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Landscape Ecology - Landscape connectivity, the extent to which a landscape facilitates the flow of ecological processes such as organism movement, has emerged as a central focus of landscape... 相似文献
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ContextVarious species of forest trees are commonly used for ornamental purposes and are therefore frequently found in nonforest ecosystems. They constitute an important component of the so-called trees outside forests (TOF). Not much is known, however, about the drivers of TOF spatial distribution either in urbanized or in agricultural landscapes since they are generally absent from forest inventories.ObjectiveThe present study focused on the spatial distribution of TOF across agricultural landscapes and their potential role in the dispersal of a forest pest insect, the pine processionary moth, Thaumetopoea pityocampa (PPM).MethodsAll the TOF belonging to the genera Pinus, Cedrus and Pseudotsuga were considered as potential hosts and inventoried within a 22 × 22 km study window. We fitted a nonstationary Poisson process to the empirical data and used the distance to the nearest building as a covariate.ResultsBoth empirical and simulated data indicated that TOF associated to human artifacts/urbanized areas constituted the main source of landscape connectivity for the PPM in the open fields under study. Because they do not account for TOF, forest inventories dramatically underestimate landscape connectivity and provide an erroneous picture of the PPM habitat distribution.ConclusionsWe conclude that TOF, especially the ornamental component, must be taken into account when it comes to understanding forest insect landscape dynamics or genetics. The omnipresence of TOF also suggests a potentially huge role in pest dispersal and invasive species expansion. 相似文献
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ContextMany connectivity metrics have been used to measure the connectivity of a landscape and to evaluate the effects of land-use changes and potential mitigation measures. However, there are still gaps in our understanding of how to accurately quantify landscape connectivity. ObjectivesA number of metrics only measure between-patch connectivity, i.e. the connectivity between different habitat patches, which can produce misleading results. This paper demonstrates that the inclusion of within-patch connectivity is important for accurate results. MethodsThe behavior of two metrics is compared: the Connectance Index (CONNECT), which measures only between-patch connectivity, and the effective mesh size (meff), which includes both within-patch and between-patch connectivity. The connectivity values of both metrics were calculated on a set of simulated landscapes. Twenty cities were then added to these landscapes to calculate the resulting changes in connectivity. ResultsWe found that when using CONNECT counter-intuitive results occurred due to not including within-patch connectivity, such as scenarios where connectivity increased with increasing habitat loss and fragmentation. These counter-intuitive results were resolved when using meff. For example, landscapes with low habitat amount may be particularly sensitive to urban development, but this is not reflected by CONNECT. ConclusionsApplying misleading results from metrics like CONNECT can have detrimental effects on natural ecosystems, because reductions in within-patch connectivity by human activities are neglected. Therefore, this paper provides evidence for the crucial need to consider the balance between within-patch connectivity and between-patch connectivity when calculating the connectivity of landscapes. 相似文献
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ContextMethods quantifying habitat patch importance for maintaining habitat network connectivity have been emphasized in helping to prioritize conservation actions. Functional connectivity is accepted as depending on landscape resistance, and several measures of functional inter-patch distance have been designed. However, how the inter-patch distance, i.e., based on least-cost path or multiple paths, influences the identification of key habitat patches has not been explored.ObjectivesWe compared the prioritization of habitat patches according to least-cost distance (LCD) and resistance distance (RD), using common binary and probabilistic connectivity metrics.MethodsOur comparison was based on a generic functional group of forest mammals with different dispersal distances, and was applied to two landscapes differing in their spatial extent and fragmentation level.ResultsWe found that habitat patch prioritization did not depend on distance type when considering the role of patch as contributing to dispersal fluxes. However, the role of patch as a connector facilitating dispersal might be overestimated by LCD-based indices compared with RD for short- and medium-distance dispersal. In particular, when prioritization was based on dispersal probability, the consideration of alternatives routes identified the connectors that probably provided functional connectivity for species in the long term. However, the use of LCD might help identify landscape areas that need critical restoration to improve individual dispersal.ConclusionsOur results provide new insights about the way that inter-patch distance is viewed changes the evaluation of functional connectivity. Accordingly, prioritization methods should be carefully selected according to assumptions about population functioning and conservation aims. 相似文献
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ContextComplex structural connectivity patterns can influence the distribution of animals in coastal landscapes, particularly those with relatively large home ranges, such as birds. To understand the nuanced nature of coastal forest avifauna, where there may be considerable overlap in assemblages of adjacent forest types, the concerted influence of regional landscape context and vegetative structural connectivity at multiple spatial scales warrants investigation.ObjectivesThis study determined whether species compositions of coastal forest bird assemblages differ with regional landscape context or with forest type, and if this is influenced by structural connectivity patterns measured at multiple spatial scales.MethodsThree replicate bird surveys were conducted in four coastal forest types at ten survey locations across two regional landscape contexts in northeast Australia. Structural connectivity patterns of 11 vegetation types were quantified at 3, 6, and 12 km spatial scales surrounding each survey location, and differences in bird species composition were evaluated using multivariate ordination analysis.ResultsBird assemblages differed between regional landscape contexts and most coastal forest types, although Melaleuca woodland bird assemblages were similar to those of eucalypt woodlands and rainforests. Structural connectivity was primarily correlated with differences in bird species composition between regional landscape contexts, and correlation depended on vegetation type and spatial scale.ConclusionsSpatial scale, landscape context, and structural connectivity have a combined influence on bird species composition. This suggests that effective management of coastal landscapes requires a holistic strategy that considers the size, shape, and configuration of all vegetative components at multiple spatial scales. 相似文献
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The loss of connectivity of natural areas is a major threat for wildlife dispersal and survival and for the conservation of
biodiversity in general. Thus, there is an increasing interest in considering connectivity in landscape planning and habitat
conservation. In this context, graph structures have been shown to be a powerful and effective way of both representing the
landscape pattern as a network and performing complex analysis regarding landscape connectivity. Many indices have been used
for connectivity analyses so far but comparatively very little efforts have been made to understand their behaviour and sensitivity
to spatial changes, which seriously undermines their adequate interpretation and usefulness. We systematically compare a set
of ten graph-based connectivity indices, evaluating their reaction to different types of change that can occur in the landscape
(habitat patches loss, corridors loss, etc.) and their effectiveness for identifying which landscape elements are more critical
for habitat conservation. Many of the available indices were found to present serious limitations that make them inadequate
as a basis for conservation planning. We present a new index (IIC) that achieves all the properties of an ideal index according
to our analysis. We suggest that the connectivity problem should be considered within the wider concept of habitat availability,
which considers a habitat patch itself as a space where connectivity exists, integrating habitat amount and connectivity between
habitat patches in a single measure. 相似文献
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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
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For many species, one important key to persistence is maintaining connectivity among local populations that allow for dispersal
and gene flow. This is probably true for carabid species (Coleoptera:Carabidae) living in the fragmented forests of the Bereg
Plain (NE Hungary and W Ukraine). Based on field data, we have drafted a landscape graph of the area representing the habitat
network of these species. Graph nodes and links represented two kinds of landscape elements: habitat (forest) patches and
corridors, respectively. The quality of habitat patches and corridors were ranked (from low (1) to high (4)), reflecting local
population sizes in the case of patches and estimated permeability in the case of corridors. We analysed (1) the positional
importance of landscape elements in maintaining the connectivity of the intact network, (2) the effect of inserting hypothetical
corridors into the network, (3) the effects of improving the quality of the existing corridors, and (4) how to connect every
patch in a cost-effective way. Our results set quantitative priorities for conservation practice by identifying important
corridors: what to protect, what to build and what to improve. Several network analytical techniques were used to account
for the directed (source-sink) and highly fragmented nature of the landscape graph. We provide conservation priority ranks
for the landscape elements and discuss the conditions for the use of particular network indices. Our study could be of extreme
relevance, since a new highway is being planned through the area. 相似文献
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For some time, ecologists have known that spatial patterns of forest structure reflected disturbance and recovery history, disturbance severity and underlying influences of environmental gradients. In spite of this awareness, historical forest structure has been little used to expand knowledge of historical fire severity. Here, we used forest structure to predict pre-management era fire severity across three biogeoclimatic zones in eastern Washington State, USA, that contained extensive mixed conifer forests. We randomly selected 10% of the subwatersheds in each zone, delineated patch boundaries, and photo-interpreted the vegetation attributes of every patch in each subwatershed using the oldest available stereo-aerial photography. We statistically reconstructed the vegetation of any patch showing evidence of early selective harvesting, and then classified them as to their most recent fire severity. Classification used published percent canopy mortality definitions and a dichotomized procedure that considered the overstory and understory canopy cover and size class attributes of a patch, and the fire tolerance of its cover type. Mixed severity fires were most prevalent, regardless of forest type. The structure of mixed conifer patches, in particular, was formed by a mix of disturbance severities. In moist mixed conifer, stand replacement effects were more widespread in patches than surface fire effects, while in dry mixed conifer, surface fire effects were more widespread by nearly 2:1. However, evidence for low severity fires as the primary influence, or of abundant old park-like patches, was lacking in both the dry and moist mixed conifer forests. The relatively low abundance of old, park-like or similar forest patches, high abundance of young and intermediate-aged patches, and widespread evidence of partial stand and stand-replacing fire suggested that variable fire severity and non-equilibrium patch dynamics were primarily at work. 相似文献
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Landscape Ecology - Climate and land-use changes affect species ranges and movements. However, these changes are usually overlooked in connectivity studies, and this could have adverse consequences... 相似文献
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We evaluated changes in the Atlantic Forest landscape over the last 40 years based on changes in boundaries and mosaics, including the hypothetical landscape resulting from the application of Brazilian laws for forest protection. Mosaics were identified as sets of land-use patches with a similar pattern of boundaries. Landscapes of different years, therefore, can be distinguished by differences in mosaics. We developed a technique to identify boundaries between patches from land-use maps using ArcGis ® and to build the patch x boundary matrix required for mosaic identification by means of a factorial and cluster analysis. The mosaics were characterized by some key uses as well as by their boundaries with other land uses. The mosaics were scored for forest conservation according to five issues: landscape permeability, cover, availability, quality, and fragmentation of forest. The values were based on land use and boundary patterns. Although Brazilian laws regarding forest protection have promoted conservation and the hypothetical legal landscape has presented the highest forest habitat availability, this expansion perpetuates a boundary pattern that complicates conservation and management, thus increasing the pressure on forest patches and favoring the further fragmentation of protected forest patches. These conclusions cannot be reached by simply recording changes in land uses. 相似文献
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Landscape Ecology - Romania is currently one of the best-connected landscapes, with high-quality habitats and a high density of brown bears. However, regional development measures are needed for... 相似文献
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In mobile animals, movement behavior can maximize fitness by optimizing access to critical resources and minimizing risk of
predation. We sought to evaluate several hypotheses regarding the effects of landscape structure on American marten foraging
path selection in a landscape experiencing forest perforation by patchcut logging. We hypothesized that in the uncut pre-treatment
landscape marten would choose foraging paths to maximize access to cover types that support the highest density of prey. In
contrast, in the post-treatment landscapes we hypothesized marten would choose paths primarily to avoid crossing openings,
and that this would limit their ability to optimally select paths to maximize foraging success. Our limiting factor analysis
shows that different resistant models may be supported under changing landscape conditions due to threshold effects, even
when a species’ response to landscape variables is constant. Our results support previous work showing forest harvest strongly
affects marten movement behavior. The most important result of our study, however, is that the influence of these features
changes dramatically depending on the degree to which timber harvest limits available movement paths. Marten choose foraging
paths in uncut landscapes to maximize time spent in cover types providing the highest density of prey species. In contrast,
following landscape perforation by patchcuts, marten strongly select paths to avoid crossing unforested areas. This strong
response to patch cutting reduces their ability to optimize foraging paths to vegetation type. Marten likely avoid non-forested
areas in fragmented landscapes to reduce risk of predation and to benefit thermoregulation in winter, but in doing so they
may suffer a secondary cost of decreased foraging efficiency. 相似文献
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ContextSpatial prioritization is an analytical approach that can be used to provide decision support in spatial conservation planning (SCP), and in tasks such as conservation area network design, zoning, planning for impact avoidance or targeting of habitat management or restoration. MethodsBased on literature, we summarize the role of connectivity as one component of relevance in the broad structure of spatial prioritization in both marine and terrestrial realms. ResultsPartially diffuse, directed connectivity can be approximated in Zonation-based multi-criteria SCP by applying hydrodynamic modelling, knowledge on species traits, and information on species occurrences and quality of habitats. Sources and destinations of larvae or propagules can be identified as separate spatial layers and taken into account in full-scale spatial prioritization involving data on biota, as well as economic factors, threats, and administrative constraints. While population connectivity is an important determinant of metapopulation persistence, the importance of marine connectivity depends on species traits and the marine environment studied. At one end of the continuum are species that occupy isolated habitats and have long pelagic larval durations in deeper sea areas with strong directional currents. At the other extreme are species with short pelagic durations that occupy fragmented habitats in shallow topographically complex sea areas with weak and variable currents. ConclusionsWe conclude that the same objectives, methods, and analysis structures are applicable to both terrestrial and marine spatial prioritization. Marine spatial conservation planning, marine spatial planning, marine zoning, etc., can be implemented using methods originated in the terrestrial realm of planning. 相似文献
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Landscape Ecology - The current biodiversity crisis has intensified the need to predict species responses to landscape modification and has renewed attention on the fundamental question of what... 相似文献
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ContextRoutine movements of large herbivores, often considered as ecosystem engineers, impact key ecological processes. Functional landscape connectivity for such species influences the spatial distribution of associated ecological services and disservices.ObjectivesWe studied how spatio-temporal variation in the risk-resource trade-off, generated by fluctuations in human activities and environmental conditions, influences the routine movements of roe deer across a heterogeneous landscape, generating shifts in functional connectivity at daily and seasonal time scales.MethodsWe used GPS locations of 172 adult roe deer and step selection functions to infer landscape connectivity. In particular, we assessed the influence of six habitat features on fine scale movements across four biological seasons and three daily periods, based on variations in the risk-resource trade-off.ResultsThe influence of habitat features on roe deer movements was strongly dependent on proximity to refuge habitat, i.e. woodlands. Roe deer confined their movements to safe habitats during daytime and during the hunting season, when human activity is high. However, they exploited exposed open habitats more freely during night-time. Consequently, we observed marked temporal shifts in landscape connectivity, which was highest at night in summer and lowest during daytime in autumn. In particular, the onset of the autumn hunting season induced an abrupt decrease in landscape connectivity.ConclusionsHuman disturbance had a strong impact on roe deer movements, generating pronounced spatio-temporal variation in landscape connectivity. However, high connectivity at night across all seasons implies that Europe’s most abundant and widespread large herbivore potentially plays a key role in transporting ticks, seeds and nutrients among habitats. 相似文献
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We hypothesized that the spatial configuration and dynamics of periurban forest patches in Barcelona (NE of Spain) played
a minor role in determining plant species richness and assemblage compared to site conditions, and particularly to both direct
(measured at plot level) and potential (inferred from landscape metrics) human-associated site disturbance. The presence of
all understory vascular plants was recorded on 252 plots of 100 m 2 randomly selected within forest patches ranging in size from 0.25 ha to 218 ha. Species were divided into 6 groups, according
to their ecology and conservation status. Site condition was assessed at plot level and included physical attributes, human-induced
disturbance and Quercus spp. tree cover. Landscape structure and dynamics were assessed from patch metrics and patch history. We also calculated
a set of landscape metrics related to potential human accessibility to forests. Results of multiple linear regressions indicated
that the variance explained for non-forest species groups was higher than for forest species richness. Most of the main correlates
corresponded to site disturbance variables related to direct human alteration, or to landscape variables associated to indirect
human effects on forests: Quercus tree cover (a proxy for successional status) was the most important correlate of non-forest species richness, which decreased
when Quercus tree cover increased. Human-induced disturbance was an important correlate of synanthropic and total species richness, which
were higher in recently managed and in highly frequented forests. Potential human accessibility also affected the richness
of most species groups. In contrast, patch size, patch shape and connectivity played a minor role, as did patch history. We
conclude that human influence on species richness in periurban forests takes place on a small scale, whereas large-scale effects
attributable to landscape structure and fragmentation are comparatively less important. Implications of these results for
the conservation of plant species in periurban forests are discussed. 相似文献
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ContextBroad-scale land conservation and management often involve applying multiple strategies in a single landscape. However, the potential outcomes of such arrangements remain difficult to evaluate given the interactions of ecosystem dynamics, resource extraction, and natural disturbances. The costs and potential risks of implementing these strategies make robust evaluation critical.ObjectivesWe used collaborative scenario modeling to compare the potential outcomes of alternative management strategies in the Two Hearted River watershed in Michigan’s Upper Peninsula to answer key questions: Which management strategies best achieve conservation goals of maintaining landscape spatial heterogeneity and conserving mature forests and wetlands? And how does an increase in wildfire and windthrow disturbances influence these outcomes?MethodsScenarios were modeled using the VDDT/TELSA state-and-transition modeling suite, and resulting land cover maps were analyzed using ArcGIS, FRAGSTATS, and R statistical software.ResultsResults indicate that blending conservation strategies, such as single-ownership forest reserves and working forest conservation easements in targeted areas of the landscape, may better achieve these goals than applying a single strategy across the same area. However, strategies that best achieve these conservation goals may increase the sensitivity of the landscape to changes in wildfire and windthrow disturbance regimes.ConclusionsThese results inform decision-making about which conservation strategy or combination of strategies to apply in specific locations on the landscape to achieve optimum conservation outcomes, how to best utilize scarce financial resources, and how to reduce the financial and ecological risks associated with the application of innovative strategies in an uncertain future. 相似文献
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ContextLand-cover changes (LCCs) could impact wildlife populations through gains or losses of natural habitats and changes in the landscape mosaic. To assess such impacts, we need to focus on landscape connectivity from a diachronic perspective.ObjectivesWe propose a method for assessing the impact of LCCs on landscape connectivity through a multi-species approach based on graph theory. To do this, we combine two approaches devised to spatialize the variation of multi-species connectivity and to quantify the importance of types of LCCs for single-species connectivity by highlighting the possible contradictory effects.MethodsWe begin with a list of landscape species and create virtual species with similar ecological requirements. We model the ecological network of these virtual species at two dates and compute the variation of a local and global connectivity metric to assess the impacts of the LCCs on their dispersal capacities.ResultsThe spatial variation of multi-species connectivity showed that local impacts range from ?6.4% to +3.2%. The assessment of the impacts of types of LCCs showed a variation in global connectivity ranging from ?45.1% for open-area reptiles to +170.2% for natural open-area birds with low-dispersion capacities.ConclusionsThis generic approach can be reproduced in a large variety of spatial contexts by adapting the selection of the initial species. The proposed method could inform and guide conservation actions and landscape management strategies so as to enhance or maintain connectivity for species at a landscape scale. 相似文献
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