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1.
Kozakiewicz Michał Gortat Tomasz Kozakiewicz Anna Barkowska Miłosława 《Landscape Ecology》1999,14(4):391-400
Bank vole, striped field mouse, wood mouse, and yellow-necked mouse populations were studied in a mosaic of field and forest habitats. Live-trapping was carried out in 8 woodlots of different sizes (1.5–9.5 ha), situated 5 to 900 m from each other and surrounded by agricultural fields. Near the study area a dense, several hundred hectare forest complex was situated. It was found that the densities of all the studied species' populations in the woodlots were positively correlated with woodlot quality. For local bank vole populations a positive correlation of density with the surface area and circumference of woodlots, as well as with the area/circumference ratio was found. A negative correlation was found for population density and the distance between a given woodlot and the forest complex. For the yellow-necked mouse a positive correlation occurred between the density of local populations and the distance to the nearest neighboring woodlot. For the striped field mouse a positive correlation was found only between the population density in each woodlot and the distance to the forest complex. The wood mouse was insensitive to the variations in woodlot features present except for woodlot quality, and hence was probably responding in density to some other factors. Four rodent species, coexisting in the field-forest habitat mosaic demonstrated different reactions to its spatial characteristics, which were mainly related to different habitat preferences, spatial behavior, and mobility of individuals of the studied species. 相似文献
2.
Terhi Riutta Eleanor M. Slade Michael D. Morecroft Daniel P. Bebber Yadvinder Malhi 《Landscape Ecology》2014,29(6):949-961
Forest ecosystems have been widely fragmented by human land use, inducing significant microclimatic and biological changes at the forest edge. If we are to rigorously assess the ecological impacts of habitat fragmentation, there is a need to effectively quantify the amount of edge habitat within a landscape, and to allow this to be modelled for individual species and processes. Edge effect may extend only a few metres or as far as several kilometres, depending on the species or process in question. Therefore, rather than attempting to quantify the amount of edge habitat by using a fixed, case-specific distance to distinguish between edge and core, the area of habitat within continuously-varying distances from the forest edge is of greater utility. We quantified the degree of fragmentation of forests in England, where forests cover 10 % of the land area. We calculated the distance from within the forest patches to the nearest edge (forest vs. non-forest) and other landscape indices, such as mean patch size, edge density and distance to the nearest neighbour. Of the total forest area, 37 % was within 30 m and 74 % within 100 m of the nearest edge. This highlights that, in fragmented landscapes, the habitats close to the edge form a considerable proportion of the total habitat area. We then show how these edge estimates can be combined with ecological response functions, to allow us to generate biologically meaningful estimates of the impacts of fragmentation at a landscape scale. 相似文献
3.
There is increasing interest in large, infrequent, natural disturbances and how they affect ecosystems. Attributes of patches produced by some natural disturbances, such as blowdowns, have seldom been measured. We measured attributes of patches produced by a large blowdown (over 10 000 ha) in northern Colorado, USA in 1997. The blowdown produced 402, 655, or 756 patches, based on three different concepts of a blowdown patch. An inverse-J relationship shows that most patches are small in size (<200 ha), while few are large. Most patches have a high percentage of blown-down trees (>50% down). Blowdown patches are highly variable in their size, perimeter length, and distance to the nearest patch. The blowdown patches are larger and have more complex shapes than patches in the surrounding forest. Mean size of blowdown patches (25 ha) may be smaller than those of crown fires in a nearby forest, but similar total areas may be affected. About 75% of the blowdown area is within 125 m of a forest not blown down, so natural tree regeneration should not be a problem. About 16,400 ha of mature spruce-fir forest is susceptible to first-year attack by spruce beetles, as this forest is within the expected dispersal distance (1.2 km) from blowdown patches where beetle reproduction is favored. Timber harvest patches differ from blowdown patches in size and distance to nearest patch. It also may be inappropriate to mimic forest blowdown patches using timber harvesting in this region, due to the rare occurrence of large blowdowns, their spatial restriction, and other factors. 相似文献
4.
A management driven investigation of landscape patterns of northern spotted owl nesting territories in the high Cascades of Oregon 总被引：2，自引：0，他引：2
Investigations using available data sought to guide short-term management decisions regarding the needs of northern spotted owl in the high Cascade Mountains of Oregon. Landscape attributes and pattern indices were measured and tested for identification of areas likely to contain northern spotted owl nests. Predictive models indicating planning standards were developed. Most landscape ecological indices were not useful. Results indicate the owl favors landscapes dominated by patches that meet definitions of late seral forest nesting habitat. The owl optimally nests in such patches at least 570 hectares in size. Landscapes with some edges, particularly around nesting habitat patches evidently do not adversely affect the owl, perhaps because they provide prey. Landscapes with extensive edges, particularly between openings and forests not suitable for nesting, are not as likely to be selected. The results are largely consistent with the owl's recovery plans, provide guidance for management, and require refinement through additional research, particularly to better determine home range sizes. 相似文献
5.
Group selection silviculture creates canopy openings that can alter connectivity in patchy forests, thereby affecting wildlife
movement and fire behavior. We examined effects of group selection silviculture on percolation (presence of continuously forested
routes across a landscape) in Sierra Nevada East-side pine forest in northern California, USA. Four ~ 250 ha project areas
were analyzed at three map resolutions in three ways: analyzing forest cover maps for percolation before and after group-selection
treatment, placing simulated group openings in forest cover maps until fragmentation occurred, and comparing project areas
to neutral maps that varied in forest cover and self-adjacency. Two project areas were fragmented (i.e., did not percolate)
prior to treatment, one resisted fragmentation, and the other became fragmented by treatment when analyzed at 30 m cell resolution.
Median simulated openings required to create fragmentation agreed well with the actual number. There was a well-defined transition
between percolating and non-percolating neutral maps; increased aggregation of forest lowered the critical value at which
forests percolated. A logistic model based on these maps predicted percolation behavior of the project areas effectively,
but alternative generating algorithms gave slightly different predictions. A graph of this model provides a straightforward
way to visualize how close a landscape is to fragmentation based on its forest cover and aggregation. In East-side Sierran
landscape, fragmentation from group-selection openings may make the landscape less hospitable to the American marten but more
resistant to crown fire. 相似文献
6.
Landscape structure in the Eastern US experienced great changes in the last century with the expansion of forest cover into
abandoned agricultural land and the clearing of secondary forest cover for urban development. In this paper, the spatial and
temporal patterns of forest cover from 1914 to 2004 in the Gwynns Falls watershed in Baltimore, Maryland were quantified from
historic maps and aerial photographs. Using a database of forest patches from six times—1914, 1938, 1957, 1971, 1999, and
2004—we found that forest cover changed, both temporally and spatially. While total forest area remained essentially constant,
turnover in forest cover was very substantial. Less than 20% of initial forest cover remained unchanged. Forest cover became
increasingly fragmented as the number, size, shape, and spatial distribution of forest patches within the watershed changed
greatly. Forest patch change was also analyzed within 3-km distance bands extending from the urban core to the more suburban
end of the watershed. This analysis showed that, over time, the location of high rates of forest cover change shifted from
urban to suburban bands which coincides with the spatial shift of urbanization. Forest cover tended to be more stable in and
near the urban center, whereas forest cover changed more in areas where urbanization was still in process. These results may
have critical implications for the ecological functioning of forest patches and underscore the need to integrate multi-temporal
data layers to investigate the spatial pattern of forest cover and the temporal variations of that spatial pattern. 相似文献
7.
Landscape history of a calcareous (alvar) grassland in Hanila,western Estonia,during the last three hundred years 总被引：10，自引：4，他引：6
The landscape history of the largest calcareous seminatural alvar site (ca. 700 ha) in Estonia, is described with the help of a historical map from 1705 and aerial photographs from 1951, and recent vegetation mapping from 1994–1996. The seminatural, species rich alvar grasslands originate and are maintained by grazing of domestic animals. Three hundred years ago the area was mainly open grassland with sparse shrubs and some fields. Forty years ago the vegetation pattern was similar, with some smaller forests and forest clear-cut areas present. Now, since grazing has ceased for ca. 40 years, only 30% of the area remains as open grassland and 70% as forest. Identification of clusters of field layer vegetation using the program TABORD resulted in 8 clusters, which agreed with the empirically determined community types. The field layer within the young pine forest (up to 20 year old pines) is similar to the open alvar grassland. In older forests, the field layer has already changed. There were no phytosociological differences found between ancient grasslands and grasslands on former arable fields or forest clear-cut areas. Decrease in species richness, compared to open grassland, was most drastic in forests of age 20–40 years where the canopy was most closed. Forests have spread more extensively in areas with deeper soil. The continuation of traditional management (grazing and tree cutting) in alvar grasslands is urgently needed in order to keep seminatural alvar grasslands open. The possibility to restore open grasslands remains as long as there is a pool of grassland species available, especially in younger forests. 相似文献
8.
9.
All the remnants of native vegetation in a 1680 km2 area of the central wheatbelt of Western Australia were assessed for use by two species of kangaroo (Western grey kangaroo Macropus fuliginosus and euro M. robustus). Use was determined from faecal pellet density. Densities over large areas (100 km2) varied with the amount of residual native vegetation in the area. The less the vegetation the lower was the faecal density, indicating that increased separation between remnants has led, over the 50–70 years since fragmentation, to lower kangaroo densities.The densities of kangaroos in 152 individual remnants of >2 ha were examined in relation to their physical attributes (e.g. area, edge length, distance to nearest remnant, presence of linkages and the vegetation types present), and to an index of isolation from human disturbance. Few remnants <2 ha were used by kangaroos.Canonical discriminant analysis showed that separation of remnants without kangaroos from those with kangaroos was associated with many of the attributes. Of these, the numbers of vegetation types and their proportions and the degree of isolation from human disturbance were of greatest importance. Regression analyses were done to obtain predictors of densities within remnants grouped according to the kangaroo species using the remnants. These showed that the importance of attributes differed for different groupings. Isolation from human disturbance was the most important factor for remnants that had either species, but not for the larger ones that had both species. For euros, density increased with the rank of the linkage to other remnants and decreased with the percentage of the remnant in open woodland. For Western grey kangaroos, rank for distance to nearest remnant was significant. Since the study area is representative of a much larger area, the findings should have wide applicability. 相似文献
10.
Harvesting and forest fire change the spatial configurations of forest habitat. We used multivariate statistical models to
evaluate the individual and cumulative effects of these two disturbances on habitat configuration in managed boreal forest
landscapes in western Canada. We evaluated three aspects of configuration (core area, inter-patch distance and shape) using
indices normalized for total habitat abundance. The two disturbances types had different effects on the three configuration
metrics in terms of both the magnitude and direction of change. We found that the magnitudes of harvesting effects were larger
than for fire. The direction of change was the same for core area and shape, but opposite for inter-patch distance which decreased
slightly after fire. The combined effects of the two disturbances are distinct from the effects of either disturbance alone,
and the effects are not always additive or compensatory for all metrics. Pre-treatment configuration was a significant covariate
in all models, and total habitat abundance was significant in 4/9 models, but these were often not the most important covariates.
In the cumulative disturbance model, covariates for the number or size of cut-blocks were significant. 相似文献
11.
Michael O’Neal Campbell 《Urban Forestry & Urban Greening》2009,8(2):87-95
Urban forestry is increasingly vital for both wildlife conservation and human use, despite frequent conflicts between these functions. A fundamental task in urban habitat and recreation forestry is the identification of those habitat characteristics important for animal species and the evaluation of these within the geographies of human presence, urban proximity and land cover variation and change. This paper examines the habitat characteristics for birds in urban built, green and greenbelt areas of Ottawa, Canada, and an area of continuous Ontario forest, to determine the effects of vegetation density and patch size, and human presence on bird presence. Bird presence was measured by point counts, and land cover was mapped using field observation and aerial photographs (1955 and 1999). At the species level, the pre-dominantly forest birds were affected by human presence and were primarily associated with tree stands in the greenbelt and continuous forest. In dense urban areas there were larger numbers of a few ‘generalist’ species. Both forested and urban (residential/commercial) environments increased in area between 1955 and 1999, creating the two types of land cover favouring the largest number of birds, while the less habituated grass/farmed areas declined in area. More informed bird conservation and recreation management will depend on paying greater attention to vegetation cover combinations with urban development. 相似文献
12.
Maurice Keith R. Welch Joan M. Brown Christopher P. Latham Roger Earl 《Landscape Ecology》2004,19(6):603-620
The Pocono mesic till barrens (PMTB) are a unique assemblage of fire-maintained shrub communities that support numerous rare species. Historically these barrens covered a large area in the vicinity of Long Pond, Pennsylvania, USA. However, due largely to regional fire suppression instituted in the early 1960s, over 70% of the area covered by barrens succeeded to fire-intolerant forest that does not support the rare species. We investigated the influence of forest proximity on barrens succession across three geomorphic types during periods of high fire frequency and fire suppression, testing the hypothesis that forest processes such as seed rain, shading, and detrital enrichment of soils enhances barrens succession through a contagion effect. Evidence of a forest contagion effect should be shown by increased rates of barrens succession with increasing proximity to the nearest forest edge. In order to detect a forest contagion effect, barrens persistence and barrens succession were modeled in proximity zones of 0-50 m, 50-100 m, 100-200 m, and greater than 200 m from the nearest forest edge. We used existing GIS data layers for fire, geomorphology, and vegetation distribution in 1938, 1963, and 1992. The layers were modified and overlain using ArcView software to determine persistence and succession rates for each unique combination of layers in each proximity zone from 1938 to 1963 (pre-fire suppression) and 1963 to 1992 (post-fire suppression). ANCOVA results indicate that proximity to the nearest forest edge significantly affected barrens persistence rates in both time periods, but succession rates were significantly affected in 1938 to 1963 only. Twenty-eight percent of the 1938 barrens succeeded to forest by 1963; 56% of the 1963 barrens became forest by 1992. Results support previous findings that barrens persistence is enhanced by increased fire frequency, and that barrens persist longer where they overlie flat glacial till than on other geomorphology types. 相似文献
13.
We address effects of large-scale forestry on landscape structure and the structure and composition of boreal bird communities in North Sweden. Specifically, we ask: after controlling for the effect of patch size, forest age and tree species composition, is there any residual effect attributable to the reduction in area of old forest? Pairs of landscape blocks (25 by 25 km) were selected to maximize area difference in human-induced disturbance, clear-cut as opposed to semi-natural old forest. Median distance to natural edge (wetlands, open water) from randomly selected points in forest was 250 and 200 m in high and low impact landscapes, respectively, indicating a high degree of ‘natural’ fragmentation of the pristine boreal landscape in the area. By contrast, median distance to clear-cut in uncut forest was 750 and 100 m, respectively. Clear-cuts in high impact landscapes were disproportionally more common in areas with contiguous forest land than in areas with spatially disjunct forest, implicating that forestry increases natural fragmentation of the landscape by subdividing larger forest tracts. Point counts along forestry roads showed that species richness and relative abundance of forest birds were higher in landscapes with low forestry impact. These differences can partly be explained by differences in age composition of forest and composition of tree species. After controlling for patch size, forest age and tree species composition, a significant effect of forestry impact remained for Sibirian species and the Tree pipitAnthus trivialis. Our results thus imply that this group of species and the Tree pipit may be sensitive to forest fragmentation. In contrast to previous Finnish studies, we found relatively small negative effects on relative abundance of species hypothesized to be negatively affected by large-scale clear-cutting forestry. However, our picture of the present does not contradict results from Finnish long-term population studies. Five factors may account for this: 1) clear-cut areas are not permanently transformed into other land use types, 2) planted forests are not completely inhabitable for species preferring older forest, 3) the majority of species in the regional pool are habitat generalists, 4) the region studied is still extensively covered with semi-natural forest, and 5) our study area is relatively close to contiguous boreal forest in Russia, a potential source area for taiga species. 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.
Forest fragmentation in Loudoun County,Virginia, USA evaluated with multitemporal Landsat imagery 总被引：1，自引：0，他引：1
In order to study forest fragmentation in the Virginia, USA Piedmont, a series of Landsat images from 1973, 1987, and 1999 covering a rapidly developing area (Loudoun County) was used to classify forest from non-forest. The classified images were analyzed using a geographic information system (GIS) to determine the spatial and temporal patterns of fragmentation, and to relate these patterns to infrared radiance provided by Landsat Enhanced Thematic Mapper Plus (ETM+) band 6. The analysis was concentrated on eleven major watersheds of Loudoun County. The relationship between urbanized area per watershed and mean fragment size showed a strong negative decay form (r
2=0.757, p<0.0001). Analysis of four landscape metrics showed increasing fragmentation of forest cover, particularly from 1987 to 1999, as well as an increase in forest edge and shape complexity. Of the landscape metrics used, the perimeter-to-area (P/A) ratio showed the strongest relationship with mean radiance of forest patches. In addition, there was a negative, linear relationship between distance from major roads and band 6 radiance of forested pixels. Overall, the study shows that landscape metrics can convey meaningful information on biophysical changes associated with forest fragmentation at broad scales. These changes suggest that ambient temperature increases associated with urban sprawl may have important, long-term implications for ecophysiological processes. 相似文献
16.
Analysing land-cover changes in relation to environmental variables in Hesse,Germany 总被引：14，自引：7，他引：14
Land-use and land-cover changes affect ecological landscape functions and processes. Hence, landscape ecologists have a central interest in a comprehensive understanding of such changes. Our study focuses on the relationships between environmental conditions and agricultural land-cover changes. We present a method to (i) characterise the major spatial-temporal processes of land-cover changes, (ii) identify the correlations between environmental attributes and land-cover changes and (iii) derive potential environmental drivers of land-cover changes in a German marginal rural landscape. The method was applied to study land-cover dynamics from 1945 to 1998 in the districts of Erda, Steinbrücken and Eibelshausen, situated in the marginal rural landscape of the Lahn-Dill Highlands, Germany. We employed land-cover data gained by the interpretation of multi-temporal aerial photographs. Various environmental variables were introduced into the analyses. We identified physical landscape attributes (elevation, slope, aspect, available water capacity and soil texture) and structural landscape dimensions (patch size, patch shape and distance between patch and nearest settlement). With the aid of GIS, K-means partitioning and canonical correspondence analysis, we investigated land-cover trajectory types, land-cover transitions at individual time intervals and their relationships to these environmental variables. Our results show that, between 1945 and 1998, land-cover changes correlated with the physical attributes of the underlying landscape. On the other hand, the structural landscape dimensions correlated with land cover only in periods of minor land-cover changes (1972–98). Greater diversity of physical landscape attributes is correlated with greater land-cover dynamics. Besides the important influence of socio-economic factors, land-cover changes in the study areas took place within the relatively stable physical constraints of the underlying landscape.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
17.
A multi-scale spatial analysis method for point data 总被引：1，自引：0，他引：1
This paper presents a nearest neighbor method for the spatial analysis of data collected from discrete field sampling sites. The method was applied to point counts of birds at permanent survey sites in the Nicolet National Forest of northeastern Wisconsin. The spatial analysis method we developed uses a Monte Carlo randomization approach to test for non-randomness not only of the mean nearest neighbor distance between n points but also the mean second nearest, third nearest,..., to (n–1)th nearest distances to reveal spatial information at multiple scales. Because the bird survey sites are not randomly distributed throughout the forest, the survey sites at which a given species was recorded were compared with random samples drawn from the total survey sites rather than from all possible points within the forest. More refined analyses restricted the randomization by (a) habitat type, in order to separate the effects of non-randomly distributed habitat types on species' distributions; and (b) north-south regions of the forest, in order to account for regional gradients in distribution which were evident for some species. Spatial patterns among the sites at which the birds were detected reveal information about the scale at which the birds are distributed in their environment and provide a more complete picture of multi-scale bird population dynamics. 相似文献
18.
The r.le programs for multiscale analysis of landscape structure using the GRASS geographical information system 总被引：8，自引：0，他引：8
Geographical information systems (GIS) are well suited to the spatial analysis of landscape data, but generally lack programs for calculating traditional measures of landscape structure (e.g., fractal dimension). Standalone programs for calculating landscape structure measures do exist, but these programs do not enable the user to take advantage of GIS facilities for manipulating and analyzing landscape data. Moreover, these programs lack capabilities for analysis with sampling areas of different size (multiscale analysis) and also lack some needed measures of landscape structure (e.g., texture).We have developed the r.le programs for analyzing landscape structure using the GRASS GIS. The programs can be used to calculate over sixty measures of landscape structure (e.g., distance, size, shape, fractal dimension, perimeters, diversity, texture, juxtaposition, edges) within sampling areas of several sizes simultaneously. Also possible are moving window analyses, which enable the production of new maps of the landscape structure within windows of a particular size. These new maps can then be used in other analyses with the GIS. 相似文献
19.
To assess the role of shifting cultivation in the loss of rainforests in Indonesia, we examined the spatial and temporal dynamics of traditional land-use north of Gunung Palung National Park in West Kalimantan. We analyzed the abundance, size, frequency, and stature (by tree size) of discrete management units (patches) as a function of land-use category and distance from the village. Data were gathered from point samples along six 1.5-km transects through the landscape surrounding the Dayak village of Kembera. Most land was managed for rice, with 5% in current production, 12% in wet-rice fallows (regenerating swamp forest), and 62% in dry-rice fallows (regenerating upland forest). The proportion of land in dry-rice increased with distance from the village; rubber gardens (17% of the total area), dominated close to the village. The size of rubber trees declined with distance, reflecting the recent establishment of rubber gardens far from the village. Fruit gardens accounted for only 4% of the area. From interviews in Kembera and three other villages, we estimated rates of primary forest clearing and documented changes in land-use. Most rice fields were cleared from secondary forest fallows. However, 17% of dry-rice fields and 9% of wet-rice fields were cleared from primary forest in 1990, resulting in the loss of approximately 12 ha of primary forest per village. Almost all dry-rice fields cleared from primary forest were immediately converted to rubber gardens, as were 39% of all dry-rice fields cleared from fallows. The rate of primary forest conversion increased dramatically from 1990 to 1995, due not to soil degradation or population growth but rather to changes in the socio-economic and political environment faced by shifting cultivators. Although the loss of primary forest is appreciable under shifting cultivation, the impact is less than that of the major alternative land-uses in the region: timber extraction and oil palm plantations. 相似文献
20.
The behavior of landscape metrics commonly used in the study of habitat fragmentation 总被引：40，自引：2，他引：38
A meaningful interpretation of landscape metrics is possible only when the limitations of each measure are fully understood, the range of attainable values is known, and the user is aware of potential shifts in the range of values due to characteristics of landscape patches. To examine the behavior of landscape metrics, we generated artificial landscapes that mimicked fragmentation processes while controlling the size and shape of patches in the landscape and the mode of disturbance growth. We developed nine series of increasingly fragmented landscapes and used these to investigate the behavior of edge density, contagion, mean nearest neighbor distance, mean proximity index, perimeter-area fractal dimension, and mass fractal dimension. We found that most of the measures were highly correlated, especially contagion and edge density, which had a near-perfect inverse correspondence. Many of the measures were linearly-associated with increasing disturbance until the proportion of disturbance on the landscape was approximately 0.40, with non-linear associations at higher proportions. None of the measures was able to differentiate between landscape patterns characterized by dispersed versus aggregated patches. The highest attainable value of each measure was altered by either patch size or shape, and in some cases, by both attributes. We summarize our findings by discussing the utility of each metric. 相似文献