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1.
This paper analyzes the interactions between land use and forest cover in the Upper Midwest, USA from 1970 to 1990. New data
are presented and interpreted to evaluate the effects of land-use changes, especially abandonment of agriculture and dispersed
development, on forest cover throughout the region. Forest-cover data were collected from Landsat satellite imagery and land
use was interpreted from aerial photographs for land parcels, based on archival maps of land ownership. In general, forest
cover increased throughout the region and throughout the period. Simultaneously, the area used for agriculture declined, much
of it being converted to natural uses, and the area of land in low density residential development increased. Forest cover
increased most rapidly on low density residential lands and in counties in which a large percentage of homes were for seasonal
use (i.e., vacation homes). The data suggest that the transformation of the region from an extractive (i.e., forestry and
agriculture) to a recreation-based service economy has played a significant role in the increasing forest cover observed throughout
the region.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
We examined the use of coarse resolution land cover data (USGS LUDA) to accurately discriminate ecoregions and landscape-scale
features important to biodiversity monitoring and management. We used land cover composition and landscape indices, correlation
and principal components analysis, and comparison with finer-grained Landsat TM data, to assess how well LUDA data discriminate
changing patterns across an agriculture-forest gradient in Minnesota, U.S.A. We found LUDA data to be most accurate at general
class levels of agriculture and forest dominance (Anderson Level I), but in consistent and limited in ecotonal areas of the
gradient and within forested portions of the study region at finer classes (Anderson Level II).
We expected LUDA to over-represent major (matrix) cover types and under-represent minor types, but this was not consistent
with all classes. 1) Land cover types respond individualistically across the gradient, changing landscape grain as well as
their spatial distribution and abundance. 2) Agriculture is not over-represented where it is the dominant land cover type,
but forest is over-represented where it is dominant. 3) Individual forest types are under-represented in an open land matrix.
4) Within forested areas, mixed deciduous-coniferous forest is over-represented by several orders of magnitude and the separate
conifer and hardwood types under-represented. Across gradual, transitional agriculture-forest areas, LUDA cover class dominance
changes abruptly in a stair-step fashion. In general, rare cover types that are discrete, such as forest in agriculture or
wetlands or water in forest, are more accurately represented than cover classes having lower contrast with the matrix. Northward
across the gradient, important changes in the proportions of conifer and deciduous forest mixtures occur at scales not discriminated
by LUDA data. Results suggest that finer-grained data are needed to map within-state ecoregions and discriminate important
landscape characteristics. LUDA data, or similar coarse resolution data sources, should be used with caution and the biases
fully understood before being applied in regional landscape management.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
The landscape matrix modifies the effect of habitat fragmentation in grassland butterflies 总被引：1，自引：0，他引：1
Erik ?ckinger Karl-Olof Bergman Markus Franzén Tomá? Kadlec Jochen Krauss Mikko Kuussaari Juha P?yry Henrik G. Smith Ingolf Steffan-Dewenter Riccardo Bommarco 《Landscape Ecology》2012,27(1):121-131
The landscape matrix is suggested to influence the effect of habitat fragmentation on species richness, but the generality
of this prediction has not been tested. Here, we used data from 10 independent studies on butterfly species richness, where
the matrix surrounding grassland patches was dominated by either forest or arable land to test if matrix land use influenced
the response of species richness to patch area and connectivity. To account for the possibility that some of the observed
species use the matrix as their main or complementary habitat, we analysed the effects on total species richness and on the
richness of grassland specialist and non-specialist (generalists and specialists on other habitat types) butterflies separately.
Specialists and non-specialists were defined separately for each dataset. Total species richness and the richness of grassland
specialist butterflies were positively related to patch area and forest cover in the matrix, and negatively to patch isolation.
The strength of the species-area relationship was modified by matrix land use and had a slope that decreased with increasing
forest cover in the matrix. Potential mechanisms for the weaker effect of grassland fragmentation in forest-dominated landscapes
are (1) that the forest matrix is more heterogeneous and contains more resources, (2) that small grassland patches in a matrix
dominated by arable land suffer more from negative edge effects or (3) that the arable matrix constitutes a stronger barrier
to dispersal between populations. Regardless of the mechanisms, our results show that there are general effects of matrix
land use across landscapes and regions, and that landscape management that increases matrix quality can be a complement to
habitat restoration and re-creation in fragmented landscapes. 相似文献
4.
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
5.
Jennifer L. Reidy Frank R. ThompsonIII Courtney Amundson Lisa O’Donnell 《Landscape Ecology》2016,31(2):365-382
Context
Golden-cheeked warblers (Setophaga chrysoparia), an endangered wood-warbler, breed exclusively in woodlands co-dominated by Ashe juniper (Juniperus ashei) in central Texas. Their breeding range is becoming increasingly urbanized and habitat loss and fragmentation are a main threat to the species’ viability.Objectives
We investigated the effects of remotely sensed local habitat and landscape attributes on point occupancy and density of warblers in an urban preserve and produced a spatially explicit density map for the preserve using model-supported relationships.Methods
We conducted 1507 point-count surveys during spring 2011–2014 across Balcones Canyonlands Preserve (BCP) to evaluate warbler habitat associations and predict density of males. We used hierarchical Bayesian models to estimate multiple components of detection probability and evaluate covariate effects on detection probability, point occupancy, and density.Results
Point occupancy was positively related to landscape forest cover and local canopy cover; mean occupancy was 0.83. Density was influenced more by local than landscape factors. Density increased with greater amounts of juniper and mixed forest and decreased with more open edge. There was a weak negative relationship between density and landscape urban land cover.Conclusions
Landscape composition and habitat structure were important determinants of warbler occupancy and density, and the large intact patches of juniper and mixed forest on BCP (>2100 ha) supported a high density of warblers. Increasing urbanization and fragmentation in the surrounding landscape will likely result in lower breeding density due to loss of juniper and mixed forest and increasing urban land cover and edge.6.
Context
Urbanization has altered many landscapes around the world and created novel contexts and interactions, such as the rural–urban interface.Objectives
We sought to address how a forest patch’s location in the rural–urban interface influences which avian species choose to occur within the patch. We predicted a negative relationship between forest bird richness and urbanization surrounding the patch, but that it would be ameliorated by the area of tree cover in the patch and matrix, and that total tree-cover area would be more influential on forest bird species richness than area of tree cover in the focal patch alone.Methods
We conducted bird surveys in 44 forest patches over 2 years in Southeast Michigan and evaluated bird presence and richness relative to patch and matrix tree cover and development density.Results
We observed 43 species, comprised of 21 Neotropical migrants, 19 residents, and three short-distance migrants. Focal-patch tree-cover area and the matrix tree-cover area were the predominant contributors to a site’s overall forest-bird species richness at the rural–urban interface, but the addition of percent of over-story vegetation and percentage of deciduous tree cover influenced the ability of the patches to support forest species, especially Neotropical migrants. Development intensity in the matrix was unrelated to species richness and only had an effect in four species models.Conclusions
Although small forest patches remain an important conservation strategy in developed environments, the influence of matrix tree cover suggests that landscape design decisions in surrounding matrix can contribute conservation value at the rural–urban interface.7.
Land use dynamics within an urbanizing non-metropolitan county in New York State (USA) 总被引：2，自引：0，他引：2
Land use/land cover data for fifteen minor civil divisions (MCDs) in Ulster County, New York (USA) were interpreted from 1968 and 1985 aerial photographs. These data were combined with ancillary physiographic and demographic data as raster layers within a computerized geographic information system (GIS). Class to class changes in land use/land cover were quantified for a study area approximately 30 kilometers by 50 kilometers. The relationships between the land use/land cover variables and the ancillary variables were modeled in a series of weighted least squares regressions employing data spatially aggregated by general soil map unit (N = 44).Between 1968 and 1985, nearly one-third of the study area changed to another land use/land cover class. Land in the urban class increased from 6.7% to 17.8% of the study area, while the forest class declined from 65.0% to 55.2%, and the agriculture class declined from 12.7% to 8.9%. Gains and losses in the remaining five major (Level I) land use/land cover classes were relatively small. Land use changes primarily involved the conversion of land from the forest, agriculture, and vacant classes to the urban class, and from the agriculture class to the forest and vacant classes. Variables accounting for the variance in the land use/land cover class proportions of the soil units were population density, highway proximity, distance to urban centers, mean elevation, mean slope gradient, and soil suitability for farming and for urban development. 相似文献
8.
Hilda A. Sánchez-de-Jesús Víctor Arroyo-Rodríguez Ellen Andresen Federico Escobar 《Landscape Ecology》2016,31(4):843-854
Context
Identifying the drivers shaping biological assemblages in fragmented tropical landscapes is critical for designing effective conservation strategies. It is still unclear, however, whether tropical biodiversity is more strongly affected by forest loss, by its spatial configuration or by matrix composition across different spatial scales.Objectives
Assessing the relative influence of forest patch and landscape attributes on dung beetle assemblages in the fragmented Lacandona rainforest, Mexico.Methods
Using a multimodel inference approach we tested the relative impact of forest patch size and landscape forest cover (measures of forest amount at the patch and landscape scales, respectively), patch shape and isolation (forest configuration indices at the patch scale), forest fragmentation (forest configuration index at the landscape scale), and matrix composition on the diversity, abundance and biomass of dung beetles.Results
Patch size, landscape forest cover and matrix composition were the best predictors of dung beetle assemblages. Species richness, beetle abundance, and biomass decreased in smaller patches surrounded by a lower percentage of forest cover, and in landscapes dominated by open-area matrices. Community evenness also increased under these conditions due to the loss of rare species.Conclusions
Forest loss at the patch and landscape levels and matrix composition show a larger impact on dung beetles than forest spatial configuration. To preserve dung beetle assemblages, and their key functional roles in the ecosystem, conservation initiatives should prioritize a reduction in deforestation and an increase in the heterogeneity of the matrix surrounding forest remnants.9.
Road Density and Landscape Pattern in Relation to Housing Density,and Ownership,Land Cover,and Soils 总被引：5，自引：0，他引：5
Roads are conspicuous components of landscapes and play a substantial role in defining landscape pattern. Previous studies
have demonstrated the link between roads and their effects on ecological processes and landscape patterns. Less understood
is the placement of roads, and hence the patterns imposed by roads on the landscape in relation to factors describing land
use, land cover, and environmental heterogeneity. Our hypothesis was that variation in road density and landscape patterns
created by roads can be explained in relation to variables describing land use, land cover, and environmental factors. We
examined both road density and landscape patterns created by roads in relation to suitability of soil substrate as road subgrade,
land cover, lake area and perimeter, land ownership, and housing density across 19 predominantly forested counties in northern
Wisconsin, USA. Generalized least squares regression models showed that housing density and soils with excellent suitability
for road subgrade were positively related to road density while wetland area was negatively related. These relationships were
consistent across models for different road types. Landscape indices showed greater fragmentation by roads in areas with higher
housing density, and agriculture, grassland, and coniferous forest area, but less fragmentation with higher deciduous forest,
mixed forest, wetland, and lake area. These relationships provide insight into the complex relationships among social, institutional,
and environmental factors that influence where roads occur on the landscape. Our results are important for understanding the
impacts of roads on ecosystems and planning for their protection in the face of continued development. 相似文献
10.
Leone M. Brown Rebecca K. Fuda Nicolas Schtickzelle Haley Coffman Audrey Jost Alice Kazberouk Eliot Kemper Emma Sass Elizabeth E. Crone 《Landscape Ecology》2017,32(8):1657-1670
Context
Landscape-scale population dynamics are driven in part by movement within and dispersal among habitat patches. Predicting these processes requires information about how movement behavior varies among land cover types.Objectives
We investigated how butterfly movement in a heterogeneous landscape varies within and between habitat and matrix land cover types, and the implications of these differences for within-patch residence times and among-patch connectivity.Methods
We empirically measured movement behavior in the Baltimore checkerspot butterfly (Euphydryas phaeton) in three land cover classes that broadly constitute habitat and two classes that constitute matrix. We also measured habitat preference at boundaries. We predicted patch residence times and interpatch dispersal using movement parameters estimated separately for each habitat and matrix land cover subclass (5 categories), or for combined habitat and combined matrix land cover classes (2 categories). We evaluated the effects of including edge behavior on all metrics.Results
Overall, movement was slower within habitat land cover types, and faster in matrix cover types. Butterflies at forest edges were biased to remain in open areas, and connectivity and patch residence times were most affected by behavior at structural edges. Differences in movement between matrix subclasses had a greater effect on predictions about connectivity than differences between habitat subclasses. Differences in movement among habitat subclasses had a greater effect on residence times.Conclusions
Our findings highlight the importance of careful classification of movement and land cover in heterogeneous landscapes, and reveal how subtle differences in behavioral responses to land cover can affect landscape-scale outcomes.11.
Broad scale ecological edge-effects are most likely common in urbanized landscapes prone to wildfire, but most edge-effect studies have focused on fine scale processes such as shade tolerance and seed dispersal. Evidence has suggested a shift from pine dominated to oak dominated forests at the interface of developed land and natural areas in the Pinelands of New Jersey with the presence of a large edge-effect due to fire suppression. The goal of this study was to assess the location, magnitude and mechanism of the shift from pine to oak cover focusing on distance to human-altered land as the driver of fire suppression and forest composition changes. Overall, fire frequency and upland pine cover decreased sharply closer to human-altered land and affected up to 420 m of adjacent upland forest. Other factors, such as prescribed fire and wetlands configurations may play a role in the interior forest dynamics, but trends toward lower upland pine forest cover and higher upland oak cover near human altered were dominant. The areal summations of distance from altered land and the use of percent change thresholds for determining the scale and magnitude of large scale ecological edge-effects could be useful to managers attempting to maintain or restore forest types in areas of high wildland–urban interface. 相似文献
12.
Min Zhao Francisco J. Escobedo Christina Staudhammer 《Urban Forestry & Urban Greening》2010,9(3):205-214
Spatial patterns of tree structure and composition were studied to assess the effects of land tenure, management regimes, and the environment on a coastal, subtropical urban forest. A total of 229 plots in remnant natural areas, private residential, public non-residential, and private non-residential land tenures were analyzed in a 1273 km2 study area encompassing the urbanized portion of Miami-Dade County, USA. Statistical mixed models of structure, composition, location, and land tenure data were used to analyze spatial patterns across the study area. A total of 1200 trees were measured of which 593 trees (49%) were located in residential areas, 67 (6%) in public non-residential areas, 135 trees (11%) in private non-residential areas, and 405 (34%) in remnant, natural areas. A total of 107 different tree species belonging to 90 genera were sampled. Basal area in residential land tenures increased towards the coast while private residential land tenures and natural areas had higher species diversity than non-residential areas. Tree height, crown light exposure, and crown area might indicate the effects of past hurricane impacts on urban forest structure. Land tenure, soil types, and urban morphology influenced composition and structure. Broadleaf evergreen trees are the most common growth form, followed by broadleaf deciduous, palms, and conifers. Exotic tree species originated mainly from Asia and 15% of all trees measured were considered exotic-highly invasive species. We discuss the use of these results as an ecological basis for management and resilience towards hurricane damage and identifying occurrence of invasive, exotic trees. 相似文献
13.
Forest conservation and land development in Puerto Rico 总被引：4，自引：1，他引：3
In the Caribbean island of Puerto Rico, rapid land-use changes over the past century have included recent land-cover conversion to urban/built-up lands. Observations of this land development adjacent to reserves or replacing dense forest call into question how the changes relate to forests or reserved lands. Using existing maps, this study first summarizes island-wide land-cover change between 1977-78 and 1991-92. Then, using binomial logit modeling, it seeks evidence that simple forest cover attributes, reserve locations, or existing land cover influence land development locations. Finally, this study quantifies land development, reserve protection and forest cover by ecological zone. Results indicate that 1) pasture is more likely to undergo land development than shrubland plus forest with low canopy density, 2) forest condition and conservation status appear unimportant in that development locations neither distinguish between classes of forest canopy development nor relate to forest patch size or reserve proximity, and 3) most land development occurs in the least-protected ecological zones. Outside the boundaries of strictly protected forest and other reserves, accessibility, proximity to existing urban areas, and perhaps desirable natural settings, serve to increase land development. Over the coming century, opportunities to address ecological zone gaps in the islands forest reserve system could be lost more rapidly in lowland ecological zones, which are relatively unprotected.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
14.
Estimating the ‘critical’ distance at which adjacent land-use degrades wetland water and sediment quality 总被引：1，自引：0，他引：1
Conversion of forested lands to agriculture or urban/residential areas has been associated with declines in stream and lake water quality. Less attention has been paid to the effects of adjacent land-uses on wetland sediment and water quality and, perhaps more importantly, the spatial scales at which these effects occur. Here we address these issues by examining variation in water and sediment nutrient levels in 73 southeastern Ontario, Canada, wetlands. We modeled the relationship between water and sediment nutrient concentrations and various measures of adjacent land-use such as forest cover and road density, measured over increasing distances from the wetland edge. We found that water nitrogen and phosphorous levels were negatively correlated with forest cover at 2250 meters from the wetland edge, while sediment phosphorous levels were negatively correlated with wetland size and forest cover at 4000 meters and positively correlated with the proportion of land within 4000 meters that is itself wetland. These results suggest that the effects of adjacent land-use on wetland sediment and water quality can extend over comparatively large distances. As such, effective wetland conservation will not be achieved merely through the creation of narrow buffer zones between wetlands and more intensive land-uses. Rather, sustaining high wetland water quality will require maintaining a heterogeneous regional landscape containing relatively large areas of natural forest and wetlands. 相似文献
15.
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
16.
Matrix quality affects probability of persistence in habitat patches in landscape simulation models while empirical studies
show that both urban and agricultural land uses affect forest birds. However, due to the fact that forest bird abundance and
species richness can be strongly influenced by local habitat factors, it is difficult to analyze matrix effects without confounding
effects from such factors. Given this, our objectives were to (1) relate human-dominated land uses to forest bird abundance
and species richness without confounding effects from other factors; (2) determine the scale at which forest birds respond
to the matrix; and (3) identify whether certain bird migratory strategies or habitat associations vary in richness or abundance
as a function of urban and agriculture land uses. Birds were surveyed at a single point count site 100 m from the edge of
23 deciduous forest patches near Ottawa, Ontario. Land uses surrounding each patch were measured within increasingly large
circles from 200 to 5000 m radius around the bird survey site. Regression results suggest that effects of urban and agricultural
land uses on forest birds (1) are not uniformly positive or negative, (2) can occur at different spatial scales, and (3) differentially
affect certain groups of species. In general, agriculture appeared to affect species at a broad spatial scale (within 5 km),
while urban land use had an impact at both a narrower spatial scale (within 1.8 km) and at the broad scale. Neotropical and
short distance migrant birds seemed to be the most sensitive to land use intensification within the matrix. Limiting urban
land use within approximately 200–1800 m of forest patches would be beneficial for Neotropical migrant birds, which are species
of growing conservation concern in temperate North America. 相似文献
17.
Sarah K. Mincey Mikaela Schmitt-Harsh Richard Thurau 《Urban Forestry & Urban Greening》2013,12(2):191-199
Declining urban tree canopy cover in the United States underscores the importance of elucidating factors that influence the distribution of urban trees. This is particularly relevant as most urban trees are located on private property while their canopies maintain ecosystem services that constitute public goods. Thus, municipalities establish institutions in the form of canopy cover goals and various policies to incentivize private actions to meet those goals. However, urban land use, as governed by municipal zoning policies, plays a role in the abundance, distribution, and potential future location of urban trees independent of policies meant specifically to manage canopy. For instance, previous research finds that lands zoned for residential and park development have the highest canopy cover relative to other land uses. Yet, little research has explored whether this conclusion holds across scales of analysis and how it might influence our understanding of potential canopy cover and relative canopy cover. Thus, we ask, does the nature of the relationship between zoning and canopy cover change between aggregated and disaggregated zoning scales and how might this knowledge improve the sustainability of urban forest management? To answer this question, we classified high resolution National Agriculture Imagery Program (NAIP) images of Bloomington, Indiana land cover and compared existing, potential and relative canopy cover across aggregated and disaggregated zones. Results demonstrate an important exception to the oft-cited theory that residential lands have higher canopy cover, a conclusion that our data supports only at the scale of an aggregated interpretation of zoning. At a disaggregated scale, residential high density zones are significantly different than all other residential zones and more akin to commercial zones in terms of all canopy metrics. For urban forest managers and urban planners, this suggests the relevance of fine-scale variation in land-use policies and related canopy cover policies. 相似文献
18.
David M. Theobald 《Landscape Ecology》2010,25(7):999-1011
Quantifying landscape dynamics is a central goal of landscape ecology, and numerous metrics have been developed to measure
the influence of human activities on natural landscapes. Composite scores that characterize human modifications to landscapes
have gained widespread use. A parsimonious alternative is to estimate the proportion of a cover type (i.e. natural) within
a spatial neighborhood to characterize both compositional and structural aspects of natural landscapes. Here I extend this
approach into a multi-scale, integrated metric and apply it to national datasets on land cover, housing density, road existence,
and highway traffic volume to measure the dynamics of natural landscapes in the conterminous US. Roughly one-third of the
conterminous US (2.6 million km2) in 1992 was classified as human-dominated. By 2001 this expanded by 80,800 km2, and forecasted residential growth by 2030 will potentially lead to an additional loss of up to 92,200 km2. Wetland cover types were particularly affected. The natural landscapes metric developed here provides a simple, robust measure
of landscape dynamics that has a direct physical interpretation related to proportion of natural habitat affected at a location,
represents landscapes as a gradient of conditions rather predicated on patch/matrix definition, and measures the spatial context
of natural areas. 相似文献
19.
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
20.
Transitions in forest fragmentation: implications for restoration opportunities at regional scales 总被引：3，自引：0，他引：3
Wickham James D. Jones K. Bruce Riitters Kurt H. Wade Timothy G. O'Neill Robert V. 《Landscape Ecology》1999,14(2):137-145
Where the potential natural vegetation is continuous forest (e.g., eastern US), a region can be divided into smaller units (e.g., counties, watersheds), and a graph of the proportion of forest in the largest patch versus the proportion in anthropogenic cover can be used as an index of forest fragmentation. If forests are not fragmented beyond that converted to anthropogenic cover, there would be only one patch in the unit and its proportional size would equal 1 minus the percentage of anthropogenic cover. For a set of 130 watersheds in the mid-Atlantic region, there was a transition in forest fragmentation between 15 and 20% anthropogenic cover. The potential for mitigating fragmentation by connecting two or more disjunct forest patches was low when percent anthropogenic cover was low, highest at moderate proportions of anthropogenic cover, and again low as the proportion of anthropogenic cover increased toward 100%. This fragmentation index could be used to prioritize locations for restoration by targeting watersheds where there would be the greatest increase in the size of the largest forest patch. 相似文献