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41.
探讨东莞市景观格局的破碎化程度可促进东莞市生态环境、社会经济的可持续发展。以景观生态学理论为指导,选用斑块数、斑块平均大小、破碎化指数、分维数、边界密度、斑块密度、景观多样性指数、景观优势度、景观破碎度指数等景观格局指数,分析东莞市1988~2006年土地镶嵌结构对景观结构的影响,探讨东莞市土地景观格局破碎化演变特征。研究表明：建设用地斑块不断入侵、同化耕地景观与自然景观斑块,研究区景观斑块数量不断增加,平均斑块面积迅速减小,表明东莞市景观破碎化程度不断加深;1995年以后研究区土地利用程度增速较慢,表明研究区在城市急剧扩张以后更注重城市的整体发展,景观破碎化的速度逐渐回归理性。 相似文献
42.
动物栖息地片断化效应以及集合种群研究现状 总被引：3，自引：0，他引：3
由于人为因素或环境的改变,导致了景观中面积较大的自然栖息地不断地被分割成片断而降低了生态功能,从而对动物产生了诸如异质效应、边缘效应、斑块格局效应、面积效应、隔离效应、干扰效应、遗传效应和种间竞争效应等影响。针对片断化结果造成的动物生境的破坏,使原来同一个动物群体之间有了空间隔离,但还存在一定联系,即分散在不同栖息片断的局部种群间个体迁移又使得“灭绝-重建”的过程得以实现的状况,论述了片断化效应、集合种群以及两者之间的微妙关系。可以认为：自然种群的空间分布形式是占据斑块状的栖息地,并且不断地转换栖息地,不断进行局部的灭绝和重建的过程。 相似文献
43.
To meet the need for research on the requirements for corridors for marshland birds, this study set out to quantify gap crossing
decisions made by reed warblers moving through the landscape. In three experiments, reed warblers were released into landscape
situations with different gap sizes and their movement towards reed patches fringing a watercourse were monitored. In all
experiments, most birds flew over the smallest gap towards the nearest reed patch. In the experiment with two gap sizes, the
probability of crossing a gap was a function of the ratio between distances to the reed patches. In the experiment with increasing
gap sizes, most birds crossed the smaller gaps frequently. Near the bigger gaps, birds did not cross the gaps; instead, they
only crossed the watercourse repeatedly. In the third experiment with more realistic landscape configurations, the birds preferred
nearby non-reed landscape elements to more distant reed patches. It is concluded that reed warblers were reluctant to cross
gaps wider than 50 m. The results suggest that the presence and size of gaps in reed patches affect reed warblers’ local gap-crossing
decisions: when given a choice, the birds prefer to cross the smallest gap. Furthermore, reed warblers may be directed towards
suitable marshlands by creating corridors of reed vegetation with gaps no wider than 50 m. The surrounding agricultural landscape
and the presence of trees and ditches could decrease the reluctance to cross gaps in corridors. 相似文献
44.
We conducted two studies on how highways affect their adjacent habitats by sampling carabid beetles (Coleoptera, Carabidae)
in patches of formerly continuous forest next to highways. (1) We sampled carabids at 14 highway intersections near Helsinki,
Finland. Each intersection (constructed 2–40 years ago) had two forested patches to study: a remnant (0.5–37.4 ha) and, isolated
from the remnant by an intersection lane, an islet (size 0.2–1.8 ha). Pitfall trap catch data (2301 carabids, 25 species)
showed that remnants hosted higher catches of three carabid species, and slightly higher species richness, than islets (patch-size
effect). Time since intersection construction had no apparent effect on carabids. Traffic volume along the intersection lane
determined the assemblage structure of carabids in dry patches, and the abundance of a forest carabid Calathus micropterus. Compared to moist patches, drier patches hosted lower catches of four generalist species; they also had different assemblages
of carabids (habitat-type effect). An interaction between patch size and habitat type for a forest generalist Pterostichus oblongopunctatus indicated that the patch-size effect was dependent on habitat type. (2) We examined possible dispersal of carabids among
forested patches that were separated by highway lanes in Drenthe, the Netherlands. We released 2696 marked individuals of
10 species, and recaptured 376 using dry pitfall traps. We found no evidence for inter-patch movement for nine forest species,
but 22 of 225 recaptured individuals of Poecilus versicolor, an eurytopic open-habitat species, had crossed the highway. Catches of seven forest species were also significantly lower
in the road verges, compared to the adjacent forests. These two studies suggest that (i) decreasing patch size negatively
affects forest-carabid catch and overall species richness, (ii) habitat type can affect the intensity of the patch-size effect,
(iii) carabid assemblages of forest fragments vary with traffic volume (which may be linked with urbanization), (iv) forest
carabids rarely cross highways, and (v) open habitats associated with road margins are dispersal barriers for forest carabids. 相似文献
45.
Raja ?Sengupta Beth ?MiddletonEmail author Chen ?Yan Michelle?Zuro Heidi?Hartman 《Landscape Ecology》2005,20(1):63-72
Field dispersal studies are seldom conducted at regional scales even though reliable information on mid-range dispersal distance is essential for models of colonization. The purpose of this study was to examine the potential distance of dispersal of Rhizophora mangle propagules by comparing deposition density with landscape characteristics of mangrove forests. Propagule density was estimated at various distances to mangrove sources (R. mangle) on beaches in southwestern Florida in both high-and low-energy environments, either facing open gulf waters vs. sheltered, respectively. Remote sensing and Geographic Information Systems were used to identify source forests and to determine their landscape characteristics (forest size and distance to deposition area) for the regression analyses. Our results indicated that increasing density of propagules stranded on beaches was related negatively to the distance of the deposition sites from the nearest stands of R. mangle and that deposition was greatly diminished 2 km or more from the source. Measures of fragmentation such as the area of the R. mangle forests were related to propagule deposition but only in low-energy environments. Our results suggest that geographic models involving the colonization of coastal mangrove systems should include dispersal dynamics at mid-range scales, i.e., for our purposes here, beyond the local scale of the forest and up to 5 km distant. Studies of mangrove propagule deposition at various spatial scales are key to understanding regeneration limitations in natural gaps and restoration areas. Therefore, our study of mid-range propagule dispersal has broad application to plant ecology, restoration, and modeling. 相似文献
46.
Individual movement is a key process affecting the distribution of animals in heterogeneous landscapes. For specialist species in patchy habitat, a central issue is how dispersal distances are related to landscape structure. We compared dispersal distances for cactus bugs (Chelinidea vittiger) on two naturally fragmented landscapes (≤ 4% suitable habitat) with different matrix structures (i.e., vegetation height of nonsuitable habitat between suitable patches). Using mark-release-recapture studies, we determined that most transfers between cactus patches occurred during the mating season. Dispersal distances were reduced by > 50% on the landscape that had reduced structural connectivity due to relatively high matrix structure and low patch density. An experiment with detailed movement pathways demonstrated that greater matrix structure decreased mean step lengths, reduced directionality, and thus decreased net displacement by > 60%. However, habitat edges between two matrix elements that differed substantially in resistance to movement were completely permeable. Therefore, the difference in distributions of dispersal distances between the two landscapes mainly reflected the average resistance of matrix habitat and not the level of matrix heterogeneity per se. Our study highlights the merits of combining estimates of dispersal distances with insights on mechanisms from detailed movement pathways, and emphasizes the difficulty of treating dispersal distances of species as fixed traits independent of landscape structure. 相似文献
47.
Michael J. Mortimer Jesse J. RichardsonJr. Jeffrey S. Huff Harry L. HaneyJr. 《Small-Scale Forestry》2007,6(1):35-47
Internationally, conservation easements are increasingly popular land management tools for private landowners, government
agencies and non-governmental organizations seeking to preserve forests and other natural settings. This paper reports a study
of the design and use of conservation easements by organizations and public agencies in the USA. More than 355 conservation
organizations and 16 state agencies holding at least 3,598 forestland easements were identified. Demonstrated shortfalls in
baseline forest inventories, record keeping, and professionally-developed management plans were evident on working forest
easements. Failure to address these shortcomings runs the risk of jeopardizing the legitimacy of the easement approach even
where favorable legal and tax conditions exist. Management restrictions varied broadly, with a minority of respondents prohibiting
such techniques as clearcutting and salvage logging. Concerns for the use of chemicals, best management practices, and streamside
management zones were commonly reflected in easement language, whereas logging road design and the cultivation of old-growth
conditions remain largely undeveloped. Implications from the US experience, where easements are relatively well-developed,
highlights the need for professional forestry advice—particularly for non-industrial or small-scale forest owners—in both
easement development and implementation, the need for careful planning, and the need to carefully consider the respective
goals of the forest landowners in crafting the easement documents. In the cases of developing nations, consideration of the
differing needs of landowners may require increased flexibility in management documents. 相似文献
48.
Testing the myriad predictions associated with the community, demographic and genetic impacts of habitat fragmentation remains a high conservation priority. Many bryophyte taxa are ideal model systems for experimentally testing such metapopulation-based and population genetic predictions due to their relatively fast colonisation-extinction rates, high substrate specificity, dominant haploid condition, and diminutive size. Herein, we review the community, demographic and population genetic impacts of habitat fragmentation on bryophytes, highlight the present knowledge gaps, and offer ideas on how experimental studies utilizing bryophytes may be used to address the broader conservation implications associated with fragmented ecosystems. Previous research suggests that dispersal limitation best explains observed patterns of abundance and distribution of bryophytes in some fragmented habitats. However, edge effects influence bryophyte community structure of border habitats especially where abrupt differences in micro-climatic conditions between the matrix and the forest remnant exist, or where the species pool contains members with inherently restricted ecological amplitudes. Existing studies do not agree on the relationship between basic attributes of bryophyte community structure (i.e., species richness and local density), and habitat area and degree of spatial-isolation. Demographic studies are a critical step in structuring conservation strategies, however surprisingly little empirical information exists as to the impacts of habitat fragmentation on plant population dynamics. We propose that bryophytes offer great potential for testing predictions with respect to plant population persistence in spatially-structured landscapes. 相似文献
49.
Lizard distribution patterns in the Tumut fragmentation “Natural Experiment” in south-eastern Australia 总被引：1，自引：0，他引：1
Lizard distribution patterns were examined in a fragmented plantation landscape in south-eastern Australia. Regression modelling was used to relate ecological variables to (1) lizard species richness, (2) lizard species composition, and (3) the presence or abundance of selected lizard species. Ecological variables covered four broad domains that affect animals: climate, space, shelter and food availability.Lizard species richness was highest at mid-elevation sites, and at locations with a large amount of native forest within 1000 m. A major change in lizard species composition was associated with elevation, the proportion of native forest within 1000 m of a site, and the abundance of springtails. The change in species composition coincided with a range of individualistic responses to environmental conditions by different lizard species. For example, with respect to shelter availability, old logs were related to the garden skink Lampropholis guichenoti, shrubs were related to the delicate skink L. delicata, and rocks were related to the red-throated skink Bassiana platynota. The garden skink was most abundant at low elevations, the delicate skink was most likely to occur at intermediate elevations, and the mountain log skink Pseudemoia entrecasteauxii was most likely to occur at high elevations. The garden skink was most abundant in areas surrounded by little native forest, whereas Maccoy’s skink Nannoscincus maccoyi and Coventry’s skink Niveoscincus coventryi were more abundant or likely to occur in areas whose context was dominated by native forest.Because animal species may respond individualistically to gradients of climate, space, shelter and food availability, continuum theory (as developed for plant ecology) may be a useful complement to fragmentation theory to explain distribution patterns. To maintain lizard diversity in the study area, it will be important to maintain maximum habitat heterogeneity at the landscape and microhabitat scales. For species otherwise threatened by plantation development, large, fairly undisturbed areas of eucalypt forest will be particularly important. 相似文献
50.
In February 1993 samples of litter from three different litter layers (upper, intermediate, and lower) were taken from a beechwood growing on basalt soil. Using the substrate-induced respiration method, we investigated the influence of fragmentation and glucose concentration on the maximum initial respiratory response. Glucose concentrations ranged between 0 and 160000 g g-1 dry weight. The initial respiratory response reached a maximum at 80000 g glucose g-1 dry weight. The addition of higher concentrations of glucose resulted in negligible changes in respiration. Litter materials of four different size classes (intact leaves, fragmented <100 mm2, <25 mm2, and <5 mm2) were amended with 80000 g glucose g-1 dry weight. Substrate-induced respiration was at a maximum in the size class <25 mm2. The addition of glucose to intact litter did not result in microbial growth. It is concluded that C is not the primary limiting element for the microflora in litter layers of the study site. Fragmentation of beech litter enabled the microorganisms to grow. Presumably, nutrients that limited microbial growth in intact litter were mobilized by the fragmentation procedure and enabled microorganisms to grow in fragmented litter materials. 相似文献