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1.
Landscape analysis and delineation of habitat patches should take into account organism-specific behavioral and perceptual
responses to landscape structure because different organisms perceive and respond to landscape features over different ranges
of spatial scales. The commonly used methods for delineating habitat based on rules of contiguity do not account for organism-specific
responses to landscape patch structure and have undesirable properties, such as being dependent on the scale of base map used
for analysis. This paper presents an improved patch delineation algorithm, “PatchMorph,” which can delineate patches across
a range of spatial scales based on three organism-specific thresholds: (1) land cover density threshold, (2) habitat gap maximum
thickness (gap threshold), and (3) habitat patch minimum thickness (spur threshold). This algorithm was tested on an “idealized”
landscape with landscape gaps and spurs of known size, and delineated patches as expected. It was then applied to delineate
patches from a neutral random fractal landscape, which showed that as the input gap and spur thickness thresholds were increased,
the number of patches decreased from 59 (low thresholds) patches to 1 (high thresholds). The algorithm was then applied to
model western yellow-billed cuckoo ( Coccyzus americanus occidentalis) nesting habitat patches based on spur and gap thresholds specific to this organism. Both these analyses showed that fewer
patches were delineated by PatchMorph than by rules of contiguity, and those patches were larger, had smoother edges, and
had fewer gaps within the patches. This algorithm has many applications beyond those presented in this paper, including habitat
suitability analysis, spatially explicit population modeling, and habitat connectivity analysis. 相似文献
2.
Spatial and temporal changes in community structure of soil organisms may result from a myriad of processes operating at a hierarchy of spatial scales, from small-scale habitat conditions to species movements among patches and large-sale landscape features. To disentangle the relative importance of spatial and environmental factors at different scales (plot, patch and landscape), we analyzed changes in Collembola community structure along a gradient of forest fragmentation, testing predictions of the Hierarchical Patch Dynamics Paradigm (HPDP) in different European biogeographic regions (Boreal, Continental, Atlantic, Mediterranean, Alpine). Using variance partitioning methods, based on partial CCAs, we observed that the independent effect of environmental processes was significantly explaining Collembola community variance in all regions, while the relative effect of spatial variables was not significant, due to the observed high levels of landscape heterogeneity along the gradient. Environmental factors at the patch and plot scales were generally significant and explained the larger part of community changes. Landscape variables were not significant across all study sites. Yet, at the landscape level, an increase in forest habitat and proximity of forest patches were showed to have an indirect influence on local community changes, by influencing microhabitat heterogeneity at lower spatial scales in all studied regions. In line with HPDP, large-scale landscape features influenced spatio-temporal changes in soil fauna communities by constraining small-scale environmental processes. In turn, these provided mechanistic understanding for diversity patterns operating at the patch scale, via shifts in community weighted mean of Collembola life-forms occurring in local communities along the fragmentation gradient. 相似文献
3.
Conservationists, managers, and land planners are faced with the difficult task of balancing many issues regarding humans
impacts on natural systems. Many of these potential impacts arise from local-scale and landscape-scale changes, but such changes
often covary, which makes it difficult to isolate and compare independent effects arising from humans. We partition multi-scale
impacts on riparian forest bird distribution in 105 patches along approximately 500 km of the Madison and Missouri Rivers,
Montana, USA. To do so, we coupled environmental information from local (within-patch), patch, and landscape scales reflecting
potential human impacts from grazing, invasive plant species, habitat loss and fragmentation, and human development with the
distribution of 28 terrestrial breeding bird species in 2004 and 2005. Variation partitioning of the influence of different
spatial scales suggested that local-scale vegetation gradients explained more unique variation in bird distribution than did
information from patch and landscape scales. Partitioning potential human impacts revealed, however, that riparian habitat
loss and fragmentation at the patch and landscape scales explained more unique variation than did local disturbances or landscape-scale
development (i.e., building density in the surrounding landscape). When distribution was correlated with human disturbance,
local-scale disturbance had more consistent impacts than other scales, with species showing consistent negative correlations
with grazing but positive correlations with invasives. We conclude that while local vegetation structure best explains bird
distribution, managers concerned with ongoing human influences in this system need to focus more on mitigating the effects
of large-scale disturbances than on more local land use issues.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Habitat fragmentation, patch quality and landscape structure are important predictors for species richness. However, conservation
strategies targeting single species mainly focus on habitat patches and neglect possible effects of the surrounding landscape.
This project assesses the impact of management, habitat fragmentation and landscape structure at different spatial scales
on the distribution of three endangered butterfly species, Boloria selene, Boloria titania and Brenthis ino. We selected 36 study sites in the Swiss Alps differing in (1) the proportion of suitable habitat (i.e., wetlands); (2) the
proportion of potential dispersal barriers (forest) in the surrounding landscape; (3) altitude; (4) habitat area and (5) management
(mowing versus grazing). Three surveys per study site were conducted during the adult flight period to estimate occurrence
and density of each species. For the best disperser B. selene the probability of occurrence was positively related to increasing proportion of wetland on a large spatial scale (radius:
4,000 m), for the medium disperser B. ino on an intermediate spatial scale (2,000 m) and for the poorest disperser B. titania on a small spatial scale (1,000 m). Nearby forest did not negatively affect butterfly species distribution but instead enhanced
the probability of occurrence and the population density of B. titania. The fen-specialist B. selene had a higher probability of occurrence and higher population densities on grazed compared to mown fens. The altitude of the
habitat patches affected the occurrence of the three species and increasing habitat area enhanced the probability of occurrence
of B. selene and B. ino. We conclude that, the surrounding landscape is of relevance for species distribution, but management and habitat fragmentation
are often more important. We suggest that butterfly conservation should not focus only on a patch scale, but also on a landscape
scale, taking into account species-specific dispersal abilities. 相似文献
5.
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
6.
Understanding the driving forces behind the distribution of threatened species is critical to set priorities for conservation
measures and spatial planning. We examined the distribution of a globally threatened bird, the corncrake ( Crex crex), in the lowland floodplains of the Rhine River, which provide an important breeding habitat for the species. We related
corncrake distribution to landscape characteristics (area, shape, texture, diversity) at three spatial scales: distinct floodplain
units (“floodplain scale”), circular zones around individual observations (“home range scale”), and individual patches (“patch
scale”) using logistic regression. Potential intrinsic spatial patterns in the corncrake data were accounted for by including
geographic coordinates and an autocovariate as predictors in the regression analysis. The autocovariate was the most important
predictor of corncrake occurrence, probably reflecting the strong conspecific attraction that is characteristic of the species.
Significant landscape predictors mainly pertained to area characteristics at the patch scale and the home range scale; the
probability of corncrake occurrence increased with potential habitat area, patch area, and nature reserve area. The median
potential habitat patch size associated with corncrake occurrence was 11.3 ha; 90% of the corncrake records were associated
with patches at least 2.2 ha in size. These results indicate that the corncrake is an area-sensitive species, possibly governed
by the males’ tendency to reside near other males while maintaining distinct territories. Our results imply that corncrake
habitat conservation schemes should focus on the preservation of sufficient potential habitat area and that existing management
measures, like delayed mowing, should be implemented in relatively large, preferably contiguous areas. 相似文献
7.
The biological integrity of stream ecosystems depends critically on human activities that affect land use/cover along stream
margins and possibly throughout the catchment. We evaluated stream condition using an Index of Biotic Integrity (IBI) and
a habitat index (HI), and compared these measures to landscape and riparian conditions assessed at different spatial scales
in a largely agricultural Midwestern watershed. Our goal was to determine whether land use/cover was an effective predictor
of stream integrity, and if so, at what spatial scale. Twenty-three sites in first-through third-order headwater streams were
surveyed by electrofishing and site IBIs were calculated based on ten metrics of the fish collection. Habitat features were
characterized through field observation, and site HIs calculated from nine instream and bank metrics. Field surveys, aerial
photograph interpretation, and geographic information system (GIS) analyses provided assessments of forested land and other
vegetation covers at the local, reach, and regional (catchment) scales.
The range of conditions among the 23 sites varied from poor to very good based on IBI and HI scores, and habitat and fish
assemblage measures were highly correlated. Stream biotic integrity and habitat quality were negatively correlated with the
extent of agriculture and positively correlated with extent of wetlands and forest. Correlations were strongest at the catchment
scale (IBI with % area as agriculture, r 2=0.50, HI with agriculture, r 2=0.76), and tended to become weak and non-significant at local scales. Local riparian vegetation was a weak secondary predictor
of stream integrity. In this watershed, regional land use is the primary determinant of stream conditions, able to overwhelm
the ability of local site vegetation to support high-quality habitat and biotic communities. 相似文献
8.
Forest managers in Canada need to model landscape pattern or spatial configurationoverlarge (100,000 km 2) 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 km 2 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
9.
Matrix quality affects probability of persistence in habitat patches in landscape simulation models while empirical studies
show that both urban and agricultural land uses affect forest birds. However, due to the fact that forest bird abundance and
species richness can be strongly influenced by local habitat factors, it is difficult to analyze matrix effects without confounding
effects from such factors. Given this, our objectives were to (1) relate human-dominated land uses to forest bird abundance
and species richness without confounding effects from other factors; (2) determine the scale at which forest birds respond
to the matrix; and (3) identify whether certain bird migratory strategies or habitat associations vary in richness or abundance
as a function of urban and agriculture land uses. Birds were surveyed at a single point count site 100 m from the edge of
23 deciduous forest patches near Ottawa, Ontario. Land uses surrounding each patch were measured within increasingly large
circles from 200 to 5000 m radius around the bird survey site. Regression results suggest that effects of urban and agricultural
land uses on forest birds (1) are not uniformly positive or negative, (2) can occur at different spatial scales, and (3) differentially
affect certain groups of species. In general, agriculture appeared to affect species at a broad spatial scale (within 5 km),
while urban land use had an impact at both a narrower spatial scale (within 1.8 km) and at the broad scale. Neotropical and
short distance migrant birds seemed to be the most sensitive to land use intensification within the matrix. Limiting urban
land use within approximately 200–1800 m of forest patches would be beneficial for Neotropical migrant birds, which are species
of growing conservation concern in temperate North America. 相似文献
10.
The role of scale in ecology is widely recognized as being of vital importance for understanding ecological patterns and processes.
The capercaillie ( Tetrao urogallus) is a forest grouse species with large spatial requirements and highly specialized habitat preferences. Habitat models at
the forest stand scale can only partly explain capercaillie occurrence, and some studies at the landscape scale have emphasized
the role of large-scale effects. We hypothesized that both the ability of single variables and multivariate models to explain
capercaillie occurrence would vary with the spatial scale of the analysis. To test this hypothesis, we varied the grain size
of our analysis from 1 to just over 1100 hectares and built univariate and multivariate habitat suitability models for capercaillie
in the Swiss Alps. The variance explained by the univariate models was found to vary among the predictors and with spatial
scale. Within the multivariate models, the best single-scale model (using all predictor variables at the same scale) worked
at a scale equivalent to a small annual home range. The multi-scale model, in which each predictor variable was entered at
the scale at which it had performed best in the univariate model, did slightly better than the best single-scale model. Our
results confirm that habitat variables should be included at different spatial scales when species-habitat relationships are
investigated. 相似文献
11.
Landscape pattern might be an important determinant of non-native plant invasions because it encompasses components influencing the availability of non-native plant propagules and disturbance regimes. We aimed at exploring the relative role of patch and landscape characteristics, compared to those of habitat type and regional human influence on non-native plant species richness. For this purpose, we identified all non-native plant species in 295 patches of four coastal habitat types across three administrative regions in NE Spain differing in the degree of human influence. For each patch, we calculated several variables reflecting habitat patch geometry (size and shape), landscape composition (distribution of land-cover categories) and landscape configuration (arrangement of patches). The last two groups of variables were calculated at five different spatial extents. Landscape composition was by far the most important group of variables associated with non-native species richness. Natural areas close to diverse and urban landscapes had a high number of non-native species while surrounding agricultural areas could buffer this effect. Regional human influence was also strongly associated with non-native species richness while habitat type was the least important factor. Differences in sensitivity of landscape variables across spatial extents proved relevant, with 100 m being the most influential extent for most variables. These results suggest that landscape characteristics should be considered for performing explicit spatial risk analyses of plant invasions. Consequently, the management of invaded habitats should focus not only at the stand scale but also at the highly influential neighbouring landscape. Prior to incorporate landscape characteristics into management decisions, sensitivity analyses should be taken into account to avoid inconsistent variables. 相似文献
12.
ContextHerbicide treatments in viticulture can generate highly contrasting mosaics of vegetated and bare vineyards, of which vegetated fields often provide better conditions for biodiversity. In southern Switzerland, where herbicides are applied at large scales, vegetated vineyards are limited in extent and isolated from one another, potentially limiting the distribution and dispersal ability of organisms. ObjectivesWe tested the separate and interactive effects of habitat amount and fragmentation on invertebrate abundance using a multi-scale framework, along with additional environmental factors. We identified which variables at which scales were most important in predicting patterns of invertebrate abundance. MethodsWe used a factorial design to sample across a gradient of habitat amount (area of vegetated vineyards, measured as percentage of landscape PLAND) and fragmentation (number of vegetated patches, measured as patch density PD). Using 10 different spatial scales, we identified the factors and scales that most strongly predicted invertebrate abundance and tested potential interactions between habitat amount and fragmentation. ResultsHabitat amount (PLAND index) was most important in predicting invertebrate numbers at a field scale (50 m radius). In contrast, we found a negative effect of fragmentation (PD) at a broad scale of 450 m radius, but no interactive effect between the two. ConclusionsThe spatial scales at which habitat amount and fragmentation affect invertebrates differ, underpinning the importance of spatially explicit study designs in disentangling the effects between habitat amount and configuration. We showed that the amount of vegetated vineyards has more influence on invertebrate abundance, but that fragmentation also contributed substantially. This suggests that efforts for augmenting the area of vegetated vineyards is more beneficial for invertebrate numbers than attempts to connect them. 相似文献
13.
ContextBeyond the recognized importance of protecting large areas of contiguous habitat, conservation efforts for many species are complicated by the fact that patch suitability may also be affected by characteristics of the landscape within which the patch is located. Currently, little is known about the spatial scales at which species respond to different aspects of the landscape surrounding an occupied patch.ObjectivesUsing grassland bird point count data, we describe an approach to evaluating scale-specific effects of landscape composition on patch occupancy.MethodsWe used data from 793 point count surveys conducted in idle and grazed grasslands across Wisconsin, USA from 2012 to 2014 to evaluate scale-dependencies in the response of grassland birds to landscape composition. Patch occupancy models were used to evaluate the relationship between occupancy and landscape composition at scales from 100 to 3000 m.ResultsBobolink (Dolichonyx oryzivorus) exhibited a pattern indicating selection for grassland habitats in the surrounding landscape at all spatial scales while selecting against other habitats. Eastern Meadowlark (Sturnella magna) displayed evidence of scale sensitivity for all habitat types. Grasshopper Sparrow (Ammodramus savannarum) showed a strong positive response to pasture and idle grass at all scales and negatively to cropland at large scales. Unlike other species, patch occupancy by Henslow’s Sparrow (A. henslowii) was primarily influenced by patch area.ConclusionsOur results suggest that both working grasslands (pasture) and idle conservation grasslands can play an important role in grassland bird conservation but also highlight the importance of considering species-specific patch and landscape characteristics for effective conservation. 相似文献
14.
Habitat fragmentation is considered one of the major conservation issues of recent decades. We tested predictions of landscape patterns in a 352,253-ha managed forest area in southeast British Columbia. We did this by focussing on forest fragmentation concerns among old-growth, harvest, and wildfire patches in 44 delineated landscapes using patch indices as measures of landscape pattern. We found no significant association between amount of harvesting and 15 old-growth patch indices. Comparisons among patch types revealed that amounts and spatial patterns of harvest patches differed little from amounts and spatial patterns of old-growth patches in control landscapes. Variability indices revealed similar variability between harvest patches and old-growth patches, and more variability between harvest patches and wildfire patches. Little of the evidence gathered in this study supported predictions of fragmentation of old-growth spatial patterns, or predicted differences between harvest spatial patterns and more naturally occurring spatial patterns. We suggest these results could be due to the relatively small amounts of harvesting and old-growth forest in these landscapes, and therefore habitat amount may be a more important factor than spatial configuration of patches in these landscapes. 相似文献
15.
Tick density and population dynamics are important factors in the ecological processes involved in pathogen circulation in
a habitat. These characteristics of tick populations are closely linked to habitat suitability, which reflects the limiting
ecological factors and landscape features affecting tick populations; however, little work has been done on the regional assessment
of habitat suitability. In this study, a regional model for the distribution and abundance of the tick Ixodes ricinus in central Spain is developed. An occurrence and an abundance model were constructed; climate and vegetation variables were
found to be the main predictors of both occurrence and density in a relatively homogeneous matrix of habitat patches, whereas
topographical variables were found to have small contributions and were therefore discarded. The residuals of the abundance
model showed good correlation with the isolation of each patch. The predictive power of the abundance model was greatly enhanced
by inclusion of the traversability (a measure of the permeability of each patch to the propagules of the metapopulation) and
recruitment (an index of the relative importance of each patch to the traffic through the entire habitat network). The removal
from the landscape of the patches whose recruitment values were in the top 10% has a critical effect on tick density, an effect
not observed when patches are removed at random. These results indicate that permanent tick populations can be sustained only
in landscapes containing a minimum network of viable sites. Graph theory and measurements of patch isolation should prove
to be important elements in the forecasting of tick abundance and the management of the features underlying the landscape
ecology of tick populations and pathogen circulation in the field. 相似文献
16.
In this paper we present a case study of spatial structure in landscape patterns for the North and South Islands of New Zealand. The aim was to characterise quantitatively landscape heterogeneity and investigate its possible scaling properties. The study examines spatial heterogeneity, in particular patchiness, at a range of spatial scales, to help build understanding on the effects of landscape heterogeneity on water movement in particular, and landscape ecology in general.We used spatial information on various landscape properties (soils, hydrogeology, vegetation, topography) generated from the New Zealand Land Resource Inventory. To analyse this data set we applied various methods of fractal analyses following the hypothesis that patchiness in selected landscape properties demonstrates fractal scaling behaviour at two structural levels: (1) individual patches; and (2) mosaics (sets) of patches.Individual patches revealed scaling behaviour for both patch shape and boundary. We found self-affinity in patch shape with Hurst exponent H from 0.75 to 0.95. We also showed that patch boundaries in most cases were self-similar and in a few cases of large patches were self-affine. The degree of self-affinity was lower for finer patches. Similarly, when patch scale decreases the orientation of patches tends to be uniformly distributed, though patch orientation on average is clearly correlated with broad scale geological structures. These results reflect a tendency to isotropic behaviour of individual patches from broad to finer scales. Mosaics of patches also revealed fractal scaling in the total patch boundaries, patch centers of mass, and in patch area distribution. All these reflect a special organisation in patchiness represented in fractal patch clustering. General relationships which interconnect fractal scaling exponents were derived and tested. These relationships show how scaling properties of individual patches affect those for mosaics of patches and vice-versa. To explain similarity in scaling behaviour in patchiness of different types we suggest that the Self-Organised Criticality concept should be used. Also, potential applications of our results in landscape ecology are discussed, especially in relation to improved neutral landscape models. 相似文献
17.
Despite good theoretical knowledge about determinants of plant species richness in mosaic landscapes, validations based on
complete surveys are scarce. We conducted a case study in a highly fragmented, traditional agricultural landscape. In 199
patches of 20 representative multi-patch-plots (MPPs, 1 ha) we recorded a total of 371 plant species. In addition to an additive
partitioning of species diversity at the (a) patch- and (b) MPP-scale, we adopted the recently proposed ‘specificity’ measure
to quantify the contribution of a spatial subunit to landscape species richness (subunit-to-landscape-contribution, SLC).
SLC-values were calculated at both scales with respect to various spatial extents. General regression models were used to
quantify the relative importance of hypothesis-driven determinants for species richness and SLC-values.
At the patch scale, habitat type was the main determinant of species richness, followed by area and elongated shape. For SLC-values,
area was more important than habitat type, and its relevance increased with the extent of the considered landscape. Influences
of elongated shape and vegetation context were minor. Differences between habitat types were pronounced for species richness
and also partly scale-dependent for SLC-values.
Relevant predictors at the MPP-scale were nonlinear habitat richness, the gradient from anthropogenic to seminatural vegetation,
and the proportions of natural vegetation and rare habitats. Linear elements and habitat configuration did not contribute
to species richness and SLC. Results at the MPP-scale were in complete accordance with the predictions of the mosaic concept.
Hence, our study represents its first empirical validation for plant species diversity in mosaic landscapes. 相似文献
18.
We employed a sliding-window approach at multiple scales (window sizes and dispersal distances) to calculate seven standard graph-theoretical metrics within a subset of a large, freshwater wetland network. In contrast to most graph analyses, which quantify connectivity at a single (global) scale or at a patch-level scale, a multi-scaled, sliding-window approach provides an assessment that bridges these two approaches to examine patch clusters. As a case study we focused on a subset of a habitat patch network in a ~20,000 km 2 area encompassing 2,782 playa wetlands in the panhandle of Texas. Playas are seasonal wetlands of the southern Great Plains of North America that form a network of regional habitat resources for wildlife. The large size of this network meant that global metrics failed to capture localized properties, so we used contour mapping to visualize continuous surfaces as functions of playa density, linkage density, and other topological traits at different window sizes and dispersal distances. This technique revealed spatial patterns in the components (i.e., the network properties of regions of the landscape at a given dispersal scale), with the spatial scale of habitat clustering varying with the size of the sliding window and dispersal distance. Using a tool familiar to landscape ecology (sliding-window methodology) in a novel way (to examine ecological networks at multiple scales), our approach provides a way to represent ecologically determined local-scale graph properties and illustrates how a multi-scaled approach is useful in examining habitat connectivity to investigate graph properties. 相似文献
19.
Several studies indicate a long-term decline in numbers of different species of voles in northern Fennoscandia. In boreal Sweden, the long-term decline is most pronounced in the grey-sided vole ( Clethrionomys rufocanus). Altered forest landscape structure has been suggested as a possible cause of the decline. However, habitat responses of grey-sided voles at the landscape scale have never been studied. We analyzed such responses of this species in lowland forests in Västerbotten, northern Sweden. Cumulated spring densities representing 22 local time series from 1980–1999 were obtained by a landscape sampling design and were related to the surrounding landscape structure of 2.5×2.5 km plots centred on each of the 22 1-ha trapping plots. In accordance with general knowledge on local habitat preferences of grey-sided voles, our study supported the importance of habitat variables such as boulder fields and old-growth pine forest at the landscape scale. Densities were negatively related to clear cuts. Habitat associations were primarily those of landscape structure related to habitat fragmentation, distance between habitat patches and patch interspersion rather than habitat patch type quantity. Local densities of the grey-sided vole were positively and exponentially correlated with spatial contiguity (measured with the fragmentation index) of old-growth pine forest, indicating critical forest fragmentation thresholds. Our results indicate that altered land use might be involved in the long-term decline of the grey-sided vole in managed forest areas of Fennoscandia. We propose two further approaches to reveal and test responses of this species to changes in landscape structure. 相似文献
20.
In eastern North America, large forest patches have been the primary target of biodiversity conservation. This conservation
strategy ignores land units that combine to form the complex emergent rural landscapes typical of this region. In addition,
many studies have focussed on one wildlife group at a single spatial scale. In this paper, studies of avian and anuran populations
at regional and landscape scales have been integrated to assess the ecological value of agricultural mosaics in southern Ontario
on the basis of the maintenance of faunal biodiversity. Field surveys of avian and anuran populations were conducted between
2001 and 2004 at the watershed and sub-watershed levels. The ecological values of land units were based on a combination of
several components including species richness, species of conservation concern (rarity), abundance, and landscape parameters
(patch size and connectivity). It was determined that habitats such as thicket swamps, coniferous plantations and cultural
savannas can play an important role in the overall biodiversity and ecological value of the agricultural landscape. Thicket
swamps at the edge of agricultural fields or roads provided excellent breeding habitat for anurans. Coniferous plantations
and cultural savannas attracted many birds of conservation concern. In many cases, the land units that provided high ecological
value for birds did not score well for frogs. Higher scores for avian and anuran populations were recorded along the Niagara
Escarpment and other protected areas as expected. However, some private land areas scored high, some spatially connected to
the protected areas and therefore providing an opportunity for private land owners to enter into a management arrangement
with the local agencies. 相似文献
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