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1.
Songbird presence is often associated with the area of suitable habitat in the surrounding landscape. However, the size of landscape for which this association is maximized is generally unknown, likely to vary among species, and may affect our ability to incorporate songbirds in landscape management. We measured the occurrence and the persistence of forest songbirds in relation to the amount of habitat measured at several scales: local (100, 200 m radius), neighborhood (400, 800 m), landscape (1.6, 3.2, 6.4 km) and regional (12–24 km), based on data from Ontario's Forest Bird Monitoring Program (1987–2005). Songbird occurrence was obtained from point count sites distributed across southern Ontario and each revisited in multiple years (mean=5.8 yr). Presence of each species at a site was associated with forest habitat area measures that account for differences in preferred forest cover types among species. Area of coniferous, deciduous and mixed forest was derived from Landsat TM imagery. Thirty‐two of the 35 species studied were area‐sensitive, and area‐sensitivity was apparent for 13–25 species at each spatial scale. For 24 species, the strength of area‐sensitivity varied with scale, suggesting the importance of local, neighborhood, landscape and regional habitat for 3, 5, 5, and 11 species respectively. As a result, the list of the five most area‐sensitive species varied depending on the scale at which habitat was described. We conclude that area‐sensitivity can occur at a broader set of scales than generally assumed, and is most pronounced at the regional scale. We suggest that a broad set of scales should be examined before taking conservation decisions based on avian area‐sensitivity.  相似文献   

2.
Mature trees and forests contain structural features such as tree hollows, large coarse woody debris and large spreading crowns that provide critical habitat for a wide range of species. These features can take hundreds of years to develop and require careful management to ensure their continued availability. Managing these features requires spatial mapping layers to facilitate landscape‐scale management. This paper outlines how a map of mature forest habitat was developed for Tasmania, Australia. The map was produced using spatial data on vegetation type, mature crown density and senescence, a global layer of forest loss data derived from satellite imagery, a database on timber harvest plans and a spatial layer on the extent of fire. The relationship between mapped mature habitat availability (high, medium, low or negligible) and tree hollow availability in wet forest areas was explored, complementing a similar published study in dry forests. The number of large trees likely to have hollows significantly increased with mapped mature habitat availability, although there was considerable variation and overlap between map categories. Data from a fauna locality database and two radio‐tracking studies showed that three of the vertebrate hollow‐using species examined (Swift Parrot, Common Brushtail Possum and the Tasmanian Long‐eared Bat) and nest records of a species reliant on large tree crowns (the Wedge‐tailed Eagle) were all more likely to occur in areas of higher mapped mature habitat availability. It is concluded that this map reflects the relative availability of tree hollows, is ecologically meaningful and will be useful when managing mature forest habitat at large spatial scales, but the variable accuracy of the map at fine scales needs to be taken into account.  相似文献   

3.
We examine existing and developing approaches to balance biodiversity conservation and timber production with the changing conservation roles of federal and nonfederal forest land ownerships in the US Pacific Northwest. At landscape scales, implementation of the reserve-matrix approach of the federal Northwest Forest Plan in 1994 was followed by proposals of alternative designs to better integrate disturbance regimes or to conserve biodiversity in landscapes of predominantly young forests through active management without reserves. At stand scales, landowners can improve habitat heterogeneity through a host of conventional and alternative silvicultural techniques. There are no state rules that explicitly require biodiversity conservation on nonfederal lands in the region. However, state forest practices rules require retention of structural legacies to enhance habitat complexity and establishment of riparian management areas to conserve aquatic ecosystems. Habitat Conservation Plans (HCPs) under the US Endangered Species Act provide regulatory incentives for nonfederal landowners to protect threatened and endangered species. A state-wide programmatic HCP has recently emerged as a multi-species conservation approach on nonfederal lands. Among voluntary incentives, the Forest Stewardship Council certification comprehensively addresses fundamental elements of biodiversity conservation; however, its tough conservation requirements may limit its coverage to relatively small land areas. Future changes in landscape management strategies on federal lands may occur without coordination with nonfederal landowners because of the differences in regulatory and voluntary incentives between ownerships. This raises concerns when potentially reduced protections on federal lands are proposed, and the capacity of the remaining landscape to compensate has been degraded.  相似文献   

4.
We examine existing and developing approaches to balance biodiversity conservation and timber production with the changing conservation roles of federal and nonfederal forest land ownerships in the US Pacific Northwest. At landscape scales, implementation of the reserve-matrix approach of the federal Northwest Forest Plan in 1994 was followed by proposals of alternative designs to better integrate disturbance regimes or to conserve biodiversity in landscapes of predominantly young forests through active management without reserves. At stand scales, landowners can improve habitat heterogeneity through a host of conventional and alternative silvicultural techniques. There are no state rules that explicitly require biodiversity conservation on nonfederal lands in the region. However, state forest practices rules require retention of structural legacies to enhance habitat complexity and establishment of riparian management areas to conserve aquatic ecosystems. Habitat Conservation Plans (HCPs) under the US Endangered Species Act provide regulatory incentives for nonfederal landowners to protect threatened and endangered species. A state-wide programmatic HCP has recently emerged as a multi-species conservation approach on nonfederal lands. Among voluntary incentives, the Forest Stewardship Council certification comprehensively addresses fundamental elements of biodiversity conservation; however, its tough conservation requirements may limit its coverage to relatively small land areas. Future changes in landscape management strategies on federal lands may occur without coordination with nonfederal landowners because of the differences in regulatory and voluntary incentives between ownerships. This raises concerns when potentially reduced protections on federal lands are proposed, and the capacity of the remaining landscape to compensate has been degraded. This paper was previously published in Biodiversity and Conservation, Volume 16(13) under doi:  相似文献   

5.
Retention forestry, which retains a portion of the original stand at the time of harvesting to maintain continuity of structural and compositional diversity, has been originally developed to mitigate the impacts of clear‐cutting. Retention of habitat trees and deadwood has since become common practice also in continuous‐cover forests of Central Europe. While the use of retention in these forests is plausible, the evidence base for its application is lacking, trade‐offs have not been quantified, it is not clear what support it receives from forest owners and other stakeholders and how it is best integrated into forest management practices. The Research Training Group ConFoBi (Conservation of Forest Biodiversity in Multiple‐use Landscapes of Central Europe) focusses on the effectiveness of retention forestry, combining ecological studies on forest biodiversity with social and economic studies of biodiversity conservation across multiple spatial scales. The aim of ConFoBi is to assess whether and how structural retention measures are appropriate for the conservation of forest biodiversity in uneven‐aged and selectively harvested continuous‐cover forests of temperate Europe. The study design is based on a pool of 135 plots (1 ha) distributed along gradients of forest connectivity and structure. The main objectives are (a) to investigate the effects of structural elements and landscape context on multiple taxa, including different trophic and functional groups, to evaluate the effectiveness of retention practices for biodiversity conservation; (b) to analyze how forest biodiversity conservation is perceived and practiced, and what costs and benefits it creates; and (c) to identify how biodiversity conservation can be effectively integrated in multi‐functional forest management. ConFoBi will quantify retention levels required across the landscape, as well as the socio‐economic prerequisites for their implementation by forest owners and managers. ConFoBi's research results will provide an evidence base for integrating biodiversity conservation into forest management in temperate forests.  相似文献   

6.
Tree cavities provide important habitat for wildlife. Effective landscape‐scale management of cavity‐dependent wildlife requires an understanding of where cavities occur, but tree cavities can be cryptic and difficult to survey. We assessed whether a landscape‐scale map of mature forest habitat availability, derived from aerial photographs, reflected the relative availability of mature trees and tree cavities. We assessed cavities for their suitability for use by wildlife, and whether the map reflected the availability of such cavities. There were significant differences between map categories in several characteristics of mature trees that can be used to predict cavity abundance (i.e. tree form and diameter at breast height). There were significant differences between map categories in the number of potential cavity bearing trees and potential cavities per tree. However, the index of cavity abundance based on observations made from the ground provided an overestimate of true cavity availability. By climbing a sample of mature trees we showed that only 5.1% of potential tree cavities detected from the ground were suitable for wildlife, and these were found in only 12.5% of the trees sampled. We conclude that management tools developed from remotely sensed data can be useful to guide decision‐making in the conservation management of tree cavities but stress that the errors inherent in these data limit the scale at which such tools can be applied. The rarity of tree cavities suitable for wildlife in our study highlights the need to conserve the tree cavity resource across the landscape, but also the importance of increasing the accuracy of management tools for decision‐making at different scales. Mapping mature forest habitat availability at the landscape scale is a useful first step in managing habitat for cavity‐dependent wildlife, but the potential for overestimating actual cavity abundance in a particular area highlights the need for complementary on‐ground surveys.  相似文献   

7.
Aim To investigate the relative role of local versus landscape factors for local species diversity of snails and slugs in conservation forests. In landscapes with small, isolated patches of semi‐natural habitats, many species that require large habitat areas have disappeared or are threatened. We asked whether small sedentary taxa that depend on local conditions, such as molluscs, are affected if total habitat area decreases in the landscape. Location Temperate broadleaved and oak‐rich forest in southern Sweden. Methods We sampled molluscs in 25 small conservation forests that are well‐spaced out over a large region. In each forest, sampling was conducted in two plots, each of 1 ha, separated by about 25–100 m. Factors potentially influencing local diversity of molluscs were measured in the plots and in the surrounding landscape at different scales (in space and time) and were analysed by stepwise multiple regression and ordination (PCA and NMS). Results We recorded 53 species, and mean species richness per forest (plots pooled) was 22.6. The pH of the plant litter predicted both species richness and composition; other local (plot) factors of lower importance were canopy openness, stony ground and tree species. The area of conservation forest (woodland key habitat) within 10 km of plots was positively associated with species richness, and was also related to species composition. Openness of the landscape (agriculture) was a negative factor, but historical plot openness (1938–59) seemed to be unimportant. In addition, climate/topography (temperature and altitude) also predicted species composition of the sites. Main conclusions We rejected the hypothesis that microhabitat factors alone, or mainly, determine local species richness and composition of land molluscs. These representatives of small, sedentary organisms seem to be substantially influenced by the surrounding landscape, which should be considered in conservation work and in plans for the protection of forest biodiversity.  相似文献   

8.
Understanding landscape correlates of local habitat integrity and community structure and the identification of spatial scales at which these associations operate are relevant for management and conservation of unique but globally threatened temporary ponds. We use a multivariate variance decomposition approach to determine taxon-specific associations of zooplankton communities banked in dry pond soils (rotifers, cladocerans, copepods) with local habitat features and landscape characteristics across four spatial scales (100 buffer strip, 1, 5, and 10 km scales). Results show similar degrees of correlation between rotifer and cladoceran communities with local habitat conditions (chiefly water quality). This is interpreted according to life-history traits of component species of wetland propagule banks. Associations with landscape features varied between communities with rotifers correlating with landscape structural features only at the buffer scale while cladocerans showed no significant correlations with landscape characteristics across all scales. Copepods were neither significantly associated with local nor landscape characteristics. The results of this study contrast strikingly with our previous population-based study, where populations of Triops cancriformis and Branchinecta orientales were significantly correlated with landuse features at the broadest scale. The combined results suggest that a three-way management scheme could be useful for conservation of zooplankton resting egg banks in this remnant wetland complex. These schemes could focus on the restoration of wetland water quality, the establishment of vegetated buffer strips around the ponds to counteract degradation resulting from runoff, and reforestation and/or the creation of hedgerows in agricultural catchments to avoid impacts resulting from broad-scale diffuse pollution fluxes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

9.
Detailed field and modelling studies have been completed at different spatial scales for the endangered arboreal marsupial, Leadbeater's Possum (Gymnobelideus leadbeateri); a species virtually confined to the ash-type eucalypt forests in the Central Highlands of Victoria, south-eastern Australia. These forests are also subject to considerable pressure to produce timber and paper products. The studies of Leadbeater's Possum highlighted the factors influencing the distribution and abundance of the species ranging from broad distribution patterns, the occupancy of habitat patches at the landscape scale, and the use of individual den sites and the quality of trees that provide food within particular stands. These scales correspond to the entire known range of the species, sub-populations within a metapopulation occupying an ensemble of patches at the landscape scale, and colonies occupying den trees in individual stands. Information on the factors influencing the distribution of Leadbeater's Possum at one spatial scale were found to be important for informing processes at another. For example, an understanding of the species habitat requirements informed the spatial distribution of habitat patches at the landscape level which, in turn, gave insights into predicted metapopulation dynamics. Each spatial scale of ecological investigation of Leadbeater's Possum had a corresponding scale of forest management, and they included: virtually the entire ash-type eucalypt resource in the region, the location of large reserves, the design of corridors and retained patches within production forest landscapes, silvicultural practices employed in individual stands, and the retention of individual trees and clusters of trees on logged sites. This range of forest management scales, and the corresponding-scaled array of ecological studies, have particular implications for the conservation of Leadbeater's Possum. The results of investigations to date have revealed that conservation efforts must focus on ash-type eucalypt forests in the Central Highlands of Victoria because populations of Leadbeater's Possum are virtually confined to these areas. Within the broadscale limits of the distribution of the species, the long-term conservation of Leadbeater's Possum will not only be dependent on large reserves, but also intermediate-scale reserves and corridors within wood production areas, as well changed silvicultural practices to better provide suitable habitat on logged sites. While each strategy will make a contribution to the persistence of Leadbeater's Possum, it also has important limitations; an outcome which highlights the need for a multi-scale approach to attempts to conserve the species. Notably, the overaching implications for the design of an array of different conservation strategies for Leadbeater's Possum could not have been derived from any single study at a particular spatial scale. Thus, the case study on Leadbeater's Possum suggests that consideration of factors at a range of scales should be an integral part of management and conservation planning, not only for this species, but for wildlife per se.  相似文献   

10.
The conservation of any species requires understanding and predicting the distribution of its habitat and resource use, including the effects of scale‐dependent variation in habitat and resource quality. Consequently, testing for resource selection at the appropriate scales is critical. We investigated how the resource selection process varies across scales, using koalas in a semi‐arid landscape of eastern Australia as a case study. We asked: at what scales does tree selection by koalas vary across regions? We tested the importance of the variation of our ecological predictors at the following scales: (i) the site‐scale (a stand of trees representing an individual koala's perception of local habitat); (ii) the landscape‐scale (10 × 10 km area representing a space within which a population of koalas exists); and (iii) a combination of these scales. We used a mixed‐modelling approach to quantify variation in selection of individual trees by koalas among sites and landscapes within a 1600 km2 study area. We found that tree species, and tree height, were the most important factors influencing tree selection, and that their effect did not vary across scales. In contrast, preferences for trees of different condition, which is the state of tree canopy health, did vary across landscapes, indicating spatial variation in the selection of trees with respect to tree condition at the landscape‐scale, but not at the site‐scale. We conclude that resource selection processes can depend on the quality of those resources at different scales and their heterogeneous nature across landscapes, highlighting the consequence of scale‐dependent ecological processes. Designing studies that capture the heterogeneity in habitat and resources used by species that have an extensive distribution is an important prerequisite for effective conservation planning and management.  相似文献   

11.
Montane tropical cloud forests, with their complex topography, biodiversity, high numbers of endemic species, and rapid rates of clearing, are a top global conservation priority. However, species distributions at local and landscape scales in cloud forests are still poorly understood, in part because few regions have been surveyed. Empirical work has focused on species distributions along elevation gradients, but spatial variation among forests at the same elevation is less commonly investigated. In this study, the first to compare tree communities across multiple Andean cloud forests at similar elevations, we surveyed trees in five ridge‐top forest reserves at the upper end of the ‘mid‐elevation diversity bulge’ (1900–2250 masl) in the Intag Valley, a heavily deforested region in the Ecuadorian Andes. We found that tree communities were distinct in reserves located as close as 10 to 35 km apart, and that spatially closer forests were not more similar to one another. Although larger (1500 to 6880 ha), more intact forests contained significantly more tree species (108–120 species/0.1 ha) than smaller (30 to 780 ha) ones (56–87 species/0.1 ha), each reserve had unique combinations of more common species, and contained high proportions of species not found in the others. Results thus suggest that protecting multiple cloud forest patches within this narrow elevational band is essential to conserve landscape‐level tree diversity, and that even small forest reserves contribute significantly to biodiversity conservation. These findings can be applied to create management plans to conserve and restore cloud forests in the Andes and tropical montane cloud forests elsewhere.  相似文献   

12.
Intensive forestry practises in the Swedish landscape have led to the loss and fragmentation of stable old‐growth habitats. We investigated relationships between landscape composition at multiple scales and the composition of saproxylic beetle assemblages in nine clear‐cut, mature managed and old‐growth spruce‐dominated forest stands in the central boreal zone of Sweden. We set out fresh spruce and birch logs and created spruce snags in 2001–2002 to experimentally test the effects of coarse woody debris (CWD) type and forest management on the composition of early and late successional, and red‐listed saproxylic beetle assemblages. We examined effects of CWD availability at 100 m, and landscape composition at 1 and 10 km on saproxylic beetle abundances. Additionally, we tested whether assemblage similarity decreased with increasing distance between sites. We collected beetles from the experimental logs using eclector and window traps in four periods during 2003. CWD was measured and landscape composition data was obtained from maps of remotely sensed data. The composition of saproxylic beetles differed among different CWD substrates and between clear‐cuts and the older stand types, however differences between mature managed and old‐growth forests were significant only for red‐listed species. Assemblage similarities for red‐listed species on clear‐cuts were more different at greater distances apart, indicating that they have more localised distributions. CWD availability within 100 m of the study sites was rarely important in determining the abundance of species, suggesting that early successional saproxylic beetles can disperse further than this distance. At a larger scale, a large area of suitable stand types within both 1 and 10 km resulted in greater abundances in the study sites for several common and habitat‐specific species. The availability of suitable habitat at scales of 1–10 km is thus likely to be important in the survival of many saproxylic species in forestry‐fragmented areas.  相似文献   

13.
We studied the effects of habitat mosaics on butterfly assemblage on multiple spatial scales: landscape, landscape element, local habitat, and microhabitat, based on the transect counts conducted along a 3.84 km route. The transect route, including 21 local habitats, passed through two distinct areas: 1.65 km of a secondary deciduous Quercus forest and the grove of a shrine in Hiraoka, and 2.19 km of a mosaic of secondary deciduous Quercus forest, grassland, and farmland in Narukawa. The diversity of the landscape elements and species richness were higher in Narukawa than in Hiraoka; the landscape mosaic enhanced the species richness in Narukawa. However, the diversity indices and specialist species (univoltine tree feeder) were decreased in this mosaic landscape. The species richness at local habitats was also increased by the mosaic of microhabitats, such as the herbaceous layer, glade, and mantle in the local habitats, whereas it was decreased by an abundant shrub layer. The ratios of species richness to abundance in the local habitats were lower than expected based on random sampling from the total of Hiraoka and Narukawa. This means that local assemblages were non-random samples from an assemblage on the landscape or regional scale, and were made up by the process of habitat selection of butterfly species in the assemblages on the landscape or regional scale. For conservation of butterfly assemblages, we recommend that woodlands should be kept without fragmentation, but with glades or small grasslands, and with clearance of the shrub layer along the path.  相似文献   

14.
Aim A better understanding of the processes driving local species richness and of the scales at which they operate is crucial for conserving biodiversity in cultivated landscapes. Local species richness may be controlled by ecological processes acting at larger spatial scales. Very little is known about the effect of landscape variables on soil biota. The aim of our study was to partly fill this gap by relating the local variation of surface‐dwelling macroarthropod species richness to factors operating at the habitat scale (i.e. land use and habitat characteristics) and the landscape scale (i.e. composition of the surrounding matrix). Location An agricultural landscape with a low‐input farming system in Central Hesse, Germany. Methods We focused on five taxa significantly differing in mobility and ecological requirements: ants, ground beetles, rove beetles, woodlice, and millipedes. Animals were caught with pitfall traps in fields of different land use (arable land, grassland, fallow land) and different habitat conditions (insolation, soil humidity). Composition of the surrounding landscape was analysed within a radius of 250 m around the fields. Results Factors from both scales together explained a large amount of the local variation in species richness, but the explanatory strength of the factors differed significantly among taxa. Land use particularly affected ground beetles and woodlice, whereas ants and rove beetles were more strongly affected by habitat characteristics, namely by insolation and soil characteristics. Local species richness of diplopods depended almost entirely on the surrounding landscape. In general, the composition of the neighbouring landscape had a lower impact on the species richness of most soil macroarthropod taxa than did land use and habitat characteristics. Main conclusions We conclude that agri‐environment schemes for the conservation of biodiversity in cultivated landscapes have to secure management for both habitat quality and heterogeneous landscape mosaics.  相似文献   

15.
Although examples are rare, conflicts between species of conservation concern can result from habitat restoration that modifies habitat to benefit a single taxon. A forest restoration program designed to enhance habitat for endangered red‐cockaded woodpeckers (Picoides borealis) may be reducing available habitat for the eastern spotted skunk (Spilogale putorius), a forest‐adapted sympatric species of conservation concern that occurs in the Ouachita National Forest, Arkansas, U.S.A. At small scales, eastern spotted skunks select early successional forest with structural diversity, whereas red‐cockaded woodpeckers prefer mature pine (Pinus spp.) habitat. We surveyed for eastern spotted skunks at 50 managed forest stands, modeled occupancy as a function of landscape‐level habitat factors to examine how features of restoration practices influenced occurrence, and compared known occupied forest stands to those where active red‐cockaded woodpecker nesting clusters were located. The most‐supported occupancy models contained forest stand age (negatively associated) and size (positively associated); suggesting eastern spotted skunks primarily occupy large patches of habitat with dense understory and overhead cover. Red‐cockaded woodpecker nesting clusters were located in smaller and older forest stands. These results suggest that increased overhead cover, which can reduce risk of avian predation, enhances occupancy by small forest carnivores such as eastern spotted skunks. Management activities that increase forest stand rotation length reduce the availability of young dense forest. The practice may enhance the value of habitat for red‐cockaded woodpeckers, but may reduce the occurrence of eastern spotted skunks. Implementing plans that consider critical habitat and extinction risks for multiple species may reduce such conservation conflict.  相似文献   

16.
Bird communities composed of habitat specialists suffer considerable loss of species following disturbance (Ecol. Monogr. 41 , 1971, 207–233). Participatory forest management (PFM) aims to ensure local ownership and support for forest conservation. This study determined if forest birds and forest quality in places under PFM is significantly higher than areas without PFM in Arabuko‐Sokoke forest. Forest quality data were collected in the PFM and no PFM zones in the Mixed forest (MF) and Cynometra Woodland (CW). Plot‐based approach was used to collect vegetation data along 1 km transects at intervals of 1 km sampling twenty transects and 200 plots in each of the study zones. Birds’ data were collected using 10‐min point‐counts along 88, 1 km long transects placed 1‐km apart sampling in 30 m radius‐plots at intervals of 100 m. Data were collected in 2008 and 2009. The results showed higher measures of forest quality in PFM zones than no PFM zones which showed higher measures of forest disturbance. The results did not show statistical differences in birds’ diversity indexes between PFM and no PFM zones indicating that the human‐induced disturbance has not reached critical ecological thresholds to affect birds’ species diversity. It can be deduced that PFM investment is leading to improved forest management.  相似文献   

17.
Aim Animal communities can be influenced by the composition of the surrounding landscape through immigration. Depending on habitat preferences, however, the effect of the landscape matrix can be positive or negative and can vary with scale. We tested this idea with arable spiders and tried to infer dispersal distances from relationships between local density and landscape composition at different spatial scales. Location Thirty‐eight landscapes around the cities of Göttingen and Giessen, Germany. Methods Spiders were captured with pitfall traps in one field of winter wheat in each landscape. Landscape composition around the fields was characterized at 11 scales from 95 m to 3 km radius by land‐use mapping and subsequent GIS analysis. Correlation tests were performed between landscape composition and local densities or species richness. Results In both study regions, local species richness was enhanced by non‐crop habitats on a landscape scale. The overall densities of wolf spiders (Lycosidae), long‐jawed spiders (Tetragnathidae), crab spiders (Thomisidae), and dwarf sheet spiders (Hahniidae) increased significantly in landscapes with high percentages of non‐crop habitats. Out of the 40 species tested, 19 responded positively to the percentage of non‐crop habitats in the surrounding landscape, and five responded negatively. Depending on the species, the spatial scales with the highest explanatory power ranged from 95 m to 3 km radius around the study fields, potentially reflecting dispersal distances. Main conclusions Arable spider species showed contrasting responses to the landscape context with respect both to the direction and to the spatial scale of the relationship. The variation in landscape requirements among species ensures high spider densities in a wide range of situations, which contributes to ecosystem resilience. However, species richness of arable spiders depends on heterogeneous landscapes with high percentages of non‐crop habitats.  相似文献   

18.
Habitat fragmentation can have a range of negative demographic and genetic impacts on disturbed populations. Dispersal barriers can be created, reducing gene flow and increasing population differentiation and inbreeding in isolated habitat remnants. Aggregated retention is a form of forestry that retains patches of forests as isolated island or connected edge patches, with the aim of ‘lifeboating’ species and processes, retaining structural features and improving connectivity. Swamp rats (Rattus lutreolus) are a cover‐dependent species that are sensitive to habitat removal. We examined the effects of aggregated retention forestry and forestry roads in native wet Eucalyptus forests on swamp rat gene flow and population genetic structure. We characterized neighbourhood size in unlogged forest to provide a natural state for comparison, and examined population structure at a range of spatial scales, which provided context for our findings. Tests of pairwise relatedness indicated significant differentiation between island and edge populations in aggregated retention sites, and across roads in unlogged sites. Spatial autocorrelation suggested a neighbourhood size of 42–55 m and revealed male‐biased dispersal. We found no genetic isolation by geographical distance at larger (>2.3 km) scales and populations were all significantly differentiated. Our results suggest that removal of mature forest creates barriers for swamp rat dispersal. In particular, roads may have long‐term impacts, while harvesting of native forests is likely to create only short‐term dispersal barriers at the local scale, depending on the rate of regeneration.  相似文献   

19.
In Europe, the consequences of commercial plantation management for birds of conservation concern are poorly understood. The European Nightjar Caprimulgus europaeus is a species of conservation concern across Europe due to population depletion through habitat loss. Pine plantation‐forest is now a key Nightjar nesting habitat, particularly in northwestern Europe, and increased understanding of foraging habitat selection is required. We radiotracked 31 Nightjars in an extensive (185‐km2) complex conifer plantation landscape in 2009 and 2010. Home‐range 95% kernels for females, paired males and unpaired males were an order of magnitude larger than song territories of paired males, emphasizing the importance of habitats beyond the song territory. Nightjars travelled a mean maximum distance of 747 m from the territory centre each night. Home‐range placement relative to landscape composition was examined by compositional analysis. Pre‐closure canopy forest (aged 5–10 years) was selected at all scales (MCP, 95% and 50% kernels), with newly planted forest (aged 0–4 years) also selected within 50% kernels. For telemetry fixes relative to habitat composition within 2 km of their territory centre, individuals again selected pre‐closure and newly planted forest, and also grazed grass heath. Open ungrazed habitat was not selected, with implications for open habitat planning for biodiversity conservation within public‐owned forests. Despite the Nightjars’ selection for younger growth, moth biomass was greater in older forest stands, suggesting that foraging site selection reflects ease of prey capture rather than prey abundance. Within large plantation‐forest landscapes, a variety of growth stages is important for this species and our results suggest that grazing of open habitats within and adjacent to forest will additionally benefit the European Nightjar.  相似文献   

20.
Changes in site occupancy across habitat patches have often been attributed to landscape features in fragmented systems, particularly when considering metapopulations. However, failure to include habitat quality of individual patches can mask the relative importance of local scale features in determining distributional changes. We employed dynamic occupancy modeling to compare the strength of local habitat variables and metrics of landscape patterns as drivers of metapopulation dynamics for a vulnerable, high‐elevation species in a naturally fragmented landscape. Repeat surveys of Bicknell's thrush Catharus bicknelli presence/non‐detection were conducted at 88 sites across Vermont, USA in 2006 and 2007. We used an organism‐based approach, such that at each site we measured important local‐scale habitat characteristics and quantified landscape‐scale features using a predictive habitat model for this species. We performed a principal component analysis on both the local and landscape features to reduce dimensionality. We estimated site occupancy, colonization, and extinction probabilities while accounting for imperfect detection. Univariate, additive, and interaction models of local habitat and landscape context were ranked using AICc scores. Both local and landscape scales were important in determining changes in occupancy patterns. An interaction between scales was detected for occupancy dynamics indicating that the relationship of the parameters to local‐scale habitat conditions can change depending on the landscape context and vice versa. An increase in both landscape‐ and local‐scale habitat quality increased occupancy and colonization probability while decreasing extinction risk. Colonization and extinction were both more strongly influenced by local habitat quality relative to landscape patterns. We also identified clear, qualitative thresholds for landscape‐scale features. Conservation of large habitat patches in high‐cover landscapes will help ensure persistence of Bicknell's thrushes, but only if local scale habitat quality is maintained. Our results highlight the importance of incorporating information beyond landscape characteristics when investigating patch occupancy patterns in metapopulations.  相似文献   

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