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1.
Habitat restoration is typically focused on reestablishing suitable conditions at a local scale, but landscape constraints may be important for keystone species with limited dispersal. We tested for time lags and examined the relative importance of local and landscape constraints on the response of the banner-tailed kangaroo rat (Dipodomys spectabilis) to restoration of Chihuahuan Desert grasslands in New Mexico, USA. Dipodomys spectabilis is a keystone species that creates habitat heterogeneity and modifies the structure of plant and animal communities. We selected 21 sites and compared density of D. spectabilis between areas treated with herbicide to control shrubs (treated areas) and paired untreated areas. We evaluated whether density of D. spectabilis depended on treatment age, local habitat quality (vegetation and soil structure), and landscape factors (treatment area and spatial connectivity). Density was greater at treated areas than at untreated areas due to a direct effect of reduced shrub cover. However, the response of D. spectabilis to restoration was lagged by a decade or more. Structural equation modeling indicated the time lag reflected a dispersal constraint as opposed to a temporal change in habitat quality. This inference was corroborated by a positive relationship between density at treated areas and connectivity to source populations. Our results indicate that density of D. spectabilis depended strongly on the spatial configuration of treated areas, which supports a landscape mosaic approach to restoration. If keystone species commonly exhibit limited dispersal ability, landscape constraints may be broadly important for shaping ecosystem structure and function after habitat restoration.  相似文献   

2.
To determine whether fire spatial and temporal scales affect foraging behavior and grazing intensity by Bison (Bison bison), we burned three different patch sizes (225, 900, and 3600 m2) across an otherwise homogeneous grassland landscape. We then monitored grazing intensity for the succeeding 14 months. During the first 5 months after the burn (August–January), the Bison grazing intensity pattern was affected by whether a plot was burned and only marginally affected by plot size. During the next 5 months (January–June), grazing intensity was unaffected by plot size, but was greatest in the unburned 225 and 3600-m2 plots. The final 4 months (June–October), grazing intensity was unaffected by treatments other than being higher in the unburned 3600-m2 plots. By the final sampling date, biomass was significantly greater in the burned plots and grazing intensity appeared to be responding to the amount of biomass present and the total amount of N present. The pattern displayed within the first 5 months after the burn is congruent with the expectations of optimal foraging theory with overmatching in the smallest plot size of 225 m2 (BioScience 37 (1987) 789–799). The next two sampling periods displayed a matching aggregate response relative to biomass availability (Oecologia 100 (1999) 107–117) and total nitrogen mass (g m−2). The temporal shift that we found in Bison response to burn patch size is, to our knowledge, the first such examination of both spatial and temporal responses by Bison to landscape heterogeneity. We now have quantitative evidence of how native herbivores can alter their foraging responses to changes in landscape structure over time.  相似文献   

3.
Animals may respond to spatial and temporal heterogeneity by altering their movement patterns. The time an animal spends in an area of a given size is termed ȁ8first-passage timeȁ9 and can be used to identify the scales at which different movement processes occur. Using first-passage time and 2-h observations, we identified nested spatial scales representing three movement behaviours for elk (Cervus elaphus) – inactive/resting (moves < 50 m), active/foraging (x̄ = 276.7 m, SD = 56.6), and active/relocating (x̄ = 1628.3 m, SD = 436.6). Our ability to identify inactive behaviour was limited by GPS accuracy. The scale separating relocating and foraging behaviour ranged 550–1650 m across individuals and varied quadratically with the mean patch size of cutover forest in an animal’s home range. We classified path segments into the 3 movement behaviours and related behaviours to local environmental conditions. Elk were likely to be inactive in areas having a low predicted use by wolves (Canis lupus), farther than 50 m from anthropogenic linear clearings, and where microclimatic conditions were cool (high shrub cover and north to east-facing slopes). In contrast, elk were most likely to forage in areas having intermediate levels of herbaceous biomass and low movement costs. Elk were most likely to be relocating when in areas of high wolf use, when close to linear clearings, and in energetically costly situations such as moving upslope. We discuss how elk use of potential foraging habitats may be restricted in this landscape by risks imposed by predators, humans, or both.  相似文献   

4.
The preservation of wild plants and animals in urban environments can be a good means to meet the demand for natural areas for recreational purposes. However, the impacts of urbanisation on native species distribution are poorly studied. A city environment has high impact on vegetal community dynamics, especially in terms of climate modification, level of perturbationand pattern of dispersion. We chose to study the three indigenous species of the genus Polypodium that are known to grow in a wide range of habitats, including forest and urban environments, and exhibit a priori a strong ability for dispersal. The aim of the study was to evaluate the factors involved in the Polypodium species distribution and to determine whether this distribution was influenced by the rural–urban gradient. The distribution of the three fern species was investigated in the city of Angers (France) at two levels: for a park (urban woodland) and for the whole city. A contrasted distribution of the three Polypodies has been recorded and shows a rural–urban gradient. This can be explained by the ecology of each species and some biological traits. It means that differences in the spatial structure of the city lead to particular patterns of distribution for these plants. Thus, preserved indigenous vegetation may be influenced in its species composition by the surrounding urban development.  相似文献   

5.
Organisms frequently show marked preferences for specific environmental conditions, but these preferences may change with landscape scale. Patterns of distribution or abundance measured at different scales may reveal something about an organism's perception of the environment. To test this hypothesis, we measured densities of two herbivorous aquatic insects that differed in body morphology and mobility in relation to current velocity measured at different scales in the upper Colorado River (Colorado, USA). Streambed densities of the caddisfly larva Agapetus boulderensis (high hydrodynamic profile, low mobility) and mayfly nymph Epeorus sp. (low hydrodynamic profile, high mobility) were assessed at 3 spatial scales: whole riffles, individual cobbles within riffles, and point locations on cobbles. Riffles were several meters in extent, cobbles measured 10–30 cm in size, and the local scale was within a few centimeters of individual larvae (themselves ca. 0.5–1.0 cm in size). We also quantified the abundance of periphytic food for these herbivores at the cobble and riffle scales. Agapetus favored slow current (<30 cm s–1) across all scales. Epeorus, by contrast, favored fast current (60–80 cm s–1) at the local and riffle scale, but not at the cobble scale. Only Agapetus showed a significant relationship to current at the cobble scale, with greatest larval densities occurring at velocities near 30 cm s–1. We had predicted an inverse correlation between grazer density and periphytic abundance; however, this occurred only for Agapetus, and then only at the cobble scale. These data suggest that organisms respond to environmental gradients at different spatial scales and that the processes driving these responses may change with scale, e.g., shifting from individual habitat selection at local and cobble scales to population responses at the riffle scale. This study also highlights the importance of using the appropriate scale of measurement to accurately assess the relationship between organisms and environmental gradients across scale.  相似文献   

6.
Disturbances such as grazing, invading species, and clear-cutting, often act at small spatial scales, and means for quantifying their impact on fine scale vegetation patterns are generally lacking. Here we adopt a set of landscape metrics, commonly used for quantifying coarse scale fragmentation, to quantify fine scale fragmentation, namely the fine scale vegetation structure. At this scale, patches often consist of individual plants smaller than 1 m2, requiring the grain of the analysis to be much smaller. We used balloon aerial photographs to map fine details of Mediterranean vegetation (pixel size <0.04 m) in experimental plots subjected to grazing and clear-cutting and in undisturbed plots. Landscape metrics are sensitive to scale. Therefore, we aggregated the vegetation map into four coarser scales, up to a resolution of 1 m, and analyzed the effect of scale on the metrics and their ability to distinguish between different disturbances. At the finest scale, six of the seven landscape metrics we evaluated revealed significant differences between treated and undisturbed plots. Four metrics revealed differences between grazed and control plots, and six metrics revealed differences between cleared and control plots. The majority of metrics exhibited scaling relations. Aggregation had mixed effects on the differences between metric values for different disturbances. The control plots were the most sensitive to scale, followed by grazing and clearing. We conclude that landscape metrics are useful for quantifying the very fine scale impact of disturbance on woody vegetation, assuming that the analysis is based on sufficiently high spatial resolution data.  相似文献   

7.
Spooner  Peter G.  Lunt  Ian D.  Okabe  Atsuyuki  Shiode  Shino 《Landscape Ecology》2004,19(5):491-499
Spatial patterning of plant distributions has long been recognised as being important in understanding underlying ecological processes. Ripley’s K-function is a frequently used method for studying the spatial pattern of mapped point data in ecology. However, application of this method to point patterns on road networks is inappropriate, as the K-function assumes an infinite homogenous environment in calculating Euclidean distances. A new technique for analysing the distribution of points on a network has been developed, called the network K-function (for univariate analysis) and network cross K-function (for bivariate analysis). To investigate its applicability for ecological data-sets, this method was applied to point location data for roadside populations of three Acacia species in a fragmented agricultural landscape of south-eastern Australia. Kernel estimations of the observed density of spatial point patterns for each species showed strong spatial heterogeneity. Combined univariate and bivariate network K-function analyses confirmed significant clustering of populations at various scales, and spatial patterns of Acacia decora suggests that roadworks activities may have a stronger controlling influence than environmental determinants on population dynamics. The network K-function method will become a useful statistical tool for the analyses of ecological data along roads, field margins, streams and other networks.This revised version was published online in May 2005 with corrections to the Cover Date.  相似文献   

8.
Spatial scale is inherent in the definition of landscape heterogeneity and diversity. For example, a landscape may appear heterogeneous at one scale but quite homogeneous at another scale. In assessing the impact of burning and grazing on the Konza Prairie Research Natural Area (a tallgrass prairie), spatial scale is extremely important. Textural contrast algorithms were applied to various scales of remote sensing data and related to landscape units for assessment of heterogeneity under a variety of burning treatments. Acquired data sets included Landsat multispectral scanner (MSS), with 80 m resolution, Landsat thematic mapper (TM), with 30 m resolution, and high resolution density sliced aerial photography (with a 5 m resolution). Results suggest that heterogeneous areas of dense patchiness (e.g., unburned areas) must be analyzed at a finer scale than more homogeneous areas which are burned at least every four years.  相似文献   

9.
Assessing the associations between spatial patterns in population abundance and environmental heterogeneity is critical for understanding various population processes and for managing species and communities. This study evaluates responses in the abundance of the European rabbit (Oryctolagus cuniculus), an important prey for predators of conservation concern in Mediterranean ecosystems, to environmental heterogeneity at different spatial scales. Multi-scale habitat models of rabbit abundance in three areas of Doñana, south-western Spain, were developed using a spatially extensive dataset of faecal pellet counts as an abundance index. The best models included habitat variables at the three spatial scales examined: distance from lagoons (broad scale), mean landscape shrub coverage and interspersion of pastures (home-range scale), and shrub and pasture cover (microhabitat scale). These variables may well have been related to the availability of food and refuge for the species at the different scales. However, the models’ fit to data and their predictive accuracy for an independent sample varied among the study regions. Accurate predictions in some areas showed that the combination of variables at various spatial scales can provide a reliable method for assessing the abundance of ecologically complex species such as the European rabbit over large areas. On the other hand, the models failed to identify abundance patterns in a population that suffered the strongest demographic collapse after viral epidemics, underlining the difficulty of generalizing this approach. In the latter case, factors difficult to implement in static models such as disease history and prevalence, predator regulation and others may underlie the lack of association. Habitat models can provide useful guidelines for the management of landscape attributes relevant to rabbits and help improve the conservation of Mediterranean communities. However, other influential factors not obviously related to environmental heterogeneity should also be analyzed in more detail.  相似文献   

10.
The influence of prey density, within-field vegetation, and the composition and patchiness of the surrounding landscape on the abundance of insect predators of cereal aphids was studied in wheat fields in eastern South Dakota, USA. Cereal aphids, aphid predators, and within-field vegetation were sampled in 104 fields over a three year period (1988–1990). The composition and patchiness of the landscape surrounding each field were determined from high altitude aerial photographs. Five landscape variables, aggregated at three spatial scales ranging from 2.6 km2 to 581 km2, were measured from aerial photographs. Regression models incorporating within-field and landscape variables accounted for 27–49% of the variance in aphid predator abundance in wheat fields. Aphid predator species richness and species diversity were also related to within-field and landscape variables. Some predators were strongly influenced by variability in the composition and patchiness of the landscape surrounding a field at a particular spatial scale while others responded to variability at all scales. Overall, predator abundance, species richness, and species diversity increased with increasing vegetational diversity in wheat fields and with increasing amounts of non-cultivated lands and increasing patchiness in the surrounding landscape.  相似文献   

11.
Spectral analysis allows the characterization of temporal (1D) or spatial (2D) patterns in terms of their scale (frequency) distribution. Cross-spectral analysis can also be used to conduct independent correlation analyses at different scales between two variables, even in the presence of a complex superposition of structures, such as structures that are shifted, have different scales or have different levels of anisotropy. These well-grounded approaches have rarely been applied to two-dimensional ecological datasets. In this contribution, we illustrate the potential of the method. We start by providing a basic methodological introduction, and we clarify some technical points concerning the computation of two-dimensional coherency and phase spectra and associated confidence intervals. First, we illustrate the method using a simple theoretical model. Next, we present a real world application: the case of patterned (gapped) vegetation in SW Niger. In this example, we investigate the functional relationships between topography and the spatial distribution of two shrub species, Combretum micranthum G. Don. and Guiera senegalensis J.F. Gmel. We show that both the global vegetation pattern and the distribution of C. micranthum are independent at all analyzable scales (i.e., from 10 to 50 m) from possible relief-induced determinisms. Additionally, the two dominant shrub species form distinct patches, thus suggesting separate niches.  相似文献   

12.
Nest locations of breeding birds are often spatially clustered. This tendency to nest together has generally been related to a patchy distribution of nesting habitat in landscape studies, but behavioral studies of species with clustered breeding patterns draw attention to the importance of social and biotic factors. Indeed, it is becoming increasingly apparent that the breeding system of many territorial, migrant birds may be semi-colonial. The reasons for, and extent of, spatial clustering in their breeding systems are not well understood. Our goal was to tease apart the influence of habitat availability and social drivers of clustered breeding in a neotropical migrant species, the hooded warbler (Wilsonia citrina). To test alternative hypotheses related to clustered habitat or conspecific attraction, we combined a habitat classification based on remote sensing with point pattern analysis of nesting sites. Nest locations (n = 150, 1999–2004), collected in a 1213 ha forested area of Southern Ontario (Canada), were analyzed at multiple spatial scales. Ripley’s K and pair-correlation functions g (uni- and bivariate) were used to test whether nests were clustered merely because potential nesting habitat was also clustered, or whether nests were additionally clustered with respect to conspecifics. Nest locations tended to be significantly clustered at intermediate distances (particularly between 240 and 420 m). Nests were randomly distributed within available habitat at larger distance scales, up to 1500 m. A reasonable hypothesis to explain the detected additional clustering, and one that is consistent with the results of several behavioral studies, is that females pack their nests more tightly than the available habitat requires to be situated closer to their neighbors’ mates. Linking spatially explicit, point pattern analysis with strong inference based on Monte Carlo tests may bring us closer to understanding the generality and reasons behind conspecific attraction at different spatial scales. F. Csillag—deceased.  相似文献   

13.
To develop a species-centered definition of landscapes, I suggest using a fractal analysis of movement patterns to identify the scales at which organisms are interacting with the patch structure of the landscape. Significant differences in the fractal dimensions of movement patterns of two species indicate that the species may be interacting with the patch structure at different scales. Fractal analysis therefore permits comparisons of landscape perceptions of different species within the same environment.I tested the utility of this fractal application by analyzing the movement patterns of three species of acridid grasshoppers (Orthoptera) in a grassland mosaic. The largest species moved up to 6 times faster than the two smaller species, and species exhibited different responses to microlandscape structure within 25-m2 plots. Further, the largest species exhibited different responses to microlandscape structure in two pastures subjected to different intensities of cattle grazing. This species thus is able to integrate information on landscape structure at broad spatial scales. Fractal analysis of movement patterns revealed that the two small species had significantly more tortuous patterns than the larger species, which suggests that these species are interacting with patch structure at a finer scale of resolution than the large species. Fractal analysis can be used to identify the perceptive resolution of a species; that is, the spatial grain and extent at which they are able to perceive and respond to heterogeneity. Analysis of movement patterns across a range of spatial scale may reveal shifts in fractal dimension that reflect transitions in how species respond to the patch structure of the landscape at different scales.  相似文献   

14.
Detailed species composition data are rapidly collected using a high-powered telescope from remote vantage points at two scales: site level and patch level. Patches constitute areas of homogeneous vegetation composition. Multiple samples of species composition are randomly located within the patches. These data are used as site-level data and are also aggregated to provide species composition data at the patch level. The site- and patch-level data are spatially integrated with high resolution (10 m), topographically-derived fields of environmental conditions, such as solar radiation, air temperature, and topographic moisture index in order to evaluate the applicability of the sampling method for modeling relationships between species composition and environmental processes.The methodology provides a balance between sampling efficiency and the accuracy of field data. Application of the method is appropriate for environments where terrain and canopy characteristics permit open visibility of the landscape. We evaluate the nature of data resulting from an implementation of the remote sampling methodology in a steep watershed dominated by closed-canopy chaparral. Analyses indicate that there is minimal bias associated with scaling the data from the site level to the patch level, despite variable patch sizes. Analysis of variance and correlation tests show that the internal floristic and environmental variability of patches is low and stable across the entire sample of patches. Comparison of regression tree models of species cover at the two scales indicates that there is little scale-dependence in the ecological processes that govern patterns of species composition between the site level and patch level. High explanatory power of the regression tree models suggests that the vegetation data are characterized at an appropriate scale to model landscape-level patterns of species composition as driven by topographically-mediated processes. Patch-level sampling reduces the influence of local stochasticity and micro-scale processes. Comparison of models between the two scales can be useful for assessing the processes and associated scales of variability governing spatial patterns of plant species.  相似文献   

15.
A comprehensive understanding of variables associated with spatial differences in community composition is essential to explain and predict biodiversity over landscape scales. In this study, spatial patterns of bird diversity in Central Kalimantan, Indonesia, were examined and associated with local-scale (habitat structure and heterogeneity) and landscape-scale (logging, slope position and elevation) environmental variables. Within the study area (c. 196 km2) local habitat structure and heterogeneity varied considerably, largely due to logging. In total 9747 individuals of 177 bird species were recorded. Akaike's information criterion (AIC) revealed that the best explanatory models of bird community similarity and species richness included both local- and landscape-scale environmental variables. Important local-scale variables included liana abundance, fern cover, sapling density, tree density, dead wood abundance and tree architecture, while important landscape-scale variables were elevation, logging and slope position. Geographic distance between sampling sites was not significantly associated with spatial variation in either species richness or similarity. These results indicate that deterministic environmental processes, as opposed to dispersal-driven stochastic processes, primarily structure bird assemblages within the spatial scale of this study and confirm that highly variable local habitat measures can be effective means of predicting landscape-scale community patterns.  相似文献   

16.
At finer scales, spatial heterogeneity can influence fire intensity and severity. To test whether Macrotermes termite mounds act as fire refugia for woody plants, we assessed effects of fire on individual plants, woody plant structure and composition in a miombo woodland in Zimbabwe, where elephants have decreased tree cover, leading to increased grass cover, fuelling greater intensity fires. We compared exposure to fire on 47 paired mound-matrix plots at three sites. Mound-based woody plants were less exposed to fire than those in matrix positions. Woody species composition differed between mound and matrix, and there were more tall trees on mounds. We assessed grass cover, elephant damage, fire damage and resprouting response for all woody plants found on 10 paired mound-matrix plots that had been equally exposed to severe late dry season fires. Grass cover was three times greater for matrix sites, where 85 % of woody species experienced heavy fire damage, compared to 29 % for mounds. Matrix species were nearly 31 times more likely than mound species to exhibit a vigorous resprouting response after fire damage, all else being equal. The distinct composition of termitaria vegetation has been attributed to edaphic factors. To this should be added the fire-retardant properties of mounds, allowing woody species that might otherwise have been excluded, to persist in a fire-prone system. Thus, spatial pattern created by termitaria is reinforced through exclusion of fire, allowing different species composition and structure. Since termitaria are important for productivity and biodiversity, the refuge effect is significant for the system.  相似文献   

17.
Based on the agricultural landscape of the Sebungwe in Zimbabwe, we investigated whether and how the spatial distribution of the African elephant (Loxodonta africana) responded to spatial heterogeneity of vegetation cover based on data of the early 1980s and early 1990s. We also investigated whether and how elephant distribution responded to changes in spatial heterogeneity between the early 1980s and early 1990s. Vegetation cover was estimated from a normalised difference vegetation index (NDVI). Spatial heterogeneity was estimated from a new approach based on the intensity (i.e., the maximum variance exhibited when a spatially distributed landscape property such as vegetation cover is measured with a successively increasing window size or scale) and dominant scale (i.e., the scale or window size at which the intensity is displayed). We used a variogram to quantify the dominant scale (i.e., range) and intensity (i.e., sill) of NDVI based congruent windows (i.e., 3.84 km × 3.84 km in a 61 km × 61 km landscape). The results indicated that elephants consistently responded to the dominant scale of spatial heterogeneity in a unimodal fashion with the peak elephant presence occurring in environments with dominant scales of spatial heterogeneity of around 457–734 m. Both the intensity and dominant scale of spatial heterogeneity predicted 65 and 68% of the variance in elephant presence in the early 1980s and in the early 1990s respectively. Also, changes in the intensity and dominant scale of spatial heterogeneity predicted 61% of the variance in the change in elephant distribution. The results imply that management decisions must take into consideration the influence of the levels of spatial heterogeneity on elephants in order to ensure elephant persistence in agricultural landscapes.  相似文献   

18.
The modifiable areal unit problem has significant implications for ecological research that involve investigating and analyzing the spatial heterogeneity of plant community. In this paper, semivariance analysis was used to evaluate the spatial characteristics of plant community in the␣transitional zone between oasis and desert. The spatial structures of the plant community were characterized using exponent model variogram parameters, including nugget (C 0) range (A 0) and sill (C 0+C). Two methods were employed to determine the scale effect of spatial heterogeneity. (1) A constant grain size (10×10 m2) and variational plot areas have been used to analyze spatial heterogeneity of the plant community. (2) The grain size was only changed to analyze spatial heterogeneity. In addition, the plot of 500×500 m2 was clustered into nested units of different shapes and different directions to analyze zoning effect. Finally, using semivariance analysis, we obtained a suitable plot area and zoning approach to weaken the scale and zoning effects. The results showed that the effects of scale on different variogram parameters had significant difference. For example, C 0 and C 0+C were very sensitive at small scales, A 0 was influenced significantly by plot area at larger scales, and C 0 and A 0 were relatively sensitive to different zoning approaches. In order to get more representative characteristic of spatial heterogeneity of the plant community, the sampling area should be more than 200×200 m2 for Nitraria sphaerocarpa populations, 100×100 m2 for Reaumuria soongorica populations, and a grain size from 20×20 m2 to 30×30 m2 for both populations.  相似文献   

19.
The degree to which habitat fragmentation affects bird incidence is species specific and may depend on varying spatial scales. Selecting the correct scale of measurement is essential to appropriately assess the effects of habitat fragmentation on bird occurrence. Our objective was to determine which spatial scale of landscape measurement best describes the incidence of three bird species (Pyriglena leucoptera, Xiphorhynchus fuscus and Chiroxiphia caudata) in the fragmented Brazilian Atlantic forest and test if multi-scalar models perform better than single-scalar ones. Bird incidence was assessed in 80 forest fragments. The surrounding landscape structure was described with four indices measured at four spatial scales (400-, 600-, 800- and 1,000-m buffers around the sample points). The explanatory power of each scale in predicting bird incidence was assessed using logistic regression, bootstrapped with 1,000 repetitions. The best results varied between species (1,000-m radius for P. leucoptera; 800-m for X. fuscus and 600-m for C. caudata), probably due to their distinct feeding habits and foraging strategies. Multi-scale models always resulted in better predictions than single-scale models, suggesting that different aspects of the landscape structure are related to different ecological processes influencing bird incidence. In particular, our results suggest that local extinction and (re)colonisation processes might simultaneously act at different scales. Thus, single-scale models may not be good enough to properly describe complex pattern–process relationships. Selecting variables at multiple ecologically relevant scales is a reasonable procedure to optimise the accuracy of species incidence models.  相似文献   

20.
Habitat fragmentation, patch quality and landscape structure are important predictors for species richness. However, conservation strategies targeting single species mainly focus on habitat patches and neglect possible effects of the surrounding landscape. This project assesses the impact of management, habitat fragmentation and landscape structure at different spatial scales on the distribution of three endangered butterfly species, Boloria selene, Boloria titania and Brenthis ino. We selected 36 study sites in the Swiss Alps differing in (1) the proportion of suitable habitat (i.e., wetlands); (2) the proportion of potential dispersal barriers (forest) in the surrounding landscape; (3) altitude; (4) habitat area and (5) management (mowing versus grazing). Three surveys per study site were conducted during the adult flight period to estimate occurrence and density of each species. For the best disperser B. selene the probability of occurrence was positively related to increasing proportion of wetland on a large spatial scale (radius: 4,000 m), for the medium disperser B. ino on an intermediate spatial scale (2,000 m) and for the poorest disperser B. titania on a small spatial scale (1,000 m). Nearby forest did not negatively affect butterfly species distribution but instead enhanced the probability of occurrence and the population density of B. titania. The fen-specialist B. selene had a higher probability of occurrence and higher population densities on grazed compared to mown fens. The altitude of the habitat patches affected the occurrence of the three species and increasing habitat area enhanced the probability of occurrence of B. selene and B. ino. We conclude that, the surrounding landscape is of relevance for species distribution, but management and habitat fragmentation are often more important. We suggest that butterfly conservation should not focus only on a patch scale, but also on a landscape scale, taking into account species-specific dispersal abilities.  相似文献   

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