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1.
Measuring habitat connectivity in complex landscapes is a major focus of landscape ecology and conservation research. Most studies use a binary landscape or patch mosaic model for describing spatial heterogeneity and understanding pattern-process relationships. While the value of landscape gradient approaches proposed by McGarigal and Cushman are recognized, applications of these newly proposed three dimensional surface metrics remain under-used. We created a gradient map of habitat quality from several GIS layers and applied three dimensional surface metrics to measure connectivity between 67 locations in Indiana, USA surveyed for one group of ecosystem service providers, flower longicorn beetles (Cerambycidae: Lepturinae). The three dimensional surface metrics applied to the landscape gradient model showed great potential to explain the differences of lepturine assemblages among the 2,211 studied landscapes (between site pairs). Surface kurtosis and its interaction with geographic distance were among the most important metrics. This approach provided unique information about the landscape through four configuration metrics. There were some uniform trends of the responses of many species to some of surface metrics, however some species responded differently to other metrics. We suggest that three dimensional surface metrics applied to a habitat surface map created with insight into species requirements is a valuable approach to understanding the spatial dynamics of species, guilds, and ecosystem services. 相似文献
2.
Empirical patterns of the effects of changing scale on landscape metrics 总被引：45，自引：2，他引：45
While ecologists are well aware that spatial heterogeneity is scale-dependent, a general understanding of scaling relationships of spatial pattern is still lacking. One way to improve this understanding is to systematically examine how pattern indices change with scale in real landscapes of different kinds. This study, therefore, was designed to investigate how a suite of commonly used landscape metrics respond to changing grain size, extent, and the direction of analysis (or sampling) using several different landscapes in North America. Our results showed that the responses of the 19 landscape metrics fell into three general categories: Type I metrics showed predictable responses with changing scale, and their scaling relations could be represented by simple scaling equations (linear, power-law, or logarithmic functions); Type II metrics exhibited staircase-like responses that were less predictable; and Type III metrics behaved erratically in response to changing scale, suggesting no consistent scaling relations. In general, the effect of changing grain size was more predictable than that of changing extent. Type I metrics represent those landscape features that can be readily and accurately extrapolated or interpolated across spatial scales, whereas Type II and III metrics represent those that require more explicit consideration of idiosyncratic details for successful scaling. To adequately quantify spatial heterogeneity, the metric-scalograms (the response curves of metrics to changing scale), instead of single-scale measures, seem necessary.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
3.
We examined the effects of matrix structure and movement responses of organisms on the relationships between 7 patch isolation metrics and patch immigration. Our analysis was based on simulating movement behaviour of two generic disperser types (specialist and generalist) across mosaic landscapes containing three landcover types: habitat, hospitable matrix and inhospitable matrix. Movement, mortality and boundary crossing probabilities of simulated individuals were linked to the landcover and boundary types in the landscapes. The results indicated that area-based isolation metrics generally predict patch immigration more reliably than distance-based isolation metrics. Relationships between patch isolation metrics and patch immigration varied between the two generic disperser types and were affected by matrix composition or matrix fragmentation. Patch immigration was always affected by matrix composition but not by matrix fragmentation. Our results do not encourage the generic use of patch isolation metrics as a substitute for patch immigration, in particular in metapopulation models where generic use may result in wrong projections of the survival probability of metapopulations. However, our examination of the factors affecting the predictive potential of patch isolation metrics should facilitate interpretation and comparison of existing patch isolation studies. Future patch isolation studies should include information about landscape structure and the dispersal distance and dispersal behaviour of the organism of interest.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
4.
Behavior of class-level landscape metrics across gradients of class aggregation and area 总被引：4，自引：3，他引：4
Habitat loss and fragmentation processes strongly affect biodiversity conservation in landscapes undergoing anthropogenic land use changes. Many attempts have been made to use landscape structure metrics to quantify the independent and joint effects of these processes. Unfortunately, ecological interpretation of those metrics has been plagued by lack of thorough understanding of their theoretical behavior. We explored behavior of 50 metrics in neutral landscapes across a 21-step gradient in aggregation and a 19-step gradient in area using a full factorial design with 100 replicates of each of the 399 combinations of the two factors to assess how well metrics reflected changes in landscape structure. Metric values from real landscapes were used to determine the extent of neutral landscape space that is represented in real landscapes. We grouped metrics into three major behavioral classes: strongly related to focal class area (n=15), strongly related to aggregation (n=7), and jointly responding to area and aggregation (n=28). Metrics strongly related to class area exhibited a variety of distinct behaviors, and many of these metrics have unique interpretations that make each of them particularly useful in certain applications. Metrics strongly related to aggregation, independent of class area, are particularly useful in assessing effects of fragmentation. Moreover, metrics in this group exhibited a range of specific behaviors, highlighting subtle but different aspects of landscape aggregation even though we controlled only one aspect of aggregation. The non-linear behavior exhibited by many metrics renders interpretation difficult and use of linear analytical techniques inappropriate under many circumstances. Ultimately, comprehensive characterization of landscapes undergoing habitat loss and fragmentation will require using several metrics distributed across behavioral groups.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
5.
A comparison of metrics predicting landscape connectivity for a highly interactive species along an urban gradient in Colorado, USA 总被引：1，自引：1，他引：0
Many organisms persist in fragmented habitat where movement between patches is essential for long-term demographic and genetic
stability. In the absence of direct observation of movement, connectivity or isolation metrics are useful to characterize
potential patch-level connectivity. However, multiple metrics exist at varying levels of complexity, and empirical data on
species distribution are rarely used to compare performance of metrics. We compared 12 connectivity metrics of varying degrees
of complexity to determine which metric best predicts the distribution of prairie dog colonies along an urban gradient of
385 isolated habitat patches in Denver, Colorado, USA. We found that a modified version of the incidence function model including
area-weighting of patches and a cost-weighted distance surface best predicted occupancy, where we assumed roads were fairly
impermeable to movement, and low-lying drainages provided dispersal corridors. We also found this result to be robust to a
range of cost weight parameters. Our results suggest that metrics should incorporate both patch area and the composition of
the surrounding matrix. These results provide guidance for improved landscape habitat modeling in fragmented landscapes and
can help identify target habitat for conservation and management of prairie dogs in urban systems. 相似文献
6.
Acknowledgment that the matrix matters in conserving wildlife in human-modified landscapes is increasing. However, the complex
interactions of habitat loss, habitat fragmentation, habitat condition and land use have confounded attempts to disentangle
the relative importance of properties of the landscape mosaic, including the matrix. To this end, we controlled for the amount
of remnant forest habitat and the level of fragmentation to examine mammal species richness in human-modified landscapes of
varying levels of matrix development intensity and patch attributes. We postulated seven alternative models of various patch
habitat, landscape and matrix influences on mammal species richness and then tested these models using generalized linear
mixed-effects models within an information theoretic framework. Matrix attributes were the most important determinants of
terrestrial mammal species richness; matrix development intensity had a strong negative effect and vegetation structural complexity
of the matrix had a strong positive effect. Distance to the nearest remnant forest habitat was relatively unimportant. Matrix
habitat attributes are potentially a more important indicator of isolation of remnant forest patches than measures of distance
to the nearest patch. We conclude that a structurally complex matrix within a human-modified landscape can provide supplementary
habitat resources and increase the probability of movement across the landscape, thereby increasing mammal species richness
in modified landscapes. 相似文献
7.
Habitat isolation can affect the distribution and abundance of wildlife, but it is an ambiguous attribute to measure. Presumably, isolation is a characteristic of a habitat patch that reflects how spatially inaccessible it is to dispersing organisms. We identified four isolation metrics (nearest-neighbor distance, Voronoi polygons, proximity index, and habitat buffers) that were representative of the different families of metrics that are commonly used in the literature to measure patch isolation. Using simulated data, we evaluated the ability of each isolation metric to predict animal dispersal. We examined the simulated movement of organisms in two types of landscapes: an artificially-generated point-pattern landscapes where patch size and shape were consistent and only the arrangement of patches varied, and realistic landscapes derived from a geographic information system (GIS) of forest-vegetation maps where patch size, shape, and isolation were variable. We tested the performance of the four isolation metrics by examining the strength of the correlation between observed immigration rate in the simulations and each patch isolation metric. We also evaluated whether each isolation metric would perform consistently under varying conditions of patch size/shape, total amount of habitat in the landscape, and proximity of the patch to the landscape edge. The results indicate that a commonly-used distance-based metric, nearest-neighbor distance, did not adequately predict immigration rate when patch size and shape were variable. Area-informed isolation metrics, such as the amount of available habitat within a given radius of a patch, were most successful at predicting immigration. Overall, the use of area-informed metrics is advocated despite the limitation that these metrics require parameterization to reflect the movement capacity of the organism studied.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
8.
Surface metrics for landscape ecology: a comparison of landscape models across ecoregions and scales
Peter J. Kedron Amy E. Frazier Gustavo A. Ovando-Montejo Jing Wang 《Landscape Ecology》2018,33(9):1489-1504
Context
The patch-mosaic model is lauded for its conceptual simplicity and ease with which conventional landscape metrics can be computed from categorical maps, yet many argue it is inconsistent with ecological theory. Gradient surface models (GSMs) are an alternative for representing landscapes, but adoption of surface metrics for analyzing spatial patterns in GSMs is hindered by several factors including a lack of meaningful interpretations.Objectives
We investigate the performance and applicability of surface metrics across a range of ecoregions and scales to strengthen theoretical foundations for their adoption in landscape ecology.Methods
We examine metric clustering across scales and ecoregions, test correlations with patch-based metrics, and provide ecological interpretations for a variety of surface metrics with respect to forest cover to support the basis for selecting surface metrics for ecological analyses.Results
We identify several factors complicating the interpretation of surface metrics from a landscape perspective. First, not all surface metrics are appropriate for landscape analyses. Second, true analogs between surface metrics and patch-based, landscape metrics are rare. Researchers should focus instead on how surface measures can uniquely measure spatial patterns. Lastly, scale dependencies exist for surface metrics, but relationships between metrics do not appear to change considerably with scale.Conclusions
Incorporating gradient surfaces into landscape ecological analyses is challenging, and many surface metrics may not have patch analogs or be ecologically relevant. For this reason, surface metrics should be considered in terms of the set of pattern elements they represent that can then be linked to landscape characteristics.9.
Forest managers in Canada need to model landscape pattern or spatial configurationoverlarge (100,000 km2) regions. This presents a scalingproblem, as landscape configuration is measured at a high spatial resolution,but a low spatial resolution is indicated for regional simulation. We present astatistical solution to this scaling problem by showing how a wide range oflandscape pattern metrics can be modelled from low resolution data. Our studyarea comprises about 75,000 km2 of boreal mixedwoodforest in northeast Alberta, Canada. Within this area we gridded a sample of 84digital forest cover maps, each about 9500 ha in size, to aresolution of 1 ha and used FRAGSTATS to compute a suite oflandscape pattern metrics for each map. We then used multivariate dimensionreduction techniques and canonical correlation analysis to model therelationship between landscape pattern metrics and simpler stand table metricsthat are easily obtained from non-spatial forest inventories. These analyseswere performed on four habitat types common in boreal mixedwood forests: youngdeciduous, old deciduous, white spruce, and mixedwood types. Using only threelandscape variables obtained directly from stand attribute tables (totalhabitatarea, and the mean and standard deviation of habitat patch size), ourstatistical models explained more than 73% of the joint variation in fivelandscape pattern metrics (representing patch shape, forest interior habitat,and patch isolation). By PCA, these five indices captured much of the totalvariability in the rich set of landscape pattern metrics that FRAGSTATS cangenerate. The predictor variables and strengths of association were highlyconsistent across habitat classes. We illustrate the potential use of suchstatistical relationships by simulating the regional, cumulative effects ofwildfire and forest management on the spatial arrangement of forest patches,using non-spatial stand attribute tables.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
10.
Megan J. Brady Clive A. McAlpine Craig J. Miller Hugh P. Possingham Greg S. Baxter 《Landscape Ecology》2009,24(7):879-891
The matrix is an important element of landscape mosaics that influences wildlife indirectly through its influence on habitat,
and directly, if they live in or move through it. Therefore, to quantify and manage habitat quality for wildlife in modified
landscapes, it is necessary to consider the characteristics of both patch and matrix elements of the whole landscape mosaic.
To isolate matrix effects from the often simultaneous and confounding influence of patch and landscape characteristics, we
identified nineteen 500 m radius landscapes in southeast Queensland, Australia with similar remnant forest patch attributes,
habitat loss, and fragmentation, but exhibiting a marked gradient from rural through high-density suburban development of
the matrix, quantified by a weighted road-length metric. We measured habitat disturbance, structure, and floristics in patch
core, patch edge and matrix landscape elements to characterise how landscape habitat quality changes for small mammals. Correlation
analyses identified that with increased matrix development intensity, human disturbance of core sites increased, predators
and exotic plant species richness in matrix sites increased, and structural complexity (e.g. logs and stumps) in the matrix
decreased. Ordination analyses showed landscape elements were most similar in habitat structure and floristics at low to moderate
levels of matrix development, suggesting enhanced landscape habitat quality. Matrix development intensity was not, however,
the greatest source of overall variation of habitat throughout landscapes. Many variables, such as landholder behaviour, complicate
the relationship. For enhanced conservation outcomes the matrix needs to be managed to control disturbances and strategically
plan for matrix habitat retention and restoration. 相似文献
11.
The influence of thematic resolution on metric selection for biodiversity monitoring in agricultural landscapes 总被引：4，自引：3，他引：4
Debra Bailey Regula Billeter Stéphanie Aviron Oliver Schweiger Felix Herzog 《Landscape Ecology》2007,22(3):461-473
The objective of this paper is to investigate the relationship between landscape pattern metrics and agricultural biodiversity
at the Temperate European scale, exploring the role of thematic resolution and a suite of biological and functional groups.
Factor analyses to select landscape-level metrics were undertaken on 25 landscapes classified at four levels of thematic resolution.
The landscapes were located within seven countries. The different resolutions were considered appropriate to taxonomic and
functional group diversity. As class-level metrics are often better correlated to ecological response, the landscape-level
metric subsets gained through exploratory analysis were additionally used to guide the selection of class-level metric subsets.
Linear mixed models were then used to detect correlations between landscape- and class-level metrics and species richness
values. Taxonomic groups with differing requirements (plants, birds, different arthropod groups) and also functional arthropod
groups were examined. At the coarse scale of thematic resolution grain metrics (patch density, largest patch index) emerged
as rough indicators for the different biological groups whilst at the fine scale a diversity metric (e.g. Simpson’s diversity
index) was appropriate. The intermediate thematic resolution offered most promise for biodiversity monitoring. Metrics included
largest patch index, edge density, nearest neighbour, the proximity index, circle and Simpson’s diversity index. We suggest
two possible applications of these metrics in the context of biodiversity monitoring and the identification of biodiversity
hot spots in European agricultural landscapes. 相似文献
12.
Estimating landscape pattern metrics from a sample of land cover 总被引：2，自引：0，他引：2
Although landscape pattern metrics can be computed directly from wall-to-wall land-cover maps, statistical sampling offers
a practical alternative when complete coverage land-cover information is unavailable. Partitioning a region into spatial units
and then selecting a subset (sample) of these units introduces artificial patch edge and patch truncation effects that may
lead to biased sample-based estimators of landscape pattern metrics. The bias and variance of sample-based estimators of status
and change in landscape pattern metrics were evaluated for four 120-km × 120-km test regions with land cover provided by the
1992 and 2001 National Land-Cover Data of the United States. Bias was generally small for both the estimators of status and
estimators of change in landscape pattern, but exceptions to this favorable result exist and it is advisable to assess bias
for the specific metrics and region of interest in any given application. A 10-km × 10-km sample block generally yielded larger
biases but smaller variances for the estimators relative to a 20-km × 20-km sample block. Stratified random sampling improved
precision of the estimators relative to simple random sampling. The methodology developed to determine properties of sample-based
estimators can be readily extended to evaluate other landscape pattern metrics, regions, and sample block sizes. 相似文献
13.
Historic range of variability in landscape structure in subalpine forests of the Greater Yellowstone Area,USA 总被引：4，自引：0，他引：4
A measure of the historic range of variability (HRV) in landscape structure is essential for evaluating current landscape
patterns of Rocky Mountain coniferous forests that have been subjected to intensive timber harvest. We used a geographic information
system (GIS) and FRAGSTATS to calculate key landscape metrics on two ∼130,000-ha landscapes in the Greater Yellowstone Area,
USA: one in Yellowstone National Park (YNP), which has been primarily shaped by natural fires, and a second in the adjacent
Targhee National Forest (TNF), which has undergone intensive clearcutting for nearly 30 years. Digital maps of the current
and historical landscape in YNP were developed from earlier stand age maps developed by Romme and Despain. Maps of the TNF
landscape were adapted from United States Forest Service Resource Information System (RIS) data. Key landscape metrics were
calculated at 20-yr intervals for YNP for the period from 1705-1995. These metrics were used to first evaluate the relative
effects of small vs. large fire events on landscape structure and were then compared to similar metrics calculated for both
pre- and post-harvest landscapes of the TNF. Large fires, such as those that burned in 1988, produced a structurally different
landscape than did previous, smaller fires (1705-1985). The total number of patches of all types was higher after 1988 (694
vs. 340-404 before 1988), and mean patch size was reduced by almost half (186 ha vs. 319-379 ha). The amount of unburned forest
was less following the 1988 fires (63% vs. 72-90% prior to 1988), yet the number of unburned patches increased by nearly an
order of magnitude (230 vs. a maximum of 41 prior to 1988). Total core area and mean core area per patch decreased after 1988
relative to smaller fires (∼73,700 ha vs. 87,000-110,000 ha, and 320 ha vs. 2,123 ha, respectively). Notably, only edge density
was similar (17 m ha−1 after 1988) to earlier landscapes (9.8-14.2 m ha−1).Three decades of timber harvesting dramatically altered landscape structure in the TNF. Total number of patches increased
threefold (1,481 after harvest vs. 437 before harvest), and mean patch size decreased by ∼70% (91.3 ha vs. 309 ha). None of
the post-harvest landscape metrics calculated for the TNF fell within the HRV as defined in YNP, even when the post-1988 landscape
was considered. In contrast, pre-harvest TNF landscape metrics were all within, or very nearly within, the HRV for YNP. While
reference conditions such as those identified by this study are useful for local and regional landscape evaluation and planning,
additional research is necessary to understand the consequences of changes in landscape structure for population, community,
ecosystem, and landscape function.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
The behavior of landscape metrics commonly used in the study of habitat fragmentation 总被引：40，自引：2，他引：38
A meaningful interpretation of landscape metrics is possible only when the limitations of each measure are fully understood, the range of attainable values is known, and the user is aware of potential shifts in the range of values due to characteristics of landscape patches. To examine the behavior of landscape metrics, we generated artificial landscapes that mimicked fragmentation processes while controlling the size and shape of patches in the landscape and the mode of disturbance growth. We developed nine series of increasingly fragmented landscapes and used these to investigate the behavior of edge density, contagion, mean nearest neighbor distance, mean proximity index, perimeter-area fractal dimension, and mass fractal dimension. We found that most of the measures were highly correlated, especially contagion and edge density, which had a near-perfect inverse correspondence. Many of the measures were linearly-associated with increasing disturbance until the proportion of disturbance on the landscape was approximately 0.40, with non-linear associations at higher proportions. None of the measures was able to differentiate between landscape patterns characterized by dispersed versus aggregated patches. The highest attainable value of each measure was altered by either patch size or shape, and in some cases, by both attributes. We summarize our findings by discussing the utility of each metric. 相似文献
15.
Westphal Michael I. Field S.A. Tyre A.J. Paton D. Possingham H.P. 《Landscape Ecology》2003,18(4):413-426
We assessed how well landscape metrics at 2, 5, and 10 km scales could explain the distribution of woodland bird species in
the Mount Lofty Ranges, South Australia. We considered 31 species that have isolated or partially isolated populations in
the region and used the Akaike Information Criterion to select a set of candidate logistic regression models. The 2 km distance
was the most appropriate scale for a plurality of the species. While the total amount of area of native vegetation around
a site was the most important determining factor, the effect of landscape configuration was also important for many species.
Most species responded positively to area-independent fragmentation, but the responses to mean patch isolation and mean patch
shape were more variable. Considering a set of candidate models for which there is reasonable support (Akaike weights > 0.10),
12 species responded negatively to landscapes with highly linear and isolated patches. No clear patterns emerged in terms
of taxonomy or functional group as to how species respond to landscape configuration. Most of the species had models with
relatively good discrimination (12 species had ROC values > 0.70), indicating that landscape pattern alone can explain their
distributions reasonably well. For six species there were no models that had strong weight of evidence, based on the AIC and
ROC criteria. This analysis shows the utility of the Akaike Information Criterion approach to model selection in landscape
ecology. Our results indicate that landscape planners in the Mount Lofty Ranges must consider the spatial configuration of
vegetation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
We argue that thematic resolution, i.e., the level of categorical detail of a thematic map expressed by the number of classes
included in the map legend, is an inherent component of the scale at which a landscape is analyzed. Changing the number of
classes can change the configuration of the patch mosaic as much as changing the grain does. We address recent calls in this
and other journals to deepen research in this topic. In particular, we report how thematic resolution affects the patchiness
of mosaics representing natural landscapes, which have seldom been studied in this respect. We selected seven 50 × 50 km landscapes
within national parks, each representative of a world biome. We applied an object-based unsupervised classification to Landsat
TM imagery of these landscapes using increasing numbers of classes, between 2 and 50, and derived curves of mean patch size
and patch density for each site. Our results are consistent with previous findings in that the patchiness of output mosaics
increases monotonically with increasing thematic resolution, with a higher rate of increase up to eight classes that declines
until it becomes roughly constant for more than 16 classes. However, this constant rate of increase is still considerable,
meaning that, at least for natural landscapes, there is no threshold beyond which the patch-mosaic model is independent of
the conceptual filter applied. This dependence on human fiat calls for re-thinking the patch-mosaic paradigm. 相似文献
17.
Studies on the distribution of mammalian carnivores in fragmented landscapes have focused mainly on structural aspects such
as patch and landscape features; similarly, habitat connectivity is usually associated with landscape structure. The influence
of food resources on carnivore patch use and the important effect on habitat connectivity have been overlooked. The aim of
this study is to evaluate the relative importance of food resources on patch use patterns and to test if food availability
can overcome structural constraints on patch use. We carried out a patch-use survey of two carnivores: the beech marten (Martes foina) and the badger (Meles meles) in a sample of 39 woodland patches in a fragmented landscape in central Italy. We used the logistic model to investigate
the relative effects on carnivore distribution of patch, patch neighbourhood and landscape scale variables as well as the
relative abundance of food resources. Our results show how carnivore movements in fragmented landscapes are determined not
only by patch/landscape structure but also by the relative abundance of food resources. The important take-home message of
our research is that, within certain structural limits (e.g. within certain limits of patch isolation), by modifying the relative
amount of resources and their distribution, it is possible to increase suitability in smaller/relatively isolated patches.
Conversely, however, there are certain thresholds above which an increase in resources will not achieve high probability of
presence. Our findings have important and generalizable consequences for highly fragmented landscapes in areas where it may
not be possible to increase patch sizes and/or reduce isolation so, for instance, forest regimes that will increase resource
availability could be implemented.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Size of a forest patch is a useful predictor of density and reproductive success of Neotropical migratory birds in much of eastern North America. Within these forested landscapes, large forest tracts appear to be sources – fragments in which surpluses of offspring are produced and can potentially colonize new fragments including woodlot sinks where reproduction fails to balance adult mortality. Within agricultural landscapes of the midwestern U.S., where forests are severely fragmented, high levels of brood parasitism by brown-headed cowbirds (Molothrus ater) and intense predation on nests generally result in low reproductive success for Neotropical migrants regardless of forest size. In some midwestern U.S. landscapes, however, the variation in reproductive success among forest fragments suggests that `source' habitat could still exist for Neotropical migrants. We used vegetation, fragment and landscape metrics to develop multivariate models that attempt to explain the variation in abundance and reproductive success of Neotropical migrants nesting in an agricultural landscape in northern Indiana, USA. We produced models that reasonably described the pattern of species richness of Neotropical migrants and the abundance of wood thrushes (Hylocichla mustelina) and several other Neotropical migrant species within 14 forest fragments. In contrast, we were unable to produce useful models of the reproductive success of wood thrushes breeding in the same forest fragments. Our results suggest that (1) abundance patterns of Neotropical migrants are probably influenced by both landscape- and fragment-scale factors; (2) multivariate analyses of Neotropical migrant abundance are not useful in modeling the corresponding patterns of reproductive success; and (3) the location of any remaining `source' habitat for Neotropical migrants breeding within agricultural landscapes in North America will be difficult to predict with indirect measures such as vegetation composition or landscape context. As a result, the potential for developing conservation strategies for Neotropical migrants will be limited without labor-intensive, direct measurements of demographic parameters. 相似文献
19.
Víctor Arroyo-Rodríguez Iraida M. González-Perez Adriana Garmendia Mireia Solà Alejandro Estrada 《Landscape Ecology》2013,28(9):1717-1727
Land-use change is forcing many animal populations to inhabit forest patches in which different processes can threaten their survival. Some threatening processes are mainly related to forest patch characteristics, but others depend principally on the landscape spatial context. Thus, the impact of both patch and landscape spatial attributes needs to be assessed to have a better understanding of the habitat spatial attributes that constraint the maintenance of populations in fragmented landscapes. Here, we evaluated the relative effect of three patch-scale (i.e., patch size, shape, and isolation) and five landscape-scale metrics (i.e., forest cover, fragmentation, edge density, mean inter-patch isolation distance, and matrix permeability) on population composition and structure of black howler monkeys (Alouatta pigra) in the Lacandona rainforest, Mexico. We measured the landscape-scale metrics at two spatial scales: within 100 and 500 ha landscapes. Our findings revealed that howler monkeys were more strongly affected by local-scale metrics. Smaller and more isolated forest patches showed a lower number of individuals but at higher densities. Population density also tended to be positively associated to matrices with higher proportion of secondary forests and arboreal crops (i.e. with greater permeability), most probably because these matrices can offer supplementary foods. The immature-to-female ratio also increased with matrix permeability, shape complexity, and edge density; habitat characteristics that can increase landscape connectivity and sources availability. The prevention of habitat loss and isolation, and the increment of matrix permeability are therefore needed for the conservation of this endangered Neotropical mammal. 相似文献
20.
Rune H. Økland Harald Bratli Wenche E. Dramstad Anette Edvardsen Gunnar Engan Wendy Fjellstad Einar Heegaard Oddvar Pedersen Heidi Solstad 《Landscape Ecology》2006,21(7):969-987
Knowledge of variation in vascular plant species richness and species composition in modern agricultural landscapes is important
for appropriate biodiversity management. From species lists for 2201 land-type patches in 16 1-km2 plots five data sets differing in sampling-unit size from patch to plot were prepared. Variation in each data set was partitioned
into seven sources: patch geometry, patch type, geographic location, plot affiliation, habitat diversity, ecological factors,
and land-use intensity. Patch species richness was highly predictable (75% of variance explained) by patch area, within-patch
heterogeneity and patch type. Plot species richness was, however, not predictable by any explanatory variable, most likely
because all studied landscapes contained all main patch types – ploughed land, woodland, grassland and other open land – and
hence had a large core of common species. Patch species composition was explained by variation along major environmental complex
gradients but appeared nested to lower degrees in modern than in traditional agricultural landscapes because species-poor
parts of the landscape do not contain well-defined subsets of the species pool of species-rich parts. Variation in species
composition was scale dependent because the relative importance of specific complex gradients changed with increasing sampling-unit
size, and because the amount of randomness in data sets decreased with increasing sampling-unit size. Our results indicate
that broad landscape structural changes will have consequences for landscape-scale species richness that are hard or impossible
to predict by simple surrogate variables. 相似文献