共查询到20条相似文献，搜索用时 31 毫秒
1.
The spatial extent and relative influence of landscape-level factors on wintering bird populations 总被引：5，自引：0，他引：5
Scott M. Pearson 《Landscape Ecology》1993,8(1):3-18
The influences of the landscape matrix (complex of habitats surrounding a study plot) and within-patch vegetation were studied in bird communities wintering in the piedmont of Georgia, USA. Variation at the landscape and within-patch levels was controlled to reduce the likelihood of confounding and spurious relationships. The landscape matrix within 500 m of each study plot was quantified from aerial photographs. Statistical models using landscape matrix and within-patch vegetation variables explained 73–84% of variation in bird abundance and diversity among sites with landscape matrix variables accounting for 30–90% of the variation. Variation in bird species richness and diversity was explained solely by landscape variables. Models for individual species such as Carolina Wrens (Thyrothorus ludovicianus) and Rufous-sided Towhees (Pipilo erythrophthalmus) had r2 > 0.80, with the landscape matrix variables accounting for the majority of this variation. However, other species like Northern Cardinals (Cardinalis cardinalis) and White-throated Sparrows (Zonotrichia albicollis) were most strongly influenced by within-plot vegetation. The landscape influence extended beyond habitats immediately adjacent to the study plots as indicated by significant variables describing variation in more distant habitat patches. These analyses illustrate a technique for comparing the strength of within-patch versus landscape influences and measuring the spatial extent of the landscape influence in fine-grained landscapes.Report No. 3955, Environmental Sciences Division, Oak Ridge National Laboratory.This research received funding from the Ecological Research Division, Office of Health and Environmental Research, U.S. Department of Energy, under Contract No. DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc. 相似文献
2.
A hierarchical neutral model for landscape analysis 总被引：11，自引：0，他引：11
Empirical studies have revealed scaled structure on a variety of landscapes. Understanding processes that produce these structures
requires neutral models with hierarchical structure. The present study presents a method for generating random maps possessing
a variety of hierarchical structures. The properties of these scaled landscapes are analyzed and compared to patterns on totally
random, unstructured landscapes. Hierar-chical structure permits percolation (i.e., continous habitat spanning the landscape) under a greater variety of conditions than found on totally random landscapes.
Habitat clusters on structured maps tend to have smaller perimeters. The clusters tend to be less clumped on sparsely occupied
landscapes and more clumped in densely occupied conditions. Hierarchical structure changes the expected spatial properties
of the landscape, indicating a strong need for this new generation of neutral models.
Research supported by the Ecological Research Division, Office to Health and Environmental Research, U.S. Department of Energy
under contract No. DE-AC05-840R21400 with Martin Marietta, Energy Systems, Inc. Environmental Sciences Publication No. 3813,
ORNL. 相似文献
3.
Sampling to characterize landscape pattern 总被引：8，自引：0，他引：8
Carolyn T. Hunsaker Robert V. O'Neill Barbara L. Jackson S. P. Timmins Daniel A. Levine Douglas J. Norton 《Landscape Ecology》1994,9(3):207-226
Current reseach suggests that metrics of landscape pattern may reflect ecological processes operating at different scales and may provide an appropriate indicator for monitoring regional ecological changes. This paper examines the extent to which a 1/16 areal subset of the landscape using equally spaced 40-km2 hexagons can characterize the spatial extent of land cover types and landscape pattern (number of types of edges, patch shape complexity, dominance, and contagion). For 200-m resolution data the hexagon subset gives a reasonable estimate of overall landscape cover but may not be adequate for monitoring uncommon land cover types such as wetlands. For agriculture and forest, their proportion of the full landscape units is only outside the 95% confidence interval of the hexagon estimate 4–8% of the time, whereas the proportions for wetland and barren areas are outside the confidence interval 11–34% of the time. The hexagon subset also does not appear to be adequate as the sole basis for monitoring landscape pattern. The values for contagion, dominance, and shape complexity calculated on the full landscape units are outside the 95% confidence interval of the hexagon estimate 27–76% of the time. Other statistical analyses include regressions between full landscape and hexagon subsets, mean differences and standard errors along with tests on number of positive and negative values, and percent relative error of hexagon estimates.Although the research described in this article has been funded in part by the U.S. Environmental Protection Agency, under Interagency Agreement DW89934921-01-0 with the U.S. Department of Energy under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc., it has not been subjected to Agency review. Therefore, it does not necessarily reflect the views of the Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.Research supported by the Landscape Characterization Project, Environmental Monitoring and Assessment Program, U.S. Environmental Protection Agency, under Interagency Agreement DW89934921-01-0 with the U.S. Department of Energy under Contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc., Environmental Sciences Division Publication No. 4090. 相似文献
4.
A hierarchical framework for the analysis of scale 总被引：18，自引：0，他引：18
Landscapes are complex ecological systems that operate over broad spatiotemporal scales. Hierarchy theory conceptualizes such systems as composed of relatively isolated levels, each operating at a distinct time and space scale. This paper explores some basic properties of scaled systems with a view toward taking advantage of the scaled structure in predicting system dynamics. Three basic properties are explored:(1) hierarchical structuring, (2) disequilibrium, and (3) metastability. These three properties lead to three conclusions about complex ecological systems. First, predictions about landscape dynamics can often be based on constraints that directly result from scaled structure. Biotic potential and environmental limits form a constraint envelope, analogous to a niche hypervolume, within which the landscape system must operate. Second, within the constraint envelope, thermodynamic and other limiting factors may produce attractors toward which individual landscapes will tend to move. Third, because of changes in biotic potential and environmental conditions, both the constraint envelope and the local attractors change through time. Changes in the constraint structure may involve critical thresholds that result in radical changes in the state of the system. An attempt is made to define measurements to predict whether a specific landscape is approaching a critical threshold.Research supported in part by the Ecological Research Division Office of Health and Environmental Research, US Department of Energy under contract No. DE-AC05-840R21400 to Martin Marietta Energy Systems Inc., and in part by the Ecosystem Studies Program, National Science Foundation, under Interagency Agreement No. NSF BSR 8315185 to the Department of Energy. Publication No. 3381, Environmental Sciences Division, Oak Ridge National Laboratory.Dr. Johnson's participation was supported in part by an appointment to the Postgraduate Research Training program under contract DE-AC05-76OR00033 between the U.S. Department of Energy and Oak Ridge Associated Universities, Oak Ridge, TN 37831. 相似文献
5.
Scale problems in reporting landscape pattern at the regional scale 总被引：30，自引：2，他引：28
R. V. O'Neill C. T. Hunsaker S. P. Timmins B. L. Jackson K. B. Jones K. H. Riitters J. D. Wickham 《Landscape Ecology》1996,11(3):169-180
Remotely sensed data for Southeastern United States (Standard Federal Region 4) are used to examine the scale problems involved
in reporting landscape pattern for a large, heterogeneous region. Frequency distributions of landscape indices illustrate
problems associated with the grain or resolution of the data. Grain should be 2 to 5 times smaller than the spatial features
of interest. The analyses also reveal that the indices are sensitive to the calculation scale,i.e., the unit area or extent over which the index is computed. This “sample area” must be 2 to 5 times larger than landscape
patches to avoid bias in calculating the indices.
Research sponsored by the Office of Research and Development, U.S. Environmental Protection Agency under IAG DW89934440-6
and DW89936104-01 with the U.S. Department of Energy under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems,
Inc. 相似文献
6.
Spatial and temporal analysis of landscape patterns 总被引：89，自引：0，他引：89
Monica G. Turner 《Landscape Ecology》1990,4(1):21-30
A variety of ecological questions now require the study of large regions and the understanding of spatial heterogeneity. Methods
for spatial-temporal analyses are becoming increasingly important for ecological studies. A grid cell based spatial analysis
program (SPAN) is described and results of landscape pattern analysis using SPAN are presentedd. Several ecological topics
in which geographic information systems (GIS) can play an important role (landscape pattern analysis, neutral models of pattern
and process, and extrapolation across spatial scales) are reviewed. To study the relationship between observed landscape patterns
and ecological processes, a neutral model approach is recommended. For example, the expected pattern (i.e., neutral model) of the spread of disturbance across a landscape can be generated and then tested using actual landscape data
that are stored in a GIS. Observed spatial or temporal patterns in ecological data may also be influenced by scale. Creating
a spatial data base frequently requires integrating data at different scales. Spatial is shown to influence landscape pattern
analyses, but extrapolation of data across spatial scales may be possible if the grain and extent of the data are specified.
The continued development and testing of new methods for spatial-temporal analysis will contribute to a general understanding
of landscape dynamics. 相似文献
7.
We hypothesized that landscape structure affects movement of individuals through the landscape, which affects the rate and pattern of disease transmission. Based on this hypothesis, we predicted a relationship between landscape structure and disease incidence in spatially structured populations. We tested this prediction for hantavirus incidence in deer mice (Penomysens moniculatus), using a novel index of habitat fragmentation for transect data. A series of four stepwise logistic regression analyses were conducted on serological and ecological data from 2837 mice from 101 sites across Canada. The significant variables, ranked in decreasing order of size of their effect on virus incidence were: human buildings, landscape composition (amount of deer mouse habitat in the 1-km radius landscape surrounding each site), landscape configuration (fragmentation of deer mouse habitat in the 1-km radius landscape surrounding each site), mean annual temperature, and seasonal variation. Our results suggest that epidemiological models should consider not only the demographic structure of the host population, but its spatial structure as well, as inferred from landscape structure. Landscape structure can have a greater effect on the pattern of distribution of a virus in its host population than other ecological variables such as climate and seasonal change. The usefulness of landscape data in epidemiological models depends on the use of the appropriate spatial scale, which can be determined empirically. Epidemiological models with a spatially structured host population can benefit from the explicit consideration of landscape structure. 相似文献
8.
Neutral models for the analysis of broad-scale landscape pattern 总被引：47，自引：19，他引：28
Robert H. Gardner Bruce T. Milne Monica G. Turnei Robert V. O'Neill 《Landscape Ecology》1987,1(1):19-28
The relationship between a landscape process and observed patterns can be rigorously tested only if the expected pattern in the absence of the process is known. We used methods derived from percolation theory to construct neutral landscape models,i.e., models lacking effects due to topography, contagion, disturbance history, and related ecological processes. This paper analyzes the patterns generated by these models, and compares the results with observed landscape patterns. The analysis shows that number, size, and shape of patches changes as a function of p, the fraction of the landscape occupied by the habitat type of interest, and m, the linear dimension of the map. The adaptation of percolation theory to finite scales provides a baseline for statistical comparison with landscape data. When USGS land use data (LUDA) maps are compared to random maps produced by percolation models, significant differences in the number, size distribution, and the area/perimeter (fractal dimension) indices of patches were found. These results make it possible to define the appropriate scales at which disturbance and landscape processes interact to affect landscape patterns. 相似文献
9.
Sensitivity of landscape pattern indices to input data characteristics on real landscapes: implications for their use in natural disturbance emulation 总被引：17，自引：6，他引：11
Baldwin David J. B. Weaver Kevin Schnekenburger Frank Perera Ajith H. 《Landscape Ecology》2004,19(3):255-271
Resource management strategies have begun to adopt natural landscape disturbance emulation as a means of minimizing risk to ecosystem integrity. Detailed understanding of the disturbance regime and the associated spatial landscape patterns are required to provide a natural baseline for comparison with the results of emulation strategies. Landscape pattern indices provide a useful tool to quantify spatial pattern for developing these strategies and evaluating their success. Despite an abundance of indices and tools to calculate these, practical knowledge of interpretation is rare. Quantifying changes in landscape pattern indices and the meaning of these changes is confounded by index sensitivity to input data characteristics such as spatial extent, spatial resolution, and thematic resolution. Sensitivity has been examined for simulated landscapes but rarely using real data for large areas as real landscapes are more difficult to manipulate systematically than simulated data. While simulated data offer a control, they do not provide an accurate portrayal of reality for practical applications. Our goal was to test the sensitivity of a suite of landscape pattern indices useful for disturbance emulation strategy development and evaluation to spatial extent, spatial resolution, and thematic resolution using current land cover data for a case study of the managed forest of Ontario, Canada. We also examined how sensitivity varies spatially across the study area. We used Landsat TM-based land cover data (> 45.5 million ha), controlling spatial extent (2,500 to 2,560,000 ha), spatial resolution (1 to 16 ha), and thematic resolution (2 to 26 classes). For each index we tested a hypothesis of insensitivity to changes in each input data characteristic using a combination of ANOVA and regression and compared our results with previous studies. Of the 18 indices studied, significant (p< 0.01) effects were found for 17 indices with changes in spatial extent, 13 indices with changes in spatial resolution and 18 indices with changes in thematic resolution. A significant (p < 0.01) linear trend accounted for the majority of the variance for all of the significant relationships identified. Most of the mean index responses were consistent with those interpreted from previous studies of simulated and real landscapes; however, sensitivity varied greatly among indices and over space. We suggest that variation in sensitivity to input data characteristics among indices and over space must be explicitly incorporated in the design of future natural disturbance emulation efforts.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
10.
11.
12.
Process-based forest landscape models are valuable tools for testing basic ecological theory and for projecting how forest
landscapes may respond to climate change and other environmental shifts. However, the ability of these models to accurately
predict environmentally-induced shifts in species distributions as well as changes in forest composition and structure is
often contingent on the phenomenological representation of individual-level processes accurately scaling-up to landscape-level
community dynamics. We use a spatially explicit landscape forest model (LandClim) to examine how three alternative formulations
of individual tree growth (logistic, Gompertz, and von Bertalanffy) influence model results. Interactions between growth models
and landscape characteristics (landscape heterogeneity and disturbance intensity) were tested to determine in what type of
landscape simulation results were most sensitive to growth model structure. We found that simulation results were robust to
growth function formulation when the results were assessed at a large spatial extent (landscape) and when coarse response
variables, such as total forest biomass, were examined. However, results diverged when more detailed response variables, such
as species composition within elevation bands, were considered. These differences were particularly prevalent in regions that
included environmental transition zones where forest composition is strongly driven by growth-dependent competition. We found
that neither landscape heterogeneity nor the intensity of landscape disturbances accentuated simulation sensitivity to growth
model formulation. Our results indicate that at the landscape extent, simulation results are robust, but the reliability of
model results at a finer resolution depends critically on accurate tree growth functions. 相似文献
13.
14.
The study of ecosystems suggests principles by which energy flows generate hierarchies in all systems. All ecosystems in the landscapes are associated with energy transformation and the convergence of transformed products toward higher hierarchical levels, the recycling of materials to dispersed backgrounds, and feedbacks to reinforce the supporting environment. A hierarchy can be seen as an organized pattern with many small units at one level contributing to fewer units at the next higher level. Due to spatial variability in the natural environment, different types and amounts of energy received on the earth are not homogeneous; this in turn generates a heterogeneous pattern on the landscape. Energy from life-support and production systems of a heterogeneous landscape is transformed and converged spatially toward consumption centers. All energy transformation can be arranged in a series. The concept of transformity is used in this paper to indicate the position of an energy flow in the series. A hierarchical system can help to explain how energy and matter can be produced and recycled through each level of energy transfer. Building on the brief reviews of the concept of hierarchy in the landscape and the theoretical development of the concept of an ecological energetic hierarchy, this paper proposes two principles of energetic hierarchy for landscape sustainability. First, the landscape must be arranged spatially according to its energy hierarchy. Evaluation of normalized energy flows (emergy) can help identify zones of different spatial hierarchies, which will help establish the strategies needed for the landscapes to be sustainable. Second, a sustainable landscape must comprise a hierarchy of self-organizing ecosystems that can enable the systems to maximize useful power at all levels of the energy hierarchy. 相似文献
15.
Disturbance is a well known modifier of landscapes. In marine systems hurricanes may not only remove or bury subtidal seagrasses but they may also impact the seed banks of these taxa. We ask whether seagrass landscape pattern and seed dispersal are influenced by physical disturbance in a subtropical deep water setting. We examined the spatial dynamics of an offshore landscape composed of the seagrass, Halophila decipiens in summer 1999 and again in 2000 after the passage of a hurricane. A towed video camera was used to collect data within a 1 km2 area and construct benthic maps of seagrass, macroalgae, hard bottom outcrops, and sediments from over 20,000 video frames. The appearance of sand and seagrass at a portion of the site in summer 2000 that was previously hard substrate verified sediment and seed movement. Although seeds released by this seagrass are deposited into sediments near parent plants, movement en masse of the seagrass seed reservoir appears to be an important component of dispersal. The generation of new landscape patches when disturbance is large and intense suggests that large-scale disturbance, resulting in the local redistribution of sediment and the seed bank, appears to mold the spatial signature of the resulting seagrass landscape in a MidShelf area. This impact of physical disturbance differs from that previously reported for factors influencing spatial arrangements of seagrass in shallow waters but has some features similar to those of large infrequent disturbances studied in terrestrial settings.
相似文献16.
17.
Forest harvest patterns and landscape disturbance processes 总被引：3，自引：0，他引：3
A physically-based model of the topographic influence on debris flow initiation and a rule-based model for wind damage were
used to assess the influence of forest clearcutting patterns (i.e., location, size, shape and distribution of cut units) on
the potential for landscape disturbance by these processes in Charley Creek watershed, Washington State, USA. Simulated clearcutting
patterns consisted of 7, 9 or 26 ha square or rectangular harvest units distributed in either an aggregated or dispersed pattern
under three stream-buffering scenarios. The slope-stability model predicted that potentially unstable ground is concentrated
along steep headwater streams and inner-gorge side-slopes. Areas susceptible to wind damage were determined from the combination
of slope, aspect, elevation, soil drainage and primary tree species. Among the variables examined here, the location of harvest
units constitutes the most important factor influencing the potential for shallow landsliding. In contrast, the location,
size, and shape of clear cuts and the interactions among these three factors significantly influenced the potential for wind
damage. Minimal correspondence between areas predicted to be potentially unstable and areas susceptible to wind damage implies
that harvest patterns designed to mitigate the potential for shallow landsliding may not necessarily reduce the potential
for wind damage. Our results demonstrate that: (1) the location of timber harvesting is more important than the geometry of
harvest activity in influencing shallow landsliding; (2) forest harvest patterns strongly influence the potential for disturbance
processes; and (3) a single cutting pattern will often fail to meet all landscape management goals.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
The scale at which plants utilize spatially distributed resources may be determined by their ability to locate sites that can sustain population growth. We developed a spatially-explicit model of the dispersal of annual plants in landscapes which were hierarchically structured, i.e., the spatial pattern of suitable sites was nested and scale-dependent. Results show that colonizing ability and extinction probability are most sensitive to the mean dispersal distance of the species. Dispersal out of the parental site, but within the immediate neighborhood, was the most efficient means for population expansion. When landscape patterns change with scale then dispersal distances determine the spatial scales of habitat utilization. As a complicating factor, the type of statistical distribution of dispersal distances also influences the colonizing ability. However, the importance of dispersal distance mean and distribution decreased as the number and connectance of suitable sites increased. The results suggest that landscape models which consider the interaction between scale dependent changes in landscape pattern and species dispersal and establishment characteristics are relevant to many issues in community ecology, invasion biology, and conservation biology. 相似文献
19.
Ecological processes such as plant–animal interactions have a critical role in shaping the structure and function of ecosystems,
but little is known of how such processes are modified by changes in landscape structure. We investigated the effect of landscape
change on mistletoe parasitism in fragmented agricultural environments by surveying mistletoes on eucalypt host trees in 24
landscapes, each 100 km2 in size, in south-eastern Australia. Landscapes were selected to represent a gradient in extent (from 60% to 2% cover) and
spatial pattern of remnant wooded vegetation. Mistletoes were surveyed at 15 sites in each landscape, stratified to sample
five types of wooded elements in proportion to their relative cover. The incidence per landscape of box mistletoe (Amyema miquelii), the most common species, was best explained by the extent of wooded cover (non-linear relationship) and mean annual rainfall.
Higher incidence occurred in landscapes with intermediate levels of cover (15–30%) and higher rainfall (>500 mm). Importantly,
a marked non-linear decline in the incidence of A. miquelii in low-cover landscapes implies a disproportionate loss of this species in remaining wooded vegetation, greater than that
attributable to decreasing forest cover. The most likely mechanism is the effect of landscape change on the mistletoebird
(Dicaeum hirundinaceum), the primary seed-dispersal vector for A. miquelii. Our results are consistent with observations that habitat fragmentation initially enhances mistletoe occurrence in agricultural
environments; but in this region, when wooded vegetation fell below a threshold of ~15% landscape cover, the incidence of
A. miquelii declined precipitously. Conservation management will benefit from greater understanding of the components of landscape structure
that most influence ecological processes, such as mistletoe parasitism and other plant–animal mutualisms, and the critical
stages in such relationships. This will facilitate action before critical thresholds are crossed and cascading effects extend
to other aspects of ecosystem function. 相似文献
20.
Fire is an important natural disturbance in the Mediterranean-climate coastal shrublands of southern California. However,
anthropogenic ignitions have increased fire frequency to the point that it threatens the persistence of some shrub species
and favors the expansion of exotic annual grasses. Because human settlement is a primary driver of increased ignitions, we
integrated a landscape model of disturbance and succession (LANDIS) with an urban growth model (UGM) to simulate the combined
effects of urban development and high fire frequency on the distribution of coastal shrublands. We tested whether urban development
would contribute to an expansion of the wildland-urban interface (WUI) and/or change in average fire return intervals and
compared the relative impacts of direct habitat loss and altered fire regimes on functional vegetation types. We also evaluated
two methods of integrating the simulation models. The development pattern predicted by the UGM was predominantly aggregated,
which minimized the expansion of the WUI and increase in fire frequency, suggesting that fire risk may be higher at intermediate
levels of urbanization due to the spatial arrangement of ignition sources and fuel. The comparison of model coupling methods
illustrated how cumulative effects of repeated fires may occur gradually as urban development expands across the landscape.
Coastal sage scrub species and resprouting chaparral were more susceptible to direct habitat loss, but increased fire frequency
was more of a concern to obligate seeder species that germinate from a persistent seed bank. Simulating different scenarios
of fire frequency and urban growth within one modeling framework can help managers locate areas of highest risk and determine
which vegetation types are most vulnerable to direct habitat loss, altered fire regimes, or both. 相似文献