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1.
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
2.
Anthropogenic habitat loss and fragmentation are the principle factors causing declines of grassland birds. Declines in burrowing
owl (Athene cunicularia) populations have been extensive and have been linked to habitat loss, primarily the decline of black-tailed prairie dog
(Cynomys ludovicianus) colonies. Development of habitat use models is a research priority and will aid conservation of owls inhabiting human-altered
landscapes. From 2001 to 2004 we located 160 burrowing owl nests on prairie dog colonies on the Little Missouri National Grassland
in North Dakota. We used multiple linear regression and Akaike’s Information Criterion to estimate the relationship between
cover type characteristics surrounding prairie dog colonies and (1) number of owl pairs per colony and (2) reproductive success.
Models were developed for two spatial scales, within 600 m and 2,000 m radii of nests for cropland, crested wheatgrass (Agropyron cristatum), grassland, and prairie dog colonies. We also included number of patches as a metric of landscape fragmentation. Annually,
fewer than 30% of prairie dog colonies were occupied by owls. None of the models at the 600 m scale explained variation in
number of owl pairs or reproductive success. However, models at the 2,000 m scale did explain number of owl pairs and reproductive
success. Models included cropland, crested wheatgrass, and prairie dog colonies. Grasslands were not included in any of the
models and had low importance values, although percentage grassland surrounding colonies was high. Management that protects
prairie dog colonies bordering cropland and crested wheatgrass should be implemented to maintain nesting habitat of burrowing
owls. 相似文献
3.
We measured the activity of mammalian predators, numbers of singing male songbirds, and predation rates on nests of songbirds (152 natural, open-cup nests and 380 artificial nests) on 38 250 m transects located along various types of forest-field edges in a wildlife management area in east-central Illinois. We then related these variables to each other and to measures of the vegetative structure of our transects that we anticipated might influence predator activity or predation rates on nests of birds characteristic of edge and shrubland habitats. Mammalian predators, particularly raccoons (Procyon lotor), were abundant in the wildlife area and present on all transects surveyed. We did not find significant relationships among the variables we measured. Rather, rates of nest predation were consistently high (>70%) and generally evenly distributed around our study site. Medium-sized, generalist mammalian predators in the midwestern United States reach their highest population densities in fragmented landscapes with abundant edge habitat, particularly agricultural edges. Areas of natural habitat in these landscapes dominated by agriculture may concentrate predators and act as ecological traps for nesting birds because they attract high densities of breeding birds that are subjected to high rates of nest predation. 相似文献
4.
Emily J. Comfort Darren A. Clark Robert G. Anthony John Bailey Matthew G. Betts 《Landscape Ecology》2016,31(6):1227-1240
Context
Testing the influence of edges on animal distributions depends on our capacity to quantify ‘edge’, particularly in heterogeneous landscapes. Habitat quality is likely to differ in instances where edges are abrupt and anthropogenic in origin, versus diffuse, disturbance-created edges.Objectives
We tested whether or not structurally distinct edge types influence northern spotted owl habitat selection and whether the relationship between edge type and use varied across spatial scales relevant to owl foraging (<3 ha) and home range selection (50–800 ha).Methods
We used remotely sensed disturbance severity data to define two distinct edge types, ‘hard’ and ‘diffuse’, following a 11,000 ha fire and subsequent salvage logging in southern Oregon. The approach quantifies the steepness of gradients directly by measuring the ‘slope’ of change in disturbance severity. We tested the degree to which 23 radio-collared spotted owls responded to edge characteristics caused by fire and logging.Results
Spotted owls showed a strong negative association with hard edge, even after accounting for habitat suitability and other confounding variables. However, this negative relationship was highly scale-dependent; spotted owls were resilient to hard edges at broad scales, but avoided the same feature at fine scales. On the other hand, spotted owls showed a positive association with diffuse edge, especially at broader scales.Conclusions
Differential use of edge types indicates that owls favor disturbances that create diffuse edge habitat (e.g. low and mixed-severity fire) and rather than abrupt boundaries created by high severity disturbance.5.
Nathan H. Schumaker Allen Brookes Jeffrey R. Dunk Brian Woodbridge Julie A. Heinrichs Joshua J. Lawler Carlos Carroll David LaPlante 《Landscape Ecology》2014,29(4):579-592
Source-sink dynamics are an emergent property of complex species–landscape interactions. A better understanding of how human activities affect source-sink dynamics has the potential to inform and improve the management of species of conservation concern. Here we use a study of the northern spotted owl (Strix occidentalis caurina) to introduce new methods for quantifying source-sink dynamics that simultaneously describe the population-wide consequences of changes to landscape connectivity. Our spotted owl model is mechanistic, spatially-explicit, individual-based, and incorporates competition with barred owls (Strix varia). Our observations of spotted owl source-sink dynamics could not have been inferred solely from habitat quality, and were sensitive to landscape connectivity and the spatial sampling schemes employed by the model. We conclude that a clear understanding of source-sink dynamics can best be obtained from sampling simultaneously at multiple spatial scales. Our methodology is general, can be readily adapted to other systems, and will work with population models ranging from simple and low-parameter to complex and data-intensive. 相似文献
6.
Elizabeth M. Glenn Damon B. Lesmeister Raymond J. Davis Bruce Hollen Anne Poopatanapong 《Landscape Ecology》2017,32(3):563-579
Context
Conservation planning for at-risk species requires understanding of where species are likely to occur, how many individuals are likely to be supported on a given landscape, and the ability to monitor those changes through time.Objectives
We developed a distribution model for northern spotted owls that incorporates both habitat suitability and probability of territory occupancy while accounting for interspecies competition.Methods
We developed range-wide habitat suitability maps for two time periods (1993 and 2012) for northern spotted owls that accounted for regional differences in habitat use and home range size. We used these maps for a long-term demographic monitoring study area to assess habitat change and estimate the number of potential territories based on available habitat for both time periods. We adjusted the number of potential territories using known occupancy rates to estimate owl densities for both time periods. We evaluated our range-wide habitat suitability model using independent survey data.Results
Our range-wide habitat maps predicted areas suitable for territorial spotted owl presence well. On the demographic study area, the amount of habitat declined 19.7% between 1993 and 2012, while our estimate of the habitat-based carrying capacity declined from 150 to 146 territories. Estimated number of occupied territories declined from 94 to 57.Conclusions
Conservation and recovery of at-risk species depends on understanding how habitat changes over time in response to factors such as wildfire, climate change, biological invasions, and interspecies competition, and how these changes influence species distribution. We demonstrate a model-based approach that provides an effective planning tool.7.
We examined responses of Siberian flying squirrels ( Pteromys volans ) to edges between nesting habitat (mature spruce forests), movement habitat (other forests, pine bogs), and open areas within their home ranges in southern Finland in 1996-2000. Radio-tracked squirrels (n=146) were generally associated to edges when they were ac tive at night. Compared to distances expected from the habitat pattern of their home range, squirrels occurred closer to high-contrast edges (of open areas) and low-contrast edges (nesting or movement forest types). Asso ciation with edges of open areas was more pronounced when squirrels were in movement habitat than in nesting habitat, possibly because of stronger channeling of movements in the former habitat. When in nesting habitat, squirrels responded more strongly to field edges than to recent clearcut edges, probably as a result of the pres ence of more deciduous trees on field edges, unlike clearcut edges. Responses to open areas were independent of spatial scale. However, responses to movement habitat from nesting habitat, and vice versa, were more pronounced over hundreds than tens of meters. Nesting cavities and dreys were generally located at random with respect to edges. We conclude that squirrel responses to edges of landscape attributes are diverse and depend both on spatial scale and edge contrast.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
8.
Brad C. Timm Kevin McGarigal Samuel A. Cushman Joseph L. Ganey 《Landscape Ecology》2016,31(6):1209-1225
Context
Organisms commonly respond to their environment across a range of scales, however many habitat selection studies still conduct selection analyses using a single-scale framework. The adoption of multi-scale modeling frameworks in habitat selection studies can improve the effectiveness of these studies and provide greater insights into scale-dependent relationships between species and specific habitat components.Objectives
Our study assessed multi-scale nest/roost habitat selection of the federally “Threatened” Mexican spotted owl (Strix occidentalis lucida) in northern Arizona, USA in an effort to provide improved conservation and management strategies for this subspecies.Methods
We conducted multi-scale habitat modeling to assess habitat selection by Mexican spotted owls using survey data collected by the USFS. Each selected covariate was included in multi-scale models at their “characteristic scale” and we used an all-subsets approach and model selection framework to assess habitat selection.Results
The “characteristic scale” identified for each covariate varied considerably among covariates and results from multi-scale models indicated that percent canopy cover and slope were the most important covariates with respect to habitat selection by Mexican spotted owls. Multi-scale models consistently outperformed their analogous single-scale counterparts with respect to the proportion of deviance explained and model predictive performance.Conclusions
Efficacy of future habitat selection studies will benefit by taking a multi-scale approach. In addition to potentially providing increased explanatory power and predictive capacity, multi-scale habitat models enhance our understanding of the scales at which species respond to their environment, which is critical knowledge required to implement effective conservation and management strategies.9.
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
10.
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
11.
Context
Urbanization and artificial light at night (ALAN) are major drivers of local biodiversity losses causing community alterations, disruption of predator-prey interactions, and ultimately, promotion of cascading effects. However, some species can colonize urban environments.
ObjectivesWe explore the role of ALAN as a driver of the colonization of urban environments by a nocturnal avian predator, the burrowing owl Athene cunicularia.
MethodsWe studied in a suburban locality in La Pampa, Argentina: (1) prey availability with pitfall traps under streetlights and control sites; (2) diet by analyzing pellets; (3) space use by deploying GPS data-loggers to breeding owls; (4) nesting habitat selection by comparing environmental variables at nest and random locations; and (5) productivity by correlating environmental variables with the number of fledglings.
ResultsFirst, streetlights altered the invertebrate availability, attracting them to illuminated areas. Second, the owl diet was more similar to the invertebrate taxa trapped at pitfall traps under streetlights than that in control traps. Third, owl space use was determined by streetlights. Owls spent more time around light sources, particularly during the nighttime. Fourth, the most important habitat feature influencing the nesting habitat selection was the distance to streetlight. Owls selected areas close to streetlights for nesting. Finally, productivity was not explained by any of our habitat variables.
ConclusionsWe demonstrate that ALAN alters the availability of invertebrates and plays a role in the diet, space use, and occupation of urban burrowing owls. Streetlights increase foraging efficiency for owls due to the clumping of prey attracted to lights. This predator-prey relationship might be only supported in suburban environments where low urbanization levels let burrowing owls nest in bare ground areas, and invertebrates are attracted to ALAN from surrounding wilder areas.
相似文献12.
Cusser Sarah Grando Carolina Zucchi Maria Imaculada López-Uribe Margarita M. Pope Nathaniel S. Ballare Kimberly Luna-Lucena Danielle Almeida Eduardo A. B. Neff John L. Young Kenneth Jha Shalene 《Landscape Ecology》2019,34(7):1825-1836
Landscape Ecology - Bees are the most important pollinators of crops worldwide. For most bees, patches of semi-natural habitat within or adjacent to crops can provide important nesting and food... 相似文献
13.
The ability to predict species occurrences quickly is often crucial for managers and conservation biologists with limited
time and funds. We used measured associations with landscape patterns to build accurate predictive habitat models that were
quickly and easily applied (i.e., required no additional data collection in the field to make predictions). We used classification
trees (a nonparametric alternative to discriminant function analysis, logistic regression, and other generalized linear models)
to model nesting habitat of red-naped sapsuckers (Sphyrapicus nuchalis), northern flickers (Colaptes auratus),tree swallows (Tachycineta bicolor), and mountain chickadees (Parus gambeli) in the Uinta Mountains of northeastern Utah, USA. We then tested the predictive capability of the models with independent
data collected in the field the following year. The models built for the northern flicker, red-naped sapsucker, and tree swallow
were relatively accurate (84%, 80%, and 75% nests correctly classified,respectively)compared to the models for the mountain
chickadee (50% nests correctly classified). All four models were more selective than a null model that predicted habitat based
solely on a gross association with aspen forests. We conclude that associations with landscape patterns can be used to build
relatively accurate, easy to use, predictive models for some species. Our results stress, however, that both selecting the
proper scale at which to assess landscape associations and empirically testing the models derived from those associations
are crucial for building useful predictive models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Landscapes are composed of a multitude of habitat types which, potentially, can influence natural enemy populations. The contribution
of specific habitat types to sustaining natural enemy populations in agricultural landscapes and the associated ecosystem
service of pest control is not well understood. We investigated how landscape composition affected parasitism rates in 22
organic Brussels sprout fields in The Netherlands. Second and third instar larvae of Plutella xylostella were placed on experimental Brussels sprout plants in Brussels sprout fields and were recovered after two days in the field.
Parasitism rates ranged between 4 and 94% and were related to landscape variables at a scale of 0.3, 1, 2 and 10 km. Univariate
analysis using a generalized linear mixed model indicated that parasitism rates were positively related with area of forests
at a scale of 1, 2 and 10 km, forest edges at a scale of 1 and 2 km and road verges at a scale of 1 km. Forest and road verges
are likely to provide food and alternative hosts for parasitoids and are less disturbed habitats than agricultural fields.
These results suggest that forests and road verges may play an important role in sustaining effective densities of parasitoids
of P. xylostella in agricultural landscapes. 相似文献
15.
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
16.
Elisa Hardt Rozely F. dos Santos Carlos L. de Pablo Pilar Martín de Agar Erico F. L. Pereira-Silva 《Landscape Ecology》2013,28(3):385-399
We evaluated changes in the Atlantic Forest landscape over the last 40 years based on changes in boundaries and mosaics, including the hypothetical landscape resulting from the application of Brazilian laws for forest protection. Mosaics were identified as sets of land-use patches with a similar pattern of boundaries. Landscapes of different years, therefore, can be distinguished by differences in mosaics. We developed a technique to identify boundaries between patches from land-use maps using ArcGis® and to build the patch x boundary matrix required for mosaic identification by means of a factorial and cluster analysis. The mosaics were characterized by some key uses as well as by their boundaries with other land uses. The mosaics were scored for forest conservation according to five issues: landscape permeability, cover, availability, quality, and fragmentation of forest. The values were based on land use and boundary patterns. Although Brazilian laws regarding forest protection have promoted conservation and the hypothetical legal landscape has presented the highest forest habitat availability, this expansion perpetuates a boundary pattern that complicates conservation and management, thus increasing the pressure on forest patches and favoring the further fragmentation of protected forest patches. These conclusions cannot be reached by simply recording changes in land uses. 相似文献
17.
Chloe F. Sato Jeff T. Wood Mellesa Schroder Damian R. Michael William S. Osborne Ken Green David B. Lindenmayer 《Landscape Ecology》2014,29(7):1225-1236
Subalpine ecosystems are centres of endemism that are important for biodiversity. However, these areas are under threat from the creation, expansion and continued modification of ski runs, activities that have largely negative effects on wildlife. Despite this threat, research on the impacts of ski runs is limited for reptiles—particularly regarding the value of remnant vegetation retained on ski runs. Here we quantify the effects of habitat loss and fragmentation (i.e., patch size, patch isolation and edge effects) on the abundance of a common subalpine lizard and on thermal regimes (a key determinant of lizard distribution) in an Australian ski resort. The number of lizards observed differed significantly with habitat type (ski runs vs. forested areas) and patch isolation, but not patch size. In addition, the edges of patches supported more lizards than any other habitat type. These patterns of lizard distribution can be explained, in part, by the differing thermal regimes in each habitat. Ski runs had significantly higher ground surface temperatures than any other habitat type, precluding their use for a considerable proportion of the activity period of a lizard. In comparison, edges were characterised by lower temperatures than ski runs, but higher temperatures than the core of forested areas, potentially providing a favourable environment for thermoregulation. Based on our results, we conclude that although modified ski runs have a negative effect on lizards, patches of remnant vegetation retained on ski runs are of value for reptiles and their conservation could help mitigate the negative effects of habitat loss caused by ski run creation. 相似文献
18.
The influence of sampling scheme and interpolation method on the power to detect spatial effects of forest birds in Ontario (Canada) 总被引：1，自引：0，他引：1
Spatial ecology is becoming an increasingly important component of resource management, and the general monitoring of how
human activities affect the distribution and abundance of wildlife. Yet most work on the reliability of sampling strategies
is based on a non-spatial analysis of variance paradigm, and little work has been done assessing the power of alternative
spatial methods for creating reliable maps of animal abundance. Such a map forms a critical response variable for multiple
scale studies relating landscape structure to biotic function. The power to reconstruct patterns of distribution and abundance
is influenced by sample placement strategy and density, the nature of spatial auto-correlation among points, and by the technique
used to extrapolate points into an animal abundance map. Faced with uncertainty concerning the influence of these factors,
we chose to first synthesize a model reference system of known properties and then evaluate the relative performance of alternative
sampling and mapping procedures using it. We used published habitat associations of tree nesting boreal neo-tropical birds,
a classified habitat map from the Manitou Lakes area of northwestern Ontario, and point count means and variances determined
from field studies in boreal Canada to create 4 simulated models of avian abundance to function as reference maps. Four point
sampling strategies were evaluated by 4 spatial mapping methods. We found mixed-cluster sampling to be an effective point
sampling strategy, particularly when high habitat fragmentation was avoided by restricting samples to habitat patches >10
ha in size. We also found that of the 4 mapping methods, only stratified ordinary point kriging (OPK) was able to generate
maps that reproduced an embedded landscape-scale spatial effect that reduced nesting bird abundance in areas of higher forest
age-class fragmentation. Global OPK was effective only for detecting broader, regional-scale differences.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Edge geometry influences patch-level habitat use by an edge specialist in south-eastern Australia 总被引：1，自引：1，他引：0
We investigated patterns in habitat use by the noisy miner (Manorina melanocephala) along farmland-woodland edges of large patches of remnant vegetation (>300 ha) in the highly fragmented box-ironbark woodlands
and forests of central Victoria, Australia. Noisy miners exclude small birds from their territories, and are considered a
significant threat to woodland bird communities in the study region. Seventeen different characteristics of edge habitat were
recorded, together with the detection or non-detection of noisy miners along 129 500-m segments of patch edge. Habitat characteristics
ranged from patch-level factors related to patch-edge geometry to site-level floristic factors. Backward (stepwise) logistic
regression analyses were used to identify habitat characteristics that were associated with the occupancy of a site by noisy
miners. After accounting for the effects of spatial autocorrelation on the occurrence of noisy miners along edges, we identified
projections of remnant vegetation from the patch edge into the agricultural matrix (e.g., corners of patches, peninsulas of
vegetation) and clumps of trees in the agricultural matrix within 100 m of the edge as significant predictors of the occupancy
of edges by noisy miners. This relationship was also confirmed in two other geographically and floristically distinct habitats
within Victoria. The use of edges with projections by noisy miners may confer advantages in interspecific territorial defence.
In light of these results, we advocate revegetation strategies that attempt to enclose projections within 100 m of the edge,
with fencing placed out to this new boundary, to reduce the likelihood of colonisation and domination of an edge by noisy
miners. Our study highlights the need for greater consideration to be given to the patterns in habitat use by aggressive edge
specialists, particularly in relation to patch-edge geometry and other human-induced components of landscapes. 相似文献
20.
An explicitly spatial, large scale, high resolution model of fire driven landscape dynamics in the Great Victoria Desert is constructed and parameterized to simulate frequency distributions of fire size and shape obtained from previous analyses of satellite chronosequences. We conclude that probabilities of fire spread cannot be constant over time, and that realistic distributions of fire size and plausible rates of fire spread can be obtained by assuming that fire spread is conditional on observed durations of windy conditions. Landscapes subject to this form of disturbance show large scale correlation structure many times greater than the average dimensions of single fires, and exhibit low frequency quasi-periodic stochastically driven oscillations in proportions of the landscape at different successional states over spatial scales exceeding 100,000 km2. Average fire return intervals are 30 yrs. Analysis of patch structure suggests that this landscape is composed of few large younger patches, embedded in a mature sea of surrounding habitat. Intermediate and late successional habitat must exist in more abundant patches somewhat smaller than young habitat. Numerous small patches of mature habitat are likely to be scattered throughout this younger habitat. The model predicts that fire size frequency distributions are relatively insensitive to changes of as much as ±50% of observed fire ignition frequency. 相似文献