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1.
To aid effective conservation and management there is a need to understand the effect of landscape on species ecology. The
aim of this research was to assess the effect of landscape parameters on breeding success of barn owls throughout the Rother
and Arun River catchments, Sussex, UK. We used a Geographic Information System to describe the habitat mosaic and landscape
structure within an estimated home range area of 3 km2 around 85 artificial nest box sites. Results showed that land cover was less heterogeneous at successful sites, with home
ranges dominated by a few habitat types of regular patch shapes. Unsuccessful nesting sites had significantly more improved
grassland, suburban land and wetlands than successful sites. Cluster analysis and Principle Components Analysis was used to
assess the similarity of the habitat mosaic within these areas and pellet analysis was undertaken to assess barn owl diet
and prey availability. Ten prey species were recovered from pellets, field vole (Microtus agrestis), common shrews (Sorex araneus) and house mice (Mus musculus) making up nearly 90% of recoveries. However box sites varied in relative proportions of small mammal, and hence prey availability.
Results indicated that land use and landscape structure can affect breeding success in barn owls. Higher levels of poor quality
small mammal habitat were associated with unsuccessful sites. However, at a landscape scale, the habitat mosaic across the
study area lacked variation, limiting analysis and clear correlations between habitat type and positive breeding success,
suggesting that a finer scale was needed in future studies utilising this approach. 相似文献
2.
Alexander Peringer Kiowa A. Schulze Ileana Stupariu Mihai-Sorin Stupariu Gert Rosenthal Alexandre Buttler François Gillet 《Landscape Ecology》2016,31(4):913-927
Context
The pasture-woodlands of Central Europe are low-intensity grazing systems in which the structural richness of dynamic forest-grassland mosaics is causal for their high biodiversity. Distinct mosaic patterns in Picea abies- and Fagus sylvatica-dominated pasture-woodlands in the Swiss Jura Mountains suggest a strong influence of tree species regeneration ecology on landscape structural properties. At the landscape scale, however, cause-effect relationships are complicated by habitat selectivity of livestock.Objectives
We asked which tree species regeneration traits and what kind of feedbacks among local-scale vegetation dynamics and landscape-scale herbivore behavior are causal for the contrasted landscape structural characteristics of Picea- and Fagus-dominated pasture-woodlands.Methods
We performed simulation experiments of mosaic pattern formation in both pasture-woodland types. The regeneration traits, namely dispersal distance, resistance to browsing and tolerance to shade, and the rules for habitat selection of cattle were modified and the corresponding shifts in landscape structure were analyzed.Results
Dispersal distance showed a significant, but only local, effect promoting forest fringe formation. Saplings’ resistance to browsing mainly determined overall tree cover, but did not influence landscape structure. At the landscape scale, both shade tolerance of saplings and selective habitat use by cattle were responsible for forest-grassland segregation: high shade tolerance triggered segregation, whereas non-selective habitat use hindered it.Conclusions
Existing local-scale theory on pasture-woodland dynamics is complemented by an herbivore-vegetation feedback among spatial scales. In low-intensity pastures, where large herbivores are preferentially “grazers” and trees form dense canopies, an intrinsic trend towards forest-grassland segregation at the expense of forest-grassland ecotones is predicted.3.
Few relevant data are available to analyze how landscape features affect the abundance and movement patterns of tropical insects.
We used mark-release-recapture techniques to study the effects of landscape structure and composition on habitat preferences
and movements of Canthon cyanellus cyanellus individuals, within a complex tropical deciduous forest landscape in South Mexico during 2004 and 2005. In total, 2,460 individuals
of C. c. cyanellus were captured, including 1,225 females and 1,235 males, out of which 124 individuals (65 females and 59 males) were recaptured
once, and 9 individuals (seven females and two males) were recaptured twice. The abundance of individuals was equally high
in large forest fragments, small forest fragments and hedgerows, but the abundance in pastures was less than half of the abundance
in the other habitat types. To disentangle the movement behaviour of the species from the spatially and temporally varying
sampling effort, we applied a Bayesian state-space modelling framework with a diffusion based movement model. Males showed
generally faster movement rate than females, and they moved faster within forests and hedgerows than within pastures. Contrary
to the assumption of the diffusion model, individuals did not move in a continuous fashion, indicated by the large fraction
of individuals that were recaptured in the site of release. However, the posterior predictive data did not deviate substantially
from the real data in terms of the mean and maximum movement distances recorded, and in terms of the dependence of movement
distance on time between captures. Our results suggest that an important component of the biota in Mexican agro-pasture landscapes
can utilize contemporary landscape elements such as hedgerows or small forest fragments in addition to large fragments of
remnant habitat. These habitats are still locally common in semi-natural ecosystems and require less intensive conservation
management. 相似文献
4.
A comprehensive understanding of variables associated with spatial differences in community composition is essential to explain
and predict biodiversity over landscape scales. In this study, spatial patterns of bird diversity in Central Kalimantan, Indonesia,
were examined and associated with local-scale (habitat structure and heterogeneity) and landscape-scale (logging, slope position
and elevation) environmental variables. Within the study area (c. 196 km2) local habitat structure and heterogeneity varied considerably, largely due to logging. In total 9747 individuals of 177
bird species were recorded. Akaike's information criterion (AIC) revealed that the best explanatory models of bird community
similarity and species richness included both local- and landscape-scale environmental variables. Important local-scale variables
included liana abundance, fern cover, sapling density, tree density, dead wood abundance and tree architecture, while important
landscape-scale variables were elevation, logging and slope position. Geographic distance between sampling sites was not significantly
associated with spatial variation in either species richness or similarity. These results indicate that deterministic environmental
processes, as opposed to dispersal-driven stochastic processes, primarily structure bird assemblages within the spatial scale
of this study and confirm that highly variable local habitat measures can be effective means of predicting landscape-scale
community patterns. 相似文献
5.
Context
Habitat loss and fragmentation may alter habitat occupancy patterns, for example through a reduction in regional abundance or in functional connectivity, which in turn may reduce the number of dispersers or their ability to prospect for territories. Yet, the relationship between landscape structure and habitat niche remains poorly known.Objectives
We hypothesized that changes in landscape structure associated with habitat loss and fragmentation will reduce the habitat niche breadth of forest birds, either through a reduction in density-dependent spillover from optimal habitat or by impeding the colonization of patches.Methods
We surveyed forest birds with point counts in eastern Ontario, Canada, and analyzed their response to loss and fragmentation of mature woodland. We selected 62 landscapes varying in both forest cover (15–45%) and its degree of fragmentation, and classified them into two categories (high versus low levels of loss and fragmentation). We determined the habitat niche breadth of 12 focal species as a function of 8 habitat structure variables for each landscape category.Results
Habitat niche breadth was narrower in landscapes with high versus low levels of loss and fragmentation of forest cover. The relative occupancy of marginal habitat appeared to drive this relationship. Species sensitivity to mature forest cover had no apparent influence on relative niche breadth.Conclusions
Regional abundance and, in turn, density-dependent spillover into suboptimal habitat appeared to be determinants of habitat niche breadth. For a given proportion of forest cover, fragmentation also appeared to alter habitat use, which could exacerbate its other negative effects unless functional connectivity is high enough to allow individuals to saturate optimal habitat.6.
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
7.
Habitat fragmentation, patch quality and landscape structure are important predictors for species richness. However, conservation
strategies targeting single species mainly focus on habitat patches and neglect possible effects of the surrounding landscape.
This project assesses the impact of management, habitat fragmentation and landscape structure at different spatial scales
on the distribution of three endangered butterfly species, Boloria selene, Boloria titania and Brenthis ino. We selected 36 study sites in the Swiss Alps differing in (1) the proportion of suitable habitat (i.e., wetlands); (2) the
proportion of potential dispersal barriers (forest) in the surrounding landscape; (3) altitude; (4) habitat area and (5) management
(mowing versus grazing). Three surveys per study site were conducted during the adult flight period to estimate occurrence
and density of each species. For the best disperser B. selene the probability of occurrence was positively related to increasing proportion of wetland on a large spatial scale (radius:
4,000 m), for the medium disperser B. ino on an intermediate spatial scale (2,000 m) and for the poorest disperser B. titania on a small spatial scale (1,000 m). Nearby forest did not negatively affect butterfly species distribution but instead enhanced
the probability of occurrence and the population density of B. titania. The fen-specialist B. selene had a higher probability of occurrence and higher population densities on grazed compared to mown fens. The altitude of the
habitat patches affected the occurrence of the three species and increasing habitat area enhanced the probability of occurrence
of B. selene and B. ino. We conclude that, the surrounding landscape is of relevance for species distribution, but management and habitat fragmentation
are often more important. We suggest that butterfly conservation should not focus only on a patch scale, but also on a landscape
scale, taking into account species-specific dispersal abilities. 相似文献
8.
We explored the usefulness of three satellite land cover data sets available to land managers in south-central Sweden for
conservation planning using four deciduous forest focal resident bird species with different habitat requirements. Habitat
suitability models using empirical species-specific habitat parameters and a Geographic Information System were applied to
evaluate and compare the degree of consistency among three different land cover data sets. The study area encompassed 10,000 km2 in a landscape mosaic of managed boreal forests and is within the distribution range of all four focal species. Although
the three land cover data sets indicated similar total amounts of deciduous forest, the habitat suitability models showed
that different land cover data yielded inconsistent results regarding the amount and distribution of suitable habitat within
5×5 km grid cells. Given this sensitivity to the choice of land cover data sets, the habitat suitability models showed positive
relationships among the selected focal species for each land cover data set separately. As expected, decreasing amounts of
suitable habitat were identified for species with higher specialisation. Thus, because habitat suitability models are an appropriate
way to gain insight into the functionality and connectivity of habitat networks, land cover data must be carefully evaluated
and if necessary combined with other landscape information for effective conservation planning. 相似文献
9.
In this study, we investigated the environmental factors driving small mammal (rodents and shrews) assemblages in permanent
habitat patches in response to a gradient of agricultural intensification. Small mammals were sampled using a trapping standard
method in the hedgerow networks of three contrasted landscapes differing by their level of land-use intensity and hedgerow
network density (BOC1: slightly intensified; BOC2: moderately intensified and POL: highly intensified). We hypothesized that
habitat and landscape characteristics have to be considered to understand the structure of local community. In that way, we
carried out a multi-scale study using environmental variables ranging from local habitat (structure and composition of the
hedgerows) to hedgerows neighbourhoods in a radius of 300 m (land cover and connectivity around hedges) and to landscape units
(three sites). During 1 year, 24 hedgerows were sampled seven times, representing a total of 1,379 captures (86% of rodents
and 14% of shrews) and eight species, dominated by the wood mouse (Apodemus sylvaticus) and the bank vole (Clethrionomys glareolus). Inter-site variability was significant and accounted for 18% of total variation in small mammal species abundances. But
intra-site variability was also highlighted: species abundance profiles may differ greatly among hedgerows within a site.
The more explanatory variables were identified at the different scales of the study: the landscape unit POL was shown to be
an important factor in structuring the community, but the predominant factors explaining differences of abundances among hedgerows
were about local habitat. In fact, the width of hedges and the tree species richness appeared to be significant and explaining
the greatest part of the total variation of the small mammal community composition. 相似文献
10.
Assessing the associations between spatial patterns in population abundance and environmental heterogeneity is critical for understanding various population processes and for managing species and communities. This study evaluates responses in the abundance of the European rabbit (Oryctolagus cuniculus), an important prey for predators of conservation concern in Mediterranean ecosystems, to environmental heterogeneity at different spatial scales. Multi-scale habitat models of rabbit abundance in three areas of Doñana, south-western Spain, were developed using a spatially extensive dataset of faecal pellet counts as an abundance index. The best models included habitat variables at the three spatial scales examined: distance from lagoons (broad scale), mean landscape shrub coverage and interspersion of pastures (home-range scale), and shrub and pasture cover (microhabitat scale). These variables may well have been related to the availability of food and refuge for the species at the different scales. However, the models’ fit to data and their predictive accuracy for an independent sample varied among the study regions. Accurate predictions in some areas showed that the combination of variables at various spatial scales can provide a reliable method for assessing the abundance of ecologically complex species such as the European rabbit over large areas. On the other hand, the models failed to identify abundance patterns in a population that suffered the strongest demographic collapse after viral epidemics, underlining the difficulty of generalizing this approach. In the latter case, factors difficult to implement in static models such as disease history and prevalence, predator regulation and others may underlie the lack of association. Habitat models can provide useful guidelines for the management of landscape attributes relevant to rabbits and help improve the conservation of Mediterranean communities. However, other influential factors not obviously related to environmental heterogeneity should also be analyzed in more detail. 相似文献
11.
A long-term decline of vole populations in boreal Sweden, especially of the grey-sided vole (Clethrionomys rufocanus Sund.), has been revealed by snap-trapping in 1971–2004. We identified important habitats for the grey-sided vole by mapping
the distribution of cumulated number of reproductive females in 1971–1978, prior to the major decline in the 1980s. Mean abundance
of C. rufocanus was higher in the western (inland) than eastern (coastland) part of the study area. As the inland appeared to represent the
most, as far as we know, pristine, abundant part of the population, we based identification of high quality habitats on inland
data only. Four habitats were more important than others and yielded nearly 86% of the reproductive females in spring: (1)
forests of dry, (2) moist and (3) wet/hydric dwarf-shrub type, in addition to (4) forest/swamp complexes rich in dwarf-shrubs.
The latter three habitats were used more frequently than expected from their occurrence in the landscape. Still, the variation
in density of reproductive females within patches of the same habitat was frequently high. This suggested that habitat composition
in the surrounding landscape, perhaps may have affected local vole density at the patch scale. Clear-cut sampling plots appeared
to be low-frequently used by reproductive females, but also by males and immatures. In conclusion, our study indicated the
importance of also studying habitat at a larger scale than that of the patch to get a deeper understanding on how habitat
influences local and regional densities and population dynamics of C. rufocanus. 相似文献
12.
Miriam M. Hansbauer Ilse Storch Felix Knauer Stefan Pilz Helmut Küchenhoff Zsolt Végvári Rafael G. Pimentel Jean Paul Metzger 《Landscape Ecology》2010,25(3):407-417
Even among forest specialists, species-specific responses to anthropogenic forest fragmentation may vary considerably. Some
appear to be confined to forest interiors, and perceive a fragmented landscape as a mosaic of suitable fragments and hostile
matrix. Others, however, are able to make use of matrix habitats and perceive the landscape in shades of grey rather than
black-and-white. We analysed data of 42 Chiroxiphia caudata (Blue Manakin), 10 Pyriglena leucoptera (White-shouldered Fire-eye) and 19 Sclerurus scansor (Rufous-breasted Leaftosser) radio-tracked in the Atlantic Rainforest of Brazil between 2003 and 2005. We illustrate how
habitat preferences may determine how species respond to or perceive the landscape structure. We compared available with used
habitat to develop a species-specific preference index for each of six habitat classes. All three species preferred old forest,
but relative use of other classes differed significantly. S. scansor perceived great contrast between old forest and matrix, whereas the other two species perceived greater habitat continuity.
For conservation planning, our study offers three important messages: (1) some forest specialist species are able to persist
in highly fragmented landscapes; (2) some forest species may be able to make use of different anthropogenic habitat types
to various degrees; whereas (3) others are restricted to the remaining forest fragments. Our study suggests species most confined
to forest interiors to be considered as potential umbrella species for landscape-scale conservation planning. 相似文献
13.
Despite good theoretical knowledge about determinants of plant species richness in mosaic landscapes, validations based on
complete surveys are scarce. We conducted a case study in a highly fragmented, traditional agricultural landscape. In 199
patches of 20 representative multi-patch-plots (MPPs, 1 ha) we recorded a total of 371 plant species. In addition to an additive
partitioning of species diversity at the (a) patch- and (b) MPP-scale, we adopted the recently proposed ‘specificity’ measure
to quantify the contribution of a spatial subunit to landscape species richness (subunit-to-landscape-contribution, SLC).
SLC-values were calculated at both scales with respect to various spatial extents. General regression models were used to
quantify the relative importance of hypothesis-driven determinants for species richness and SLC-values.
At the patch scale, habitat type was the main determinant of species richness, followed by area and elongated shape. For SLC-values,
area was more important than habitat type, and its relevance increased with the extent of the considered landscape. Influences
of elongated shape and vegetation context were minor. Differences between habitat types were pronounced for species richness
and also partly scale-dependent for SLC-values.
Relevant predictors at the MPP-scale were nonlinear habitat richness, the gradient from anthropogenic to seminatural vegetation,
and the proportions of natural vegetation and rare habitats. Linear elements and habitat configuration did not contribute
to species richness and SLC. Results at the MPP-scale were in complete accordance with the predictions of the mosaic concept.
Hence, our study represents its first empirical validation for plant species diversity in mosaic landscapes. 相似文献
14.
Multi-scale models of grassland passerine abundance in a fragmented system in Wisconsin 总被引:1,自引:1,他引:0
Fragmentation of grasslands has been implicated in grassland bird population declines. Multi-scale models are being increasingly
used to assess potential factors that influence grassland bird presence, abundance, and productivity. However, studies rarely
assess fragmentation metrics, and seldom evaluate more than two scales or interactions among scales. We evaluated the relative
importance of characteristics at multiple scales to patterns in relative abundance of Savannah Sparrow (Passerculus sandwichensis), Grasshopper Sparrow (Ammodramus savannarum), Eastern Meadowlark (Sturnella magna), and Bobolink (Dolichonyx oryzivorus). We surveyed birds in 74 southwestern Wisconsin pastures from 1997 to 1999 and compared models with explanatory variables
from multiple scales: within-patch vegetation structure (microhabitat), patch (macrohabitat), and three landscape extents.
We also examined interactions between macrohabitat and landscape factors. Core area of pastures was an important predictor
of relative abundance, and composition of the landscape was more important than configuration. Relative abundance was frequently
higher in pastures with more core area and in landscapes with more grassland and less wooded area. The direction and strength
of the effect of core pasture size on relative abundance changed depending on amount of wooded area in the landscape. Relative
abundance of grassland birds was associated with landscape variables more frequently at the 1200-m scale than at smaller scales.
To develop better predictive models, parameters at multiple scales and their interactive effects should be included, and results
should be evaluated in the context of microhabitat variability, landscape composition, and fragmentation in the study area. 相似文献
15.
Habitat corridors and the conservation of small mammals in a fragmented forest environment 总被引:7,自引:1,他引:6
Andrew F. Bennett 《Landscape Ecology》1990,4(2-3):109-122
At Naringal in south-western Victoria, Australia, clearing of the original forest environment has created an agricultural landscape dominated by grazed pastures of introduced grasses. Remnant forest vegetation is re-stricted to small patches of less than 100 ha in size, that are loosely linked by narrow forested strips along road reserves and creeks. Six native and two introduced species of small terrestrial mammal (< 2 kg) occur within this environment. The native mammals, being dependent upon forest vegetation, were less tolerant to forest fragmentation than were the introduced species that also persist in farmland and farm buildings. The native mammals displayed an increasing frequency of occurrence in successively larger size-classes of forest patches. Those species with the greatest body-weight were the most vulnerable to habitat loss. All species of small mammal occurred in narrow habitat corridors of forest vegetation on roadsides. The resident status, seasonal variation in relative abundance, patterns of reproduction, and movements of each species were monitored in two habitat corridors during a 25-month trapping study. The corridors were found to facilitate continuity between otherwise-isolated populations of small mammals in this locality in two ways: firstly, by providing a pathway for the dispersal of single animals between patches; and secondly, by enabling gene flow through populations resident within the corridors. The small size of forest remnants at Naringal, and the vulnerability of species with low population sizes, emphasize the importance of preserving a mosaic of numerous habitat patches that together will support regional populations of sufficient size for longer-term persistence. The continuity between remnant habitats that is provided by a network of habitat corridors is an essential, and critical, component of this conservation strategy. 相似文献
16.
The ability to predict species occurrences quickly is often crucial for managers and conservation biologists with limited
time and funds. We used measured associations with landscape patterns to build accurate predictive habitat models that were
quickly and easily applied (i.e., required no additional data collection in the field to make predictions). We used classification
trees (a nonparametric alternative to discriminant function analysis, logistic regression, and other generalized linear models)
to model nesting habitat of red-naped sapsuckers (Sphyrapicus nuchalis), northern flickers (Colaptes auratus),tree swallows (Tachycineta bicolor), and mountain chickadees (Parus gambeli) in the Uinta Mountains of northeastern Utah, USA. We then tested the predictive capability of the models with independent
data collected in the field the following year. The models built for the northern flicker, red-naped sapsucker, and tree swallow
were relatively accurate (84%, 80%, and 75% nests correctly classified,respectively)compared to the models for the mountain
chickadee (50% nests correctly classified). All four models were more selective than a null model that predicted habitat based
solely on a gross association with aspen forests. We conclude that associations with landscape patterns can be used to build
relatively accurate, easy to use, predictive models for some species. Our results stress, however, that both selecting the
proper scale at which to assess landscape associations and empirically testing the models derived from those associations
are crucial for building useful predictive models.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
The factors responsible for widespread declines of grassland birds in the United States are not well understood. This study,
conducted in the short-grass prairie of eastern Wyoming, was designed to investigate the relationship between variation in
habitat amount, landscape heterogeneity, prey resources, and spatial variation in grassland bird species richness. We estimated
bird richness over a 5-year period (1994–1998) from 29 Breeding Bird Survey locations. Estimated bird richness was modeled
as a function of landscape structure surrounding survey routes using satellite-based imagery (1996) and grasshopper density
and richness, a potentially important prey of grassland birds. Model specification progressed from simple to complex explanations
for spatial variation in bird richness. An information-theoretic approach was used to rank and select candidate models. Our
best model included measurements of habitat amount, habitat arrangement, landscape matrix, and prey diversity. Grassland bird
richness was positively associated with grassland habitat; was negatively associated with habitat dispersion; positively associated
with edge habitats; negatively associated with landscape matrix attributes that may restrict movement of grassland bird; and
positively related to grasshopper richness. Collectively, 62% of the spatial variation in grassland bird richness was accounted
for by the model (adj-R2 = 0.514). These results suggest that the distribution of grassland bird species is influenced by a complex mixture of factors
that include habitat area affects, landscape pattern and composition, and the availability of prey. 相似文献
18.
The distribution and abundance of species are shaped by local and landscape processes, but the dominant processes may differ
with scale and increasing human disturbance. We investigated population responses of two pool-breeding amphibian species to
differences in local and landscape characteristics in suburbanizing, southeastern New Hampshire, USA. In 2003 and 2004, we
sampled 49 vernal pools for spotted salamander (Ambystoma maculatum) and wood frog (Lithobates sylvaticus) egg masses. Using egg masses as a proxy for breeding-female population size, we examined the relative influence of five
land-use and three isolation variables at two scales (300 and 1000 m) and five wetland variables on egg-mass abundance. For
both species, road density at the landscape scale (1000 m) and hydroperiod most strongly predicted egg-mass abundance, with
abundance decreasing as roads became denser and hydroperiods shortened. Wetland isolation was also an important predictor,
with abundance greatest at more isolated pools, suggesting that both species concentrate at isolated pools when alternative
breeding sites are scarce. Surprisingly, no 300-m parameters were strongly associated with salamander egg-mass abundance,
whereas several landscape parameters were. In suburbanizing areas, it is at least as important to consider landscape-scale
road density as to consider hydroperiod when designing conservation plans for these species. Furthermore, both isolated and
clustered pools provide these species important habitat and may require protection. Finally, the conceptual framework for
spotted-salamander management must be expanded so that spatial configuration at the landscape scale becomes a regular, integrated
component of conservation planning for this species. 相似文献
19.
Landscape connectivity is considered important for species persistence, but linkages among landscape populations (metalandscape connectivity) may be necessary to ensure the long-term viability of some migratory songbirds at a broader regional scale. Because of regional
source-sink dynamics, these species can maintain steady populations within extensively fragmented landscapes (landscape sinks)
owing to high levels of immigration from source landscapes. We undertook a modeling study to identify the conditions under
which immigration, an index of metalandscape connectivity, could rescue declining populations of songbirds in heavily disturbed
landscapes. In general, low to moderate levels of immigration (m = 0–20%) were sufficient to rescue species with low edge-sensitivity in landscapes where<70% habitat had been destroyed.
At the other extreme, moderate to high levels of immigration (m = 11–40%) were usually required to rescue highly edge-sensitive species in these same landscapes. Very high levels of immigration
(m>40%) were required to rescue highly edge-sensitive species in extensively fragmented landscapes that had lost >50% habitat,
or when any landscape lost ≥50% habitat gradually over a period of 100 or more years (r = 0.5% habitat lost/year). Paradoxically higher levels of immigration were thus necessary to offset population declines when
habitat was lost gradually than when it was lost quickly, where population response lagged behind landscape change. This implies
that the importance of metalandscape connectivity for population viability may not be fully appreciated in landscapes undergoing
rapid rates of change. Natural immigration rates for migratory songbirds match the very high levels (>40%) we found necessary
to sustain populations in heavily disturbed landscapes, which underscores the importance of metalandscape connectivity for
the continued persistence of many migratory songbirds in the face of widespread habitat loss and fragmentation. 相似文献
20.
Cultural landscapes of Germany are patch-corridor-matrix mosaics for an invasive megaforb 总被引:1,自引:0,他引:1
Predicting the vulnerability of landscapes to both the initial colonisation and the subsequent spread of invasive species
remains a major challenge. The aim of this study was to assess the relative importance of sub-patch level factors and landscape
factors for the invasion of the megaforb Heracleum mantegazzianum. In particular, we tested which factors affect the presence in suitable habitat patches and the cover-percentage within invaded
patches. For this purpose, we used standard (logistic) regression modelling techniques. The regression analyses were based
on inventories of suitable habitat patches in 20 study areas (each 1 km2) in cultural landscapes of Germany. The cover percentage in invaded patches was independent from landscape factors, except
for patch shape, and even unsatisfactorily explained by sub-patch level factors included in the analysis (R
2 = 0.19). In contrast, presence of H. mantegazzianum was affected by both local and landscape factors. Woody habitat structure decreased the occurrence probability, whereas vicinity
to transport corridors (rivers, roads), high habitat connectivity, patch size and perimeter-area ratio of habitat patches
had positive effects. The significance of corridors and habitat connectivity shows that dispersal of H. mantegazzianum through the landscape matrix is limited. We conclude that cultural landscapes of Germany function as patch-corridor-matrix
mosaics for the spread of H. mantegazzianum. Our results highlight the importance of landscape structure and habitat configuration for invasive spread. Furthermore,
this study shows that both local and landscape factors should be incorporated into spatially explicit models to predict spatiotemporal
dynamics and equilibrium stages of plant invasions. 相似文献