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1.
This study examined the effects of habitat fragmentation on meadow vole (Microtus pennsylvanicus) population dynamics in experimental landscape patches. The study was conducted from May–November 1993 at the Miami University
Ecology Research Center. Eight 0.1-ha small mammal enclosures were used. Four enclosures contained a 160 m2 nonfragmented patch and four enclosures contained four 40 m2 fragmented patches. Thus, each treatment was replicated 4 times in a systematic research design. The patches in both treatments
contained high-quality habitat surrounded by low-quality matrix. Six pairs of adult meadow voles were released in each enclosure
on 27 May 1993. Populations were monitored by live-trapping and radio-telemetry methods. Significantly greater densities of
female voles were found during October in the fragmented treatment compared to the nonfragmented treatment. Also, significantly
more females than males were found in the fragmented treatment compared to the nonfragmented treatment for the total study
period. Significantly more subadult and juvenile males were found in the matrix versus the patch of the nonfragmented treatment
compared to the fragmented treatment. Males in the fragmented treatment had significantly greater mean home range size than
males or females in the nonfragmented treatment. There appears to exist a relationship between patch fragmentation and the
social structure of meadow vole populations; this relationship appears to function as a population regulatory mechanism. 相似文献
2.
A large-scale experimental landscape study was conducted to examine the use of corridors and the forest matrix habitat by the hispid cotton rat (Sigmodon hispidus). The role of micro- habitat selection by S. hispidus in influencing routes of movement was also investigated. The experimental landscape consisted of ten 1.64-ha patches (each 128×128 m) established in a loblolly (Pinus teada) forest. Four of the patches were isolated while the other six were connected in pairs by a 32-m wide corridor. Cotton rats (N=96) were simultaneously released into both an isolated and connected patch, and monitored by radiotelemetry for 10 days. We found that the forest matrix was not a barrier to movements of cotton rats. Fifty percent of the cotton rats moved through the matrix. Corridors had no significant effect on the number of animals leaving connected patches (60%) compared to isolated patches (50%). However, corridors were the preferred route to leave a connected patch. Colonization success for cotton rats leaving connected and isolated patches did not significantly differ. Cotton rats exhibited micro-habitat preferences and these preferences differed within patch/corridor and matrix habitats. In patch/corridor habitats, cotton rats selected sites with tall (>1 m) shrubs and high percent cover. In the forest matrix, cotton rats selected sites with abundant cover by vines and low tree canopy cover. Movement patterns of Sigmodon hispidus are not strongly influenced by large-scale landscape spatial structures. Micro-habitat selection, however, does influence movement patterns. These findings have important implications regarding habitat connectivity for small mammals. 相似文献
3.
Small mammals in heterogeneous environments have been found to disperse along corridors connecting habitat patches. Corridors may have different survivability values depending on their size and the degree of cover they provide. This deterministic model tests the effects of varying corridor quality on the demographics of a metapopulation of Peromyscus leucopus. Two types of corridors are defined based on the probability of survival during a dispersal event. Results indicate that mortality during movement through corridors influences metapopulation demographics. We found that:
- Any connection between two isolated patches is better than no connection at all in terms of persistence and population size at equilibrium.
- Metapopulations with exclusively high quality corridors between patches have a larger population size at equilibrium than do those with one or more low quality corridors.
- Increasing the number of high quality corridors between patches has a positive effect on the size of the metapopulation while increasing the number of low quality corridors has a negative effect.
- The addition to a metapopulation of a patch connected by low quality corridors has a negative effect on the metapopulation size. This suggest the need for caution in planning corridors in a managed landscape.
- There is no relationship between the number of corridors and the metapopulation size at equilibrium when the number of connected patches is held constant.
- Geometrically isolated patches connected by low quality corridors are most vulnerable to local extinctions.
4.
To assess corridor effects on movement in Peromyscus polionotus (old-field mice), we used a set of three experimental landscapes that contained multiple patches (1.64 ha) of usable, open habitat embedded in a loblolly pine (Pinus taeda) forest matrix. Some patches were connected by corridors and others were isolated (unconnected). We introduced mice to nest boxes in experimental patches and followed them through the landscapes via trapping. We found weak evidence that the presence of corridors decreased the probability that P. polionotus (particularly females) would disperse or disappear from a patch. In the process of live trapping the patches, we also encountered `feral' P. polionotus, Sigmodon hispidus (cotton rats), and Peromyscus gossypinus (cotton mice). The average number of feral animals did not differ between isolated and connected patches. This suggests that corridors do not act as drift fences that `sieve' individuals out of the matrix and into the patches. However, more male than female P. polionotus and S. hispidus were trapped in isolated patches. This intersexual difference did not exist in connected patches. 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.
Studies investigating animal response to habitat in marine systems have mainly focused on habitat preference and complexity.
This study is one of the first to investigate the affect of benthic habitat corridors and their characteristics on dispersal
and colonization by estuarine macrofuana. In this study, mark-recapture field experiments using artificial seagrass units
(ASUs) assessed the effects of seagrass corridors, interpatch distance (5 m vs. 10 m), and the ratio of corridor width to
patch width (0.5 m:1 m vs. 0.25 m:1 m) on dispersal of two benthic organisms: the highly mobile grass shrimp, Palaemonetes sp., and the less mobile bay scallop, Argopecten irradians, in two estuarine systems in southeastern North Carolina (NC). The presence of a seagrass corridor, interpatch distance,
and corridor width to patch width ratios did not significantly affect shrimp or scallop dispersal to receiver patches. Bay
scallop dispersal to receiver patches was significantly higher at one site (Drum Shoals) with relatively high flow, compared
to a second site (Middle Marsh) with lower flow. We then examined colonization of estuarine macrofauna to seagrass patches
with and without corridors to determine which, if any, taxonomic groups respond positively to corridors at scales of 10 m
and over 1 month. Colonization of estuarine macrofauna to seagrass patches was enhanced in the presence of corridors at a
relatively large interpatch distance (10 m), which was statistically significant for relatively slow moving polychaete worms.
Thus, although benthic habitat corridors may facilitate dispersal of relatively slow moving estuarine animals between otherwise
isolated seagrass patches, several common seagrass fauna such as grass shrimp and bay scallops apparently use water currents
to rapidly disperse across the seagrass/sand landscape. 相似文献
7.
Corridors are predicted to benefit populations in patchy habitats bypromoting movement, which should increase population densities, gene flow, andrecolonization of extinct patch populations. However, few investigators haveconsidered use of the total landscape, particularly the possibility ofinterpatch movement through matrix habitat, by small mammals. This studycompares home range sizes of 3 species of small mammals, the cotton mouse(Peromyscus gossypinus), old-field mouse (P.polionotus) and cotton rat (Sigmodon hispidus)between patches with and without corridors. The study site was in S. Carolina,USA. Corridor presence did not have astatistically significant influence on average home range size. Habitatspecialization and sex influenced the probability of an individual movingbetween 2 patches without corridors. The results of this study suggest thatsmall mammals may be more capable of interpatch movement without corridors thanis frequently assumed.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
8.
This study investigated the efficacy of linear landscape elements in fragmented landscapes as corridors for perennial grassland
species with short-range seed dispersal. Corridors are assumed to be essential for the persistence of metapopulations in fragmented
landscapes, but it is unclear to what extent linear landscape elements such as ditch banks and road verges can function as
corridors for those species. The principal factors that determine the rate of migration through corridors include the width
and habitat quality of patches within a corridor (expressed as the population growth rate λ) and the dispersal capacity of
plants (expressed as the slope α of the relationship between seed number and log-distance).
A cellular automation model was used to simulate the effects of the principal factors on the rate of migration. Simulations
with different levels of the principal factors showed highly significant and positive main effects of dispersal capacity,
habitat quality and width of corridors on the migration rate. Significant interactions existed between dispersal capacity
× width and dispersal capacity × habitat quality (p<0.0001), indicating that the effects of width and habitat quality depended
on the dispersal capacity. In narrow corridors most of the dispersed seeds were deposited outside the corridor, which significantly
reduced migration rates, especially for species with long-range dispersal (α=−0.4). In wide corridors (up to 20 m), seed losses
were much smaller and migration rates approximated those of continuous habitats. The contribution of the few long-range seeds
to the rate of migration was significant when habitat quality was high (population growth rates up to 2.5). However, in all
simulations migration rates were very low,i.e.<5 m/yr.
It is concluded that linear landscape elements are not effective corridors in fragmented landscapes for plants with short-range
seed dispersal, because migration rates are low (<5 m/yr), landscape elements vary in the percentage of high quality patches,
and refugia and suitable habitat patches are frequently several kilometres apart, making a cohesive infrastructure of corridors
for plants elusive. It is argued that the best way to conserve endangered plant species that encounter dispersal barriers
is to harvest seeds from nearby source populations and introduce them as suitable habitats. 相似文献
9.
Connectivity, or the integration of populations into a single demographic unit, is an often desired, but largely untested
aspect of wildlife corridors. Using a corridor system that was established at least 85 years prior, we investigated the extent
of connectivity provided. This was undertaken using a combined ecological and genetic approach with connectivity estimated
by gene flow. Vegetation within the corridor was found to be comparable in physical structure and species composition to that
within the connected patches and the two target species (Melomys cervinipes and Uromys caudimaculatus) were shown to occur along the corridor but not within the surrounding matrix. These factors indicated that the corridor
was suitable for use as a model system. The population structure (weights of individuals, sex ratios and the percentage of
juveniles) of both species were also similar within the corridor and the connected patches suggesting that the corridor provided
the resources necessary to sustain breeding populations along its length. Despite this, populations in patches linked by the
corridor were found to show the same significant levels of genetic differentiation as those in isolated habitats. M. cervinipes, but not U. caudimaculatus, also showed population differentiation within the continuous habitat. Although based on only one corridor system, these
results clearly demonstrate that connectivity between connected populations will not always be achieved by the construction
or retention of a corridor and that connectivity cannot be inferred solely from the presence of individuals, or breeding populations,
within the corridor.
C. Wilson: deceased 相似文献
10.
Animal behavior, cost-based corridor models, and real corridors 总被引：2，自引：1，他引：1
Corridors are popular conservation tools because they are thought to allow animals to safely move between habitat fragments, thereby maintaining landscape connectivity. Nonetheless, few studies show that mammals actually use corridors as predicted. Further, the assumptions underlying corridor models are rarely validated with field data. We categorized corridor use as a behavior, to identify animal-defined corridors, using movement data from fishers (Martes pennanti) tracked near Albany, New York, USA. We then used least-cost path analysis and circuit theory to predict fisher corridors and validated the performance of all three corridor models with data from camera traps. Six of eight fishers tracked used corridors to connect the forest patches that constitute their home ranges, however the locations of these corridors were not well predicted by the two cost-based models, which together identified only 5 of the 23 used corridors. Further, camera trap data suggest the cost-based corridor models performed poorly, often detecting fewer fishers and mammals than nearby habitat cores, whereas camera traps within animal-defined corridors recorded more passes made by fishers, carnivores, and all other non-target mammal groups. Our results suggest that (1) fishers use corridors to connect disjunct habitat fragments, (2) animal movement data can be used to identify corridors at local scales, (3) camera traps are useful tools for testing corridor model predictions, and (4) that corridor models can be improved by incorporating animal behavior data. Given the conservation importance and monetary costs of corridors, improving and validating corridor model predictions is vital. 相似文献
11.
Frauke Ecke Pernilla Christensen Per Sandström Birger Hörnfeldt 《Landscape Ecology》2006,21(4):485-497
Several studies indicate a long-term decline in numbers of different species of voles in northern Fennoscandia. In boreal Sweden, the long-term decline is most pronounced in the grey-sided vole (Clethrionomys rufocanus). Altered forest landscape structure has been suggested as a possible cause of the decline. However, habitat responses of grey-sided voles at the landscape scale have never been studied. We analyzed such responses of this species in lowland forests in Västerbotten, northern Sweden. Cumulated spring densities representing 22 local time series from 1980–1999 were obtained by a landscape sampling design and were related to the surrounding landscape structure of 2.5×2.5 km plots centred on each of the 22 1-ha trapping plots. In accordance with general knowledge on local habitat preferences of grey-sided voles, our study supported the importance of habitat variables such as boulder fields and old-growth pine forest at the landscape scale. Densities were negatively related to clear cuts. Habitat associations were primarily those of landscape structure related to habitat fragmentation, distance between habitat patches and patch interspersion rather than habitat patch type quantity. Local densities of the grey-sided vole were positively and exponentially correlated with spatial contiguity (measured with the fragmentation index) of old-growth pine forest, indicating critical forest fragmentation thresholds. Our results indicate that altered land use might be involved in the long-term decline of the grey-sided vole in managed forest areas of Fennoscandia. We propose two further approaches to reveal and test responses of this species to changes in landscape structure. 相似文献
12.
Frauke Ecke Pernilla Christensen Ralf Rentz Mats Nilsson Per Sandström Birger Hörnfeldt 《Landscape Ecology》2010,25(4):551-560
Changes in forest landscape structure have been suggested as a likely contributing factor behind the long-term decline in
the numbers of cyclic grey-sided voles (Clethrionomys rufocanus) in northern Fennoscandian lowland regions in contrast to mountain regions due to the absence of forest management in the
mountains. This study, for the first time, formally explored landscape structure in 29 lowland (LF) and 14 mountain forest
(MF) landscapes (each 2.5 × 2.5 km) in northern Sweden, and related the results to the cumulated spring trapping index of
the grey-sided vole in 2002–2006. The grey-sided vole showed striking contrasts in dynamics close in space and time. The MF
landscapes were characterized by larger patches and less fragmentation of preferred forest types. The grey-sided vole was
trapped in all of 14 analyzed MF landscapes but only in three out of 29 of the LF landscapes. MF and LF landscapes with grey-sided
vole occurrence were characterized by similar focal forest patch size (mean 357 ha, minimum 82 ha and mean 360 ha, minimum
79 ha, respectively). In contrast, these MF compared to the LF landscapes were characterized by larger patches of preferred
forest types and less fragmented preferred forest types and by a lower proportion of clear-cut areas. The present results
suggest that landscape structure is important for the abundance of grey-sided voles in both regions. However, in the mountains
the change from more or less seasonal dynamics to high-amplitude cycles between the mid 1990s and 2000s cannot be explained
by changes in landscape structure. 相似文献
13.
Effective conservation management for species that function as metapopulations requires an understanding of population dynamics
at the landscape scale. The water vole, Arvicola amphibius, is one such species. Water voles have recently undergone a significant decline in the UK, as a result of habitat loss and
predation from the introduced American mink, Neovison vison. Large reed bed and grazing marsh sites can provide refuge habitats for water voles from mink predation, in which case populations
within these sites could sustain metapopulations in the surrounding landscape where conditions are less favourable. We carried
out a study using a stochastic patch occupancy model to determine the long term viability of water vole metapopulations in
the wider landscape around a series of extensive reed bed and grazing marsh sites designated as National Key Sites for water
voles. The results of our model simulations show that a large protected core site, or mainland, is essential in maintaining
the long term viability of these systems. Our results also show how these metapopulations could be enhanced by increasing
patch numbers through habitat creation and/or restoration and suggest what the minimum effective size of created or restored
patches should be. The study shows how population modelling can provide insight into some effective practical ways of enhancing
the viability of water vole metapopulations at the landscape scale. Furthermore it demonstrates that extensive wetlands are
an appropriate focus for water vole conservation measures. 相似文献
14.
Cultural landscapes of Germany are patch-corridor-matrix mosaics for an invasive megaforb 总被引：1，自引：0，他引：1
Predicting the vulnerability of landscapes to both the initial colonisation and the subsequent spread of invasive species
remains a major challenge. The aim of this study was to assess the relative importance of sub-patch level factors and landscape
factors for the invasion of the megaforb Heracleum mantegazzianum. In particular, we tested which factors affect the presence in suitable habitat patches and the cover-percentage within invaded
patches. For this purpose, we used standard (logistic) regression modelling techniques. The regression analyses were based
on inventories of suitable habitat patches in 20 study areas (each 1 km2) in cultural landscapes of Germany. The cover percentage in invaded patches was independent from landscape factors, except
for patch shape, and even unsatisfactorily explained by sub-patch level factors included in the analysis (R
2 = 0.19). In contrast, presence of H. mantegazzianum was affected by both local and landscape factors. Woody habitat structure decreased the occurrence probability, whereas vicinity
to transport corridors (rivers, roads), high habitat connectivity, patch size and perimeter-area ratio of habitat patches
had positive effects. The significance of corridors and habitat connectivity shows that dispersal of H. mantegazzianum through the landscape matrix is limited. We conclude that cultural landscapes of Germany function as patch-corridor-matrix
mosaics for the spread of H. mantegazzianum. Our results highlight the importance of landscape structure and habitat configuration for invasive spread. Furthermore,
this study shows that both local and landscape factors should be incorporated into spatially explicit models to predict spatiotemporal
dynamics and equilibrium stages of plant invasions. 相似文献
15.
The urban matrix was recently shown to be a mosaic of heterogeneous dispersal habitats. We conducted a playback experiment of mobbing calls to examine the probabilities of forest birds to cross a distance of 50 m over urban matrix with different land-cover types in an urban area. We treated the reciprocal of the crossing probabilities as a movement resistance for forest birds. We drew resistance surfaces based on the land-cover maps of urban Sapporo. We applied a circuit theory to examine the relative role of a detour route consisting of a riparian corridor and urban matrix for dispersing forest bird individuals from continuous forest to an isolated green space in the midst of an urban area. Our results showed that wood cover had the highest crossing probability, while open land (grassland and pavement) had the lowest probabilities. Buildings and water surface displayed an intermediate probability. Resistance surfaces and flow maps at 25- and 50-m resolutions were very similar and suggested that dispersing individuals are likely to use the intervening building areas that dominate the urban matrix rather than detour through riparian corridors. Our results showed the useful combination of experimental approaches and circuit theory, and the importance of the spatial configuration of corridors, as well as the composition and management of dispersal habitats, to landscape connectivity. 相似文献
16.
Since the fragmentation of natural habitats is one of the most serious problems for many endangered species, it is highly interesting to study the properties of fragmented landscapes. As a basic property, landscape connectivity and its effects on various ecological processes are frequently in focus. First, we discuss the relevance of some graph properties in quantifying connectivity. Then, we propose a method how to quantify the relative importance of habitat patches and corridors in maintaining landscape connectivity. Our combined index explicitly considers pure topological properties and topographical measures, like the quality of both patches (local population size) and corridors (permeability). Finally, for illustration, we analyze the landscape graph of the endangered, brachypterous bush-cricket Pholidoptera transsylvanica. The landscape contains 11 patches and 13 corridors and is situated on the Aggtelek Karst, NE-Hungary. We characterize the importance of each node and link of the graph by local and global network indices. We show how different measures of connectivity may suggest different conservation preferences. We conclude, accordingly to our present index, by identifying one specific habitat patch and one specific corridor being in the most critical positions in maintaining connectivity.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
17.
Context
Habitat edges are integral features of conservation corridors and can influence corridor function and effectiveness. Edge orientation is linked to corridor design and can shape edge responses by changing habitat conditions along edges as well as contrast between conserved habitats and transformed areas.
ObjectivesWe assess whether corridor orientation affects butterfly assemblages in conservation corridors. To do this, we investigate how edge orientation influences butterfly diversity and abundance along forestry plantation edges, and compare this to another important design variable, corridor width.
MethodsButterflies were recorded along the sunny austral north- and shady austral south-orientated edges in grassland conservation corridors that dissect forestry plantations, as well as corridor interior sites. Species richness, abundance and similarity to interior sites were modelled using local habitat variables (ambient temperature, floral resources, and time of day), as well as corridor design variables (corridor width, orientation and an estimate of edge contrast influenced by orientation).
ResultsBoth edge orientation and corridor width were important for butterfly diversity along corridor edges. Wider corridors enhanced overall species richness and promoted similarity between edge and interior habitats. Concurrently, grassland specialist species preferred the sunnier edges (i.e., north facing in the southern hemisphere) while forest- specialists showed a preference for the shadier edges (south facing edges). Edge orientation influenced resident butterflies more strongly than transient butterflies and influenced specialists more strongly than generalists.
ConclusionsCorridor orientation and width are complementary design variables for butterfly conservation. Wide corridors at a variety of orientations benefit different subsets of the butterfly assemblage, and the whole corridor (including both edges) is important to consider in conservation planning to capture all biodiversity.
相似文献18.
The effects of landscape composition and physiognomy on metapopulation size: the role of corridors 总被引：5，自引：0，他引：5
We develop and analyze a model that examines the effects of corridor quality, quantity, and arrangement on metapopulation sizes. These ideas were formerly investigated by Lefkovitch and Fahrig (1985) and Henein and Merriam (1990). Our simulations provide results similar to the Henein and Merriam model, indicating that the quality of corridors in a landscape and their arrangement will influence the size of a metapopulation. We then go one step further, describing how corridor arrangement alters the metapopulation, and provide a method for predicting which corridor arrangements should support larger metapopulations. In contrast to the Henein and Merriam model, we find that the number of corridor connections has no influence on the size of a metapopulation in a landscape unless there is an accompanying change in the uniformity of the distribution of corridor connections among patches. 相似文献
19.
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
20.
We introduce a novel approach to building corridors in spatial conservation prioritization. The underlying working principle is the use of a penalty structure in an iterative algorithm used for producing a spatial priority ranking. The penalty term aims to prevent loss or degradation of structural connections, or, equivalently, to promote to a higher rank landscape elements that are required to keep networks connected. The proposed method shows several convenient properties: (1) it does not require a priori specification of habitat patches, end points or related thresholds, (2) it does not rely on resistance coefficients for different habitats, (3) it does not require species targets, and (4) the cost of additional connectivity via corridors can be quantified in terms of habitat quality lost across species. Corridor strength and width parameters control the trade-off between increased structural connectivity via corridors and other considerations relevant to conservation planning. Habitat suitability or dispersal suitability layers used in the analysis can be species specific, thus allowing analysis both in terms of structural and functional connectivity. The proposed method can also be used for targeting habitat restoration, by identifying areas of low habitat quality included in corridors. These methods have been implemented in the Zonation software, and can be applied to large scale and high resolution spatial prioritization, effectively integrating corridor design and spatial conservation prioritization. Since the method operates on novel principles and combines with a large number of features already operational in Zonation, we expect it to be of utility in spatial conservation planning. 相似文献