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1.
Effects of area and isolation of woodland patches on herbaceous plant species richness across Great Britain 总被引：5，自引：2，他引：5
Petit Sandrine Griffiths Leila Smart Simon S. Smith Geoff M. Stuart Rick C. Wright Simon M. 《Landscape Ecology》2004,19(5):463-471
Richness of Ancient Woodland Indicator plant species was analysed in 308 woodland patches that were surveyed during the Countryside Survey of Great Britain carried out in 1998. The Countryside Survey recorded vegetation plots and landscape structure in 569 stratified 1 km sample squares and developed a remotely-sensed land cover map of the UK. Using these datasets, we tested the hypothesis that Ancient Woodland Indicator species richness in woodland fragments was limited by patch area, shape and spatial isolation and that woodland patches located in the lowland region of Great Britain would respond differently than those in the upland region. The variation in Ancient Woodland Indicator species richness in the British lowlands (n = 218) was mainly explained by patch area and two measures of connectivity, the length of hedgerows and lines of trees in the 1 km square and the area of woodland within 500 m of the vegetation plot. By contrast, variation in Ancient Woodland Indicator species richness in the British uplands (n = 90) was related to Ellenberg scores of the vegetation communities sampled – a surrogate for habitat quality – and no significant effect of spatial structure was detected. It therefore appears that the degree of fragmentation of woodland in the British lowlands limits the distribution of Ancient Woodland Indicator species, while in the uplands, failed colonisation is a matter of habitat quality rather than a result of landscape structure.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
2.
Robert J. Rolls 《Biological conservation》2011,(1):339-349
Water resource development in coastal river catchments contributes to poor fish assemblage health due to the effects of barriers to migration and altered flow regimes. Impacts of migration barriers on fish assemblages depend primarily on the location of each barrier within the river network and migration needs of regional fish fauna. This study examined how temporal and spatial patterns in the distribution and composition of fish assemblages was associated with varying estuarine connectivity and migration barriers in higher altitude reaches in the eastern Hunter River catchment, temperate Australia. Species richness and abundances of diadromous species were expected to be greater in a tributary catchment with unrestricted connectivity to the Hunter River estuary when compared to a neighbouring tributary catchment with restricted connectivity. Six diadromous species were sampled only, or in greater abundances, in the unrestricted tributary when compared to the restricted tributary. As a consequence, assemblage composition in the restricted tributary was dominated by non-diadromous species. Greater abundances of the amphidromous Cox’s gudgeon (Gobiomorphus coxii) were sampled in the unrestricted tributary following their estuarine-freshwater upstream juvenile migration period when compared to the restricted tributary. Differences in the accumulations of migratory species immediately downstream of upland barriers between the two levels of estuary connectivity indicate that migration barriers in lowland reaches have significant effects throughout the entire catchment. Results of this study indicate that the location of each barrier to migration within river networks has varying consequences for catchment-scale connectivity loss and assessing the impacts of multiple barriers. Determining the effects and most appropriate management of migration barriers requires that all obstructions within a river network are recognised, as multiple barriers can have cumulative and interacting consequences for freshwater fish fauna, especially diadromous species. 相似文献
3.
Conservation actions frequently need to be scheduled because both funding and implementation capacity are limited. Two approaches to scheduling are possible. Maximizing gain (MaxGain) which attempts to maximize representation with protected areas, or minimizing loss (MinLoss) which attempts to minimize total loss both inside and outside protected areas. Conservation planners also choose between setting priorities based solely on biodiversity pattern and considering surrogates for biodiversity processes such as connectivity. We address both biodiversity processes and habitat loss in a scheduling framework by comparing four different prioritization strategies defined by MaxGain and MinLoss applied to biodiversity patterns and processes to solve the dynamic area selection problem with variable area cost. We compared each strategy by estimating predicted species’ occurrences within a landscape after 20 years of incremental reservation and loss of habitat. By incorporating species-specific responses to fragmentation, we found that you could improve the performance of conservation strategies. MinLoss was the best approach for conserving both biodiversity pattern and process. However, due to the spatial autocorrelation of habitat loss, reserves selected with this approach tended to become more isolated through time; losing up to 40% of occurrences of edge-sensitive species. Additionally, because of the positive correlation between threats and land cost, reserve networks designed with this approach contained smaller and fewer reserves compared with networks designed with a MaxGain approach. We suggest a possible way to account for the negative effect of fragmentation by considering both local and neighbourhood vulnerability to habitat loss. 相似文献
4.
Spatial and temporal landscape patterns have long been recognized to influence biological processes, but these processes often
operate at scales that are difficult to study by conventional means. Inferences from genetic markers can overcome some of
these limitations. We used a landscape genetics approach to test hypotheses concerning landscape processes influencing the
demography of Lahontan cutthroat trout in a complex stream network in the Great Basin desert of the western US. Predictions
were tested with population- and individual-based analyses of microsatellite DNA variation, reflecting patterns of dispersal,
population stability, and local effective population sizes. Complementary genetic inferences suggested samples from migratory
corridors housed a mixture of fish from tributaries, as predicted based on assumed migratory life histories in those habitats.
Also as predicted, populations presumed to have greater proportions of migratory fish or from physically connected, large,
or high quality habitats had higher genetic variability and reduced genetic differentiation from other populations. Populations
thought to contain largely non-migratory individuals generally showed the opposite pattern, suggesting behavioral isolation.
Estimated effective sizes were small, and we identified significant and severe genetic bottlenecks in several populations
that were isolated, recently founded, or that inhabit streams that desiccate frequently. Overall, this work suggested that
Lahontan cutthroat trout populations in stream networks are affected by a combination of landscape and metapopulation processes.
Results also demonstrated that genetic patterns can reveal unexpected processes, even within a system that is well studied
from a conventional ecological perspective. 相似文献
5.
Identification of functional corridors with movement characteristics of brown bears on the Kenai Peninsula,Alaska 总被引：2，自引：1，他引：2
Tabitha A. Graves Sean Farley Michael I. Goldstein Christopher Servheen 《Landscape Ecology》2007,22(5):765-772
We identified primary habitat and functional corridors across a landscape using Global Positioning System (GPS) collar locations
of brown bears (Ursus arctos). After deriving density, speed, and angular deviation of movement, we classified landscape function for a group of animals
with a cluster analysis. We described areas with high amounts of sinuous movement as primary habitat patches and areas with
high amounts of very directional, fast movement as highly functional bear corridors. The time between bear locations and scale
of analysis influenced the number and size of corridors identified. Bear locations should be collected at intervals ≤6 h to
correctly identify travel corridors. Our corridor identification technique will help managers move beyond the theoretical
discussion of corridors and linkage zones to active management of landscape features that will preserve connectivity. 相似文献
6.
Are hedgerows effective corridors between fragments of woodland habitat? An evidence-based approach 总被引：1，自引：1，他引：1
Anthropogenic modification of the countryside has resulted in much of the landscape consisting of fragments of once continuous
habitat. Increasing habitat connectivity at the landscape-scale has a vital role to play in the conservation of species restricted
to such remnant patches, especially as species may attempt to track zones of habitat that satisfy their niche requirements
as the climate changes. Conservation policies and management strategies frequently advocate corridor creation as one approach
to restore connectivity and to facilitate species movements through the landscape. Here we examine the utility of hedgerows
as corridors between woodland habitat patches using rigorous systematic review methodology. Systematic searching yielded 26
studies which satisfied the review inclusion criteria. The empirical evidence currently available is insufficient to evaluate
the effectiveness of hedgerow corridors as a conservation tool to promote the population viability of woodland fauna. However,
the studies did provide anecdotal evidence of positive local population effects and indicated that some species use hedgerows
as movement conduits. More replicated and controlled field investigations or long-term monitoring are required in order to
allow practitioners and policy makers to make better informed decisions about hedgerow corridor creation and preservation.
The benefits of such corridors in regard to increasing habitat connectivity remain equivocal, and the role of corridors in
mitigating the effects of climate change at the landscape-scale is even less well understood. 相似文献
7.
Deanna H. Olson Paul D. Anderson Christopher A. Frissell Hartwell H. Welsh Jr. David F. Bradford 《Forest Ecology and Management》2007
Stream–riparian areas represent a nexus of biodiversity, with disproportionate numbers of species tied to and interacting within this key habitat. New research in Pacific Northwest headwater forests, especially the characterization of microclimates and amphibian distributions, is expanding our perspective of riparian zones, and suggests the need for alternative designs to manage stream–riparian zones and their adjacent uplands. High biodiversity in riparian areas can be attributed to cool moist conditions, high productivity and complex habitat. All 47 northwestern amphibian species have stream–riparian associations, with a third being obligate forms to general stream–riparian areas, and a quarter with life histories reliant on headwater landscapes in particular. Recent recognition that stream-breeding amphibians can disperse hundreds of meters into uplands implies that connectivity among neighboring drainages may be important to their population structures and dynamics. Microclimate studies substantiate a “stream effect” of cool moist conditions permeating upslope into warmer, drier forests. We review forest management approaches relative to headwater riparian areas in the U.S. Pacific Northwest, and we propose scenarios designed to retain all habitats used by amphibians with complex life histories. These include a mix of riparian and upslope management approaches to address the breeding, foraging, overwintering, and dispersal functions of these animals. We speculate that the stream microclimate effect can partly counterbalance edge effects imposed by upslope forest disturbances, hence appropriately sized and managed riparian buffers can protect suitable microclimates at streams and within riparian forests. We propose one approach that focuses habitat conservation in headwater areas – where present management allows extensive logging – on sensitive target species, such as tailed frogs and torrent salamanders that often occur patchily. Assuming both high patchiness and some concordance among the distribution of sensitive species, protecting areas with higher abundances of these animals could justify less protection of currently unoccupied or low-density habitats, where more intensive forest management for timber production could occur. Also, we outline an approach that protects juxtaposed headwater patches, retaining connectivity among sub-drainages using a 6th-field watershed spatial scale for assuring well-distributed protected areas across forested landscapes. However, research is needed to test this approach and to determine whether it is sufficient to buffer downstream water quality and habitat from impacts of headwater management. Offering too-sparse protection everywhere is likely insufficient to conserve headwater habitats and biodiversity, while our alternative targeted protection of selected headwaters does not bind the entire forest landscape into a biodiversity reserve. 相似文献
8.
Biodiversity conservation in human-modified landscapes of Mesoamerica: Past, present and future 总被引：1，自引：0，他引：1
Fabrice A.J. DeClerck Robin Chazdon Jeffrey C. Milder Alejandra Martinez-Salinas 《Biological conservation》2010,143(10):2301-2313
Mesoamerica provides a unique context for biodiversity conservation in managed landscapes because of its geography, history of human intervention, and present conservation and development initiatives. The long and narrow form of the Mesoamerican landmass, and its division by a central mountain range, has served as both a bridge and a barrier. Conservation efforts in Mesoamerica are unique for the emphasis they place on regional connectivity through the Mesoamerican Biological Corridor and on biodiversity conservation in managed landscapes. The emphasis on conservation in agricultural systems has fostered innovations in payment for ecosystem services, and provides novel insights on the functional role that biodiversity plays in the provisioning of ecosystem services. The increasing rate of economic development in the region and the advent of new payment for ecosystem service schemes have provided new opportunities for forest regeneration and restoration. However, the small scale of private landholdings and the diversity of land uses featured in the region, while contributing to biodiversity conservation due to their structural and floristic complexity, present challenges for biodiversity monitoring and management. 相似文献
9.
Todd R. Lookingbill Andrew J. Elmore John B. Churchill Joshua B. Johnson 《Biological conservation》2010,143(4):974-320
Parks and other protected lands can provide important source habitat and act as valuable dispersal corridors in urbanizing environments. However, most wetlands within protected areas are managed in isolation without consideration of the broader landscape connections. We studied the importance of wetland habitat connectivity and landscape context to bat activity in five National Parks along a gradient of increasing urbanization within the Mid-Atlantic United States. Ninety-six Anabat stations were set up throughout the parks, from which we derived the characteristic spatial scales at which bat activity was associated with wetlands. This information was used in a graph theoretic framework to construct network models of potential landscape connectivity for those species that had positive associations with wetland land cover. We found that the importance of wetlands as a predictor of bat activity varied on a species-by-species basis and increased when network measures were used that accounted for connected area in a broad spatial context. The results demonstrate that both area and connectivity of wetland foraging habitat may act as orthogonal variables to availability of roosting habitat in explaining the distribution of highly mobile species. We use the results to illustrate the value of network analysis to guide the coordinated management of two of the parks’ most valued natural resources - wetlands and bats. 相似文献
10.
Extirpation, colonization, and habitat dynamics of a keystone species along an urban gradient 总被引：1，自引：0，他引：1
Using 5 years of patch occupancy data for 384 habitat fragments, we evaluated population and habitat dynamics of the black-tailed prairie dog in urban habitat remnants in the rapidly developing landscape of Denver, CO, USA. Specifically, we evaluated the landscape factors, including fragment area, age, and connectivity, that characterize the habitat fragments most likely to be colonized by prairie dogs, as well as those experiencing local extinctions. In addition, we determined which patch types were most often removed by land development. Sites in proximity to colonies were more likely to be colonized by prairie dogs. Local extinctions were most common on isolated colonies, and older and more isolated colonies were more likely to be extirpated by human activity. In general, smaller and older habitat patches were at the highest risk of being lost to land development. Our results provide observations of dynamic changes to the distribution of a potential keystone species in an urban area, which can be used to inform island biogeographic and metapopulation models for wildlife persistence in developing landscapes. Although populations are currently in decline, most local extinctions are the direct result of human activity, and we suggest that prairie dogs in this area can persist with appropriate management. 相似文献