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991.
Positive effects of forest fragmentation,independent of forest amount,on bat abundance in eastern Ontario,Canada 总被引:1,自引:0,他引:1
While studies have found that bat abundance is positively related to the amount of forest cover in a landscape, the effects
of forest fragmentation (breaking apart of forest, independent of amount) are less certain, with some indirect evidence for
positive effects of fragmentation. However, in most of these studies, the variables used to quantify fragmentation are confounded
with forest amount, making it difficult to interpret the results. The purpose of this study was to examine how forest amount
and forest fragmentation independently affect bat abundance. We conducted acoustic bat surveys at the centers of 22 landscapes
throughout eastern Ontario, Canada, where landscapes were chosen to avoid a correlation between forest amount and forest fragmentation
(number of patches) at multiple spatial scales, while simultaneously controlling for other variables that could affect bat
activity. We found that the effects of forest amount on bat relative abundance were mixed across species (positive for Lasiurus borealis, negative for Perimyotis subflavus and Lasionycteris noctivagans). When there was evidence for an effect of forest fragmentation, independent of forest amount, on bat relative abundance,
the effect was positive (Myotis septentrionalis, Myotis lucifugus and Lasiurus borealis). We suggest that the mechanism driving the positive responses to fragmentation is higher landscape complementation in more
fragmented landscapes; that is, increased access to both foraging and roosting sites for these bat species. We conclude that
fragmented landscapes that maximize complementation between roosting and foraging sites should support a higher diversity
and abundance of bats. 相似文献
992.
993.
Luis J. Villanueva-Rivera Bryan C. Pijanowski Jarrod Doucette Burak Pekin 《Landscape Ecology》2011,26(9):1233-1246
In this paper we present an introduction to the physical characteristics of sound, basic recording principles as well as several
ways to analyze digital sound files using spectrogram analysis. This paper is designed to be a “primer” which we hope will
encourage landscape ecologists to study soundscapes. This primer uses data from a long-term study that are analyzed using
common software tools. The paper presents these analyses as exercises. Spectrogram analyses are presented here introducing
indices familiar to ecologists (e.g., Shannon’s diversity, evenness, dominance) and GIS experts (patch analysis). A supplemental
online tutorial provides detailed instructions with step by step directions for these exercises. We discuss specific terms
when working with digital sound analysis, comment on the state of the art in acoustic analysis and present recommendations
for future research. 相似文献
994.
Soundscape ecology is being proposed as a new synthesis that leverages two important fields of study: landscape ecology and
acoustic ecology. These fields have had a rich history. Running “in parallel” for over three decades now, soundscape ecology
has the potential to unite these two (among other) fields in ways that provide new perspectives on the acoustics of landscapes.
Each of us was involved in the “birth” of these two fields. We each reflect here on the rich history of landscape ecology
and acoustic ecology and provide some thoughts on the future of soundscape ecology as a new perspective. 相似文献
995.
996.
Populations at the periphery of a species’ range often show reduced genetic variability within populations and increased genetic
divergence among populations compared to those at the core, but the mechanisms that give rise to this core-periphery pattern
in genetic structure can be multifaceted. Peripheral population characteristics may be a product of historical processes,
such as founder effects or population expansion, or due to the contemporary influence of landscape context on gene flow. We
sampled collared lizards (Crotaphytus collaris) at four locations within the northern Flint Hills of Kansas, which is at the northern periphery of their range, to determine
the genetic variability and extent of genetic divergence among populations for ten microsatellite loci (n = 229). We found low genetic variability (average allelic richness = 3.37 ± 0.23 SE; average heterozygosity = 0.54 ± 0.05
SE) and moderate population divergence (average FST = 0.08 ± 0.01 SE) among our sample sites relative to estimates reported in the literature at the core of the species’ range
in Texas. We also identified differences in dispersal rates among sampling locations. Gene flow within the Flint Hills was
thus greater than for other peripheral populations of collared lizards, such as the Missouri glade system where most of the
mesic grasslands have been converted to forest since the last glacial retreat, which appears to have greatly impeded gene
flow among populations. Our findings signify the importance of considering landscape context when evaluating core-peripheral
trends in genetic diversity and population structure. 相似文献
997.
Conservation strategies should be based on a solid understanding of processes underlying species response to landscape change.
In forests fragmented by agriculture, elevated nest predation rates have been reported in many forest bird species, especially
near edges. In intensively-managed forest landscapes, timber harvesting might also be associated with negative edge effects
or broader “context” effects on some species when the matrix provides additional resources to their major nest predators.
In this study, we hypothesized that proximity to a forest edge and proportion of cone-producing plantations will increase
nest predation risk in fragments of relatively undisturbed forest. We focused on the Brown Creeper (Certhia americana), an indicator species of late-seral forests. We compared habitat configuration and composition at four spatial scales (0.14,
0.5, 1 and 2 km) around 54 nests and related daily nest survival rate to the distance to the nearest forest edge, mean patch
size of late-seral forest (r = 141 m), proportion of non-forested lands (r = 141 m), density of maintained roads (r = 1 km), proportion of cone-producing spruce plantations (r = 2 km), and year. The best model included distance to the nearest edge and proportion of cone-producing plantations. Distance
of nests to the nearest edge was the best individual predictor of daily nest survival. A larger sample of nests showed a significant
threshold in distance to the nearest forest edge; nests located at least 100 m away were more likely to fledge young. These
results suggest that even in managed forest landscapes, matrix effects can be important and some bird species may exhibit
negative edge effects. 相似文献
998.
In Central Europe vast wetland areas have been converted into agricultural land over the past few centuries. Long-term spatially
explicit reconstructions of wetland cover changes at regional scale are rare but such information is vital for setting appropriate
wetland conservation and restoration goals. In this study wetland cover change over the past 150 years was analyzed for the
Canton Zurich (Switzerland) using information from historical and current topographical maps. Mapping instructions changed
significantly over time, i.e., wetlands were mapped more conservatively on older maps. Therefore a technique was developed
to account for changes in mapping instructions and to reconstruct a series of comparable maps spanning 1850–2000. Wetland
cover dramatically decreased from 13,759 ha in 1850 (more than 8% of the total study area) to 1,233 ha in 2000 (less than
1%). Largest loss is observed for the first half of the twentieth century when more than 50% of the total wetland loss occurred.
In 1850, almost all wetland patches were connected in two large networks defined by a 500 m buffer around all wetland patches
to account for typical dispersal distances of wetland animals. Despite extensive wetland loss, this networks remained largely
intact until 1950, but then collapsed into many medium and small networks consisting of only few wetland patches. In addition
to the direct loss of wetland habitats increased habitat fragmentation is limiting metapopulation dynamics and hindering genetic
exchange between populations. Amphibians and other wetland animals are particularly prone to habitat fragmentation because
of their limited migration abilities. This may lead to time-delayed extinction in the future because current species occurrence
might rather reflect historical than current wetland cover and habitat configuration. Future restoration efforts should focus
on reestablishing connectivity between remaining smaller wetland networks. 相似文献
999.
Thomas Ledermann 《European Journal of Forest Research》2011,130(4):521-531
In this study, a non-linear model was developed that predicts the five-year change of height to crown base (HCB) of Norway
spruce (Picea abies [L.] Karst.). Data were available from the Austrian National Forest Inventory and comprised 2,419 trees from 1,637 permanent
sample plots measured during 1981 and 2002. The dynamic model explained 36% of the variation in the observed change of HCB.
It is well behaved and meets biological expectations. Based on five independent data sets, the predictive ability of the new
dynamic model was compared to an already existing static crown ratio model. For this comparison, the models were applied as
follows: the new ∆ HCB model was used to predict the change in HCB directly. For the semi-dynamic method, the static model
was applied at the end and at the start of the growth period to obtain two estimates of HCB. The difference of these two estimates
was then added to the initial HCB. For the static method, the model was only applied at the end of the prediction period to
obtain the new estimate of HCB. Except for one plot, the new ∆ HCB model yielded the smallest BIAS and the highest precision,
followed by the semi-dynamic and the static method. Because the independent data sets cover a broad range of age classes and
thinning regimes, the validation results also indicate that the new ∆ HCB is robust and the effect of stand management is
adequately represented. 相似文献
1000.
Robert Brus Dalibor Ballian Peter Zhelev Marija Pandža Martin Bobinac Jane Acevski Yannis Raftoyannis Kristjan Jarni 《European Journal of Forest Research》2011,130(4):657-670
We examined leaf and mature seed cone variation of Juniperus oxycedrus L. subsp. oxycedrus in 12 natural populations across the species range in the Balkan Peninsula. We measured 10 morphological traits from a minimum
of 100 leaves in each of 190 individuals, and two morphological traits from 30–50 seed cones in each of 94 females. High phenotypic
variation was found, but no geographical structure or cline across populations was detected for any of the studied traits.
Mean values of comparable leaf and cone morphological traits did not differ considerably from values reported elsewhere. Gender
dimorphism in leaf morphology was detected, but it was not distributed uniformly throughout the studied area. An ANOVA model
with both nested and crossed effects revealed that the largest proportion of the total variation was, as expected, contained
within populations, partly as among-tree variation (18–47%, depending on the trait) and partly as within-tree variation (33–77%),
which was remarkably high. Gender dimorphism explained only 0–3% of the total variation. Differences among populations (2–23%)
were significant for all studied traits except one; however, PCA showed no clear geographical differentiation of the studied
populations. This lack of phylogeographical structure may be the consequence of repeatedly occurring colonisation-retreat
scenarios and suggests the existence of several small refugial populations scattered over a large part of the Balkan Peninsula
in the Pleistocene. Further research including palaeobotanical and molecular genetic studies will be needed to better understand
the forces that shaped current variation patterns of J. oxycedrus L. subsp. oxycedrus in the Balkan Peninsula. 相似文献