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1.
Cabot's tragopan Tragopan caboti is an endemic and endangered pheasant of the lower montane forests of southeastern China. The typical habitats of the tragopan have been seriously fragmented because of forest management for timber production and farmland reclamation in recent years. The effects of the fragment size and isolation on the distribution of the cabot's tragopan were studied in Wuyanling Natural Reserve. Thirty one habitat fragments (2.5-48.5 ha) surrounded by non-habitat sapling coniferous forests, in an intensively managed forested landscape, were surveyed over four seasons for the occurrence of cabot's tragopan. Five of the 31 fragments were occupied in all four seasons and nine were not occupied. Both landscape and habitat factors affected the occurrence of cabot's tragopan, with landscape factors having the greatest effect. Large and less isolated habitat fragments containing a larger amount of the tree Daphniphyllum macropodum were occupied significantly more often than small, isolated fragments. The appearance of cabot's tragopan in the habitat fragments was best explained by the size of the fragments, the distance to the nearest suitable habitat and the amount of macropdous daphniphyllum trees. Our results could be used to improve the management of the forests where Cabot's tragopan occurs in southeastern China. 相似文献
2.
在达尔文(1859)看来,新物种只有通过竞争或者自然选择的方式淘汰原有物种才能进入由其他物种占据的生境并成功定居下来。然而,新物种进入生境并成功定居还有另外一个途径,那就是由于超级居群能在全球尺度上改变整个地球环境,从而能在原有环境中创造出一些全新的微环境来,正是这些全新的微环境使新物种避开了和原有定居者的剧烈竞争,很容易地进入了一直由其他物种占据的生境中并成功地定居下来。换句话说,超级居群导致了全球环境的分化,导致了全球尺度上的生境多样性。同时,超级居群通过环境的异质化为新物种准备好了很多全新的微环境,新物种在全新的微环境中的成功定居实现了新物种和原有定居者的长期共存。而这种长期共存导致了整个生物圈的生物多样性的增加。超级居群是地球上很多新环境的创造者,是生境多样性和生物多样性之间的桥梁,据此就能很容易地解释新物种为什么不时能和原有定居者共存甚至依赖于原有定居者,从而导致二者间剧烈竞争缺失的现象。 相似文献
3.
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
4.
Effects of land ownership and landscape-level factors on rare-species richness in natural areas of southern Ontario,Canada 总被引:5,自引:0,他引:5
Lovett-Doust J. Biernacki M. Page R. Chan M. Natgunarajah R. Timis G. 《Landscape Ecology》2003,18(6):621-633
Surprisingly few studies have considered the extent to which the nature of the ownership of land is associated with differences
in biodiversity. We analysed ownership and other landscape-level effects on rare-species richness for both globally- and regionally-rare
biota (including birds, herpetofauna, butterflies, mammals, and plants) in 289 designated natural areas (NAs) in southern
Ontario, Canada. Information about each NA −including area, number of plant communities, ownership status and details of species
diversity were collected from published sources. Length of perimeter of NA, relative isolation, and an estimate of fragmentation
were measured using image analysis and GIS techniques. NAs were in general relatively small, with mean area of 158 ha (median
85 ha, range from 0.9 to 1278 ha) for private NAs; public NAs had mean area of 132 ha (median 16 ha, range from 0.1 to 1481
ha). Mean number of plant communities was 4.6 (median 4, range 1- 13) at private NAs and 3.8 (median 3, range 1-16) at public
NAs. Our results show that, of several landscape-level factors, area had the greatest effects on rare-species richness and
other biotic indices. Effects of area were followed by effects of plant community diversity, however this was itself significantly
affected by area and the extent of perimeter of the NA. Both these factors were followed by effects of ownership of the NA
and by effects of isolation of the NA (represented by minimum distance to nearest NA and by number of NAs in 10 km radius).
Other landscape- level factors did not appear to have overall significant effects. Variation in area accounted for 0.1% to
29% of variation in number of rare species, with lower values for globally-rare, than for regionally-rare taxa. For all biotic
groups, public ownership of NAs was associated with significantly greater rare-species richness compared to private ownership,
even after other factors such as area were controlled. For all globally-rare biota except butterflies, area of NA had greater
effects on rare-species richness than did ownership. Richness of regionally- rare birds was more affected by plant community
diversity than by area of NA. Number of recorded plant communities accounted from 2.1% of variation in number of globally-rare
plant species to as high as 31% of variation in regionally-rare butterflies. The diversity of plant communities was itself
influenced by total site area (accounting for 45% of variation), extent of elongation of the NA, and both external- and interior-
edge perimeters. Public NAs had greatest numbers of rare biota and so should be a significant focus for conservation programs.
Smaller, privately-owned patches of natural area dominate (by number and area) in this densely populated region and their
significance should not be overlooked.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
In this paper we show how the spatialconfiguration of habitat quality affects the spatial spread of apopulation in a heterogeneous environment. Our main result is thatfor species with limited dispersal ability and a landscape withisolated habitats, stepping stone patches of habitat greatlyincrease the ability of species to disperse. Our results showthat increasing reproductive rate first enables and thenaccelerates spatial spread, whereas increasing the connectivity has aremarkable effect only in case of low reproductive rates. Theimportance of landscape structure varied according to thedemographic characteristics of the population. To show this wepresent a spatially explicit habitat model taking into accountpopulation dynamics and habitat connectivity. The population dynamicsare based on a matrix projection model and are calculated on eachcell of a regular lattice. The parameters of the Leslie matrix dependon habitat suitability as well as density. Dispersal between adjacentcells takes place either unrestricted or with higher probability inthe direction of a higher habitat quality (restricted dispersal).Connectivity is maintained by corridors and stepping stones ofoptimal habitat quality in our fragmented model landscape containinga mosaic of different habitat suitabilities. The cellular automatonmodel serves as a basis for investigating different combinations ofparameter values and spatial arrangements of cells with high and lowquality.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
6.
The ability to predict species occurrences quickly is often crucial for managers and conservation biologists with limited
time and funds. We used measured associations with landscape patterns to build accurate predictive habitat models that were
quickly and easily applied (i.e., required no additional data collection in the field to make predictions). We used classification
trees (a nonparametric alternative to discriminant function analysis, logistic regression, and other generalized linear models)
to model nesting habitat of red-naped sapsuckers (Sphyrapicus nuchalis), northern flickers (Colaptes auratus),tree swallows (Tachycineta bicolor), and mountain chickadees (Parus gambeli) in the Uinta Mountains of northeastern Utah, USA. We then tested the predictive capability of the models with independent
data collected in the field the following year. The models built for the northern flicker, red-naped sapsucker, and tree swallow
were relatively accurate (84%, 80%, and 75% nests correctly classified,respectively)compared to the models for the mountain
chickadee (50% nests correctly classified). All four models were more selective than a null model that predicted habitat based
solely on a gross association with aspen forests. We conclude that associations with landscape patterns can be used to build
relatively accurate, easy to use, predictive models for some species. Our results stress, however, that both selecting the
proper scale at which to assess landscape associations and empirically testing the models derived from those associations
are crucial for building useful predictive models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Johnson Chris J. Boyce Mark S. Mulders Robert Gunn Anne Gau Rob J. Cluff H. Dean Case Ray L. 《Landscape Ecology》2004,19(8):869-882
Multiscale analyses are widely employed for wildlife-habitat studies. In most cases, however, each scale is considered discrete and little emphasis is placed on incorporating or measuring the responses of wildlife to resources across multiple scales. We modeled the responses of three Arctic wildlife species to vegetative resources distributed at two spatial scales: patches and collections of patches aggregated across a regional area. We defined a patch as a single or homogeneous collection of pixels representing 1 of 10 unique vegetation types. We employed a spatial pattern technique, three-term local quadrat variance, to quantify the distribution of patches at a larger regional scale. We used the distance at which the variance for each of 10 vegetation types peaked to define a moving window for calculating the density of patches. When measures of vegetation patch and density were applied to resource selection functions, the most parsimonious models for wolves and grizzly bears included covariates recorded at both scales. Seasonal resource selection by caribou was best described using a model consisting of only regional scale covariates. Our results suggest that for some species and environments simple patch-scale models may not capture the full range of spatial variation in resources to which wildlife may respond. For mobile animals that range across heterogeneous areas we recommend selection models that integrate resources occurring at a number of spatial scales. Patch density is a simple technique for representing such higher-order spatial patterns. 相似文献
8.
Inja Yeon Mi Young SongMyoung Ho Sohn Hak Jin HwangYang Jae Im Do Hoon KimHee Won Park Chang Ik Zhang 《Fisheries Research》2011,112(3):179-188
Landings in the blue crab, Portunus trituberculatus, fishery in Korean waters of the Yellow Sea have declined substantially from 11,000 t in the 1980s to 2,300 t in 2004. Blue crab habitat quality in the Yellow Sea has been degraded by anthropogenic activities including sand mining, land reclamation, and coastal pollution. Various traditional management measures have been implemented, including closed seasons during spawning and size limits, but these measures alone have been unsuccessful to conserve blue crab stocks. Consequently, a total allowable catch and a stock-rebuilding program using an ecosystem-based management approach were implemented in 2003 and 2006, respectively to rebuild blue crab stocks and restore habitats. This program involved assessment of both blue crab stock status and trammel-net fishery impacts at an ecosystem-level using an ecosystem-based fisheries assessment method (
[Zhang et al., 2009] and [Zhang et al., 2010]), which considered fishery data from catch and effort time-series, crab population biology, and ecosystem characteristics, including habitats and environmental conditions. Recent (2008) management status indices have shown significant positive change compared to conditions in 2000 with respect to sustainability of the stock and fishery and with regards to biodiversity and ecosystem habitat quality. 相似文献
9.
The conversion of forests and farmlands to human settlements has negative impacts on many native species, but also provides
resources that some species are able to exploit. American Crows (Corvus brachyrhynchos), one such exploiter, create concern due to their impact as nest predators, disease hosts, and cultural harbingers of evil.
We used various measures of crow abundance and resource use to determine crows’ response to features of anthropogenic landscapes
in the Puget Sound region of the United States. We examined land cover and land use composition at three spatial scales: study
sites (up to 208 ha), crow home ranges within sites (18.1 ha), and local land cover (400 m2). At the study site and within-site scales crow abundance was strongly correlated with land cover providing anthropogenic
resources. In particular, crows were associated with the amount of ‘maintained forest’ cover, and were more likely to use
grass and shrub cover than forest or bare soil cover. Although crows did not show a generalized response to an edge variable,
they exhibited greater use of patchy habitat created by human settlements than of native forests. Radio-tagged territorial
adults used resources within their home ranges relatively evenly, suggesting resource selection had occurred at a larger spatial
scale. The land conversion pattern of new suburban and exurban settlements creates the mix of impervious surfaces and maintained
vegetation that crows use, and in our study area crow populations are expected to continue to increase.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Maintaining connectivity among local populations in a fragmented landscape is crucial for the survival of many species. For
isolated habitat patches, stochastic fluctuations and reduced gene flow can lead to high risk of extinction. The connectivity
of the landscape is especially crucial for the carabid species living in the fragmented forests of the Bereg plain (NE Hungary
and W Ukraine) because a highway will be constructed through the plain. Our purpose is to (1) evaluate the impacts of three
possible highway tracks, (2) suggest a solution that is realistic with less impact on connectivity than other plans and (3)
discuss how to decrease the disadvantageous effects of each track. Our results, based on a network analysis of landscape graph
of patches and ecological corridors, indicate that the intended highway could have deleterious consequences on forest-living
carabids. Relatively simple actions, like the establishment of stepping stones, could compensate for the loss of habitat connectivity
and promote the survival of carabids, or minor modifications in one possible track could diminish its adverse effects. While
many other studies would be needed for a comprehensive assessment of the biotic impact of the highway, we provide an example
on the usefulness of network analysis for land use management.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献