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21.
Change in spatial characteristics of forest openings in the Klamath Mountains of northwestern California,USA 总被引:4,自引:0,他引:4
Carl N. Skinner 《Landscape Ecology》1995,10(4):219-228
Change in the spatial characteristics of forest openings was investigated in three forested watersheds in north-western Siskiyou County, California totalling approximately 24,600 hectares. Watersheds with minimal human disturbance were chosen for study. However, fire suppression has been pervasive throughout. Characteristics of forest openings (area, perimeter, distance between neighboring openings) were measured on aerial photographs taken 41 years apart. An index of regional form was determined for the landscape. Shape complexity for each opening was calculated using two indices based upon fractals. Significant differences were found using the Kolmogorov-Smirnov two-sample test between the perimeters, areas, distance from sample point to nearest opening, and distance between neighboring openings. The perimeters and areas became smaller, and the distances from the sample point to the nearest opening and between neighboring openings became greater over the 41 years between aerial photo sets. The estimated area occupied by openings decreased from 25.8 % to 15.6 % of the study area. No significant difference was found in the shape of the openings except as the shape indices were influenced by changes in size of the openings.This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. 相似文献
22.
Landscape-ecological mapping of the Netherlands 总被引:1,自引:0,他引:1
Kees J. Canters Cees P. den Herder Aart A. de Veer Paul W. M. Veelenturf Rein W. de Waal 《Landscape Ecology》1991,5(3):145-162
The Landscape-ecological Mapping of the Netherlands project (LMN project) started in 1983 with the aim of establishing a landscape-ecological database for use in developing and evaluating national land-use plans. The project, working with grid cells of 1 km2, has four working objectives: a) development of mapping potential for basic landscape-ecological data, b) assessment of susceptibility to interventions, c) evaluation of significance for nature conservation and d) production of vulnerability maps, as a combination of susceptibility and significance. In addition to information on soil, groundwater, ecotopes, flora and fauna, the database also incorporates information on physiographical features and entire landscapes. The resulting database is a geographic information system (GIS). This article describes the second phase of the project (1985–1989), covering the Randstad area, and focusses on the methods and the applications potential of the database. 相似文献
23.
The relationship between fine-scale spatial patterns of forage abundance and the feeding patterns of large ungulates is not well known. We compared these patterns for areas grazed in winter by elk and bison in a sagebrush-grassland landscape in northern Yellowstone National Park. At a fine scale, the spatial distribution of mapped feeding stations in 30 m × 30 m sites was found to be random where there were no large patches devoid of vegetation. In areas similar to the mapped sites, the underlying spatial distribution pattern of biomass was also determined to be random. At a broad scale, forage biomass differed among communities across the northern range but forage quality did not. These results suggest that ungulates are feeding randomly within forage patches (fine scale) but may select feeding sites based upon forage abundance at broader, landscape scales. Contrary to what has been suggested in other systems, ungulates were not overmatching at finer scales. 相似文献
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26.
桂花在园林景观设计中的应用 总被引:2,自引:0,他引:2
对桂花植物造景的配置原则、园林应用进行概述和研究,提出因地制宜、层次错落、季相变化、背景烘托、民族传统的配置原则,并就园林应用上桂花的独立造景,桂花与其他植物的配置,桂花与山石、建筑物的配置作了分述。 相似文献
27.
The influence of sampling scheme and interpolation method on the power to detect spatial effects of forest birds in Ontario (Canada) 总被引:1,自引:0,他引:1
Spatial ecology is becoming an increasingly important component of resource management, and the general monitoring of how
human activities affect the distribution and abundance of wildlife. Yet most work on the reliability of sampling strategies
is based on a non-spatial analysis of variance paradigm, and little work has been done assessing the power of alternative
spatial methods for creating reliable maps of animal abundance. Such a map forms a critical response variable for multiple
scale studies relating landscape structure to biotic function. The power to reconstruct patterns of distribution and abundance
is influenced by sample placement strategy and density, the nature of spatial auto-correlation among points, and by the technique
used to extrapolate points into an animal abundance map. Faced with uncertainty concerning the influence of these factors,
we chose to first synthesize a model reference system of known properties and then evaluate the relative performance of alternative
sampling and mapping procedures using it. We used published habitat associations of tree nesting boreal neo-tropical birds,
a classified habitat map from the Manitou Lakes area of northwestern Ontario, and point count means and variances determined
from field studies in boreal Canada to create 4 simulated models of avian abundance to function as reference maps. Four point
sampling strategies were evaluated by 4 spatial mapping methods. We found mixed-cluster sampling to be an effective point
sampling strategy, particularly when high habitat fragmentation was avoided by restricting samples to habitat patches >10
ha in size. We also found that of the 4 mapping methods, only stratified ordinary point kriging (OPK) was able to generate
maps that reproduced an embedded landscape-scale spatial effect that reduced nesting bird abundance in areas of higher forest
age-class fragmentation. Global OPK was effective only for detecting broader, regional-scale differences.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
28.
Verbeylen Goedele De Bruyn Luc Adriaensen Frank Matthysen Erik 《Landscape Ecology》2003,18(8):791-805
In determining isolation effects in fragmented populations, the landscape matrix is not often considered. Usually simple distance
measures are used to quantify degree of isolation. We tested the effect of the matrix on the presence of red squirrels in
354 wooded patches in the Brussels Region, by comparing several isolation measures. These were 1) distance to the nearest
source patch, 2) the Hanski-measure (a combination of distance to and size of all possible sources), 3) effective distances
calculated from different least cost models using the ArcView grid extension ‘Cost Distance’ (a combination of distance and
resistance of the landscape, with different resistances for different landscape types) and 4) some combinations of the Hanski-measure
and the effective distances. Size and quality of the target patches were always included in the tests of the predictive power
of different isolation measures on squirrel presence/absence. All variables examined (patch size, quality and isolation) significantly
influenced squirrel presence. Models using the effective distances gave the best results. Models including the Hanski-measure
improved significantly when Euclidean distance was replaced by effective distance, showing that parameterisation of matrix
resistance added significant additional explanatory power when modelling squirrel presence.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
29.
The historical range of variability (HRV) has been suggested as a coarse filter approach to maintain ecosystem sustainability
and resiliency. The historical range of variability in forest age structure for the central eastern Cascade Range in Washington
State, USA was developed from historical fire return intervals and the manner in which fire acted as both cyclic and stochastic
processes. The proportions of seven forest structural stages calculated through these processes were applied to the area of
each forest series within the central eastern Cascades landscape. Early successional forest stages were more common in high
elevation forest than low elevation forest. The historical proportion of old growth and late successional forest varied from
38 to 63 percent of the forested landscape. These process-based estimates are consistent with those developed from forest
structural information. HRV is a valuable planning tool for ecosystem conservation purposes, but must be applied to real landscapes
with consideration of both temporal and spatial scale.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
30.
Mouillot Florent Ratte Jean-Pierre Joffre Richard Moreno Jose Manuel Rambal Serge 《Landscape Ecology》2003,18(7):665-674
Based on recent needs to accurately understand fire regimes and post-fire vegetation resilience at a supra-level for carbon cycle studies, this article focusses on the coupled history of fire and vegetation pattern for 40 years on a fire-prone area in central Corsica (France). This area has been submitted since the beginning of the 20th century to land abandonment and the remaining land management has been largely controlled by frequent fires. Our objectives were to rebuild vegetation and fire maps in order to determine the factors which have driven the spatial and temporal distribution of fires on the area, what were the feed backs on the vegetation dynamics, and the long-term consequences of this inter-relationship. The results show a stable but high frequency of small fires, coupled with forest expansion over the study period. The results particularly illustrate the spatial distribution of fires according to topography and vegetation, leading to a strong contrast between areas never burnt and areas which have been burnt up to 7 times. Fires, when occuring, affect on average 9 to 12% of the S, SE and SW facing slopes (compared to only 2 to 5% for the N facing slopes), spread recurrently over ridge tops, affect all the vegetation types but reburn preferentially shrublands and grasslands. As these fire-proning parameters have also been shown to decrease the regeneration capacity of forests, this study highlights the needs in spatial studies (both in terms of fire spread and vegetation dynamic) to accurately apprehend vegetation dynamic and functionning in fire-prone areas.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献