abandoned farmlands. We surveyed birds in abandoned farmlands with varied patch area, habitat, and landscape variables in Kushiro district, eastern Hokkaido, northern Japan. We also surveyed birds in 15 ha of the remaining wetlands as a reference habitat. We used abundance-based hierarchical community model (HCM) to estimate patch-level estimates of abundance of each species based on sampling plots data that only partially covered the studied patches. We observed 14 wetland species and analyzed them with HCM. Abandoned farmland patch areas had significant positive effects on the densities of two species. Tree densities and shrub coverage exerted positive and negative effects on some species. Amounts of surrounding wetland/grassland had positive effects on many species. Ensemble of species-level models suggested that 24.7 ha and 10.6 ha of abandoned farmlands would be needed to harbor a comparable total abundance and species richness in 15-ha wetlands, respectively. These required amounts can be increased/decreased depending on the covariates. The use of HCM allows us to predict species-and community-level responses under varied conditions based on incomplete sampling data. A quantity of 1.6 times larger areas of abandoned farmlands may be required to restore wetland bird communities in eastern Hokkaido.

show abstract

“…One factor that has been cause for confusion in edge studies is the cascading impact of direct and indirect responses [15]. Ultimately, most edge effects that are described are indirect inasmuch as species are usually responding to altered distributions of their resources, often driven by abiotic changes.…”

Section: Introductionmentioning

confidence: 99%

“…This has led some researchers to try to isolate responses caused solely by the presence of edges from patterns that can be linked to measurable gradients with respect to edge distance (e.g., light levels, floristic changes, etc.). However, studies that attempt to determine if observed edge gradients are "really" edge effects, or are instead caused by some other underlying environmental gradient can be missing the point [15]. Even if some local environmental variable can be found that is the direct cause of an observed edge response (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…(movement and aquatic studies were not included). For each study, we recorded study location (a), focal taxa (b), the types of edges studied and whether the studies took place on only one side of an edge or both sides (c), for one-sided edge studies (in forest only), what type of habitat was adjacent to the focal patch (d), and what response type was measured at the community, species, and process levels (e) [16]), if that gradient itself is caused by edges, then the response is, ultimately, an edge response [15]. This is important because if there is an attempt to separate edge responses from edges, it becomes much more difficult to predict where those environmental gradients are likely to occur in space.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Closing Persistent Gaps in Knowledge About Edge Ecology

Ries

Murphy

Wimp

et al. 2017

Curr Landscape Ecol Rep

View full text Add to dashboard Cite

Edge effects are one of the most extensively studied ecological phenomena of the past 100 years. Despite the stillcommon perception that edge effects are overly complex and idiosyncratic, we do know a lot about the mechanisms that underlie them. A major review from 2004 described four fundamental mechanisms that cause most edge patterns. In general, altered resource distributions due to often-predictable gradients in the edge environment as well as access to multiple resources across edges accounts for the fundamental differences between habitat edges and interiors. However, altered species interactions near edges are another fundamental component of edge ecology and remain difficult to predict. Here, we follow up on that 2004 review and show that the same four mechanisms described there remain sufficient to explain most edge responses, but we highlight some new developments. Notably, we find that edge studies have widened to include many new habitat types, a more diverse taxa and broader regions of the world. Yet, even recent studies were often not designed to quantify critical metrics such as the depth or magnitude of edge influence. Further, sample sizes and study design continue to contribute to spurious variability and make comparing results difficult. These problems make extrapolation to larger scales problematic and a lack of effective tools for extrapolation complicate this goal even further. We offer suggestions on a set of best practices for designing edge studies and propose that future research should shift more towards extrapolation across landscapes.

show abstract

Towards a better mechanistic understanding of edge effects

Cited by 27 publications

References 27 publications

The importance of core habitat for a threatened species in changing landscapes

The importance of core habitat for a threatened species in changing landscapes

How much abandoned farmland is required to harbor comparable species richness and abundance of bird communities in wetland? Hierarchical community model suggests the importance of habitat structure and landscape context

Closing Persistent Gaps in Knowledge About Edge Ecology

Contact Info

Product

Resources

About