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1.
Robert M. Scheller Wayne D. Spencer Heather Rustigian-Romsos Alexandra D. Syphard Brendan C. Ward James R. Strittholt 《Landscape Ecology》2011,26(10):1491-1504
Natural resource managers are often challenged with balancing requirements to maintain wildlife populations and to reduce
risks of catastrophic or dangerous wildfires. This challenge is exemplified in the Sierra Nevada of California, where proposals
to thin vegetation to reduce wildfire risks have been highly controversial, in part because vegetation treatments could adversely
affect an imperiled population of the fisher (Martes pennanti) located in the southern Sierra Nevada. The fisher is an uncommon forest carnivore associated with the types of dense, structurally
complex forests often targeted for fuel reduction treatments. Vegetation thinning and removal of dead-wood structures would
reduce fisher habitat value and remove essential habitat elements used by fishers for resting and denning. However, crown-replacing
wildfires also threaten the population’s habitat, potentially over much broader areas than the treatments intended to reduce
wildfire risks. To investigate the potential relative risks of wildfires and fuels treatments on this isolated fisher population,
we coupled three spatial models to simulate the stochastic and interacting effects of wildfires and fuels management on fisher
habitat and population size: a spatially dynamic forest succession and disturbance model, a fisher habitat model, and a fisher
metapopulation model, which assumed that fisher fecundity and survivorship correlate with habitat quality. We systematically
varied fuel treatment rate, treatment intensity, and fire regime, and assessed their relative effects on the modeled fisher
population over 60 years. After estimating the number of adult female fishers remaining at the end of each simulation scenario,
we compared the immediate negative effects of fuel treatments to the longer-term positive effect of fuel treatment (via reduction
of fire hazard) using structural equation modeling. Our simulations suggest that the direct, negative effects of fuel treatments
on fisher population size are generally smaller than the indirect, positive effects of fuel treatments, because fuels treatments
reduced the probability of large wildfires that can damage and fragment habitat over larger areas. The benefits of fuel treatments
varied by elevation and treatment location with the highest net benefits to fisher found at higher elevations and within higher
quality fisher habitat. Simulated fire regime also had a large effect with the largest net benefit of fuel treatments occurring
when a more severe fire regime was simulated. However, there was large uncertainty in our projections due to stochastic spatial
and temporal wildfires dynamic and fisher population dynamics. Our results demonstrate the difficulty of projecting future
populations in systems characterized by large, infrequent, stochastic disturbances. Nevertheless, these coupled models offer
a useful decision-support system for evaluating the relative effects of alternative management scenarios; and uncertainties
can be reduced as additional data accumulate to refine and validate the models. 相似文献
2.
As the concepts of landscape ecology have been incorporated into otherdisciplines, the influence of spatial patterns on animal abundance anddistribution has attracted considerable attention. However, there remains asignificant gap in the application of landscape ecology theories and techniquesto wildlife research. By combining landscape ecology techniques withtraditionalwildlife habitat analysis methods, we defined an organism-centeredperspectivefor breeding bald eagles (Haliaeetus leucocephalus) alongthe Hudson River, New York, USA. We intensively monitored four pairs ofbreedingeagles during the 1999 and 2000 breeding seasons, and collected detailedinformation on perch and forage locations. Our analysis focused on threecritical habitat elements: available perch trees, access to foraging areas, andfreedom from human disturbance. We hypothesized that eagle habitat selectionrelative to each of these elementswould vary with the spatial scale of analysis, and that these scalingrelationships would vary among habitat elements. We investigated two elementsofspatial scale: grain and local extent. Grain was defined as the minimum mappingunit; local extent was defined by the size of an analysis window placed aroundeach focal point. For each habitat element, we quantified habitat use over arange of spatial scales. Eagles displayed scale-dependent patterns of habitatuse in relation to all habitat features, including multi-scale andthreshold-like patterns. This information supports the existence ofscale-dependant relationships in wildlife habitat use and allowed for a moreaccurate and biologically relevant evaluation of Hudson River breeding eagle habitat.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
3.
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
4.
Small-scale effects of historical land use and topography on post-cultural tree species composition in an Alpine valley in southern Switzerland 总被引：1，自引：0，他引：1
Investigations of spatial patterns in forest tree species composition are essential in the understanding of landscape dynamics,
especially in areas of land-use change. The specific environmental factors controlling the present patterns, however, vary
with the scale of observation. In this study we estimated abundance of adult trees and tree regeneration in a Southern Alpine
valley in Ticino, Switzerland. We hypothesized that, at the present scale, spatial pattern of post-cultural tree species does
not primarily depend on topographic features but responds instead to small-scale variation in historical land use. We used
multivariate regression trees to relate species abundances to environmental variables. Species matrices were comprised of
single tree species abundance as well as species groups. Groups were formed according to common ecological species requirements
with respect to shade tolerance, soil moisture and soil nutrients. Though species variance could only be partially explained,
a clear ranking in the relative importance of environmental variables emerged. Tree basal area of formerly cultivated Castanea sativa (Mill.) was the most important factor accounting for up to 50% of species’ variation. Influence of topographic attributes
was minor, restricted to profile curvature, and partly contradictory in response. Our results suggest the importance of biotic
factors and soil properties for small-scale variation in tree species composition and need for further investigations in the
study area on the ecological requirements of tree species in the early growing stage. 相似文献
5.
Sara Vallecillo Virgilio Hermoso Hugh P. Possingham Lluís Brotons 《Landscape Ecology》2013,28(8):1517-1528
In response to the processes threatening biodiversity such as habitat loss, effective selection of priority conservation areas is required. However, reserve selection methods usually ignore the drivers of future habitat changes, thus compromising the effectiveness of conservation. In this work, we formulated an approach to explicitly quantify the impact of fire on conservation areas, considering such disturbance as a driver of land-cover changes. The estimated fire impact was integrated as a constraint in the reserve selection process to tackle the likely threats or opportunities that fire disturbance might cause to the targeted species depending on their habitat requirements. In this way, we selected conservation areas in a fire-prone Mediterranean region for two bird assemblages: forest and open-habitat species. Differences in conservation areas selected before and after integrating the impact of fire in the reserve selection process were assessed. Integration of fire impact for forest species moved preferences towards areas that were less prone to burn. However, a larger area was required to achieve the same conservation goals. Conversely, integration of fire impacts for open-habitat species shifted preferences towards conservation areas in locations where the persistence of their required habitat is more likely (i.e. shrublands). In other words, we prioritized the conservation of not only the current distribution of open-habitat birds, but also the disturbance process (i.e. fire) that favours their preferred habitat and distributions in the long term. Finally, this work emphasizes the need to consider the opposing potential impacts of wildfires on species for an effective conservation planning. 相似文献
6.
Habitat for wide-ranging species should be addressed at multiple scales to fully understand factors that limit populations.
The marbled murrelet (Brachyramphus marmoratus), a threatened seabird, forages on the ocean and nests inland in large trees. We developed statistical relationships between
murrelet use (occupancy and abundance) and habitat variables quantified across many spatial scales (statewide to local) and
two time periods in California and southern Oregon, USA. We also addressed (1) if old-growth forest fragmentation was negatively
associated with murrelet use, and (2) if some nesting areas are more important than others due to their proximity to high
quality marine habitat. Most landscapes used for nesting were restricted to low elevation areas with frequent fog. Birds were
most abundant in unfragmented old-growth forests located within a matrix of mature second-growth forest. Murrelets were less
likely to occupy old-growth habitat if it was isolated (> 5 km) from other nesting murrelets. We found a time lag in response
to fragmentation, where at least a few years were required before birds abandoned fragmented forests. Compared to landscapes
with little tono murrelet use, landscapes with many murrelets were closer to the ocean's bays, river mouths, sandy shores,
submarine canyons, and marine waters with consistently high primary productivity. Within local landscapes (≤ 800ha), inland
factors limited bird abundance, but at the broadest landscape scale studied (3200 ha), proximity to marine habitat was most
limiting. Management should focus on protecting or creating large, contiguous old-growth forest stands, especially in low-elevation
areas near productive marine habitat.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Responses of Chilean forest birds to anthropogenic habitat fragmentation across spatial scales 总被引：1，自引：1，他引：0
Although it is recognized that anthropogenic forest fragmentation affects habitat use by organisms across multiple spatial
scales, there is uncertainty about these effects. We used a hierarchical sampling design spanning three spatial scales of
habitat variability (landscape > patch > within-patch) and generalized mixed-effect models to assess the scale-dependent responses
of bird species to fragmentation in temperate forests of southern Chile. The abundances of nine of 20 bird species were affected
by interactions across spatial scales. These interactions resulted in a limited effect of within-patch habitat structure on
the abundance of birds in landscapes with low forest cover, suggesting that suitable local habitats, such as sites with dense
understory cover or large trees, are underutilized or remain unused in highly fragmented landscapes. Habitat specialists and
cavity-nesters, such as tree-trunk foragers and tapaculos, were most likely to exhibit interactions across spatial scales.
Because providing additional sites with dense understory vegetation or large habitat trees does not compensate the negative
effect of the loss of forest area on bird species, conservation strategies should ensure the retention of native forest patches
in the mixed-use landscapes. 相似文献
8.
Fulé Peter Z. Crouse Joseph E. Heinlein Thomas A. Moore Margaret M. Covington W. Wallace Verkamp Greg 《Landscape Ecology》2003,18(5):465-486
Fire regime characteristics of high-elevation forests on the North Rim of the Grand Canyon, Arizona, were reconstructed from fire scar analysis, remote sensing, tree age, and forest structure measurements, a first attempt at detailed reconstruction of the transition from surface to stand-replacing fire patterns in the Southwest. Tree densities and fire-/non-fire-initiated groups were highly mixed over the landscape, so distinct fire-created stands could not be delineated from satellite imagery or the oldest available aerial photos. Surface fires were common from 1700 to 1879 in the 4,400 ha site, especially on S and W aspects. Fire dates frequently coincided with fire dates measured at study sites at lower elevation, suggesting that pre-1880 fire sizes may have been very large. Large fires, those scarring 25% or more of the sample trees, were relatively infrequent, averaging 31 years between burns. Four of the five major regional fire years occurred in the 1700s, followed by a 94-year gap until 1879. Fires typically occurred in significantly dry years (Palmer Drought Stress Index), with severe drought in major regional fire years. Currently the forest is predominantly spruce-fir, mixed conifer, and aspen. In contrast, dendroecological reconstruction of past forest structure showed that the forest in 1880 was very open, corresponding closely with historical (1910) accounts of severe fires leaving partially denuded landscapes. Age structure and species composition were used to classify sampling points into fire-initiated and non-fire-initiated groups. Tree groups on nearly 60% of the plots were fire-initiated; the oldest such groups appeared to have originated after severe fires in 1782 or 1785. In 1880, all fire-initiated groups were less than 100 years old and nearly 25% of the groups were less than 20 years old. Non-fire-initiated groups were significantly older (oldest 262 years in 1880), dominated by ponderosa pine, Douglas-fir, or white fir, and occurred preferentially on S and W slopes. The mixed-severity fire regime, transitioning from lower-elevation surface fires to mixed surface and stand-replacing fire at higher elevations, appeared not to have been stable over the temporal and spatial scales of this study. Information about historical fire regime and forest structure is valuable for managers but the information is probably less specific and stable for high-elevation forests than for low-elevation ponderosa pine forests.This revised version was published online in May 2005 with corrections to the Cover Date. 相似文献
9.
To determine how vegetation pattern in early successional forests may be related to plant traits and types of disturbance,
we measured percent cover of individual taxa annually in a South Carolina Pinus elliottii forest, starting one year before, and ending four years after harvest and tree girdling disturbances were applied. The 17
most important taxa surveyed were grouped into four regeneration strategies chosen a priori, and the spatial patterns of these
groups and of the soil were investigated using global variability, semivariograms and kriged maps. We also examined spatial
correlations across years, across taxa, and between species and soil disturbance. Seed bank taxa represented by Dichanthelium spp. increased rapidly and formed large patches, and then quickly declined. Taxa that regenerate by newly dispersed seeds,
represented by Rhus copallina and Rubus spp. occurred at first in a few patches, and became widespread later. Stump sprouters, represented by Quercus spp. and Myrica cerifera, had rapid increases in cover, but their spatial patterns were largely determined by their pre-disturbance patterns. Prunus serotina, which relies on both sprouting and dispersed seed, had moderate cover and a random distribution. Within-species temporal
correlation of spatial pattern was lower in girdled than in harvested plots, and was not clearly related to regeneration strategy.
Forest floor disturbance was patchy and affected the pattern of Dichanthelium spp. in the harvested plots. Negative correlations between herbs and woody plants in harvested plots reflected the role of
biotic (i.e., successional) filters on vegetation pattern. Surprisingly, no spatial correlations were detected between the
nitrogen fixer, Myrica cerifera and other taxa in this N-limited system. In comparing the spatial and temporal patterns, we found kriged maps more informative
than analysis of semivariograms alone. The maps and correlation statistics demonstrated that regeneration traits, spatial
patterns of soil disturbances, and interactions among taxa influence dynamics of the spatial patterns of the plants. We also
demonstrated that disturbance types affected the importance and interactions among these three factors, and caused different
spatial patterns of the plant taxa. 相似文献
10.
The storm that struck France on december 26th and 28th 1999 felled 140 million m3 of timber and had a high economic, social and landscape impact. This event offered the opportunity to study large-scale patterns in populations of forest insect pests that would benefit from the abundant breeding material. A large-scale survey was carried out in France in 2000 to sample the most frequently observed species developing on spruce (Ips typographus, Pityogene schalcographus) and pine (Tomicus piniperda, Ips sexdentatus) in 898 locations distributed throughout wind-damaged areas. The local abundance of each species scored on a 0 to 5 scale was analysed using geostatistical estimators to explore the extent and intensity of spatial autocorrelation, and was related to site, stand, and neighbourhood landscape metrics of the forest cover (in particular the interconnection with broadleaf forest patches) found within dispersal distance. All species but I. sexdentatus, which was much less abundant, displayed large-scale spatial dependence and regional variations in abundance. Lower infestation levels per tree (windfalls and standing trees) were observed in stands with a high proportion of wind-damaged trees, which was interpreted as the result of beetles distributing themselves among the available breeding material. More infestations were observed in wind-broken trees as compared to wind-felled trees. More importantly, populations showed significant relationships with the structure of coniferous stands (in particular with the number of coniferous patches). T. piniperda population levels were negatively correlated to the amount of coniferous edge shared with broadleaf forest patches, possibly because of the disruptive effect of non-host volatiles on host-finding processes at the landscape-scale. The differences observed between species regarding patterns and relationships to site, stand, and forest cover characteristics are discussed in relation to the ecological characteristics of each species. 相似文献
11.
Harvesting and forest fire change the spatial configurations of forest habitat. We used multivariate statistical models to
evaluate the individual and cumulative effects of these two disturbances on habitat configuration in managed boreal forest
landscapes in western Canada. We evaluated three aspects of configuration (core area, inter-patch distance and shape) using
indices normalized for total habitat abundance. The two disturbances types had different effects on the three configuration
metrics in terms of both the magnitude and direction of change. We found that the magnitudes of harvesting effects were larger
than for fire. The direction of change was the same for core area and shape, but opposite for inter-patch distance which decreased
slightly after fire. The combined effects of the two disturbances are distinct from the effects of either disturbance alone,
and the effects are not always additive or compensatory for all metrics. Pre-treatment configuration was a significant covariate
in all models, and total habitat abundance was significant in 4/9 models, but these were often not the most important covariates.
In the cumulative disturbance model, covariates for the number or size of cut-blocks were significant. 相似文献
12.
The distribution and abundance of a species may be simultaneously influenced by both local-scale habitat features and the
broader patch and landscape contexts in which these populations occur. Different factors may influence patch occupancy (presence–absence)
versus local abundance (number of individuals within patches), and at different scales, and thus ideally both occupancy and
abundance should be investigated, especially in studies that seek to understand the consequences of land management on species
persistence. Our study evaluated the relative influences of variables associated with the local habitat patch, hillside (patch
context), and landscape context on patch occupancy and abundance of the collared lizard (Crotaphytus collaris) within tallgrass prairie managed under different fire and grazing regimes in the northern Flint Hills of Kansas, USA. Using
a multi-model information-theoretic approach that accounted for detection bias, we found that collared lizard abundance and
occupancy was influenced by factors measured at both the local habitat and landscape scales. At a local scale, collared lizard
abundance was greatest on large rock ledges that had lots of crevices, high vegetation complexity, and were located higher
up on the hillslope. At the landscape scale, collared lizard abundance and occupancy were both higher in watersheds that were
burned frequently (1–2 year intervals). Interestingly, grazing only had a significant effect on occupancy and abundance within
less frequently burned (4-year burn interval) watersheds. Our results suggest that, in addition to the obvious habitat needs
of this species (availability of suitable rock habitat), land-management practices have the potential to influence collared
lizard presence and abundance in the grasslands of the Flint Hills. Thus, mapping the availability of suitable habitat is
unlikely to be sufficient for evaluating species distributions and persistence in such cases without consideration of landscape
management and disturbance history. 相似文献
13.
We evaluated the effects of aspen patch area and orientation (relative to North and an elevational gradient) on the early
breeding season abundance and species richness of migratory and resident birds in the northern ungulate winter range of the
Yellowstone ecosystem, USA. Using an information-theoretic model selection approach, we found patch area and basal area of
aspen to be the most important covariates for long distance migrants, and patch orientation relative to elevational gradient
the most important covariate for residents/short-distance migrants. Basal area of live aspen and aspen snags was marginally
important for both migratory strategies, likely because aspen snags are an important habitat for most cavity-nesting species.
Landscape ecological theory postulates passive interception of dispersing or migrating organisms by patches of suitable habitat.
Our results suggest that residents/short-distance migrants are intercepted by patches that are oriented perpendicular to the
elevational gradient of our study region resulting in greater abundances and species richness in those patches. However, long-distance
migrants appear to use aspen patches without regard to orientation, but rather to patch area. 相似文献
14.
Widespread adoption of genetically modified glyphosate-resistant (GR) crops in the US has dramatically changed the agricultural
landscape to one that selects for establishment and spread of weedy species resistant to glyphosate, a commonly applied herbicide.
Weed species that possess the means to readily spread across the landscape will be contained by weed management strategies
that limit weed establishment and prevent seed set. An empirically-derived simulation model was developed to explore GR Conyza canadensis spread in relation to characteristics of the agricultural landscape. C. canadensis seeds are carried in the wind and move among fields and therefore, access high quality habitat (GR crops) at long distances.
The baseline scenario was the current GR adoption levels in many US agricultural landscapes with corn and soybean rotated
annually. Alternate scenarios examined the interacting effects of management uniformity (GR crop adoption) and increased landscape
richness (three crops: corn, soybean, alfalfa, instead of two), over a 10 year simulation period. When landscape uniformity
increased (increased GR corn adoption), 3× more fields would be infested with the resistant biotype and a specific field would
have up to 24% greater likelihood of being infested compared to the current GR crop adoption levels. Increased landscape richness
(adding alfalfa as a third crop) slightly decreased GR C. canadensis abundance. Reduced GR management uniformity by way of reducing GR soybeans to half their current adoption levels had the
greatest impact on spread and prevented GR C. canadensis from reaching high abundance. Large-scale reliance on glyphosate for weed management has increased high-fitness habitat and
will result in rapid spread of glyphosate-resistant weeds. Without significant reductions of glyphosate use and without spatial
coordination of weed and crop management practices, GR weeds will continue to spread rapidly and impact agricultural practices
in areas reliant on glyphosate. 相似文献
15.
Scale-dependent determinants of heterogeneity in fire frequency in a coniferous boreal forest of eastern Canada 总被引：1，自引：0，他引：1
Despite the recognized importance of fire in North American boreal forests, the relative importance of stochastic and determinist
portions of intra-regional spatial variability in fire frequency is still poorly understood. The first objective of this study
is to identify sources of spatial variability in fire frequency in a landscape of eastern Quebec’s coniferous boreal forest.
Broad-scale environmental factors considered included latitude, longitude, human activities and belonging to a given bioclimatic
domain, whereas fine-scale factors included slope, position on the slope, aspect, elevation, surficial deposit and drainage.
The average distance to waterbodies was also considered as a potential intermediate-scale source of variability in fire frequency.
In order to assess these environmental factors’ potential influence, they were incorporated into a proportional hazard model,
a semi-parametric form of survival analysis. We also used a digital elevation model in order to evaluate the dominant aspect
within neighborhoods of varying sizes and successively incorporated these covariates into the proportional hazard model. We
found that longitude significantly affects fire frequency, suggesting a maritime influence on fire frequency in this coastal
landscape. We also found that position on the slope was related to fire frequency since hilltops and upperslopes were subject
to a lower fire frequency. Dominant aspect was also related to fire frequency, but only when characterized within a neighborhood
delimited by 4,000 to 10,000-m radii (5,027–31,416 ha). A 2–6-fold variation in fire frequency can be induced by geographic
and topographic contexts, suggesting a substantial intra-regional heterogeneity in disturbance regime with potential consequences
on forest dynamics and biodiversity patterns. Implications for forest management are also briefly discussed.
Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
16.
Forest insects cause defoliation disturbances with complex spatial dynamics. These are difficult to measure but critical for models of disturbance risk that inform forest management. Understanding of spatial dynamics has lagged behind other disturbance processes because traditional defoliation sketch map data often suffered from inadequate precision or spatial resolution. We sought to clarify the influence of underlying habitat characteristics on outbreak patterns by combining forest plots, GIS data and defoliation intensity maps modeled from Landsat imagery. We quantified dependence of defoliation on spatial patterns of host abundance, phenology, topography, and pesticide spray for a recent gypsy moth outbreak (2000–2001), in a mixed deciduous forest in western Maryland, USA. We used semivariograms and hierarchical partitioning to quantify spatial patterns and variable importance. Habitat characteristics from plot data explained 21 % of defoliation variance in 2000 from tree density, phenological asynchrony, pesticide spray status, and landform index and 34 % of the variance in 2001 from previous-year defoliation, relative abundance of non-host species, phenological asynchrony, pesticide spray status, and relative slope position. Spatial autocorrelation in residual defoliation ranged over distances of 788 m in 2000 and 461 m in 2001, corresponding well with gypsy moth larval dispersal distances (100 m to 1 km). Un-measured processes such as predation, virus and pathogen occurrence likely contribute to unexplained variance. Because the spatial dynamics of these factors are largely unknown, our results support modeling gypsy moth defoliation as a function of dependence on significant exogenous characteristics and residual spatial pattern matching. 相似文献
17.
Eric J. Gustafson Mark E. Kubiske Brian R. Sturtevant Brian R. Miranda 《Landscape Ecology》2013,28(9):1785-1800
The Aspen-FACE experiment generated 11 years of empirical data on the effect of CO2 enrichment and elevated ozone on the growth of field-grown trees (maple, birch and six aspen clones) in northern Wisconsin, but it is not known how these short-term plot-level responses might play out at the landscape scale over multiple decades where competition, succession and disturbances interact with tree-level responses. In this study we used a forest landscape model (LANDIS-II) to scale these site level results to broader temporal and spatial scales. These general principles emerged from the results. (1) The productivity of taxa under future conditions is the primary determinant of short-term taxon dominance. (2) Longer-term, longevity and shade tolerance may supersede productivity as the determinant of importance, depending on the disturbance regime. This result offers hope that, even in the face of atmospheric changes, managers may have some control over future forest composition and carbon sequestration through modification of disturbance regimes. (3) Changes in the abundance of taxa were mostly gradual and none of the taxa were extirpated from the landscape, even under treatments for which they were poorly adapted. This suggests that as atmospheric conditions change, abrupt extirpations are expected to be rare. (4) Similarly, different taxa fared relatively well under different treatments. This suggests that maintaining species and genetic diversity is a prudent forest management strategy in the face of global change. (5) Accounting for spatial processes is important because seed dispersal and establishment may limit the ability of some species to colonize available habitat. 相似文献
18.
Kirtland’s warblers (Dendroica kirtlandii) persist in a naturally patchy environment of young, regenerating jack pine forests (i.e., 5–23 years old) created after
wildfires and human logging activities. We examined how changing landscape structure from 26 years of forest management and
wildfire disturbances influenced population size and spatial dispersion of male Kirtland’s warblers within their restricted
breeding range in northern Lower Michigan, USA. The male Kirtland’s warbler population was six times larger in 2004 (1,322)
compared to 1979 (205); the change was nonlinear with 1987 and 1994 identified as significant points of change. In 1987, the
population trend began increasing after a slowly declining trend prior to 1987, and the rate of increase appeared to slow
after 1994. Total amount of suitable habitat and the relative area of wildfire-regenerated habitat were the most important
factors explaining population trend. Suitable habitat increased 149% primarily due to increasing plantations from forest management.
The relative amount and location of wildfire-regenerated habitat modified the distribution of males among various habitat
types, and the spatial variation in their abundance across the primary breeding range. These findings indicate that the Kirtland’s
warbler male population shifted its use of habitat types temporally and spatially as the population increased and as the relative
availability of habitats changed through time. We demonstrate that researchers and managers need to consider not only habitat
quality, but the temporal and the spatial context of habitat availability and population levels when making habitat restoration
decisions. 相似文献
19.
Much of what is known about avian species-habitat relations has been derived from studies of birds at local scales. It is
entirely unclear whether the relations observed at these scales translate to the larger landscape in a predictable linear
fashion. We derived habitat models and mapped predicted abundances for three forest bird species of eastern North America
using bird counts, environmental variables, and hierarchical models applied at three spatial scales. Our purpose was to understand
habitat associations at multiple spatial scales and create predictive abundance maps for purposes of conservation planning
at a landscape scale given the constraint that the variables used in this exercise were derived from local-level studies.
Our models indicated a substantial influence of landscape context for all species, many of which were counter to reported
associations at finer spatial extents. We found land cover composition provided the greatest contribution to the relative
explained variance in counts for all three species; spatial structure was second in importance. No single spatial scale dominated
any model, indicating that these species are responding to factors at multiple spatial scales. For purposes of conservation
planning, areas of predicted high abundance should be investigated to evaluate the conservation potential of the landscape
in their general vicinity. In addition, the models and spatial patterns of abundance among species suggest locations where
conservation actions may benefit more than one species. 相似文献
20.
William D. Dijak Brice B. Hanberry Jacob S. Fraser Hong S. He Wen J. Wang Frank R. ThompsonIII 《Landscape Ecology》2017,32(7):1365-1384