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1.
We investigated roost selection by Barbastella barbastellus in a mountainous area of central Italy. Twenty-five bats, mostly lactating females, were radio-tracked to 33 roost trees. Trees in unmanaged woodland were favoured as roost trees; woodland subject to limited logging was used in proportion to availability, and areas where open woodland and pasture occurred were avoided. Selection depended on tree condition (dead beech trees were preferred) and height (roost trees were taller than random ones). Cavity selection was based on cavity type, height and entrance direction: roost cavities were mainly beneath loose bark, at a greater height above ground and facing south more frequently than random cavities. Untouched areas of mature woodland should be preserved to provide roosting conditions for B. barbastellus. In logged areas, harvesting protocols should save dead and mature trees; frequent roost switching and small colony size imply that large numbers of roost trees are needed.  相似文献   

2.
Agricultural intensification in Northern Ireland has brought about large-scale changes to the landscape with a detrimental effect on biodiversity. Between 1996 and 1998, we surveyed a stratified random sample of 1 km squares for bats using a spot-sample technique and time expansion bat detector to establish linear and area habitat associations. Bats strongly selected water bodies with bankside vegetation, treelines, and deciduous and mixed woodland edge, avoiding open areas such as upland/unimproved grassland and improved grassland. Of three sympatric pipistrelle species (Pipistrellus pipistrellus, P. pygmaeus and P. nathusii), two were shown to forage in different habitats; P. pipistrellus being more of a ‘generalist’, foraging in a wider variety of habitats than P. pygmaeus, a ‘specialist’ which foraged in a smaller range of habitats. Nyctalus leisleri selected parkland/amenity grassland, deciduous woodland edge and rivers/canals and avoided improved grassland, hedgerows, whilst Myotis spp. selected deciduous woodland centre, lake/reservoir margins and rivers/canals. Reduction in area and quality of inland water, deciduous woodlands and field boundaries in Northern Ireland may impact on bat populations. Habitat management should focus on improving those habitats which are selected by bats, including the maintenance and enhancement of connecting linear habitats.  相似文献   

3.
Determining the habitat requirements of a species is fundamental to effective conservation, particularly if the species is declining in areas where its habitat is being modified. Multi-scaled investigations of habitat use are essential because different selection processes may operate at different scales. I examined the habitat use of a declining woodland passerine, the rufous treecreeper (Climacteris rufa), at three spatial scales (landscape, woodland and territory) in the wheatbelt of Western Australia. Preferential habitat use was exhibited at all scales. At the landscape scale, wandoo (Eucalyptus wandoo) woodland was used at a significantly greater rate than three other common vegetation types. Territory use within woodlands was positively related to the density of hollow-bearing logs, the density of nest sites, and tree age. Within an individual territory, nest sites (hollows) were favoured if they had a spout angle of ?50° to the horizontal and an entrance size of between 5 and 10 cm. The rufous treecreeper preferentially used habitat with traits characteristic of old-growth wandoo woodland. Degradation of wandoo through habitat modification (e.g. grazing, logging, fire and removal of deadwood) represents a significant threat to the persistence of treecreepers.  相似文献   

4.
The influence of environmental factors on species richness and species composition may be manifested at different spatial levels. Exploring these relationships is important to understand at which spatial scales certain species and organism groups become sensitive to fragmentation and changes in habitat quality. At different spatial scales we evaluated the potential influence of 45 factors (multiple regression, PCA) on saproxylic oak beetles in 21 smaller broadleaved Swedish forests of conservation importance (woodland key habitats, WKH). Local amount of dead wood in forests is often assumed to be important, but two landscape variables, area of oak dominated woodland key habitats within 1 km of sites and regional amount of dead oak wood, were the main (and strong) predictors of variation in local species richness of oak beetles. The result was similar for red-listed beetles associated with oak. Species composition of the beetles was also best predicted by area of oak woodland key habitat within 1 km, with canopy closure as the second predictor. Despite suitable local quality of the woodland key habitats, the density of such habitat patches may in many areas be too low for long-term protection of saproxylic beetles associated with broadleaved temperate forests. Landscapes with many clustered woodland key habitats rich in oak should have high priority for conservation of saproxylic oak beetles.  相似文献   

5.
Populations of the European wildcat (Felis silvestris) are only slowly recovering in Central Europe after a severe decline in the last centuries and require specific conservation plans in many areas. However, detailed information on wildcat occurrence and habitat requirements is still scarce and controversial. We present a fine-scale habitat selection model for wildcats based on detailed species and land use information and evaluate its accuracy to predict habitat distribution in new areas. We analysed habitat use within home ranges using single locations of 12 radio-tracked individuals from south western Germany. Several competing models were fitted and compared using generalised linear mixed models (GLMM) and information-theoretic approaches. Radio-tracking data of 9 and 10 wildcats from two distant areas were used to evaluate the models. The selected model predicted habitat associated to close distance to forest, watercourses and meadows and a critical distance to villages, single houses and roads. To predict area suitable for home ranges we superimposed rules derived from home range attributes at a higher level of selection. Predictions from the combination of the fine-scale habitat model and home range rules matched well with more than 2000 wildcat observations of south-western Germany. We discuss the application of the model in wildcat conservation for finding potential reintroduction sites, identifying small isolated populations and aiding in the evaluation of the needs of mitigation and compensation within the scope of the European Habitats Directive.  相似文献   

6.
Black kites (Milvus migrans) are vulnerable and in decline within Europe. Here, we investigate selection of foraging and breeding habitat in a high-priority population in the Italian pre-Alps. Compared to a random distribution, kites foraged preferentially near water, over extensively managed grassland and within 1 km of nest-sites. Urban areas were positively selected near lakes but otherwise avoided. Foraging performance was higher over water than over terrestrial habitats. Kites nested on cliffs and trees and preferentially near water, far from paths and villages and in rugged and steep micro-sites. Tree-nests were located in the most mature tree in the stand. Productivity was positively related to the availability of water bodies. Therefore, food availability and human disturbance/persecution limited foraging and breeding performance. Guidelines to maintain or enhance current population levels include: (1) setting up reserves covering 10% of the areas within 1 km of large lakes; (2) converting current derelict coppice-woodland to high forest; and (3) enhancing subsidies for extensively managed grassland. Our results highlight the importance of cross-scale models integrating selection of foraging and breeding habitat and reinforce the importance of the spatial configuration of key resources for more realistic conservation management in mosaic landscapes.  相似文献   

7.
Historical records show that large areas of lowland heath have been planted with coniferous woodland. Such sites will increasingly be targeted for heathland restoration in order to achieve the objectives set by current conservation policy. Therefore information on management to achieve effective restoration is a priority for research. In this study we examined the size, composition and distribution of the seed bank beneath conifer plantations of different ages at two important heathland sites in Britain. Changes in the physical and chemical properties of heathland soil under the plantations were also described. There were significant, exponential declines in the mean density of viable heather seeds with plantation age at both sites. However, relatively large seed banks survived for 40 years and under some circumstances for more than 70 years, suggesting that restoration on first rotation sites is unlikely to be seed limited. There were small, but significant differences in the soil nutrient status under the plantations compared to the adjacent heaths. It was concluded that the main constraint on heathland regeneration is likely to be the burial of the seed bank by a thick layer of conifer leaf litter. The mechanical removal of this layer has been shown to be practically feasible.  相似文献   

8.
Information about geographic distributions is required for species conservation and management. Ultimately, this information is derived from records of occurrence. However, the reliability and availability of occurrence records are variable. A conceptual framework for evaluating the reliability of occurrence records is provided. Only records associated with physical evidence, especially a museum voucher specimen, are considered verified. However, errors in species identification or location are possible even for verified records. In addition, biases exist in occurrence records because they generally are collected haphazardly. Other sources of bias include sampling error associated with small areas or range limits and aspects of the species’ biology that make it unlikely to be documented. A practical method is provided for interpreting a species’ distribution in a particular area given a paucity of reliable occurrence records. Factors that must be considered for including such areas of interest within the range of a species include: (1) plausible reason for the paucity of records; (2) continuous suitable habitat between the area of interest and localities of reliable occurrence; and (3) absence of biogeographic breaks in the distribution of other organisms with similar evolutionary histories. The possible distribution of wolverine (Gulo gulo) and Canada lynx (Lynx canadensis) in New Mexico provides a case study of this approach. It is concluded that the mountains of north-central New Mexico should be considered within the natural range of wolverine and Canada lynx.  相似文献   

9.
Understanding the impact of indirect habitat loss resulting from avoidance of human infrastructure is an important conservation priority. We evaluated resource selection for 10 global positioning system collared northern mountain woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada, with seasonal resource selection functions (RSF) developed at the second-order (landscape) and third-order (within home range) scales. To estimate how much habitat was lost due to avoidance, we estimated the zone of influence (ZOI) around multiple developments and modeled realized and potential habitat. Potential habitat was approximated by removing the ZOI from RSF models. By calculating the spatial difference between potential and realized habitat we estimated the amount of indirect habitat loss. Caribou displayed hierarchical avoidance of development, with the greatest avoidance occurring at the second-order. During both seasons caribou avoided high-use roads by 2 km and low-use roads by 1 km. In winter, caribou avoided town by 9 km compared to 3 km in summer. However, in summer caribou avoided mines by 2 km and cabins and camps by 1.5 km, while in winter when human activity was low, avoidance of these features was minor. As a result of avoidance of the cumulative ZOI, approximately 8% and 2% of high quality habitat was lost in the study area in winter and summer, respectively. Our study provides an approach to identify the extent and quality of habitat influenced by indirect avoidance. Conservation efforts should prioritize protecting areas of high quality habitat degraded by avoidance in the vicinity of human development.  相似文献   

10.
Single trees and small patches of trees in farmland are conspicuous components of agricultural landscapes around the world, but their value for the conservation of biodiversity is not well known. In this study, arboreal mammals were censused by using hair-sampling tubes in small patches of woodland (single trees to patches <1.0 ha) in cleared farmland adjacent to a linear network of woodland known to support resident populations of arboreal mammals. Ninety-one small isolates were stratified by size (single trees or small patches) and distance from the linear network to test the capacity of animals to cross habitat ‘gaps’. The genus Petaurus (small gliding marsupials), the most commonly detected taxon, was recorded in 31% of hair-tubes (98 of 316). It occurred in 21% of sites in isolated trees and patches, and in all linear strips. A logistic regression model demonstrated that Petaurus sp. was most likely to occur in isolates in close proximity to linear strips and other patches of woodland. Ninety-five per cent of sites at which this taxon occurred were within 75 m of the linear network. This threshold corresponds with the maximum distance that animals can glide in a single movement between trees. The size of isolates did not influence utilisation rates. Such isolates are smaller than a single home range and were probably used to supplement home ranges centred on the linear network, by providing additional foraging habitat and den sites. Protection and restoration of isolated trees and small woodland clumps in cleared landscapes contributes to mammal conservation and this study provides quantitative data that can assist landscape design and habitat restoration in rural environments.  相似文献   

11.
In parts of Australia, extensive areas of cleared land are now being planted with commercial plantations of native eucalypts. Questions arise about the extent to which such plantations can rectify previous loss of habitat and contribute to biodiversity conservation. This study assessed abundance of bird species (as one aspect of biodiversity) on 105 sites (25 cleared land, 58 plantations and 22 native forest) in two regions of rural Victoria, south-eastern Australia. Generalised linear modelling was used to assess some of the landscape and habitat variables that contributed to the value of plantation sites for particular groups of bird species. These models demonstrated the importance of on-site habitat variables in explaining the abundance of groups of bird species, with landscape context making small additional contributions.Mean abundance of forest and woodland birds was higher in eucalypt plantations than cleared farmland, and marginally lower than in native forest. Patterns differed between bird guilds. For example, insectivores that forage in the canopy and tall shrub layers were at least as common in plantations as in native forest, with birds in the latter group using young eucalypts as if they were tall shrubs. Birds that forage from open ground among trees were more common in plantations than native forest, and may benefit substantially from the new habitat fortuitously provided for them. This group includes several species that have declined in natural woodland habitats. Nectarivores, carnivores and birds that forage among low shrubs were less common in plantations than in native forest. Insectivores that forage from eucalypt bark made little use of plantations. Different approaches to plantation design and management would be needed to cater for groups such as these. Specific measures include planting of rough-barked eucalypts in addition to smooth-barked species, and provision of artificial hollows. Retention of existing remnants of native forest (e.g. old trees and forest patches) is a priority, to supply habitat elements that would otherwise be missing for long periods.  相似文献   

12.
The dehesa (oak woodland) is an extensive agro-pastoral ecosystem characteristic of the Western Mediterranean countries which is suffering a great transformation process since 1950. Although its distribution largely overlaps with several endangered species, there is scarce information on how they use this human-transformed habitat. We studied the foraging habitat selection of one of them, the cinereous vulture Aegypius monachus. We radio-tracked 14 cinereous vultures in one of the largest European colonies from 1998 to 2000. Used and available habitats were compared at two scales using compositional analysis. Moreover, we developed a distance-based GLMM for assessing habitat selection in this central-place forager species, by taking into account the spatial distribution of habitat patches in relation to the location of the colony. Home ranges overlapped over a total surface of 592,527 ha around the colony, and both individual home ranges and travel foraging distances (mean 27.86 km, maximum 86 km) were larger during the breeding season. All cinereous vultures avoided agricultural lands within their home ranges throughout the year. Habitat use in relation to the distance to the colony pointed out that dehesas were positively selected in spite of being on average far away from the colony than other habitats, a result that was consistent among individuals and seasons. The cinereous vulture thus depends for its conservation not only on the protection of breeding areas, as has been so far considered, but also on the maintenance of well-conserved dehesas close to the colonies. Preserving the cinereous vultures could contribute to the economic sustainability of dehesas by attracting PAC funds for their traditional low-intensity exploitation. Although other species may also benefit from this study since cinereous vulture could be a “flagship” for the large-scale conservation of Mediterranean oak woodlands and associated biodiversity, more fine local management guidelines should be performed on the basis of studies on more sensitive species.  相似文献   

13.
To provide sustainable income from forestlands, large areas in the tropics are planted with “agricultural” trees, such as oil palm and rubber, and “industrial” trees, such as Acacia mangium and Gmelina arborea. To examine how native forest birds use such plantations, we surveyed in 2005 the avifauna at Sabah Softwoods, a plantation in southeastern Sabah, Malaysian Borneo. We focused on A. mangium, Albizia (Paraserianthes falcataria), oil palm (Elaeis guineensis), and logged native forest, and compared our results to those of a study conducted at the same plantation in 1982. The number of forest species in the industrial groves did not change dramatically between 1982 and 2005, even though the trees had been cropped several times and the plantation was, by 2005, completely surrounded by cleared land and far removed from primary forest. However, as is common in logged or isolated forests throughout the world, certain primary forest groups (e.g., muscicapine flycatchers) have been extirpated from the entire plantation area. The industrial groves also lacked some larger species of kingfisher, woodpeckers, and canopy frugivores. Nevertheless, numerous primary forest taxa (ca. 50% of species) were found in mature industrial tree groves. Albizia attracted the most species of birds, followed closely by Acacia. Both tree types underpinned relatively complex secondary forests that attracted forest birds. In contrast, younger groves of Acacia and Albizia held mainly open country and scrub species. Oil palm, as a remarkably simple and unusual habitat, attracted few bird species. Sustained occurrence of forest birds in all groves of exotic trees at Sabah Softwoods was substantially enhanced by the relatively rich avifauna of the logged native forest remaining in substantial stands throughout the plantation.  相似文献   

14.
Natural areas are becoming increasingly fragmented and embedded in an urban matrix. Natural and semi-natural areas at the urban/wildland interface are threatened by a variety of ‘edge effects’, and are especially vulnerable to invasion by introduced plants, with suburban gardens acting as significant sources of alien propagules. Urban/wildland interfaces also provide access for humans, leading to various types of disturbance. Alien plant invasions are one of the biggest threats facing remaining natural areas on the Cape Peninsula, South Africa. The area provides an ideal opportunity to study the dynamics of invasions at the urban/wildland interface, since the largest natural area, the Table Mountain National Park (TMNP), is surrounded by the city of Cape Town. We explored invasion patterns in Newlands Forest (a small section of the TMNP) and detailed the roles of habitat features and distance from putative source populations in three main habitat types: natural Afromontane forest, riverine woodland habitats, and plantations of exotic pines (Pinus radiata and P. pinaster). We also examined the role of disturbance in driving invasions in two of these habitat types (Afromontane forest and pine plantations). We hypothesized that alien richness and alien stem density would decrease with distance from the urban/wildland interface, and that alien richness and alien stem density would increase with increasing levels of human disturbance.Distance from putative source populations and levels of anthropogenic disturbance influenced alien richness in Newlands Forest but not alien stem density. Alien richness decreased significantly with distance from presumed sources in the pine habitat, and increased significantly with disturbance in the forest habitat. Percentage overstorey cover and soil pH were important environmental variables associated with alien plant species. A socio-economic approach is discussed as being the most effective approach to the management and prevention of alien plant species in Newlands Forest.  相似文献   

15.
Conservation of remaining woodland caribou (Rangifer tarandus caribou) populations requires land management strategies that not only maintain caribou habitat, but also favour habitat connectivity. This study presents and field tests graph theory-based measures of landscape connectivity, and demonstrate an association between the distribution of woodland caribou and well-connected winter habitat. Cost values for the intervening land cover types were determined based on the probability of selection relative to high-quality winter habitat. Habitat connectivity was then represented by linking high-quality habitat patches along least-cost paths through this parameterized cost surface. A randomization procedure was used to assess the animal’s association with habitat connected at increasing distance thresholds to identify appropriate scales of response. A strong relationship was obtained between large clusters of high-quality winter habitat patches and winter GPS telemetry location points (November 1-March 15) from two woodland caribou herds in Manitoba, Canada. This relationship was stronger when only late winter location points (January 1-March 15) were used. Our results highlight the importance of accounting for the spatial configuration of habitat on the landscape and the intervening land cover types when assessing range quality for woodland caribou. They also provide support for the use of graph theory to assist in identifying core activity areas for woodland caribou and key linkages between these areas and other parts of the landscape.  相似文献   

16.
Tropical forest fragmentation affects animal and plant populations in different ways. For plants, early stages (seed to seedling) are more sensitive to habitat alteration than adults, and can shape their future spatial patterns. Therefore, studying how seed germination and seedling growth and survival vary at different spatiotemporal scales enhances our understanding about plant recruitment in fragmented ecosystems. In this study we examine if, and to what extent, recruitment at early life-stages of Xymalos monospora (Monomiaceae), a bird-dispersed Afrotropical tree, differs between and within forest fragments that vary in size, surrounding matrix and microhabitats. Three years of field experiments (2004-2006) in south-east Kenya, revealed that patterns of seed germination and seedling survival and growth were largely inconsistent, both in space and time. Recruitment was not consistently higher in larger or less disturbed fragments. At smaller spatial scales within forest fragments, recruitment was subject to high between-year variation too, with decreased germination in gaps only in the dry year of 2004. However, performance of seeds and seedlings was consistently better away from than under conspecific fruiting trees. Our results imply that fragmented tree populations of X. monospora may become age-structured, or ultimately go extinct, if recruitment fails in subsequent years. This may especially affect populations in small, disturbed forest fragments, where seed dispersal and buffering against stochastic processes are generally reduced. Exotic plantations bordering indigenous forest fragments may provide suitable conditions for native tree recruitment; hence, forest expansion through enrichment planting should be considered in future conservation plans.  相似文献   

17.
We studied dispersal in 27 radio-collared Florida panthers Puma concolor coryi in southern Florida from 1986 to 2000. Male dispersal was longer (mean=68.4 km) than that of females (mean=20.3 km), tended to be circular, frustrated, and of insufficient length to ameliorate inbreeding. Females were philopatric and established home ranges that were less than one home range width away from their natal ranges. All females were successful in establishing territories, whereas males were successful 63% of the time. Dispersing panthers avoided moving toward the southeast and into an area of limited forest cover. Independence and the initiation of dispersal occurred at about 14 months of age and lasted for an average of 7.0-9.6 months for females and males, respectively. On average, Florida panthers disperse shorter distances than are typical for western populations of Puma concolor. A recent increase in long distance male dispersal events may be related to an increase in reproduction and population density resulting from the introduction of female cougars P. c. stanleyana into south Florida. Although the population exhibits the behavioral ability to colonize nearby vacant range, females have yet to do so. Successful dispersal to these areas could be facilitated by habitat restoration and translocation of females.  相似文献   

18.
More than half of the world's population of the little bastard Tetrax tetrax lives in the Iberian Peninsula, where it is mostly dependent for survival on extensive agricultural areas. The species has declined dramatically, chiefly due to changes in agricultural practices, and is now globally ‘Near Threatened’. Knowledge of its habitat requirements is crucial to reverse the trend of habitat deterioration. Winter habitat preferences were studied in a region dominated by extensive cereal farming in Southern Portugal, comparing the characteristics of sites used by 54 flocks with those of randomly selected sites within the study area. The birds preferred recent fallows and grassy vegetation of mid-size (about 11-20 cm) and mid-density (about 11-50% cover). They tended to concentrate on the tops of hills and to avoid disturbed areas near roads and houses. Overall, the observed preferences suggest that predator avoidance is a significant factor in habitat selection. To improve habitat suitability for little bustard, managers of key wintering areas should minimize permanent sources of human disturbance, encourage rotations with frequent fallows, and favour moderate levels of grazing to manipulate vegetation height and cover. Particular attention should be given to the upper parts of the hills.  相似文献   

19.
This study investigated associations between the relative abundance of the threatened ngwayir (western ringtail possum, Pseudocheirus occidentalis) and anthropogenic disturbances at local and landscape scales within the publicly-managed jarrah (Eucalyptus marginata) forests of south-western Australia. Logging, fire, fox (Vulpes vulpes) control and forest fragmentation were investigated in relation to the relative abundance of ngwayir at 90 sites within an area of 285,000 ha east of Manjimup; the location of the last remaining substantial population of ngwayir in jarrah forest. Overall, ngwayir abundance was greatest in areas with limited anthropogenic disturbance. At the local-scale, ngwayir abundance was negatively associated with greater fire intensity. At the landscape-scale, it was positively associated with fox control and negatively associated with forest fragmentation and distance from non-remnant vegetation (i.e., agriculture and tree plantations). Abundance was also greatest in predominantly unlogged landscapes and in forests that had been regrowing for an average of 40 years since the landscape was most recently logged, in other words, where logging was historically least intense. Interactions between fox control efforts and forest fragmentation were also important. This study emphasises the importance of conducting research at appropriate spatial scales and to account for the synergistic effects of the causes of decline. An adaptive management approach to the mitigation of the agents of decline is recommended.Indirect evidence indicates that high value habitat for ngwayir has in all likelihood been selectively cleared for agriculture, owing to its fertile and productive nature. Habitat loss is, therefore, also likely to be a major cause of the modern decline of the species. While many jarrah forest areas that support remaining high abundances of the ngwayir have been incorporated into reserves, conservation of ngwayir habitat and populations outside reserves also will be essential for the recovery and long-term viability of the species.  相似文献   

20.
Using random amplified polymorphic DNA (RAPD) markers, we examined genetic variability of the moss Thuidium cymbifolium (Thuidiaceae) sampled from three types of spruce (Picea asperata) stands: an intact stand, naturally regenerated stands after clearcut harvests, and planted stands after clearcut harvests in the Miyaluo area, western Sichuan of China. Stands of the latter two types were of various age since the last clearcut. Results showed that the population of T. cymbifolium from the intact stand displayed the highest level of genetic diversity, and populations from the planted stands exhibited significantly higher levels than the naturally regenerated stands. In planted stands, genetic variation within populations increased over time. These findings indicated that habitat destruction by forest harvesting led to the reduction in genetic variation within populations, but that given time, artificial reforestation after clearcut was effective in promoting the recovery of genetic diversity in the recolonized moss species. Therefore, lengthening the normal felling rotation of plantations should be favored to restore and conserve genetic diversity in recolonized species. In addition, thinning young plantations via selective logging may provide heterogenous microhabitats similar to those in the old stands, and thereby facilitate the development of bryophyte communities and the increase of genetic variation of the recolonized mosses.  相似文献   

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