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1.
Zharikov et al. (2006: Landscape Ecology 21:107–120) modeled the nest-site habitat use of marbled murrelets (Brachyramphus marmoratus) in Desolation Sound (DS) and Clayoquot Sound (CS), British Columbia. They compared known nest sites, located with radio-telemetry,
with randomly-located points within the same areas. Their conclusions suggest that murrelets tended to nest in disproportionately
smaller fragments within the more disturbed DS landscape; streams, steeper slopes, and lower elevations were selected in both
landscapes; murrelets nested closer to recent clearcuts than would be expected in the DS landscape; and survivorship of nestlings
was greater in areas with recent clearcuts and was positively correlated with recent habitat fragmentation. These conclusions
are contrary to current management guidelines in British Columbia, and therefore require close scrutiny. Our detailed examination
reveals flaws in their use of data, application of modeling, and most seriously, interpretation of the results. Problems include:
conceptual errors in the interpretation of models; inappropriate spatial resolution; confusing use and interpretation of fragmentation
and patch size data; overemphasis of statistically significant but biologically trivial results; and ignoring some contradictory
studies. We conclude that it would be risky to apply the results from Zharikov et al. in the selection of murrelet nesting
habitat for management purposes in British Columbia. Our review identifies issues that may arise in other ecological modeling
studies and stresses the need for biological realism in addition to statistical rigour. 相似文献
2.
Habitat for wide-ranging species should be addressed at multiple scales to fully understand factors that limit populations.
The marbled murrelet (Brachyramphus marmoratus), a threatened seabird, forages on the ocean and nests inland in large trees. We developed statistical relationships between
murrelet use (occupancy and abundance) and habitat variables quantified across many spatial scales (statewide to local) and
two time periods in California and southern Oregon, USA. We also addressed (1) if old-growth forest fragmentation was negatively
associated with murrelet use, and (2) if some nesting areas are more important than others due to their proximity to high
quality marine habitat. Most landscapes used for nesting were restricted to low elevation areas with frequent fog. Birds were
most abundant in unfragmented old-growth forests located within a matrix of mature second-growth forest. Murrelets were less
likely to occupy old-growth habitat if it was isolated (> 5 km) from other nesting murrelets. We found a time lag in response
to fragmentation, where at least a few years were required before birds abandoned fragmented forests. Compared to landscapes
with little tono murrelet use, landscapes with many murrelets were closer to the ocean's bays, river mouths, sandy shores,
submarine canyons, and marine waters with consistently high primary productivity. Within local landscapes (≤ 800ha), inland
factors limited bird abundance, but at the broadest landscape scale studied (3200 ha), proximity to marine habitat was most
limiting. Management should focus on protecting or creating large, contiguous old-growth forest stands, especially in low-elevation
areas near productive marine habitat.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
Burger and Page (this volume) evaluated our models of habitat preferences and breeding success of a threatened seabird, the
marbled murrelet (Brachyramphus marmoratus), based on the largest available set of confirmed nest-sites found in coastal old-growth forest of the Pacific North-West.
We believe our study documented novel and unexpected patterns of landscape-level distribution of marbled murrelets in both
heavily logged and relatively intact old-growth landscapes and provided insights into how these patterns influence their reproduction,
and, eventually, management. Considering the importance of the issue and to ensure appropriate and responsible use of the
information we welcome discussion, detailed scrutiny and evaluation of our original results. Burger and Page claim to have
identified flaws with model interpretation, data quality, statistical approaches, presentation and interpretation of our results
that would invalidate our conclusions. We respond that most of their critique is irrelevant and/or misdirected with respect
to our study and the interpretation of GIS data models, and that valid aspects of their claims do not critically affect our
conclusions. 相似文献
4.
The influence of forest harvesting on landscape spatial patterns and old-growth-forest fragmentation in southeast British Columbia 总被引：2，自引：0，他引：2
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
5.
Measuring edge effects in complex landscapes is often confounded by the presence of different kinds of natural and anthropogenic
edges, each of which may act differently on organisms inhabiting habitat patches. In such landscapes, proportions of different
habitats surrounding nests within patches often vary and may affect nesting success independently of distance to edges. We
developed methods to measure and study the effects of multiple edges and varying habitat composition around nests on the breeding
success of the Acadian flycatcher (Empidonax virescens), an understory, open-cup nesting songbird. The Kaskaskia River in Southwestern Illinois was our study area and consists
of wide (>1000-m) floodplain corridors embedded in an agricultural matrix with a variety of natural (wide rivers, backwater
swamps, and oxbow lakes) and anthropogenic (internal openings, and agricultural) habitats. We also measured vegetation structure
around each nest. Nest survival increased with increasing nest concealment, and probabilities of brood parasitism increased
with increasing distances from anthropogenic and natural water-related openings surrounding nests. The magnitude of these
effects was small, probably because the landscape is saturated with nest predators and brood parasites. These results illustrate
the importance of considering both larger landscape context and details of natural and anthropogenic disturbances when studying
the effects of habitat fragmentation on wildlife. 相似文献
6.
Estimating the consequences of habitat fragmentation on extinction risk in dynamic landscapes 总被引：7，自引：0，他引：7
Analyzing the population dynamic consequences of spatio-temporal changes in landscape structure is a formidable challenge for spatial ecology. One key population dynamic process in fragmented landscapes is the influence of isolation on colonization rate and thereby on the occurrence of species in habitat fragments, but it is not obvious how isolation should be measured in landscapes that are affected by on-going habitat loss and fragmentation. We suggest the following procedure for the measurement of spatio-temporal isolation. First, a historical record of habitat loss and fragmentation in the landscape is prepared based on snapshots of the extent of the suitable habitat for the focal species. Second, a metapopulation model is used to simulate the occurrence of the species in this landscape, assuming the empirically observed landscape change. The model-predicted pattern of habitat occupancy at a particular point in time (usually the present time) is then compared with empirical observations on the occurrence of the species. We describe a metapopulation model that has been constructed for this purpose, and we apply it to a changing landscape of boreal forests in eastern Finland. We give an example on the occurrence of four threatened polyporous fungi in 18 small fragments of old-growth forest. In none of the species does the current isolation of the fragments nor the time since their isolation explain the occurrence of the species in the study fragments, but in three species the model-predicted occupancy probability had a significant effect on the observed abundance of the species. The model-predicted occupancy probabilities were also calculated by ignoring past landscape changes, that is, by assuming that the landscape had remained in the present configuration for a long time. These probabilities had a significant effect on the abundance of only one of the four species, suggesting that the occurrence of the species tracks landscapes changes with a noticable time lag.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
7.
Forest bird species exhibit noticeable seasonal behavioral changes that might lead to contrasting effects of landscape pattern
upon species abundance and performance. We assessed if the effect of patch and habitat attributes on the landscape use of
thorn-tailed rayaditos (Aphrastura spinicauda), a forest bird in a relict patchy forest in northern Chile, varied temporally in association with changes in the behavior
of individuals linked to breeding vs. non-breeding conditions. We also assessed the relationship between nest success and
patch and habitat attributes, as nest success might be associated to the density rayaditos during the breeding season. We
found that density of rayaditos was affected by patch size and functional connectivity but not by habitat structure and that
the magnitude of the effect of patch size was greater during the non-breeding season, thus supporting the existence of a temporally
variable effect of landscape pattern. Similarly, the nest success of rayaditos was positively affected by functional connectivity
and negatively by structural connectivity. We hypothesize that these results emerged from the interaction among territorial
behavior, resource limitation and predation risk. Despite the variable intensity of the effect of patch size upon density,
however, this landscape attribute, in addition to connectivity, is essential for the persistence of rayaditos at this relict
patchy forest landscapes. 相似文献
8.
There exists a gradient in dispersal behavior from passive to active, which reflects organisms’ dependence upon currents vs. self-propelled movement. We asked: Do currents modify organism–landscape interactions to influence recruitment success along this dispersal gradient? Using a spatially-explicit cellular model, we simulated the recruitment success of three generalized dispersal strategies (walkers, swimmers, and drifters) through hierarchically structured benthic landscapes. We evaluated the relative recruitment success (recruited population size, overall area occupied, time to recruit) of the three dispersal strategies in similar landscapes, as well as the consequences of varying the total proportion of habitat suitable for recruitment, and the scale and pattern of habitat patchiness on recruitment success. In the presence of currents, swimmers and drifters generally recruited over larger areas and in less time than walkers. Differences among the dispersal strategies’ recruitment success were most pronounced when an intermediate number of good habitat cells (16–48% of landscape) were broadly dispersed across the landscape. Although recruitment success always increased with increasing proportion of good habitat, drifters were more sensitive, and swimmers less sensitive, to these landscape changes than walkers. We also found that organisms dispersing within currents typically responded non-linearly (logarithmically or exponentially) to increasing proportion of total good habitat, whereas walkers more often responded linearly. 相似文献
9.
Effects of landscape structure and forest reserve location on old-growth forest bird species in Northern Finland 总被引：4，自引：0，他引：4
Brotons Lluís Mönkkönen Mikko Huhta Esa Nikula Ari Rajasärkkä Ari 《Landscape Ecology》2003,18(4):377-393
Old-growth forest birds in Fennoscandia have sharply declined in numbers during the last decades apparently due to commercial
forest harvesting and fragmentation of old-growth forests. Conservation measures have led to the establishment of a forest
reserve network to assure the persistence of forest birds at a regional scale. However, little is known about the effects
of landscape structure within and around the reserves on the distribution of old-growth forest birds. We used a hierarchical
approach to address the questions of how landscape structure and composition within forest reserves, landscape composition
of surrounding areas and reserve location affect the abundance of resident, old-growth forest birds in the Northern Finnish
forest reserve network. The positive role of particular landscape features on bird distribution indicates that both the proportion
of old-growth forests and the structure of boreal landscape mosaic has an important role in determining the distribution of
these birds. The landscape composition surrounding the reserves proved to be only a weak predictor in species distribution
models, which argues against the primary role of the surrounding matrix in determining species distribution within forest
reserves. Reserves located near the Russian border showed a higher abundance of old-growth birds than more western ones. Once
east-west gradients in overall landscape composition had been accounted for, however, reserves did not differ significantly
in the number of species present. These results suggest that landscape gradients, rather than ecological processes such as
the presence of source areas located along the border with Russia, are the main determinant of the distribution of old-growth
forest birds in the Finnish reserve network. We propose that to enhance regional persistence of old-growth forest birds, conservation
efforts should be primarily directed towards the protection and enhancement of forest habitat quality and natural heterogeneity
of landscapes within targeted areas.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Michael C. Wimberly 《Landscape Ecology》2006,21(1):35-46
Although landscape ecology emphasizes the effects of spatial pattern on ecological processes, most neutral models of species–habitat relationships have treated habitat as a static constraint. Do the working hypotheses derived from these models extend to real landscapes where disturbances create a shifting mosaic? A spatial landscape simulator incorporating vegetation dynamics and a metapopulation model was used to compare species in static and dynamic landscapes with identical habitat amounts and spatial patterns. The main drivers of vegetation dynamics were stand-replacing disturbances, followed by gradual change from early-successional to old-growth habitats. Species dynamics were based on a simple occupancy model, with dispersal simulated as a random walk. As the proportion of available habitat (p) decreased from 1.0, species occupancy generally declined more rapidly and reached extinction at higher habitat levels in dynamic than in static landscapes. However, habitat occupancy was sometimes actually higher in dynamic landscapes than in static landscapes with similar habitat amounts and patterns. This effect was most pronounced at intermediate amounts of habitat (p = 0.3?0.6) for mobile species that had high colonization rates, but were unable to cross non-habitat patches. Differences between static and dynamic landscapes were contingent upon the initial metapopulation size and the shapes of disturbances and the resulting habitat patterns. Overall, the results demonstrate that dispersal-limited species exhibit more pronounced critical behavior in dynamic landscapes than is predicted by simple neutral models based on static landscapes. Thus, caution should be exercised in extending generalizations derived from static landscape models to disturbance-driven landscape mosaics. 相似文献
11.
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
12.
Previous research has suggested that ducks and songbirds may benefit from prairie landscapes that consist primarily of contiguous
grasslands. However, the relative importance of landscape-level vs. local characteristics on mechanisms underlying observed
patterns is unclear. We measured effects of grassland amount and fragmentation on upland and wetland songbird and duck density
and nest success, and on some nest predators, across 16 landscapes in southern Alberta, Canada. We compared these landscape-level
effects with local-scale responses, including distance to various edges and vegetation characteristics. We also evaluated
several statistical approaches to comparing effects of habitat characteristics at multiple spatial scales. Few species were
influenced by grassland amount or fragmentation. In contrast, distance to edge and local vegetation characteristics had significant
effects on densities and nest success of many species. Previous studies that reported effects of landscape characteristics
may have detected patterns driven by local mechanisms. As a corollary, results were very sensitive to statistical model structure;
landscape level effects were much less apparent when local characteristics were included in the models. 相似文献
13.
The distribution of the northern brown bandicoot (Isoodon macrourus), a medium-sized ground-dwelling marsupial, was examined in habitat fragments within the urban landscape of the city of Brisbane,
Australia. From surveys conducted in 68 fragments, bandicoots were found to be present in 33 (49%) despite widespread habitat
loss and fragmentation. Logistic regression analysis revealed that of 13 measured independent variables, functional connectivity
was the only factor that significantly predicted the presence of bandicoots within fragments, with connectivity positively
correlated with the likelihood of occupation. Functional connectivity was equated to the likelihood of bandicoot immigration
into the focal fragment from the nearest occupied fragment, based on the estimated resistance to movement offered by the intervening
matrix. Within Brisbane, riparian habitat fragments typically have a relatively high level of functional connectivity, as
thin strips of vegetation fringing waterways serve as corridors between larger riparian areas and facilitate the movement
of bandicoots between patches. Analyses based on the Akaike Information Criterion revealed that the optimal model based on
landscape context variables was convincingly better supported by the data than the optimal model produced from fragment characteristics.
However, it is important to examine both internal attributes of habitat fragments and external features of the surrounding
landscape when modelling the distribution of ground-dwelling fauna in urban environments, or other landscapes with a highly
variable matrix. As urban centres throughout the world expand, it is crucial that the ecology of local wildlife be considered
to ensure functional connection is maintained between habitat patches, especially for the conservation of species that are
highly susceptible to fragmentation. 相似文献
14.
Habitat fragmentation is expected to disrupt dispersal, and thus we explored how patch metrics of landscape structure, such as percolation thresholds used to define landscape connectivity, corresponded with dispersal success on neutral landscapes. We simulated dispersal as either a purely random process (random direction and random step lengths) or as an area-limited random walk (random direction, but movement limited to an adjacent cell at each dispersal step) and quantified dispersal success for 1000 individuals on random and fractal landscape maps across a range of habitat abundance and fragmentation. Dispersal success increased with the number of cells a disperser could search (m), but poor dispersers (m<5) searching via area-limited dispersal on fractal landscapes were more successful at locating suitable habitat than random dispersers on either random or fractal landscapes. Dispersal success was enhanced on fractal landscapes relative to random ones because of the greater spatial contagion of habitat. Dispersal success decreased proportionate to habitat loss for poor dispersers (m=1) on random landscapes, but exhibited an abrupt threshold at low levels of habitat abundance (p<0.1) for area-limited dispersers (m<10) on fractal landscapes. Conventional metrics of patch structure, including percolation, did not exhibit threshold behavior in the region of the dispersal threshold. A lacunarity analysis of the gap structure of landscape patterns, however, revealed a strong threshold in the variability of gap sizes at low levels of habitat abundance (p<0.1) in fractal landscapes, the same region in which abrupt declines in dispersal success were observed. The interpatch distances or gaps across which dispersers must move in search of suitable habitat should influence dispersal success, and our results suggest that there is a critical gap-size structure to fractal landscapes that interferes with the ability of dispersers to locate suitable habitat when habitat is rare. We suggest that the gap structure of landscapes is a more important determinant of dispersal than patch structure, although both are ultimately required to predict the ecological consequences of habitat fragmentation. 相似文献
15.
We studied the effects of anthropogenic edges on predation and parasitism of forest bird nests in an agriculturally fragmented
landscape and a continuously forested landscape in Ontario, Canada. Nesting data were collected at 1937 nests across 10 species
in the fragmented landscape from 2002–2008, and 464 nests across 4 species in the continuously forested landscape from 2006–2008.
Brood parasitism only occurred in the fragmented landscape, and was positively related to the proportion of rural grassland
and row crop habitats within 500-m of nests. Daily nest survival was negatively related to the density of roads within 500-m
of nests in the fragmented landscape, but was not influenced by distance to anthropogenic edge in either landscape. Predation
rates were higher in the fragmented landscape for Ovenbird and Rose-breasted Grosbeak nests, but did not differ between landscapes
for Veery and American Redstart nests. Uniformly high predation in the fragmented landscape may be a result of (1) matrix
predators that penetrate deep (>300 m) into the forest interior, or (2) the additive effect of forest-dependent and matrix-associated
predators that results in high predation pressure in both edge and interior habitats. Further research focused on the identification
of nest predators, their population dynamics, and habitat use is required to understand the underlying mechanisms leading
to uniformly high nest predation in fragmented landscapes. 相似文献
16.
Kibale National Park, within the Albertine Rift, is known for its rich biodiversity. High human population density and agricultural
conversion in the surrounding landscape have created enormous resource pressure on forest fragments outside the park. Kibale
presents a complex protected forest landscape comprising intact forest inside the park, logged areas inside the park, a game
corridor with degraded forest, and forest fragments in the landscape surrounding the park. To explore the effect of these
different levels of forest management and protection over time, we assessed forest change over the previous three decades,
using both discrete and continuous data analyses of satellite imagery. Park boundaries have remained fairly intact and forest
cover has been maintained or increased inside the park, while there has been a high level of deforestation in the landscape
surrounding the park. While absolute changes in land cover are important changes in vegetation productivity, within land cover
classes are often more telling of longer term changes and future directions of change. The park has lower Normalized Difference
Vegetation Index (NDVI) values than the forest fragments outside the park and the formerly logged area—probably due to forest
regeneration and early succession stage. The corridor region has lower productivity, which is surprising given this is also
a newer regrowth region and so should be similar to the logged and forest fragments. Overall, concern can be raised for the
future trajectory of this park. Although forest cover has been maintained, forest health may be an issue, which for future
management, climate change, biodiversity, and increased human pressure may signify troubling signs. 相似文献
17.
Naugle David E. Higgins Kenneth F. Nusser Sarah M. Johnson W. Carter 《Landscape Ecology》1999,14(3):267-276
We evaluated the influence of scale on habitat use for three wetland-obligate bird species with divergent life history characteristics and possible scale-dependent criteria for nesting and foraging in South Dakota, USA. A stratified, two-stage cluster sample was used to randomly select survey wetlands within strata defined by region, wetland density, and wetland surface area. We used 18-m (0.1 ha) fixed radius circular-plots to survey birds in 412 semipermanent wetlands during the summers of 1995 and 1996. Variation in habitat use by pied-billed grebes (Podilymbus podiceps) and yellow-headed blackbirds (Xanthocephalus xanthocephalus), two sedentary species that rarely exploit resources outside the vicinity of nest wetlands, was explained solely by within-patch variation. Yellow-headed blackbirds were a cosmopolitan species that commonly nested in small wetlands, whereas pied-billed grebes were an area-sensitive species that used larger wetlands regardless of landscape pattern. Area requirements for black terns (Chlidonias niger), a vagile species that typically forages up to 4 km away from the nest wetland, fluctuated in response to landscape structure. Black tern area requirements were small (6.5 ha) in heterogeneous landscapes compared to those in homogeneous landscapes (15.4–32.6 ha). Low wetland density landscapes composed of small wetlands, where few nesting wetlands occurred and potential food sources were spread over large distances, were not widely used by black terns. Landscape-level measurements related to black tern occurrence extended past relationships between wetlands into the surrounding matrix. Black terns were more likely to occur in landscapes where grasslands had not been tilled for agricultural production. Our findings represent empirical evidence that characteristics of entire landscapes, rather than individual patches, must be quantified to assess habitat suitability for wide-ranging species that use resources over large areas. 相似文献
18.
To aid effective conservation and management there is a need to understand the effect of landscape on species ecology. The
aim of this research was to assess the effect of landscape parameters on breeding success of barn owls throughout the Rother
and Arun River catchments, Sussex, UK. We used a Geographic Information System to describe the habitat mosaic and landscape
structure within an estimated home range area of 3 km2 around 85 artificial nest box sites. Results showed that land cover was less heterogeneous at successful sites, with home
ranges dominated by a few habitat types of regular patch shapes. Unsuccessful nesting sites had significantly more improved
grassland, suburban land and wetlands than successful sites. Cluster analysis and Principle Components Analysis was used to
assess the similarity of the habitat mosaic within these areas and pellet analysis was undertaken to assess barn owl diet
and prey availability. Ten prey species were recovered from pellets, field vole (Microtus agrestis), common shrews (Sorex araneus) and house mice (Mus musculus) making up nearly 90% of recoveries. However box sites varied in relative proportions of small mammal, and hence prey availability.
Results indicated that land use and landscape structure can affect breeding success in barn owls. Higher levels of poor quality
small mammal habitat were associated with unsuccessful sites. However, at a landscape scale, the habitat mosaic across the
study area lacked variation, limiting analysis and clear correlations between habitat type and positive breeding success,
suggesting that a finer scale was needed in future studies utilising this approach. 相似文献
19.
Effects of landscape structure on nest predation in roadsides of a midwestern agroecosystem: a multiscale analysis 总被引：1，自引：1，他引：0
Bergin Timothy M. Best Louis B. Freemark Kathryn E. Koehler Kenneth J. 《Landscape Ecology》2000,15(2):131-143
Nest predation is an important cause of mortality for many bird species, especially in grassland ecosystems where generalist predators have responded positively to human disturbance and landscape fragmentation. Our study evaluated the influence of the composition and configuration of the surrounding landscape on nest predation. Transects consisting of 10 artificial ground nests each were set up in 136 roadsides in six watersheds in south-central Iowa. Nest predation on individual roadside transects ranged from 0 to 100% and averaged 23%. The relationship of landscape structure within spatially-nested landscapes surrounding each roadside transect (within 200, 400, 800, 1200, and 1600 m of the transect line) to nest predation was evaluated by using multiple regression and canonical correlation analyses. The results of this multiscale landscape analysis demonstrated that predation on ground nests was affected by the surrounding landscape mosaic and that nest predators with different-sized home ranges and habitat affinities responded to landscapes in different ways. In general, wooded habitats were associated with greater nest predation, whereas herbaceous habitats (except alfalfa/pasture) either were associated with less nest predation or were not important. Different landscape variables were important at different spatial scales. Whereas some block-cover habitats such as woodland were important at all scales, others such as rowcrops and alfalfa/pasture were important at large scales. Some strip-cover habitats such as gravel roads and paved roads were important at small scales, but others such as wooded roadsides were important at all all scales. Most landscape metrics (e.g., mean patch size and edge density) were important at large scales. Our study demonstrated that the relationships between landscape structure and predator assemblages are complex, thus making efforts to enhance avian productivity in agricultural landscapes a difficult management goal. 相似文献
20.
Nicolas Morellet Bram Van Moorter Bruno Cargnelutti Jean-Marc Angibault Bruno Lourtet Joël Merlet Sylvie Ladet A. J. Mark Hewison 《Landscape Ecology》2011,26(7):999-1010
Understanding how patterns of habitat selection vary in relation to landscape structure is essential to predict ecological
responses of species to global change and inform management. We investigated behavioural plasticity in habitat selection of
roe deer (Capreolus capreolus) in relation to variable habitat availability across a heterogeneous agricultural landscape at the home range and landscape
scales. As expected, woodland was heavily selected, but we found no functional response for this habitat, i.e. no shift in
habitat selection with changing habitat availability, possibly due to the presence of hedgerows which were increasingly selected
as woodlands were less abundant. Hedgerows may thus function as a substitutable habitat for woodlands by providing roe deer
with similar resources. We observed a functional response in the use of hedgerows, implying some degree of landscape complementation
between hedgerows and open habitats, which may in part compensate for lower woodland availability. We also expected selection
for woodland to be highest at the wider spatial scale, especially when this habitat was limiting. However, our results did
not support this hypothesis, but rather indicated a marked influence of habitat composition, as both the availability and
distribution of resources conditioned habitat selection. There was no marked between-sex difference in the pattern of habitat
selection at either scale or between seasons at the landscape scale, however, within the home range, selection did differ
between seasons. We conclude that landscape structure has a marked impact on roe deer habitat selection in agricultural landscapes
through processes such as landscape complementation and supplementation. 相似文献