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1.
The distribution of the northern brown bandicoot (Isoodon macrourus), a medium-sized ground-dwelling marsupial, was examined in habitat fragments within the urban landscape of the city of Brisbane,
Australia. From surveys conducted in 68 fragments, bandicoots were found to be present in 33 (49%) despite widespread habitat
loss and fragmentation. Logistic regression analysis revealed that of 13 measured independent variables, functional connectivity
was the only factor that significantly predicted the presence of bandicoots within fragments, with connectivity positively
correlated with the likelihood of occupation. Functional connectivity was equated to the likelihood of bandicoot immigration
into the focal fragment from the nearest occupied fragment, based on the estimated resistance to movement offered by the intervening
matrix. Within Brisbane, riparian habitat fragments typically have a relatively high level of functional connectivity, as
thin strips of vegetation fringing waterways serve as corridors between larger riparian areas and facilitate the movement
of bandicoots between patches. Analyses based on the Akaike Information Criterion revealed that the optimal model based on
landscape context variables was convincingly better supported by the data than the optimal model produced from fragment characteristics.
However, it is important to examine both internal attributes of habitat fragments and external features of the surrounding
landscape when modelling the distribution of ground-dwelling fauna in urban environments, or other landscapes with a highly
variable matrix. As urban centres throughout the world expand, it is crucial that the ecology of local wildlife be considered
to ensure functional connection is maintained between habitat patches, especially for the conservation of species that are
highly susceptible to fragmentation. 相似文献
2.
Linear habitats are becoming increasingly common as a consequence of habitat fragmentation, and may provide the sole habitat
for some species. Hedgerows are linear features that can vary substantially in structure and quality. Having surveyed 180
hedgerows, in four locations, and sampled their small mammal communities we examined the effect of physical hedgerow attributes
on the abundance of small mammal species. Using three elements of landscape structure, we explored whether variation was best
explained by the Random Sample Hypothesis (that small islands represent a random sample of those species populating larger
areas), or by the Fragmentation Hypothesis (that species abundance will decrease with a loss of habitat area). We tested the
relationship between the relative abundance of small mammals and 1. hedgerow connectivity; 2. total habitat availability and
3. local habitat complexity. We then explored the predictive power of combinations of these habitat variables. Connectivity
was a positive predictor of wood mice Apodemus sylvaticus, and hedgerow gappiness was a negative predictor of bank voles Clethrionomys glareolus. The total amount of habitat available (hedgerow width, height and length) was a positive indicator of total small mammal
biomass. These results support the Fragmentation Hypothesis that species abundance and distribution decrease with a loss of
habitat area. The preservation of linear and associated habitats may therefore be important in maintaining metapopulations
of the species we studied. 相似文献
3.
We studied the effects of habitat fragmentation, measured as forest stand size and isolation, on the distribution of Eurasian red squirrels (Sciurus vulgaris). Squirrel density was surveyed during four years in 46 forest stands (0.1–500 ha) in a forest landscape in south-central Sweden. The only factor that significantly influenced a density index was the proportion of spruce within a habitat fragment. Neither fragment size nor degree of isolation were significant. Furthermore, none of the interactions with year were significant, suggesting the same pattern in all four years. Thus, the effect of habitat fragmentation in this study seems to be only pure habitat loss, i.e. halving the proportion of preferred habitat in the landscape should result in a halving of the red squirrel population. Therefore, the landscape can be viewed as functionally continuous for the squirrels, although the preferred habitat was divided into fragments. The most likely explanation for the difference between this study and other studies on squirrels that found effects due to habitat fragmentation is a combination of shorter distances and less hostile surroundings in our study area. To identify landscape effects requires multiple studies because single studies usually consider only one landscape. 相似文献
4.
Effects of area and isolation of woodland patches on herbaceous plant species richness across Great Britain 总被引:5,自引:2,他引:5
Petit Sandrine Griffiths Leila Smart Simon S. Smith Geoff M. Stuart Rick C. Wright Simon M. 《Landscape Ecology》2004,19(5):463-471
Richness of Ancient Woodland Indicator plant species was analysed in 308 woodland patches that were surveyed during the Countryside Survey of Great Britain carried out in 1998. The Countryside Survey recorded vegetation plots and landscape structure in 569 stratified 1 km sample squares and developed a remotely-sensed land cover map of the UK. Using these datasets, we tested the hypothesis that Ancient Woodland Indicator species richness in woodland fragments was limited by patch area, shape and spatial isolation and that woodland patches located in the lowland region of Great Britain would respond differently than those in the upland region. The variation in Ancient Woodland Indicator species richness in the British lowlands (n = 218) was mainly explained by patch area and two measures of connectivity, the length of hedgerows and lines of trees in the 1 km square and the area of woodland within 500 m of the vegetation plot. By contrast, variation in Ancient Woodland Indicator species richness in the British uplands (n = 90) was related to Ellenberg scores of the vegetation communities sampled – a surrogate for habitat quality – and no significant effect of spatial structure was detected. It therefore appears that the degree of fragmentation of woodland in the British lowlands limits the distribution of Ancient Woodland Indicator species, while in the uplands, failed colonisation is a matter of habitat quality rather than a result of landscape structure.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
5.
The effects of habitat fragmentation on species richness and composition have been extensively studied. However, little is known about how fragmentation affects functional diversity patterns. Fragmentation can indeed affect functional diversity directly (e.g. by promoting traits associated to long-distance dispersal when fragment isolation increases) or indirectly (e.g. by decreasing species richness, hence trait diversity, when fragment area decreases). Here, we used structural equation modeling to determine whether factors associated to forest fragmentation, namely area, habitat heterogeneity, spatial isolation and age have a direct effect on forest herb functional diversity. Using occurrence data from 243 forest fragments located in northern France and six plant life-history traits, we estimated species richness and calculated functional diversity in each of these 243 forest fragments. We found that species richness was the primary driver of functional diversity in these fragments, with a strong positive and direct relationship between species richness and functional diversity. Interestingly, both fragment isolation and age had a direct negative effect on functional diversity independent of their effects on species richness. Isolation selected life-history traits associated with long-distance dispersal, while age selected for life-history traits typical of forest habitat specialists. Isolated and/or older forest fragments are thus at greater risk of local species and functional extinctions, and hence making these forest fragments particularly vulnerable to future global changes. 相似文献
6.
Metapopulation theory and habitat fragmentation: a review of holarctic breeding bird studies 总被引:15,自引:0,他引:15
Paul Opdam 《Landscape Ecology》1991,5(2):93-106
Metapopulations are conceived as spatially structured populations consisting of distinct units (subpopulations), separated by space or barriers, and connected by dispersal movements. Metapopulations characteristically demonstrate a turnover of local populations going extinct and becoming re-established, resulting in a distribution pattern that shifts over time. Metapopulation theory is used to analyse the effects of habitat fragmentation on birds in the temperate zone, integrating various explanations for the paucity of species in isolated ecotopes.There is some evidence that turnover of local populations occurs in fragmented systems. A few studies based on time series demonstrate the local extinction rate to be related to the size of the habitat fragment, whereas the recolonization rate depends on the degree of isolation. Most evidence comes from short-term pattern studies in which the probability of occurrence was found to depend on the size of habitat fragments, on their relative position in the landscape and on the density of corridors lowering the landscape resistance. These data are consistent with predictions from metapopulation theory. However, almost all investigations consider wood fragmentation in agricultural landscapes, and there is a great need for studies in naturally fragmented landscapes as well as for studies focussing on other, less predictable, habitat types. 相似文献
7.
Estimating the consequences of habitat fragmentation on extinction risk in dynamic landscapes 总被引:7,自引:0,他引:7
Analyzing the population dynamic consequences of spatio-temporal changes in landscape structure is a formidable challenge for spatial ecology. One key population dynamic process in fragmented landscapes is the influence of isolation on colonization rate and thereby on the occurrence of species in habitat fragments, but it is not obvious how isolation should be measured in landscapes that are affected by on-going habitat loss and fragmentation. We suggest the following procedure for the measurement of spatio-temporal isolation. First, a historical record of habitat loss and fragmentation in the landscape is prepared based on snapshots of the extent of the suitable habitat for the focal species. Second, a metapopulation model is used to simulate the occurrence of the species in this landscape, assuming the empirically observed landscape change. The model-predicted pattern of habitat occupancy at a particular point in time (usually the present time) is then compared with empirical observations on the occurrence of the species. We describe a metapopulation model that has been constructed for this purpose, and we apply it to a changing landscape of boreal forests in eastern Finland. We give an example on the occurrence of four threatened polyporous fungi in 18 small fragments of old-growth forest. In none of the species does the current isolation of the fragments nor the time since their isolation explain the occurrence of the species in the study fragments, but in three species the model-predicted occupancy probability had a significant effect on the observed abundance of the species. The model-predicted occupancy probabilities were also calculated by ignoring past landscape changes, that is, by assuming that the landscape had remained in the present configuration for a long time. These probabilities had a significant effect on the abundance of only one of the four species, suggesting that the occurrence of the species tracks landscapes changes with a noticable time lag.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
8.
Studies on the distribution of mammalian carnivores in fragmented landscapes have focused mainly on structural aspects such
as patch and landscape features; similarly, habitat connectivity is usually associated with landscape structure. The influence
of food resources on carnivore patch use and the important effect on habitat connectivity have been overlooked. The aim of
this study is to evaluate the relative importance of food resources on patch use patterns and to test if food availability
can overcome structural constraints on patch use. We carried out a patch-use survey of two carnivores: the beech marten (Martes foina) and the badger (Meles meles) in a sample of 39 woodland patches in a fragmented landscape in central Italy. We used the logistic model to investigate
the relative effects on carnivore distribution of patch, patch neighbourhood and landscape scale variables as well as the
relative abundance of food resources. Our results show how carnivore movements in fragmented landscapes are determined not
only by patch/landscape structure but also by the relative abundance of food resources. The important take-home message of
our research is that, within certain structural limits (e.g. within certain limits of patch isolation), by modifying the relative
amount of resources and their distribution, it is possible to increase suitability in smaller/relatively isolated patches.
Conversely, however, there are certain thresholds above which an increase in resources will not achieve high probability of
presence. Our findings have important and generalizable consequences for highly fragmented landscapes in areas where it may
not be possible to increase patch sizes and/or reduce isolation so, for instance, forest regimes that will increase resource
availability could be implemented.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
9.
Kevin Watts Amy E. Eycott Phillip Handley Duncan Ray Jonathan W. Humphrey Christopher P. Quine 《Landscape Ecology》2010,25(9):1305-1318
The focus of biodiversity conservation is shifting to larger spatial scales in response to habitat fragmentation and the need
to integrate multiple landscape objectives. Conservation strategies increasingly incorporate measures to combat fragmentation
such as ecological networks. These are often based on assessment of landscape structure but such approaches fail to capitalise
on the potential offered by more ecologically robust assessments of landscape function and connectivity. In this paper, we
describe a modelling approach to identifying functional habitat networks and demonstrate its application to a fragmented landscape
where policy initiatives seek to improve conditions for woodland biodiversity including increasing woodland cover. Functional
habitat networks were defined by identifying suitable habitat and by modelling connectivity using least-cost approaches to
account for matrix permeability. Generic focal species (GFS) profiles were developed, in consultation with stakeholders, to
represent species with high and moderate sensitivity to fragmentation. We demonstrated how this form of analysis can be used
to aid the spatial targeting of conservation actions. This ‘targeted’ action scenario was tested for effectiveness against
comparable scenarios, which were based on random and clumped actions within the same landscape. We tested effectiveness using
structural metrics, network-based metrics and a published functional connectivity indicator. Targeting actions within networks
resulted in the highest mean woodland area and highest connectivity indicator value. Our approach provides an assessment of
landscape function by recognising the importance of the landscape matrix. It provides a framework for the targeting and evaluation
of alternative conservation options, offering a pragmatic, ecologically-robust solution to a current need in applied landscape
ecology. 相似文献
10.
Nicolas Morellet Bram Van Moorter Bruno Cargnelutti Jean-Marc Angibault Bruno Lourtet Joël Merlet Sylvie Ladet A. J. Mark Hewison 《Landscape Ecology》2011,26(7):999-1010
Understanding how patterns of habitat selection vary in relation to landscape structure is essential to predict ecological
responses of species to global change and inform management. We investigated behavioural plasticity in habitat selection of
roe deer (Capreolus capreolus) in relation to variable habitat availability across a heterogeneous agricultural landscape at the home range and landscape
scales. As expected, woodland was heavily selected, but we found no functional response for this habitat, i.e. no shift in
habitat selection with changing habitat availability, possibly due to the presence of hedgerows which were increasingly selected
as woodlands were less abundant. Hedgerows may thus function as a substitutable habitat for woodlands by providing roe deer
with similar resources. We observed a functional response in the use of hedgerows, implying some degree of landscape complementation
between hedgerows and open habitats, which may in part compensate for lower woodland availability. We also expected selection
for woodland to be highest at the wider spatial scale, especially when this habitat was limiting. However, our results did
not support this hypothesis, but rather indicated a marked influence of habitat composition, as both the availability and
distribution of resources conditioned habitat selection. There was no marked between-sex difference in the pattern of habitat
selection at either scale or between seasons at the landscape scale, however, within the home range, selection did differ
between seasons. We conclude that landscape structure has a marked impact on roe deer habitat selection in agricultural landscapes
through processes such as landscape complementation and supplementation. 相似文献
11.
Habitat loss and fragmentation of natural and semi-natural habitats are considered as major threats to plant species richness.
Recently several studies have pinpointed the need to analyse past landscape patterns to understand effects of fragmentation,
as the response to landscape change may be slow in many organisms, plants in particular. We compared species richness in continuously
grazed and abandoned grasslands in different commonplace rural landscapes in Sweden, and analysed effects of isolation and
area in three time-steps (100 and 50 years ago and today). Old cadastral maps and aerial photographs were used to analyse
past and present landscape patterns in 25 sites. Two plant diversity measures were investigated; total species richness and
species density. During the last 100 years grassland area and connectivity have been reduced by about 90%. Present-day habitat
area was positively related to total species richness in both habitats. There was also a relationship to habitat area 50 years
ago for continuously grazed grasslands. Only present management was related to species density: continuously grazed grasslands
had the highest species density. There were no relationships between grassland connectivity, present or past, and any diversity
measure. We conclude that landscape history is not directly important for present-day plant diversity patterns in ordinary
landscapes, although past grassland management is a prerequisite for the grassland habitats that can be found there today.
It is important that studies are conducted, not only in very diverse landscapes, but also in managed landscapes in order to
assess the effects of fragmentation on species. 相似文献
12.
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
13.
The understanding and prediction of the responses of animal populations to habitat fragmentation is a central issue in applied
ecology. The identification of habitat variables associated to patch occupancy is particularly important when habitat quality
is affected by human activities. Here, we analyze the influence of patch and landscape characteristics on patch occupancy
by the subterranean herbivorous rodent Ctenomys porteousi. Patch occupancy was monitored in a network of 63 habitat patches identified by satellite imagery analysis which extends
along almost the whole distributional range for C. porteousi. Suitable habitat for the occurrence of C. porteousi is highly fragmented and represents <10% of the total area in its distributional range. The distribution of C. porteousi in the patch network is affected not only by characteristics of the habitat patches, but also by those of the surrounding
landscape matrix. Significant differences between occupied and empty patches were found in several environmental variables.
Overall, occupied patches were larger, less vegetated, more connected, and had larger neighbor patches than empty patches.
A stepwise procedure on a generalized linear model selected four habitat variables that explain patch occupancy in C. porteousi; it included the effects of habitat quality in the matrix surrounding the patch, average vegetation cover in the patch, minimum
vegetation cover in the matrix surrounding the patch, and the area of the nearest neighbor patch. These results indicate that
patch occupancy in C. porteousi is strongly influenced by the availability and quality of habitat both in the patch and in the surrounding landscape matrix. 相似文献
14.
Tim Diekötter Hans Baveco Paul Arens Carmen Rothenbühler Regula Billeter Daniela Csencsics Riccardo De Filippi Frederik Hendrickx Marjan Speelmans Paul Opdam Marinus J. M. Smulders 《Landscape Ecology》2010,25(3):449-461
Habitat fragmentation has been generally regarded detrimental to the persistence of many species, especially those with limited dispersal abilities. Yet, when exactly habitat elements become functionally disconnected very much depends on the dispersal ability of a species in combination with the landscape’s composition in which it occurs. Surprisingly, for many small and ground-walking generalists knowledge at what spatial scale and to what extent landscape structure affects dispersal is very scarce. Because it is flightless, the bush cricket Pholidoptera griseoaptera may be regarded susceptible to fragmentation. We applied habitat occupancy surveys, population genetic analyses and movement modelling to investigate the performance of P. griseoaptera in an agricultural mosaic landscape with suitable habitat patches of varying size and isolation. Despite its presumed dispersal limitation we could show that P. griseoaptera occupied the majority of suitable habitats, including small and isolated patches, showed a very low and non-significant genetic differentiation (F ST = 0.0072) and, in the model, managed to colonize around 73% of all suitable habitat patches within one generation under weak and strong landscape-effect scenarios. We conclude that P. griseoaptera possesses the behavioural attributes (frequent inter-patch dispersal) necessary to persist in this landscape characterized by a patchy distribution of habitat elements. Yet, sound recommendations to landscape planning and conservation require more research to determine whether this represents a general behaviour of the species or a behavioural adaptation to this particular landscape. 相似文献
15.
Although many empirical and theoretical studies have elucidated the effects of habitat fragmentation on the third trophic level, little attention has been paid to the impacts of this driver on more generalist groups of non-hymenopteran parasitoids. Here, we used the highly-diverse group of tachinid flies as an alternative model to test the effects of landscape fragmentation on insect parasitoids. Our aims were: (i) to evaluate the relative importance of habitat area and connectivity losses and their potential interaction on tachinid diversity, (ii) to test whether the effects of habitat fragmentation changes seasonally, and (iii) to further assess the effect of habitat diversity on tachinid diversity and whether different parasitoid-host associations modify the species richness response to fragmentation. In 2012 a pan-trap sampling was conducted in 18 semi-natural grasslands embedded in intensive agricultural landscapes along statistically orthogonal gradients of habitat area, connectivity and habitat diversity. We found an interaction between habitat area and connectivity indicating that tachinid abundance and species richness were more negatively affected by habitat loss in landscapes with low rather than with relatively large habitat connectivity. Although tachinid communities exhibited large within-year species turnover, we found that the effects of landscape fragmentation did not change seasonally. We found that habitat diversity and host association did not affect tachinid species diversity. Our results have important implications for biodiversity conservation as any attempts to mitigate the negative effects of habitat loss need to take the general level of habitat connectivity in the landscape into account. 相似文献
16.
Importance of Wetland Landscape Structure to Shorebirds Wintering in an Agricultural Valley 总被引:2,自引:1,他引:2
Only recently has the influence of landscape structure on habitat use been a research focus in wetland systems. During non-breeding
periods when food can be locally limited, wetland spatial pattern across a landscape may be of great importance in determining
wetland use. We studied the influence of landscape structure on abundances of wintering Dunlin (Calidris alpina) and Killdeer (Charadrius vociferus) observed on wetlands in the agricultural Willamette Valley of Oregon, USA, during two winters (1999–2000, 2000–2001) of
differing rainfall. We examined (1) shorebird use within a sample of 100 km2 regions differing in landscape structure (hectares of shorebird habitat [wet, unvegetated]) and (2) use of sites differing
in landscape context (area of shorebird habitat within a species-defined radius). For use of sites, we also assessed the influence
of two local characteristics: percent of soil exposed and area of wet habitat. We analyzed data using linear regression and
information-theoretic modeling. During the dry winter (2000–2001), Dunlin were attracted to regions with more wetland habitat
and their abundances at sites increased with greater area of shorebird habitat within both the site and the surrounding landscape.
In contrast, Dunlin abundances at sites were related to availability of habitat at only a local scale during the wet winter
(1999–2000). Regional habitat availability was of little importance in predicting Killdeer distributions, and Killdeer site
use appeared unrelated to habitat distributions at both landscape and local scales. Results suggest prioritizing sites for
conservation that are located in areas with high wetland coverage. 相似文献
17.
The effects of habitat area and fragmentation are confounded in many studies. Since a reduction in habitat area alone reduces
patch size and increases patch isolation, many studies reporting fragmentation effects may really be documenting habitat-area
effects. We designed an experimental landscape system in the field, founded on fractal neutral landscape models, to study
arthropod community responses to clover habitat in which we adjusted the level of fragmentation independently of habitat area.
Overall, habitat area had a greater and more consistent effect on morphospecies richness than fragmentation. Morphospecies
richness doubled between 10 and 80% habitat, with the greatest increase occurring up to 40% habitat. Fragmentation had a more
subtle and transient effect, exhibiting an interaction at intermediate levels of habitat only at the start of the study or
in the early-season (June) survey. In these early surveys, morphospecies richness was higher in clumped 40–50% landscapes
but higher in fragmented landscapes at 60–80% habitat. Rare or uncommon species are expected to be most sensitive to fragmentation
effects, and we found a significant interaction with fragmentation at intermediate levels of habitat for these types of morphospecies
in early surveys. Although the effects of fragmentation are expected to amplify at higher trophic levels, all trophic levels
exhibited a significant fragmentation effect at intermediate levels of habitat in these early surveys. Predators/parasitoids
were more sensitive to habitat area than herbivores, however. Thus, our results confirm that habitat area is more important
than fragmentation for predicting arthropod community responses, at least in this agricultural system. 相似文献
18.
Oliver Robertson Martine Maron Yvonne Buckley Clive McAlpine 《Landscape Ecology》2013,28(10):1975-1987
Globally, modification of landscapes for agriculture has had a strong influence on the distribution and abundance of biota. In particular, woodland-dependent birds are under threat across agricultural landscapes in Britain, North America and Australia, with their decline and extirpation attributed to the loss and fragmentation of habitat. Other native species have become over-abundant in response to anthropogenic landscape change and have strong interactive effects on avian assemblage structure. In eastern Australia, the hyper-aggressive noisy miner (Manorina melanocephala) often dominates woodlands in agricultural landscapes through interspecific competition, resulting in declines of species richness of woodland-dependent birds. We aimed to determine the relative influence and importance of interspecific competition, in situ habitat structure and landscape structure for woodland-dependent bird species at the landscape level. We recorded species-specific landscape incidence of woodland-dependent birds in 24 agricultural-woodland mosaics (25 km2) in southern Queensland, Australia. We selected extensively cleared landscapes (10–23 % woodland cover) where fragmentation effects are expected to be greatest. We applied generalised linear models and hierarchical partitioning to quantify the relative importance of the landscape-level incidence of the noisy miner, mistletoe abundance, shrub cover, woodland extent, woodland subdivision and land-use intensity for the incidence of 46 species of woodland birds at the landscape-scale. The landscape-level incidence of the noisy miner was the most important explanatory variable across the assemblage. Both in situ habitat structure and landscape structure were of secondary importance to interspecific aggression, although previous research suggests that the increasing incidence of the noisy miner in fragmented agricultural landscapes is itself a consequence of anthropogenic changes to landscape structure. Species’ responses to fragmentation varied from positive to negative, but complex habitat structure had a consistently positive effect, suggesting in situ restoration of degraded habitats could be a conservation priority. Landscape wide conservation of woodland-dependent bird populations in agricultural landscapes may be more effective if direct management of noisy miner populations is employed, given the strong negative influence of this species on the incidence of woodland-dependent birds among landscapes. 相似文献
19.
The effects of woodlot size and isolation, in relation to habitat fragmentation, on the distribution of the red squirrel were studied. In The Netherlands, 50 woodlots (0.55–13.78 ha) were surveyed in an agricultural landscape for the presence of red squirrel. In 26 woodlots squirrel dreys (nests) were found. Logit regression analysis showed that woodlot size and the area per woodlot covered with coniferous trees were the best predictors of squirrel presence. Addition of isolation variables by means of a stepwise forward regression method showed significant effects of the distance to a large, permanently inhabited wood and the amount of surrounding wood. No effect was found for the distance to the nearest woodlot (>0.5 ha). The model could be further improved by adding a measure of the amount of hedgerows surrounding a woodlot. 相似文献
20.
Yuri Zharikov David B. Lank Falk Huettmann Russell W. Bradley Nadine Parker Peggy P. -W. Yen Laura A. Mcfarlane-Tranquilla Fred Cooke 《Landscape Ecology》2006,21(1):107-120
We studied habitat selection and breeding success in marked populations of a protected seabird (family Alcidae), the marbled
murrelet (Brachyramphus marmoratus), in a relatively intact and a heavily logged old-growth forest landscape in south-western Canada. Murrelets used old-growth
fragments either proportionately to their size frequency distribution (intact) or they tended to nest in disproportionately
smaller fragments (logged). Multiple regression modelling showed that murrelet distribution could be explained by proximity
of nests to landscape features producing biotic and abiotic edge effects. Streams, steeper slopes and lower elevations were
selected in both landscapes, probably due to good nesting habitat conditions and easier access to nest sites. In the logged
landscape, the murrelets nested closer to recent clearcuts than would be expected. Proximity to the ocean was favoured in
the intact area. The models of habitat selection had satisfactory discriminatory ability in both landscapes. Breeding success
(probability of nest survival to the middle of the chick rearing period), inferred from nest attendance patterns by radio-tagged
parents, was modelled in the logged landscape. Survivorship was greater in areas with recent clearcuts and lower in areas
with much regrowth, i.e. it was positively correlated with recent habitat fragmentation. We conclude that marbled murrelets
can successfully breed in old-growth forests fragmented by logging. 相似文献