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1.
Besides providing habitat to the grizzly bear (Ursus arctos) and other wildlife, the Rocky Mountain foothills of Alberta, Canada hosts considerable mining, seismic oil and gas exploration
and production, and forest harvesting activities. Worldwide, such human activities influence the configuration and composition
of the landscape. We assessed seismic cutline effects on landscape structure and grizzly bear use during early summer of 1999
and 2000. We studied five female and two male bears, which were GPS-collared in the spring following den emergence. The area
available to this population was stratified into 49 km2 hexagon-shaped sub-landscapes. The scale of this stratification was determined by patterns of bear movement. Fourteen compositional
and configurational landscape metrics were calculated within each landscape unit, and bear use points were pooled or ‘binned’
within each unit. Landscape use was related to landscape metrics using a Generalized Linear Model (GLM). We found that seismic
cutline proportion did not explain landscape use by grizzly bears; however secondary effects of cutlines on landscape structure
did. Declining use was mainly associated with increasing proportions of closed forest, and increasing variation of inter-patch
distances, while use was mainly increasing with increasing mean patch size. An earlier investigation had demonstrated that
adding seismic cutlines to grizzly bear habitat caused increases in the variation of inter-patch distances. Since the landscape
structure of this grizzly bear population will continue to change as a function of increased levels of resource extraction
activities in the near future, it is crucial to further study the detailed meaning of landscape structure at the large and
small scale for effective conservation efforts. 相似文献
2.
David J. Augustine Stephen J. Dinsmore Michael B. Wunder Victoria J. Dreitz Fritz L. Knopf 《Landscape Ecology》2008,23(6):689-697
Sylvatic plague is a major factor influencing the dynamics of black-tailed prairie dog (Cynomys ludovicianus) colonies in the western Great Plains. We studied the nesting response of the mountain plover (Charadrius montanus), a grassland bird that nests on prairie dog colonies, to plague-driven dynamics of prairie dog colonies at three sites in
the western Great Plains. First, we examined plover nest distribution on colonies that were previously affected by plague,
but that had been recovering (expanding) for at least 6 years. Plovers consistently nested in both young (colonized in the
past 1–2 years) and old (colonized for 6 or more years) portions of prairie dog colonies in proportion to their availability.
Second, we examined changes in plover nest frequency at two sites following plague epizootics, and found that mountain plover
nest numbers declined relatively rapidly (≤2 years) on plague-affected colonies. Taken together, our findings indicate that
available plover nesting habitat associated with prairie dog colonies closely tracks the area actively occupied by prairie
dogs each year. Given the presence of plague throughout most of the mountain plover’s breeding range in the western Great
Plains, important factors affecting plover populations likely include landscape features that determine the scale of plague
outbreaks, the distance that plovers move in response to changing breeding habitat conditions, and the availability and quality
of alternate breeding habitat within the landscape. 相似文献
3.
Habitat specificity indices reflect richness (α) and/or distinctiveness (β) components of diversity. The latter may be defined by α and γ (landscape) diversity in two alternative ways: multiplicatively () and additively (). We demonstrate that the original habitat specificity concept of Wagner and Edwards (Landscape Ecol 16:121–131, 2001) consists of three independent components: core habitat specificity (uniqueness of the species composition), patch area and
patch species richness. We describe habitat specificity as a family of indices that may include either area or richness components,
or none or both, and open for use of different types of mean in calculation of core habitat specificity. Core habitat specificity
is a beta diversity measure: the effective number of completely distinct communities in the landscape. Habitat specificity
weighted by species number is a gamma diversity measure: the effective number of species that a patch contributes to landscape
richness. We compared 12 habitat specificity indices by theoretical reasoning and by use of field data (vascular plant species
in SE Norwegian agricultural landscapes). Habitat specificity indices are strongly influenced by weights for patch area and
patch species richness, and the relative contribution of rare vs. common species (type of mean). The relevance of properties
emphasized by each habitat specificity index for evaluation of patches in a biodiversity context is discussed. Core habitat
specificity is emphasized as an ecologically interpretable measure that specifically addresses patch uniqueness while habitat
specificity weighted by species number combines species richness and species composition in ways relevant for conservation
biological assessment.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
We evaluated support for four alternate hypotheses explaining the distribution of breeding Brown-headed Cowbirds (Molothrus ater) in forests at varying distances from the forest edge in three Midwestern USA landscapes with varying amounts of forest fragmentation
(core forest area ranged from 5 to 70%). We focused on breeding cowbirds’ use of forest because of the risk of nest parasitism
to forest-dwelling hosts and to identify factors affecting breeding cowbird habitat selection. We compared distances of cowbird
locations in the forest from the forest edge (“edge distances”) to distances of random forest locations in the entire landscape
or within individual cowbird home ranges. We analyzed 1322 locations of 84 cowbirds across three landscapes. We found support
for the landscape context hypothesis that breeding cowbird preference for forest edge varied with landscape context. Ninety
percent of cowbird locations were within 150–350 m of forest edge, despite the overall availability of forest at greater distances
from edge (as far as 500–1450 m) both within cowbird home ranges and the entire forested landscape. Cowbird preference for
edge varied by landscape context largely due to differences in the availability of forest edge. In a highly fragmented forest
cowbirds utilized the entire forest and likely viewed it as “all edge.” In less fragmented forests, cowbirds preferred edge.
We consider how variation in cowbird edge preference might relate to patterns in host abundance, host diversity, and host
quality because cowbird movements indicate they are capable of using forest farther from edges. 相似文献
5.
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
6.
Aude Ernoult Sylviano Freiré-Diaz Estelle Langlois Didier Alard 《Landscape Ecology》2006,21(5):631-639
This landscape study was based on the sampling of 20 replicated landscape sites (1 km2 each) that were located within the floodplain of the river Seine. For each site, 13 landscape variables were measured at
three dates (1963–1985–2000). The aim of this study was to investigate the overall landscape variability through its different
dimensions (space vs. time) and to assess the relative importance of each dimension. We used a new statistical method, i.e.,
partial triadic analysis (PTA), which allowed us to assess both (1) the spatial variability of the floodplain landscape and
its dynamics in time and (2) the dynamic trajectories of the landscape variables for each site. The results showed, at the
floodplain scale, the same landscape pattern has emerged since 1963, although a major trend was observed which consisted in
a decrease in meadows resulting from an increase in arable crops. At the site scale, landscape sites, even if they were all
influenced by this general trend during the 40-year period, showed contrasting trajectories. These results suggest that similar
sites in 2000 do not necessarily share common histories and that contrasting sites in 2000 may have originated from similar
patterns in 1963. The issue of biodiversity surrogates is then discussed, suggesting that new landscape metrics should be
developed, emphasising spatial variability and (or) temporal dynamics. 相似文献
7.
Robert A. Long Therese M. Donovan Paula MacKay William J. Zielinski Jeffrey S. Buzas 《Landscape Ecology》2011,26(3):327-340
Terrestrial carnivores typically have large home ranges and exist at low population densities, thus presenting challenges
to wildlife researchers. We employed multiple, noninvasive survey methods—scat detection dogs, remote cameras, and hair snares—to
collect detection–nondetection data for elusive American black bears (Ursus americanus), fishers (Martes pennanti), and bobcats (Lynx rufus) throughout the rugged Vermont landscape. We analyzed these data using occupancy modeling that explicitly incorporated detectability
as well as habitat and landscape variables. For black bears, percentage of forested land within 5 km of survey sites was an
important positive predictor of occupancy, and percentage of human developed land within 5 km was a negative predictor. Although
the relationship was less clear for bobcats, occupancy appeared positively related to the percentage of both mixed forest
and forested wetland habitat within 1 km of survey sites. The relationship between specific covariates and fisher occupancy
was unclear, with no specific habitat or landscape variables directly related to occupancy. For all species, we used model
averaging to predict occurrence across the study area. Receiver operating characteristic (ROC) analyses of our black bear
and fisher models suggested that occupancy modeling efforts with data from noninvasive surveys could be useful for carnivore
conservation and management, as they provide insights into habitat use at the regional and landscape scale without requiring
capture or direct observation of study species. 相似文献
8.
Nest locations of breeding birds are often spatially clustered. This tendency to nest together has generally been related
to a patchy distribution of nesting habitat in landscape studies, but behavioral studies of species with clustered breeding
patterns draw attention to the importance of social and biotic factors. Indeed, it is becoming increasingly apparent that
the breeding system of many territorial, migrant birds may be semi-colonial. The reasons for, and extent of, spatial clustering
in their breeding systems are not well understood. Our goal was to tease apart the influence of habitat availability and social
drivers of clustered breeding in a neotropical migrant species, the hooded warbler (Wilsonia citrina). To test alternative hypotheses related to clustered habitat or conspecific attraction, we combined a habitat classification
based on remote sensing with point pattern analysis of nesting sites. Nest locations (n = 150, 1999–2004), collected in a 1213 ha forested area of Southern Ontario (Canada), were analyzed at multiple spatial scales.
Ripley’s K and pair-correlation functions g (uni- and bivariate) were used to test whether nests were clustered merely because potential nesting habitat was also clustered,
or whether nests were additionally clustered with respect to conspecifics. Nest locations tended to be significantly clustered
at intermediate distances (particularly between 240 and 420 m). Nests were randomly distributed within available habitat at
larger distance scales, up to 1500 m. A reasonable hypothesis to explain the detected additional clustering, and one that
is consistent with the results of several behavioral studies, is that females pack their nests more tightly than the available
habitat requires to be situated closer to their neighbors’ mates. Linking spatially explicit, point pattern analysis with
strong inference based on Monte Carlo tests may bring us closer to understanding the generality and reasons behind conspecific
attraction at different spatial scales.
F. Csillag—deceased. 相似文献
9.
Metapopulation models are frequently used for analysing species–landscape interactions and their effect on structure and dynamic
of populations in fragmented landscapes. They especially support a better understanding of the viability of metapopulations.
In such models, the processes determining metapopulation viability are often modelled in a simple way. Animals’ dispersal
between habitat fragments is mostly taken into account by using a simple dispersal function that assumes the underlying process
of dispersal to be random movement. Species-specific dispersal behaviour such as a systematic search for habitat patches is
likely to influence the viability of a metapopulation. Using a model for metapopulation viability analysis, we investigate
whether such specific dispersal behaviour affects the predictions of ranking orders among alternative landscape configurations
rated regarding their ability to carry viable metapopulations. To incorporate dispersal behaviour in the model, we use a submodel
for the colonisation rates which allows different movement patterns to be considered (uncorrelated random walk, correlated
random walk with various degrees of correlation, and loops). For each movement pattern, the landscape order is determined
by comparing the resulting mean metapopulation lifetime Tm of different landscape configurations. Results show that landscape orders can change considerably between different movement
patterns. We analyse whether and under what circumstances dispersal behaviour influences the ranking orders of landscapes.
We find that the ‘competition between patches for migrants’ – i.e. the fact that dispersers immigrating into one patch are
not longer available as colonisers for other patches – is an important factor driving the change in landscape ranks. The implications
of our results for metapopulation modelling, planning and conservation are discussed. 相似文献
10.
Comparing the landscape level perceptual abilities of forest sciurids in fragmented agricultural landscapes* 总被引:8,自引:2,他引:6
Perceptual range is the maximum distance from which an animal can perceive the presence of remote landscape elements such as patches of habitat. Such perceptual abilities are of interest because they influence the probability that an animal will successfully disperse to a new patch in a landscape. Furthermore, understanding how perceptual range differs between species may help to explain differential species sensitivity to patch isolation. The objective of this research was to assess the perceptual range of eastern chipmunks (Tamias striatus), gray squirrels (Sciurus carolinensis), and fox squirrels (Sciurus niger) in fragmented agricultural landscapes. Animals were captured in remote woodlots and translocated to unfamiliar agricultural fields. There they were released at different distances from a woodlot and their movements towards or away from the woodlot were used to assess their ability to perceive forested habitat. Observed perceptual ranges of approximately 120 m for chipmunks, 300 m for gray squirrels, and 400 m for fox squirrels, suggest that differences in landscape-level perceptual abilities may influence the occurrence of these species in isolated habitat patches. 相似文献
11.
Changes in land use affect species interactions and population dynamics by modifying the spatial template of trophic interaction
and the availability of resources in time and space. We developed a process-based spatially explicit model for evaluating
the effects of land use on species viability by modelling foraging performance and energy sequestration in a stage structured,
three-trophic population model. The model is parameterized with realistic parameters for a ladybeetle–aphid–host plant interaction,
and is run in four realistic landscapes in the Czech Republic. We analysed whether changes in crop selection and fertilizer
input could explain the dramatic and unexplained decline in abundance of the ladybeetle Coccinella septempunctata in the Czech Republic from 1978 to 2005. The results indicate that a major reduction in fertilizer input after the transition
to a market economy, resulting in lower aphid population densities in cereal crops and negatively affecting energy sequestration,
survival and reproduction of ladybeetles, provides a sufficient explanation for the observed population decline. Simulations
further indicated that the population viability of C. septempunctata is highly dependent on availability of aphid prey in crops, in particular cereal, which serves as their major reproduction
habitat. The results demonstrate how the abundance of naturally occurring predators, which are instrumental for biological
pest control, depends upon the spatial resource template that are provided at the landscape scale. 相似文献
12.
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
13.
The degree to which habitat fragmentation affects bird incidence is species specific and may depend on varying spatial scales.
Selecting the correct scale of measurement is essential to appropriately assess the effects of habitat fragmentation on bird
occurrence. Our objective was to determine which spatial scale of landscape measurement best describes the incidence of three
bird species (Pyriglena leucoptera, Xiphorhynchus fuscus and Chiroxiphia caudata) in the fragmented Brazilian Atlantic forest and test if multi-scalar models perform better than single-scalar ones. Bird
incidence was assessed in 80 forest fragments. The surrounding landscape structure was described with four indices measured
at four spatial scales (400-, 600-, 800- and 1,000-m buffers around the sample points). The explanatory power of each scale
in predicting bird incidence was assessed using logistic regression, bootstrapped with 1,000 repetitions. The best results
varied between species (1,000-m radius for P. leucoptera; 800-m for X. fuscus and 600-m for C. caudata), probably due to their distinct feeding habits and foraging strategies. Multi-scale models always resulted in better predictions
than single-scale models, suggesting that different aspects of the landscape structure are related to different ecological
processes influencing bird incidence. In particular, our results suggest that local extinction and (re)colonisation processes
might simultaneously act at different scales. Thus, single-scale models may not be good enough to properly describe complex
pattern–process relationships. Selecting variables at multiple ecologically relevant scales is a reasonable procedure to optimise
the accuracy of species incidence models. 相似文献
14.
Reclamation usually involves modification of the local environment to achieve some biotic target, but if the influence of
Landscape Condition on that target is great, we may fail to meet it despite efforts at the local-level. We sought to determine
the relative influence of local- and landscape-level habitat on aquatic plant diversity in shallow open-water wetlands. Furthermore,
we asked whether the influence of Landscape Condition should be attributed to direct (dispersal-related) effects, or to the
indirect effect of landscape variables that influence local habitat quality. Finally, we asked if spatial scale (300–2000 m)
would affect conclusions about the relative influence of local- and landscape-level effects. Using structural equation modeling,
we found that Local Condition is consistently more influential than Landscape Condition. As landscape size increases, the
relative importance of Landscape Condition declines and there is a trade-off between its direct and indirect components. At
≤500 m direct landscape effects were of greater importance than indirect effects, whereas indirect effects of Landscape Condition
became more important at ≥1500 m. This suggests that the dominant mechanism by which land use influences diversity depends
on the spatial extent of the landscape. We recommend that reclamation designs include a high proportion of wetland habitat
and incorporate seeding/planting if diverse plant communities are desired. Additionally, we note that the influence of the
landscape is strongest within 300 m. Thus, the focus of reclamation efforts should remain at the in-lake level and the immediate
surroundings: this is where efforts will achieve the greatest effect on aquatic plant diversity. 相似文献
15.
Zharikov et al. (2006: Landscape Ecology 21:107–120) modeled the nest-site habitat use of marbled murrelets (Brachyramphus marmoratus) in Desolation Sound (DS) and Clayoquot Sound (CS), British Columbia. They compared known nest sites, located with radio-telemetry,
with randomly-located points within the same areas. Their conclusions suggest that murrelets tended to nest in disproportionately
smaller fragments within the more disturbed DS landscape; streams, steeper slopes, and lower elevations were selected in both
landscapes; murrelets nested closer to recent clearcuts than would be expected in the DS landscape; and survivorship of nestlings
was greater in areas with recent clearcuts and was positively correlated with recent habitat fragmentation. These conclusions
are contrary to current management guidelines in British Columbia, and therefore require close scrutiny. Our detailed examination
reveals flaws in their use of data, application of modeling, and most seriously, interpretation of the results. Problems include:
conceptual errors in the interpretation of models; inappropriate spatial resolution; confusing use and interpretation of fragmentation
and patch size data; overemphasis of statistically significant but biologically trivial results; and ignoring some contradictory
studies. We conclude that it would be risky to apply the results from Zharikov et al. in the selection of murrelet nesting
habitat for management purposes in British Columbia. Our review identifies issues that may arise in other ecological modeling
studies and stresses the need for biological realism in addition to statistical rigour. 相似文献
16.
Artificial neural networks were used to quantify the distribution of macroinvertebrate functional feeding groups (FFGs) in
relation to physical variables and to land-cover in the Adour–Garonne stream system (SW France; 116,000 km2). The relative abundances of 5 FFGs were calculated from macroinvertebrate data recorded at 165 sampling sites. Each site
was characterized using 5 physical variables (elevation, stream order, stream width, distance from the source, slope) and
3 land-cover variables (% forested, % urban areas, % agricultural areas). The sites were first classified using the Self-Organizing
Map algorithm (SOM), according to the physical and land-cover variables. Two major clusters of sites corresponded to anthropogenically
modified and natural areas, respectively. Anthropogenically modified areas were clearly divided into agricultural and urban
landscapes. Each major cluster was divided into 3–4 subsets of sites according to a topographic gradient of physical variables.
To examine the variability of the communities, FFG proportions at the 165 sites were examined on the SOM trained with physical
and land-cover variables. When the riverine landscape was natural, FFG patterns responded to the upstream–downstream gradient
in physical variables. When the landscape was altered by agriculture or urbanization, the effects of land-cover on FFGs overcame
the influence of the physical variables. The categorization of the landscape into forested, agricultural, and urban areas
was relevant to detect changes in FFG patterns. In light of increasing development along riparian zones, the use of SOMs to
detect responses of FFGs to landscape alterations at regional scales exemplifies an effective technique for assessing river
health based on ecological indicator groups. 相似文献
17.
Landscape context influences many aspects of songbird ecology during the breeding season. The importance of landscape context
at stopover sites for migrating songbirds, however, has received less attention. In particular, landscape context may affect
the availability and quality of food for refueling during stopovers, which is critical for successful migration. We evaluated
the influence of woody habitat cover in the surroundings of stopover sites at several spatial extents on the hourly changes
of body mass in two species of European-African forest-dwelling songbird migrants (Willow Warbler, Phylloscopus trochilus, and the Eurasian Redstart, Phoenicurus phoenicurus). Data were sampled by standardized methods from a network of ringing stations throughout Europe during the falls of 1994–1996.
In both species, hourly body mass gain calculated for first captures increased with woody habitat cover. We found a similar
logarithmic relationship for both species, although for Willow Warblers mass gain was more strongly related to the habitat
cover within 5 km, in contrast to 3 km for Redstarts. For Willow Warblers, where sufficient data are available for each year,
the relationship is consistent over the years. The shape of the relationship suggests existence of a threshold of landscape
suitability for refueling at stopover sites: in sites with less than 10% of woody habitat cover, birds tend to lose body mass
or to gain mass at a lower rate.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Overgaard Hans J. Ekbom Barbara Suwonkerd Wannapa Takagi Masahiro 《Landscape Ecology》2003,18(6):605-619
The influence of landscape structure on anopheline mosquito density and diversity was studied in a comparison of agricultural
and forested landscapes in northern Thailand. Agriculture locations had significantly higher landscape diversity, more patches,
smaller mean patch sizes, and more complex patch shapes than forest locations. Mosquito collections were undertaken during
both dry and wet seasons from October 1997 to December 1999. The density of two forest-associated species, Anopheles maculatus s.s. and Anopheles minimus s.l., both primary malaria vectors in Thailand, was significantly higher in forest locations in at least one season. The
density of two paddy field-associated species, Anopheles aconitus and Anopheles hyrcanus group did not differ between locations. Anopheles aconitus is a secondary malaria vector and An. hyrcanus group is not considered as a vector in Thailand. The density of An. minimus s.l. was positively related to forest mean patch size, various water and paddy field landscape metrics and negatively related
to landscape diversity. Anopheles hyrcanus group was also positively related to water metrics. Anopheline species diversity was negatively related to landscape diversity.
Forest fragmentation resulting from human economic activities often increases landscape heterogeneity, which may result in
a reduction in anopheline species diversity, as was the case in this study. There are indications that the effect of fruit
orchards on anopheline diversity might be different in the dry season compared to the wet season. Fruit orchard landscape
metrics affected species diversity negatively in the dry season and positively in the wet season. One reason for this could
be that pesticides are typically applied in fruit orchards during the dry season. The conversion of forests to fruit orchards
is a major land-use change in northern Thailand. These results show the complexity of vector status in northern Thailand and
that vector and agriculture pest control are intricately interrelated. It is therefore important to include both the public
health and agricultural sectors in controlling malaria vectors in the country. Our results also indicate that if landscape
management should be used for malaria control in northern Thailand large-scale reduction and fragmentation of forest cover
would be needed. Such drastic actions do not agree well with current global objectives concerning forest and biodiversity
conservation
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
In an increasingly human-dominated landscape, effective management of disturbance-maintained ecosystems, such as grasslands
and savannas, is critical to the conservation of biodiversity. Yet, the response of individual organisms to landscapes created
by disturbances and management is rarely studied. In this study, we examined the endangered Karner blue butterfly, Lycaeides melissa samuelis, in a heterogeneous oak savanna. Our objective was to quantify the butterfly’s habitat use and behavior to assess the effects of prescribed burning. The oak
savanna management in Ohio, USA divides each Karner blue site (n = 4) into three units. Each one-third unit is then burned, mowed, or unmanaged in an annual rotation within each site, and
the result is a fire return interval of ~3 years. Our surveys measured habitat use, while behavior observations quantified
reproduction and foraging for the two annual broods. Our habitat use results showed burned treatments were recolonized quickly,
but there was not a clear selection for burned treatments. Foraging rates were similar in all treatments; however, females
oviposited significantly less in unmanaged treatments (only 5 of 127 ovipositions). This oviposition preference was likely
due to habitat degradation and the availability of recently burned, early successional habitat. Since Karner blues avoided
reproduction in units unburned for ≥4 years, these units could be burned to create high quality early successional habitat.
These results demonstrate how behavioral decisions can be pivotal forces driving spatial population dynamics. Our case study
demonstrates how a fine-scale landscape perspective combined with measurements of behavioral processes can assist with management
decision-making. 相似文献
20.
Birds can serve as useful model organisms to investigate community level consequences of forestry practices. In this study
we investigated the relationships between wintering bird communities and habitat and landscape characteristics of lowland
managed forests in Northern Italy. This area is characterized by the spread of the black locust, an alien species that has
been favored by forestry practices at the expense of natural oak forests. Birds were censused in winter by point counts in
randomly selected plots of 50 m radius. We first addressed bird community–habitat relationships by means of habitat structure
measurements, then we investigated bird community–landscape relationships by using GIS techniques. We used generalized linear
models (GLM) to test for the effects of habitat and landscape variables on bird community parameters (namely bird species
richness, diversity and abundance). Bird community parameters were influenced by oak biomass and tree age, and by oak area
and core area, while the other forest habitat types showed less influence. In forest management terms, the main conclusion
is that the retention of native oaks is the keyfactor for the conservation of winter bird diversity in local deciduous woods.
At the habitat level black locust harvesting may be tolerated, provided that old, large, native oaks are retained in all local
woodlots to preserve landscape connectivity and foraging resources. At the landscape meso-scale, large native oak patches,
should be preserved or, where necessary, restored.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献