共查询到20条相似文献,搜索用时 31 毫秒
1.
Controlling spatial structure of forested landscapes: a case study towards landscape management 总被引:6,自引:0,他引:6
Emin Z. Baskent 《Landscape Ecology》1999,14(1):83-97
2.
The protean relationship between boreal forest landscape structure and red squirrel distribution at multiple spatial scales 总被引:3,自引:0,他引:3
This paper investigates two fundamental questions in landscape ecology: what influence does landscape context, or the composition of the matrix, have on an animals’ response to landscape structure, and how does this relationship extrapolate between landscapes? We investigate how the distribution of North American red squirrels (Tamiasciurus hudsonicus) in the boreal mixedwood forest is influenced by anthropogenically (forest harvest) and naturally (forest fire) derived landscape structure. We studied the presence and absence of red squirrels over two years in three landscape types: one managed for timber harvest, one recently burned by wildfire, and a third unburned unmanaged landscape. Landscape composition and configuration, measured at several spatial scales, predicted red squirrel’s distribution in all three landscapes, but the significant landscape variables changed across spatial scales, across time, and across landscapes. These findings emphasize the variability in landscape structure/animal distribution relationships, and enforce the need to link pattern-finding studies, such as this one, with searches for the mechanisms behind the observed pattern. 相似文献
3.
Frauke Ecke Pernilla Christensen Per Sandström Birger Hörnfeldt 《Landscape Ecology》2006,21(4):485-497
Several studies indicate a long-term decline in numbers of different species of voles in northern Fennoscandia. In boreal Sweden, the long-term decline is most pronounced in the grey-sided vole (Clethrionomys rufocanus). Altered forest landscape structure has been suggested as a possible cause of the decline. However, habitat responses of grey-sided voles at the landscape scale have never been studied. We analyzed such responses of this species in lowland forests in Västerbotten, northern Sweden. Cumulated spring densities representing 22 local time series from 1980–1999 were obtained by a landscape sampling design and were related to the surrounding landscape structure of 2.5×2.5 km plots centred on each of the 22 1-ha trapping plots. In accordance with general knowledge on local habitat preferences of grey-sided voles, our study supported the importance of habitat variables such as boulder fields and old-growth pine forest at the landscape scale. Densities were negatively related to clear cuts. Habitat associations were primarily those of landscape structure related to habitat fragmentation, distance between habitat patches and patch interspersion rather than habitat patch type quantity. Local densities of the grey-sided vole were positively and exponentially correlated with spatial contiguity (measured with the fragmentation index) of old-growth pine forest, indicating critical forest fragmentation thresholds. Our results indicate that altered land use might be involved in the long-term decline of the grey-sided vole in managed forest areas of Fennoscandia. We propose two further approaches to reveal and test responses of this species to changes in landscape structure. 相似文献
4.
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
5.
With return times between 20 and 100 years, ice storms are a primary disturbance type for temperate forests of eastern North
America. Many studies have been conducted at the forest patch and plot scales to examine relations between damage and variables
describing site, composition and structure. This paper presents results from a landscape scale study of fragmentation relations
with damage in eastern Ontario forests. Data previously collected for two independent and spatially non-overlapping patch
level damage studies were used. A Generalized Linear Model (GLM) was used to analyse relations between damage and fragmentation
metrics representing patch isolation, edge density, and the relative size and distribution of patches in the landscape. The
metrics were applied using spatial extents of 1 × 1 km and 4 × 4 km, following analyses of the variability of numbers of patches
and of the lacunarity of forest patterns over a range of extents. The results showed that patch isolation, as measured by
the mean Euclidean distance between patches (ENN) was significantly related to damage. 相似文献
6.
Although abrupt changes (i.e. thresholds) have been precisely defined in simulated landscapes, such changes in the structure
of real landscapes are not well understood. We tested for threshold occurrence in three common deforestation patterns in the
Brazilian Amazon: small properties regularly distributed along roads (fishbone), irregularly distributed small properties
(independent settlements), and large properties. We analyzed differences between real deforestation patterns, and tested the
capacity of simulated landscape with different aggregation degrees to predict threshold occurrence. Three 8×8 km sites (replicates)
with more than 90% of forest in 1984 and less than 30% in 1998 were selected/simulated for each deforestation pattern. Thresholds
were observed for fishbone and large property patterns, especially when considering the connectivity index, although threshold
incidences were more frequently observed in simulated landscapes. The capacity of simulated landscapes to predict the exact
threshold point in real landscapes was limited, even when considering highly aggregate simulations. However, the general trend
in landscape structural changes was similar in real and simulated landscapes. Thresholds occurred at the beginning of the
deforestation for mean patch size and at an intermediate stage, corresponding to the percolation threshold, for connectivity,
isolation and fragmentation. Threshold behavior for connectivity index might suggest that the survival of strictly forest
species will sharply decrease when the proportion of forest reach values <0.60, indicating that conservation efforts should
be done to maintain forest cover above this limit. Significant differences observed among the real deforestation patterns,
especially in patch isolation and number of fragments, can have significant consequences for conservation. The independent
settlement pattern is, without a doubt, the least favorable of them, resulting in a higher level of fragmentation, whereas
the large property and fishbone patterns may be less detrimental if connectivity among the remnant forest patches is preserved. 相似文献
7.
Effects of remote sensor spatial resolution and data aggregation on selected fragmentation indices 总被引:3,自引:0,他引:3
Santiago Saura 《Landscape Ecology》2004,19(2):197-209
Analyzing the effect of scale on landscape pattern indices has been a key research topic in landscape ecology. The lack of
comparability of fragmentation indices across spatial resolutions seriously limits their usefulness while multi-scale remotely
sensed data are becoming increasingly available. In this paper, we examine the effect of spatial resolution on six common
fragmentation indices that are being used within the Third Spanish National Forest Inventory. We analyse categorical data
derived from simultaneously gathered Landsat-TM and IRS-WiFS satellite images, as well as TM patterns aggregated to coarser
resolutions through majority rules. In general, majority rules tend to produce more fragmented patterns than actual sensor
ones. It is suggested that sensor point spread function should be specifically considered to improve comparability among satellite
images of varying pixel sizes. Power scaling-laws were found between spatial resolution and several fragmentation indices,
with mean prediction errors under 10% for number of patches and mean patch size and under 5% for edge length. All metrics
but patch cohesion indicate lower fragmentation at coarser spatial resolutions. In fact, an arbitrarily large value of patch
cohesion can be obtained by resampling the pattern to smaller pixel sizes. An explanation and simple solution for correcting
this undesired behaviour is provided. Landscape division and largest patch index were found to be the least sensitive indices
to spatial resolution effects.
This revised version was published online in May 2005 with corrections to the Cover Date.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Habitat configuration has important implications for the persistence of faunal and floral populations at a variety of spatial
scales. Forest harvesting alters habitat configurations. However, measuring and predicting such alterations remains challenging,
in part because previously developed metrics of habitat configuration are often not statistically independent of habitat amount.
Thus, their ability to measure independent effects of habitat configurations and habitat amount on ecosystem components such
as wildlife populations has been limited. Here, we evaluate habitat configuration based on newly developed metrics that are
independent of habitat amount but do not depend on regression residuals of abundance and configuration relationships on any
population of landscapes. We use these new metrics to measure and predict changes in habitat configuration following forest
harvesting in the boreal forest of Alberta, Canada. Our findings clearly demonstrate changes in habitat configuration resulting
from forest harvesting can be predicted precisely with information about initial habitat patch structure and harvesting patterns.
Because forest harvesting has significant implications for habitat configuration, accurately predicting these changes is critical
for determining if forest harvesting strategies are sustainable for ecosystem components and processes. This study provides
a set of novel, robust metrics for tracking landscape-scale changes in habitat configuration in harvested boreal forests. 相似文献
9.
Historic range of variability in landscape structure in subalpine forests of the Greater Yellowstone Area,USA 总被引:4,自引:0,他引:4
A measure of the historic range of variability (HRV) in landscape structure is essential for evaluating current landscape
patterns of Rocky Mountain coniferous forests that have been subjected to intensive timber harvest. We used a geographic information
system (GIS) and FRAGSTATS to calculate key landscape metrics on two ∼130,000-ha landscapes in the Greater Yellowstone Area,
USA: one in Yellowstone National Park (YNP), which has been primarily shaped by natural fires, and a second in the adjacent
Targhee National Forest (TNF), which has undergone intensive clearcutting for nearly 30 years. Digital maps of the current
and historical landscape in YNP were developed from earlier stand age maps developed by Romme and Despain. Maps of the TNF
landscape were adapted from United States Forest Service Resource Information System (RIS) data. Key landscape metrics were
calculated at 20-yr intervals for YNP for the period from 1705-1995. These metrics were used to first evaluate the relative
effects of small vs. large fire events on landscape structure and were then compared to similar metrics calculated for both
pre- and post-harvest landscapes of the TNF. Large fires, such as those that burned in 1988, produced a structurally different
landscape than did previous, smaller fires (1705-1985). The total number of patches of all types was higher after 1988 (694
vs. 340-404 before 1988), and mean patch size was reduced by almost half (186 ha vs. 319-379 ha). The amount of unburned forest
was less following the 1988 fires (63% vs. 72-90% prior to 1988), yet the number of unburned patches increased by nearly an
order of magnitude (230 vs. a maximum of 41 prior to 1988). Total core area and mean core area per patch decreased after 1988
relative to smaller fires (∼73,700 ha vs. 87,000-110,000 ha, and 320 ha vs. 2,123 ha, respectively). Notably, only edge density
was similar (17 m ha−1 after 1988) to earlier landscapes (9.8-14.2 m ha−1).Three decades of timber harvesting dramatically altered landscape structure in the TNF. Total number of patches increased
threefold (1,481 after harvest vs. 437 before harvest), and mean patch size decreased by ∼70% (91.3 ha vs. 309 ha). None of
the post-harvest landscape metrics calculated for the TNF fell within the HRV as defined in YNP, even when the post-1988 landscape
was considered. In contrast, pre-harvest TNF landscape metrics were all within, or very nearly within, the HRV for YNP. While
reference conditions such as those identified by this study are useful for local and regional landscape evaluation and planning,
additional research is necessary to understand the consequences of changes in landscape structure for population, community,
ecosystem, and landscape function.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
In order to document the extent of landscape fragmentation for a section of the New Jersey Pine Barrens region, we have used satellite image and spatial analysis to monitor landscape change between 1972 and 1988. Land-cover patterns were quantified by mean, number, and size of patches; and amount of edges between land cover types. During the intervening sixteen year period, fractal dimension, diversity, and contagion generally decreased while dominance, disturbance and edges increased, indicating a trend to a more dissected and disturbed landscape. There was an increase in the number of forest patches and a significant decrease in the average size of forest patches. In contrast, the mean patch size for the non-forest category has increased as a result of a coalescence of patches. The landscape fragmentation is shown by a downward shift in the distribution of forest patches by size class. These changes in landscape pattern have implications for many ecological processes and resources. Management practices need to consider landscape fragmentation in the Pinelands National Reserve in order to preserve the essential character of the Pine Barrens landscape. 相似文献
11.
Acknowledgment that the matrix matters in conserving wildlife in human-modified landscapes is increasing. However, the complex
interactions of habitat loss, habitat fragmentation, habitat condition and land use have confounded attempts to disentangle
the relative importance of properties of the landscape mosaic, including the matrix. To this end, we controlled for the amount
of remnant forest habitat and the level of fragmentation to examine mammal species richness in human-modified landscapes of
varying levels of matrix development intensity and patch attributes. We postulated seven alternative models of various patch
habitat, landscape and matrix influences on mammal species richness and then tested these models using generalized linear
mixed-effects models within an information theoretic framework. Matrix attributes were the most important determinants of
terrestrial mammal species richness; matrix development intensity had a strong negative effect and vegetation structural complexity
of the matrix had a strong positive effect. Distance to the nearest remnant forest habitat was relatively unimportant. Matrix
habitat attributes are potentially a more important indicator of isolation of remnant forest patches than measures of distance
to the nearest patch. We conclude that a structurally complex matrix within a human-modified landscape can provide supplementary
habitat resources and increase the probability of movement across the landscape, thereby increasing mammal species richness
in modified landscapes. 相似文献
12.
Positive effects of forest fragmentation,independent of forest amount,on bat abundance in eastern Ontario,Canada 总被引:1,自引:0,他引:1
While studies have found that bat abundance is positively related to the amount of forest cover in a landscape, the effects
of forest fragmentation (breaking apart of forest, independent of amount) are less certain, with some indirect evidence for
positive effects of fragmentation. However, in most of these studies, the variables used to quantify fragmentation are confounded
with forest amount, making it difficult to interpret the results. The purpose of this study was to examine how forest amount
and forest fragmentation independently affect bat abundance. We conducted acoustic bat surveys at the centers of 22 landscapes
throughout eastern Ontario, Canada, where landscapes were chosen to avoid a correlation between forest amount and forest fragmentation
(number of patches) at multiple spatial scales, while simultaneously controlling for other variables that could affect bat
activity. We found that the effects of forest amount on bat relative abundance were mixed across species (positive for Lasiurus borealis, negative for Perimyotis subflavus and Lasionycteris noctivagans). When there was evidence for an effect of forest fragmentation, independent of forest amount, on bat relative abundance,
the effect was positive (Myotis septentrionalis, Myotis lucifugus and Lasiurus borealis). We suggest that the mechanism driving the positive responses to fragmentation is higher landscape complementation in more
fragmented landscapes; that is, increased access to both foraging and roosting sites for these bat species. We conclude that
fragmented landscapes that maximize complementation between roosting and foraging sites should support a higher diversity
and abundance of bats. 相似文献
13.
Fire and grazing are ecological processes that frequently interact to modify landscape patterns of vegetation. There is empirical
and theoretical evidence that response of herbivores to heterogeneity is scale-dependent however the relationship between
fire and scale of heterogeneity is not well defined. We examined the relationship between fire behavior and spatial scale
(i.e., patch grain) of fuel heterogeneity. We created four heterogeneous landscapes modeled after those created by a fire–grazing
interaction that differed in grain size of fuel patches. Fire spread was simulated through each model landscape from 80 independent,
randomly located ignition points. Burn area, burn shape complexity and the proportion of area burnt by different fire types
(headfire, backfire and flankfire) were all affected by the grain of fuel patch. The area fires burned in heterogeneous landscapes
interacted with the fuel load present in the patch where ignition occurred. Burn complexity was greater in landscapes with
small patch grain than in landscapes with large patch grain. The proportion of each fire type (backfire, flankfire and headfire)
was similar among all landscapes regardless of patch grain but the variance of burned area within each of the three fire types
differed among treatments of patch grain. Our landscape fire simulation supports the supposition that feedbacks between landscape
patterns and ecological processes are scale-dependent, in this case spatial scale of fuel loading altering fire spread through
the landscape. 相似文献
14.
David A. Etheridge David A. MacLean Robert G. Wagner Jeremy S. Wilson 《Landscape Ecology》2006,21(4):509-524
Historical and future projected landscape patterns and changes caused by harvesting and silviculture were evaluated for a
189,000 ha, intensively managed forest in New Brunswick, Canada. We compared changes in species composition, age classes,
and patch characteristics (area, size, density, edge, shape, and core area) between 1945, 2002, and projections to 2027 (based
on the landowner's spatial forest management plan). In 1945, the landbase was 40% softwood, 37% mixed hardwood–softwood, 10%
hardwood, and 9% softwood–cedar. From 1945 to 2002 and 2027, respectively, softwood forest area increased by 2 and 11%, mixedwood
decreased by 19 and 20%, and hardwood area increased by 15 and 14%, and softwood–cedar increased by 6% and then decreased
by 7%. In 1945, forest >70 years old comprised 85% of the landscape, but declined to 44% in 2002 and was projected to encompass
41% in 2027. Increased area harvested, decreasing harvest patch size, and protection against natural disturbances resulted
in progressively smaller mean and less variable patch sizes from 1945 to 2002. Based upon the 25-year forest management plan,
this trend was projected to continue, with the exception of nine patches >1000 ha created by 2027, eight of which were softwood
plantations. Stand type successional dynamics were highly variable in both harvested and non-harvested areas, and in some
cases were unexpected. Few of the 1945 stand types remained static by 2002, with 42 and 35% of mixedwood shifting to softwood
as a result of harvesting, and to hardwood as a result of both harvesting and spruce budworm (Choristoneura fumiferana Clem.) outbreaks in the 1950s and 1970s. This study demonstrates the strong cumulative effect of forest management on landscape
patterns, especially the socially mandated drive for smaller clearcuts resulting in the loss of large patches. 相似文献
15.
Increasing land ownership fragmentation in the United States is causing concerns with respect to its ecological implications
for forested landscapes. This is especially relevant given that human influence is one of the most significant driving forces
affecting the forest landscape. A method for generating realistic land ownership maps is needed to evaluate the effects of
ownership fragmentation on forest landscapes in combination with other natural processes captured in forest process models.
Ownership patterns from human activities usually generate landscape boundary shapes different from those arising from natural
processes. Spatial characteristics among ownership types – e.g., private, public ownership – may also differ. To address these
issues, we developed the Fragmented Land Ownership Spatial Simulator (FLOSS) to generate ownership patterns that reflect the
Public Land Survey System (PLSS) shapes and various patch size distributions among different types of ownership (e.g., private,
public). To evaluate FLOSS performance, we compared the simulated patterns with various ownership fragmentation levels to
the actual ownership patterns in the Missouri Ozarks by using selected landscape indices. FLOSS generated landscapes with
spatial characteristics similar to actual landscapes, suggesting that it can simulate different levels of ownership fragmentation.
This will allow FLOSS to serve as a feasible tool for evaluating forest management applications by spatially allocating various
management scenarios in a realistic way. The potentials and limitations of FLOSS application are discussed. 相似文献
16.
Simulating the cumulative effects of multiple forest management strategies on landscape measures of forest sustainability 总被引:1,自引:2,他引:1
While the cumulative effects of the actions of multiple owners have long been recognized as critically relevant to efforts
to maintain sustainable forests at the landscape scale, few studies have addressed these effects. We used the HARVEST timber
harvest simulator to predict the cumulative effects of four owner groups (two paper companies, a state forest and non-industrial
private owners) with different management objectives on landscape pattern in an upper Michigan landscape managed primarily
for timber production. We quantified trends in landscape pattern metrics that were linked to Montreal Process indicators of
forest sustainability, and used a simple wildlife habitat model to project habitat trends. Our results showed that most trends
were considered favorable for forest sustainability, but that some were not. The proportion of all age classes and some forest
types moved closer to presettlement conditions. The trend for the size of uneven-aged patches was essentially flat while the
average size of patches of the oldest and youngest age classes increased and the size of patches of the remaining age classes
decreased. Forest fragmentation generally declined, but edge density of age classes increased. Late seral forest habitat increased
while early successional habitat declined. The owners use different management systems that cumulatively produce a diversity
of habitats. Our approach provides a tool to evaluate such cumulative effects on other landscapes owned by multiple owners.
The approach holds promise for helping landowner groups develop and evaluate cooperative strategies to improve landscape patterns
for forest sustainability. 相似文献
17.
Surface metrics: an alternative to patch metrics for the quantification of landscape structure 总被引:6,自引:3,他引:3
Modern landscape ecology is based on the patch mosaic paradigm, in which landscapes are conceptualized and analyzed as mosaics
of discrete patches. While this model has been widely successful, there are many situations where it is more meaningful to
model landscape structure based on continuous rather than discrete spatial heterogeneity. The growing field of surface metrology
offers a variety of surface metrics for quantifying landscape gradients, yet these metrics are largely unknown and/or unused
by landscape ecologists. In this paper, we describe a suite of surface metrics with potential for landscape ecological application.
We assessed the redundancy among metrics and sought to find groups of similarly behaved metrics by examining metric performance
across 264 sample landscapes in western Turkey. For comparative purposes and to evaluate the robustness of the observed patterns,
we examined 16 different patch mosaic models and 18 different landscape gradient models of landscape structure. Surface metrics
were highly redundant, but less so than patch metrics, and consistently aggregated into four cohesive clusters of similarly
behaved metrics representing surface roughness, shape of the surface height distribution, and angular and radial surface texture.
While the surface roughness metrics have strong analogs among the patch metrics, the other surface components are largely
unique to landscape gradients. We contend that the surface properties we identified are nearly universal and have potential
to offer new insights into landscape pattern–process relationships.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
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
19.
Víctor Arroyo-Rodríguez Iraida M. González-Perez Adriana Garmendia Mireia Solà Alejandro Estrada 《Landscape Ecology》2013,28(9):1717-1727
Land-use change is forcing many animal populations to inhabit forest patches in which different processes can threaten their survival. Some threatening processes are mainly related to forest patch characteristics, but others depend principally on the landscape spatial context. Thus, the impact of both patch and landscape spatial attributes needs to be assessed to have a better understanding of the habitat spatial attributes that constraint the maintenance of populations in fragmented landscapes. Here, we evaluated the relative effect of three patch-scale (i.e., patch size, shape, and isolation) and five landscape-scale metrics (i.e., forest cover, fragmentation, edge density, mean inter-patch isolation distance, and matrix permeability) on population composition and structure of black howler monkeys (Alouatta pigra) in the Lacandona rainforest, Mexico. We measured the landscape-scale metrics at two spatial scales: within 100 and 500 ha landscapes. Our findings revealed that howler monkeys were more strongly affected by local-scale metrics. Smaller and more isolated forest patches showed a lower number of individuals but at higher densities. Population density also tended to be positively associated to matrices with higher proportion of secondary forests and arboreal crops (i.e. with greater permeability), most probably because these matrices can offer supplementary foods. The immature-to-female ratio also increased with matrix permeability, shape complexity, and edge density; habitat characteristics that can increase landscape connectivity and sources availability. The prevention of habitat loss and isolation, and the increment of matrix permeability are therefore needed for the conservation of this endangered Neotropical mammal. 相似文献
20.
Ludwig John A. Eager Robert W. Bastin Gary N. Chewings Vanessa H. Liedloff Adam C. 《Landscape Ecology》2002,17(2):157-171
The cover, number, size, shape, spatial arrangement and orientation of vegetation patches are attributes that have been used
to indicate how well landscapes function to retain, not ‘leak’, vital system resources such as rainwater and soil. We derived
and tested a directional leakiness index (DLI) for this resource retention function. We used simulated landscape maps where
resource flows over map surfaces were directional and where landscape patch attributes were known. Although DLI was most strongly
related to patch cover, it also logically related to patch number, size, shape, arrangement and orientation. If the direction
of resource flow is multi-directional, a variant of DLI, the multi-directional leakiness index (MDLI) can be used. The utility
of DLI and MDLI was demonstrated by applying these indices to three Australian savanna landscapes differing in their remotely
sensed vegetation patch attributes. These leakiness indices clearly positioned these three landscapes along a function-dysfunction
continuum, where dysfunctional landscapes are leaky (poorly retain resources).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献