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1.
The distribution and abundance of a species may be simultaneously influenced by both local-scale habitat features and the
broader patch and landscape contexts in which these populations occur. Different factors may influence patch occupancy (presence–absence)
versus local abundance (number of individuals within patches), and at different scales, and thus ideally both occupancy and
abundance should be investigated, especially in studies that seek to understand the consequences of land management on species
persistence. Our study evaluated the relative influences of variables associated with the local habitat patch, hillside (patch
context), and landscape context on patch occupancy and abundance of the collared lizard (Crotaphytus collaris) within tallgrass prairie managed under different fire and grazing regimes in the northern Flint Hills of Kansas, USA. Using
a multi-model information-theoretic approach that accounted for detection bias, we found that collared lizard abundance and
occupancy was influenced by factors measured at both the local habitat and landscape scales. At a local scale, collared lizard
abundance was greatest on large rock ledges that had lots of crevices, high vegetation complexity, and were located higher
up on the hillslope. At the landscape scale, collared lizard abundance and occupancy were both higher in watersheds that were
burned frequently (1–2 year intervals). Interestingly, grazing only had a significant effect on occupancy and abundance within
less frequently burned (4-year burn interval) watersheds. Our results suggest that, in addition to the obvious habitat needs
of this species (availability of suitable rock habitat), land-management practices have the potential to influence collared
lizard presence and abundance in the grasslands of the Flint Hills. Thus, mapping the availability of suitable habitat is
unlikely to be sufficient for evaluating species distributions and persistence in such cases without consideration of landscape
management and disturbance history. 相似文献
2.
Nest locations of breeding birds are often spatially clustered. This tendency to nest together has generally been related
to a patchy distribution of nesting habitat in landscape studies, but behavioral studies of species with clustered breeding
patterns draw attention to the importance of social and biotic factors. Indeed, it is becoming increasingly apparent that
the breeding system of many territorial, migrant birds may be semi-colonial. The reasons for, and extent of, spatial clustering
in their breeding systems are not well understood. Our goal was to tease apart the influence of habitat availability and social
drivers of clustered breeding in a neotropical migrant species, the hooded warbler (Wilsonia citrina). To test alternative hypotheses related to clustered habitat or conspecific attraction, we combined a habitat classification
based on remote sensing with point pattern analysis of nesting sites. Nest locations (n = 150, 1999–2004), collected in a 1213 ha forested area of Southern Ontario (Canada), were analyzed at multiple spatial scales.
Ripley’s K and pair-correlation functions g (uni- and bivariate) were used to test whether nests were clustered merely because potential nesting habitat was also clustered,
or whether nests were additionally clustered with respect to conspecifics. Nest locations tended to be significantly clustered
at intermediate distances (particularly between 240 and 420 m). Nests were randomly distributed within available habitat at
larger distance scales, up to 1500 m. A reasonable hypothesis to explain the detected additional clustering, and one that
is consistent with the results of several behavioral studies, is that females pack their nests more tightly than the available
habitat requires to be situated closer to their neighbors’ mates. Linking spatially explicit, point pattern analysis with
strong inference based on Monte Carlo tests may bring us closer to understanding the generality and reasons behind conspecific
attraction at different spatial scales.
F. Csillag—deceased. 相似文献
3.
Matthew J. Smith Matthew G. Betts Graham J. Forbes Daniel G. Kehler Maryse C. Bourgeois Stephen P. Flemming 《Landscape Ecology》2011,26(5):709-721
Landscape composition and configuration, often termed as habitat loss and fragmentation, are predicted to reduce species population
viability, partly due to the restriction of movement in the landscape. Unfortunately, measuring the effects of habitat loss
and fragmentation on functional connectivity is challenging because these variables are confounded, and often the motivation
for movement by target species is unknown. Our objective was to determine the independent effects of landscape connectivity
from the perspective of a mature forest specialist—the northern flying squirrel (Glaucomys sabrinus). To standardize movement motivation, we translocated 119 squirrels, at varying distances (0.18–3.8 km) from their home range
across landscapes representing gradients in both habitat loss and fragmentation. We measured the physical connectedness of
mature forest using an index of connectivity (landscape coincidence probability). Patches were considered connected if they
were within the mean gliding distance of a flying squirrel. Homing success increased in landscapes with a higher connectivity
index. However, homing time was not strongly predicted by habitat amount, connectivity index, or mean nearest neighbour and
was best explained as a simple function of sex and distance translocated. Our study shows support for the independent effects
of landscape configuration on animal movement at a spatial scale that encompasses several home ranges. We conclude that connectivity
of mature forest should be considered for the conservation of some mature forest specialists, even in forest mosaics where
the distinction between habitat and movement corridors are less distinct. 相似文献
4.
Population recovery is difficult for species that require large contiguous areas of habitat, particularly within areas of
heterogeneous land ownerships. Ecologically, potential for recovery success requires assessment of quantity, quality, and
distribution of available habitat. Our objective was to evaluate habitat for a possible Louisiana black bear recovery in southeastern
Texas. First, we categorized land cover and identified remote areas of highly suitable habitat. Next, we used the individual
based simulation model J-walk to estimate ability of female black bears to move among remote habitat patches. Then, we applied
graph theory to J-walk output to evaluate overall connectivity of remote habitat. An estimated 225,626 ha of remote habitat
were identified in 901 patches, most of which was located within the eastern half of the study area. Network analysis showed
specific areas where targeted conservation efforts may help black bear population expansion throughout the study region. Ultimately,
enough habitat area exists to sustain a black bear population and it is best connected among public and private lands largely
within the eastern half of the study area. Habitat evaluation will need to be revisited if black bears establish themselves
locally and actual habitat use data become available. Regardless, our analysis demonstrates an important first step that may
be incorporated into a larger adaptive management framework, updated, and replicated as more-detailed habitat suitability
and land use data are available. 相似文献
5.
Effects of spatial habitat heterogeneity on habitat selection and annual fecundity for a migratory forest songbird 总被引:1,自引:1,他引:0
Understanding how spatial habitat patterns influence abundance and dynamics of animal populations is a primary goal in landscape
ecology. We used an information-theoretic approach to investigate the association between habitat patterns at multiple spatial
scales and demographic patterns for black-throated blue warblers (Dendroica caerulescens) at 20 study sites in west-central Vermont, USA from 2002 to 2005. Sites were characterized by: (1) territory-scale shrub
density, (2) patch-scale shrub density occurring within 25 ha of territories, and (3) landscape-scale habitat patterns occurring
within 5 km radius extents of territories. We considered multiple population parameters including abundance, age ratios, and
annual fecundity. Territory-scale shrub density was most important for determining abundance and age ratios, but landscape-scale
habitat structure strongly influenced reproductive output. Sites with higher territory-scale shrub density had higher abundance,
and were more likely to be occupied by older, more experienced individuals compared to sites with lower shrub density. However,
annual fecundity was higher on sites located in contiguously forested landscapes where shrub density was lower than the fragmented
sites. Further, effects of habitat pattern at one spatial scale depended on habitat conditions at different scales. For example,
abundance increased with increasing territory-scale shrub density, but this effect was much stronger in fragmented landscapes
than in contiguously forested landscapes. These results suggest that habitat pattern at different spatial scales affect demographic
parameters in different ways, and that effects of habitat patterns at one spatial scale depends on habitat conditions at other
scales. 相似文献
6.
Conservation of populations in fragmented habitats is often based on spatially realistic metapopulation theory, which predicts
negative relationships between patch extinction and area and patch colonization and isolation. Cost-distance metrics have
been developed to integrate habitat quality into measures of connectivity, and thus may improve predictive power of the area-isolation
paradigm. Few studies use empirical data to compare predictive performance of complex cost-distance metrics to simple metrics
relying on Euclidean distances. We used 3 years of presence–absence data to examine relative influence of habitat quality,
habitat area, and connectivity on occupancy and extinction rates for Poliocitellus franklinii (Franklin’s ground squirrel), a rare grassland species of conservation concern. We calculated connectivity using nearest-neighbor
(NN) and incidence function model (IFM) metrics based on Euclidean and cost-distances. Habitat quality, area, and connectivity
were all positive predictors for occupancy, but only isolation was a positive predictor of extinction. P. franklinii does not appear to be a tallgrass prairie obligate, but the species distribution is limited by isolation of suitable grassland
habitat. A simple NN metric measuring Euclidean distance between a target area and nearest occupied source outperformed IFM
(Euclidean and cost-distance) in predicting occupancy and extinction for P. franklinii. Although NN metrics are criticized for considering only the contribution of the source nearest to a target, this simplicity
may be acceptable when measuring connectivity for rare species with few occupied habitat patches within dispersal distance. 相似文献
7.
We used field surveys and Geographic Information System data to identify landscape-scale habitat associations of American
martens (Martes americana) and to develop a model to predict their occurrence in northeastern California. Systematic surveys using primarily enclosed
track plates, with 10-km spacing, were conducted across a 27,700 km2 area of largely forested, mountain terrain. Martens were detected at 20/184 (10.8%) of the sample units, aggregated in three
distinct regions. We investigated habitat selection at multiple scales using circular assessment areas of 3, 20, and 80 km2. The model for the largest assessment area best fit the data and included the following predictors: amount of reproductive
habitat, number of habitat patches and land ownership category. These results support the hypothesis that martens select habitat
based upon broad scale landscape conditions and that these conditions vary with ownership. We tested the model using an independent
set of data, collected primarily during the winter. Poor fit of the test data in some locations raised concerns that our model,
which was developed using data collected during the snow-free season, may not predict winter distribution well. We are investigating
possible causes for the seasonal variation and until they can be incorporated our model represents a conservative view of
marten habitat suitability based on summer occupancy. During the summer months, which is the reproductive season, martens
are predicted to occur largely in relatively undisturbed landscapes where high-elevation, late-successional forests are common.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Understanding interactions between roadways and population structure and movements of wildlife is key to mitigating “road
effects” associated with increasing urbanization of the landscape. Aquatic turtles are a useful focal group because (1) population
persistence is sensitive to mortality of individuals upon roads; (2) turtles frequently move among wetlands and encounter
roads, and (3) turtles are an important component of vertebrate biomass in aquatic ecosystems. From 2005 to 2007, we examined
the effects of urbanization on local- and landscape-scale populations of turtles. To do so, we sampled and marked turtles
in 15 ponds arranged along a steep, urban–rural gradient in central New York State. We captured 494 turtles, representing
327 individuals, the majority of which were common snapping turtles Chelydra serpentina (n = 191) and eastern painted turtles Chrysemys picta picta (n = 122). At the local population (pond) scale, a higher proportion of female snapping turtles in ponds was associated with
lower road densities within 500 m of ponds. The mean size of both species of turtle increased in ponds with a lower density
of roads within 100 m. At the landscape-level, we observed fewer turtles dispersing through urbanized habitat than forested,
and fewer movements through areas with a higher density of roads. Our study suggests that roads alter both local- and landscape-level
turtle populations through a loss of female turtles, and by reducing movement between ponds. By extension, the study targets
key landscape features upon which to focus mitigation efforts. 相似文献
9.
Besides providing habitat to the grizzly bear (Ursus arctos) and other wildlife, the Rocky Mountain foothills of Alberta, Canada hosts considerable mining, seismic oil and gas exploration
and production, and forest harvesting activities. Worldwide, such human activities influence the configuration and composition
of the landscape. We assessed seismic cutline effects on landscape structure and grizzly bear use during early summer of 1999
and 2000. We studied five female and two male bears, which were GPS-collared in the spring following den emergence. The area
available to this population was stratified into 49 km2 hexagon-shaped sub-landscapes. The scale of this stratification was determined by patterns of bear movement. Fourteen compositional
and configurational landscape metrics were calculated within each landscape unit, and bear use points were pooled or ‘binned’
within each unit. Landscape use was related to landscape metrics using a Generalized Linear Model (GLM). We found that seismic
cutline proportion did not explain landscape use by grizzly bears; however secondary effects of cutlines on landscape structure
did. Declining use was mainly associated with increasing proportions of closed forest, and increasing variation of inter-patch
distances, while use was mainly increasing with increasing mean patch size. An earlier investigation had demonstrated that
adding seismic cutlines to grizzly bear habitat caused increases in the variation of inter-patch distances. Since the landscape
structure of this grizzly bear population will continue to change as a function of increased levels of resource extraction
activities in the near future, it is crucial to further study the detailed meaning of landscape structure at the large and
small scale for effective conservation efforts. 相似文献
10.
Rebecca Lange Tim Diekötter Lisa A. Schiffmann Volkmar Wolters Walter Durka 《Landscape Ecology》2012,27(3):381-392
Unlike rare or specialised species, widespread abundant species have often been neglected when studying effects of habitat
fragmentation. However, recently, it was shown that in the widespread abundant bush cricket Pholidoptera griseoaptera gene flow becomes restricted when the share of suitable habitat dropped below a threshold of 20% at the landscape scale.
Here, using the same highly fragmented landscape, we studied the impact of habitat configuration and matrix quality on genetic
variation and population differentiation of P. griseoaptera at a small spatial scale. We investigated four clusters of three populations that were either disconnected or connected and
had either low quality (arable land) or high quality (grassland) matrix. The number of alleles was significantly lower in
disconnected than in connected clusters, irrespective of matrix quality. Genetic differentiation was equally high in the two
disconnected clusters and in the connected cluster with low quality matrix (G
ST ≥ 0.030; D ≥ 0.082), whereas it was significantly reduced when connected habitats were embedded in a high quality grassland matrix (G
ST = 0.004; D = 0.011). Analyses of least-cost paths showed that grassy landscape elements in fact represent high quality matrix, but that
linear grassy margins are costly for dispersal. The effect of habitat configuration on genetic diversity may be explained
by lower effective population sizes in disconnected habitats. The fact that only the connected populations in high quality
matrix were not differentiated indicates that landscape management should simultaneously consider habitat configuration and
matrix quality to effectively promote small and dispersal-limited species, also at small spatial scales. 相似文献
11.
Identification of functional corridors with movement characteristics of brown bears on the Kenai Peninsula,Alaska 总被引:2,自引:1,他引:2
Tabitha A. Graves Sean Farley Michael I. Goldstein Christopher Servheen 《Landscape Ecology》2007,22(5):765-772
We identified primary habitat and functional corridors across a landscape using Global Positioning System (GPS) collar locations
of brown bears (Ursus arctos). After deriving density, speed, and angular deviation of movement, we classified landscape function for a group of animals
with a cluster analysis. We described areas with high amounts of sinuous movement as primary habitat patches and areas with
high amounts of very directional, fast movement as highly functional bear corridors. The time between bear locations and scale
of analysis influenced the number and size of corridors identified. Bear locations should be collected at intervals ≤6 h to
correctly identify travel corridors. Our corridor identification technique will help managers move beyond the theoretical
discussion of corridors and linkage zones to active management of landscape features that will preserve connectivity. 相似文献
12.
Habitat fragmentation often has negative consequences for genetic diversity, and thereby for the viability of populations.
However, these negative consequences might be counteracted by gene flow as the latter provides functional connectivity between
apparently isolated habitat fragments. Gene flow is itself influenced by landscape structure and composition, and it is therefore
important to understand the relationship between gene flow and landscape structure and composition. We used linear LAD regression
models to investigate the relationship between contemporary gene flow by pollen in the rare, insect-pollinated forest tree
Sorbus domestica and several landscape features. None of the landscape components—which included closed forest, deep valleys, open land and
settlements—proved to be an impermeable barrier to gene flow by pollen. We found evidence that settlements, large open areas,
and a pronounced topography increased long-distance gene flow in the landscape as compared to a random model including all
possible gene flow trajectories. These results are encouraging from a conservation view, as gene flow in species pollinated
by generalist insects seems to provide functional connectivity and may help to maintain genetic diversity in rare plant species
in fragmented landscapes. 相似文献
13.
Robert M. Scheller Wayne D. Spencer Heather Rustigian-Romsos Alexandra D. Syphard Brendan C. Ward James R. Strittholt 《Landscape Ecology》2011,26(10):1491-1504
Natural resource managers are often challenged with balancing requirements to maintain wildlife populations and to reduce
risks of catastrophic or dangerous wildfires. This challenge is exemplified in the Sierra Nevada of California, where proposals
to thin vegetation to reduce wildfire risks have been highly controversial, in part because vegetation treatments could adversely
affect an imperiled population of the fisher (Martes pennanti) located in the southern Sierra Nevada. The fisher is an uncommon forest carnivore associated with the types of dense, structurally
complex forests often targeted for fuel reduction treatments. Vegetation thinning and removal of dead-wood structures would
reduce fisher habitat value and remove essential habitat elements used by fishers for resting and denning. However, crown-replacing
wildfires also threaten the population’s habitat, potentially over much broader areas than the treatments intended to reduce
wildfire risks. To investigate the potential relative risks of wildfires and fuels treatments on this isolated fisher population,
we coupled three spatial models to simulate the stochastic and interacting effects of wildfires and fuels management on fisher
habitat and population size: a spatially dynamic forest succession and disturbance model, a fisher habitat model, and a fisher
metapopulation model, which assumed that fisher fecundity and survivorship correlate with habitat quality. We systematically
varied fuel treatment rate, treatment intensity, and fire regime, and assessed their relative effects on the modeled fisher
population over 60 years. After estimating the number of adult female fishers remaining at the end of each simulation scenario,
we compared the immediate negative effects of fuel treatments to the longer-term positive effect of fuel treatment (via reduction
of fire hazard) using structural equation modeling. Our simulations suggest that the direct, negative effects of fuel treatments
on fisher population size are generally smaller than the indirect, positive effects of fuel treatments, because fuels treatments
reduced the probability of large wildfires that can damage and fragment habitat over larger areas. The benefits of fuel treatments
varied by elevation and treatment location with the highest net benefits to fisher found at higher elevations and within higher
quality fisher habitat. Simulated fire regime also had a large effect with the largest net benefit of fuel treatments occurring
when a more severe fire regime was simulated. However, there was large uncertainty in our projections due to stochastic spatial
and temporal wildfires dynamic and fisher population dynamics. Our results demonstrate the difficulty of projecting future
populations in systems characterized by large, infrequent, stochastic disturbances. Nevertheless, these coupled models offer
a useful decision-support system for evaluating the relative effects of alternative management scenarios; and uncertainties
can be reduced as additional data accumulate to refine and validate the models. 相似文献
14.
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
15.
Adrian D. Manning David B. Lindenmayer Simon C. Barry Henry A. Nix 《Landscape Ecology》2006,21(7):1119-1133
The threatened superb parrot of south-eastern Australia exemplifies many of the challenges associated with research on wide-raging
organisms which live ‘off-reserve’. Challenges include that most land is privately owned and that landscape use by such organisms
does not always conform to traditional schematic and categorical landscape/fragmentation models. A multi-scale approach for
embedding the detection of site-level and landscape context effects into landscape sampling design and subsequent statistical
analysis is presented. The superb parrot was found scattered at varying densities throughout the agricultural landscapes of
the South-West Slopes, much of which was privately owned. It responded to site-level variables and the surrounding landscape
context. Overall, the superb parrot favoured lower elevation sites which were dominated by scattered, open woodlands, where
Blakely’s red gum was a significant component. Mean plant productivity within 2 km, levels of woody tree cover within 3 km
and (with caveats) length of roads within 3 km had a major effect on site-level response, indicating conditions in the surrounding
local landscape are important to the superb parrot. This multi-scale response requires a multi-scale conservation and restoration
strategy. The importance of open tree cover and amounts of Blakely’s red gum are a matter for concern, due to a general lack
of tree regeneration and the particular susceptibility of Blakely’s red gum to dieback. The scattered trees in the agricultural
matrix were important to the superb parrot, suggesting that it views these landscapes as a continuum of usable habitat. Strategies
for restoration of larger habitat remnants should also include regeneration of trees in scattered pattern in the wider landscape,
and Blakely’s red gum should be part of any strategy along with other key species such as yellow and white box. The landscape
sampling approach successfully addressed the challenges of whole-landscape research. This highlights the value of ‘off-reserve’
studies across whole landscapes. 相似文献
16.
Hanem G. Abouelezz Therese M. Donovan Ruth M. Mickey James D. Murdoch Mark Freeman Kimberly Royar 《Landscape Ecology》2018,33(8):1301-1318
Context
The analysis of individual movement choices can be used to better understand population-level resource selection and inform management.Objectives
We investigated movements and habitat selection of 13 bobcats in Vermont, USA, under the assumption individuals makes choices based upon their current location. Results were used to identify “movement-defined” corridors.Methods
We used GPS-collars and GIS to estimate bobcat movement paths, and extracted statistics on land cover proportions, topography, fine-scale vegetation, roads, and streams within “used” and “available” space surrounding each movement path. Compositional analyses were used to determine habitat preferences with respect to landcover and topography; ratio tests were used to determine if used versus available ratios for vegetation, roads, and streams differed from 1. Results were used to create travel cost maps, a primary input for corridor analysis.Results
Forested and scrub-rock land cover were most preferred for movement, while developed land cover was least preferred. Preference depended on the composition of the “available” landscape: Bobcats moved?>?3 times more quickly through forest and scrub-rock habitat when these habitats were surrounded by agriculture or development than when the available buffer was similarly composed. Overall, forest edge, wetland edge and higher stream densities were selected, while deep forest core and high road densities were not selected. Landscape-scale connectivity maps differed depending on whether habitat suitability, preference, or selection informed the travel cost map.Conclusions
Both local and landscape scale land cover characteristics affect habitat preferences and travel speed of bobcats, which in turn can inform management and conservation activities.17.
Fine-scale landscape change can alter dispersal patterns of animals, thus influencing connectivity or gene flow within a population.
Furthermore, dispersal patterns of different species may be influenced by the landscape in varying ways. Our research first
aimed to examine whether the spatial genetic structure within populations of closely related bird species differs in response
to the same landscape. Second, we examined whether individual-level movement characteristics are a mechanistic driver of these
differences. We generated a priori predictions of how landscape features will influence dispersal (particularly the response
of individuals to habitat boundaries both natural and human-induced) based on a movement model developed by Fahrig (Funct
Ecol 21:1003–1015, 2007). This model allowed us to predict genetic relatedness patterns in populations of two passerine bird species with different
life-history traits from Queensland, Australia (yellow-throated scrubwren Sericornis citreogularis, a habitat specialist; white-browed scrubwren Sericornis frontalis, a habitat generalist). We quantified our predictions using cost-distance modelling and compared these to observed pairwise
genetic distances (a
r
) between individuals as calculated from microsatellite markers. Mantel tests showed that our a priori models correlated with
genetic distance. Euclidean distance was most closely correlated to genetic distance for the generalist species (r = 0.093, P = 0.002), and landscape models that included the avoidance of unsuitable habitat were best for the specialist species (r = 0.107, P = 0.001). Our study showed that predictable movement characteristics may be the mechanism driving differences in genetic
relatedness patterns within populations of different bird species. 相似文献
18.
The understanding and prediction of the responses of animal populations to habitat fragmentation is a central issue in applied
ecology. The identification of habitat variables associated to patch occupancy is particularly important when habitat quality
is affected by human activities. Here, we analyze the influence of patch and landscape characteristics on patch occupancy
by the subterranean herbivorous rodent Ctenomys porteousi. Patch occupancy was monitored in a network of 63 habitat patches identified by satellite imagery analysis which extends
along almost the whole distributional range for C. porteousi. Suitable habitat for the occurrence of C. porteousi is highly fragmented and represents <10% of the total area in its distributional range. The distribution of C. porteousi in the patch network is affected not only by characteristics of the habitat patches, but also by those of the surrounding
landscape matrix. Significant differences between occupied and empty patches were found in several environmental variables.
Overall, occupied patches were larger, less vegetated, more connected, and had larger neighbor patches than empty patches.
A stepwise procedure on a generalized linear model selected four habitat variables that explain patch occupancy in C. porteousi; it included the effects of habitat quality in the matrix surrounding the patch, average vegetation cover in the patch, minimum
vegetation cover in the matrix surrounding the patch, and the area of the nearest neighbor patch. These results indicate that
patch occupancy in C. porteousi is strongly influenced by the availability and quality of habitat both in the patch and in the surrounding landscape matrix. 相似文献
19.
Biodiversity persistence in non-woody tropical farmlands is poorly explored, and multi-species assessments with robust landscape-scale
designs are sparse. Modeled species occupancy in agricultural mosaics is affected by multiple factors including survey methods
(convenience-based versus systematic), landscape-scale agriculture-related variables, and extent of remnant habitat. Changes
in seasonal crops can additionally alter landscape and habitat conditions thereby influencing species occupancy. We investigated
how these factors affect modeled occupancy of 56 resident bird species using a landscape-scale multi-season occupancy framework
across 24 intensively cultivated and human-dominated districts in Uttar Pradesh state, north India. Convenience-based roadside
observations provided considerable differences in occupancy estimates and associations with remnant habitat and intensity
of cultivation relative to systematic transect counts, and appeared to bias results to roadside conditions. Modeled occupancy
of only open-area species improved with increasing intensity of cultivation, while remnant habitat improved modeled occupancy
of scrubland, wetland and woodland species. Strong seasonal differences in occupancy were apparent for most species across
all habitat guilds. Further habitat loss will be most detrimental to resident scrubland, wetland and woodland species. Uttar
Pradesh’s agricultural landscape has a high conservation value, but will require a landscape-level approach to maintain the
observed high species richness. Obtaining ecological information from unexplored landscapes using robust landscape-scale surveys
offers substantial advantages to understand factors affecting species occupancy, and is necessary for efficient conservation
planning. 相似文献
20.
Conservation strategies should be based on a solid understanding of processes underlying species response to landscape change.
In forests fragmented by agriculture, elevated nest predation rates have been reported in many forest bird species, especially
near edges. In intensively-managed forest landscapes, timber harvesting might also be associated with negative edge effects
or broader “context” effects on some species when the matrix provides additional resources to their major nest predators.
In this study, we hypothesized that proximity to a forest edge and proportion of cone-producing plantations will increase
nest predation risk in fragments of relatively undisturbed forest. We focused on the Brown Creeper (Certhia americana), an indicator species of late-seral forests. We compared habitat configuration and composition at four spatial scales (0.14,
0.5, 1 and 2 km) around 54 nests and related daily nest survival rate to the distance to the nearest forest edge, mean patch
size of late-seral forest (r = 141 m), proportion of non-forested lands (r = 141 m), density of maintained roads (r = 1 km), proportion of cone-producing spruce plantations (r = 2 km), and year. The best model included distance to the nearest edge and proportion of cone-producing plantations. Distance
of nests to the nearest edge was the best individual predictor of daily nest survival. A larger sample of nests showed a significant
threshold in distance to the nearest forest edge; nests located at least 100 m away were more likely to fledge young. These
results suggest that even in managed forest landscapes, matrix effects can be important and some bird species may exhibit
negative edge effects. 相似文献