نتایج جستجو برای: habitat changes

تعداد نتایج: 918380  

2006
William L. Gaines Kenneth J. Raedeke

We used logistic regression to derive scaled resource selection functions (RSFs) for female black bears at two study areas in the North Cascades Mountains. We tested the hypothesis that the influence of roads would result in potential habitat effectiveness (RSFs without the influence of roads) being greater than realized habitat effectiveness (RSFs with roads). Roads consistently had a negative...

Journal: :محیط زیست طبیعی 0
فرهاد عطایی کارشناس ارشد زیستگاه ها و تنوع زیستی، دانشکده محیط زیست و انرژی، دانشگاه آزاد اسلامی، واحد علوم و تحقیقات تهران، ایران محمود کرمی استاد گروه محیط زیست، دانشکده محیط زیست و انرژی، دانشگاه آزاد اسلامی، واحد علوم و تحقیقات تهران، ایران محمد کابلی استادیار گروه محیط زیست، دانشکده منابع طبیعی، دانشگاه تهران، ایران

brown bear (ursus arctos) is one of the most important carnivores in iran. however, information on its habitat associations is scared. based on ecological niche factor analysis (enfa) method, a summer habitat suitability model was developed for this species in the southern part of alborz protected area. our results showed that, brown bears prefer higher altitudes and northern aspects in their p...

Journal: :TheScientificWorldJournal 2001
C L Rowe W A Hopkins J D Congdon

Habitat contamination can alter numerous biological processes in individual organisms. Examining multiple individual-level responses in an integrative fashion is necessary to understand how individual health or fitness reflects environmental contamination. Here we provide an example of such an integrated perspective based upon recent studies of an amphibian (the bullfrog, Rana catesbeiana ) tha...

2016
Betsy A. Bancroft Joshua J. Lawler Nathan H. Schumaker

Climate change and land-use change are projected to be the two greatest drivers of biodiversity loss over the coming century. Land-use change has resulted in extensive habitat loss for many species. Likewise, climate change has affected many species resulting in range shifts, changes in phenology, and altered interactions. We used a spatially explicit, individual-based model to explore the effe...

2002
STEVEN F. RAILSBACK BRET C. HARVEY

Despite their promise for simulating natural complexity, individual-based models (IBMs) are rarely used for ecological research or resource management. Few IBMs have been shown to reproduce realistic patterns of behavior by individual organisms. To test our IBM of stream salmonids and draw conclusions about foraging theory, we analyzed the IBM’s ability to reproduce six patterns of habitat sele...

2005
LISA A. SCHULTE ANNA M. PIDGEON DAVID J. MLADENOFF

Evaluating bird population trends requires baseline data. In North America the earliest population data available are those from the late 1960s. Forest conditions in the northern Great Lake states (U.S.A.), however, have undergone succession since the region was originally cut over around the turn of the twentieth century, and it is expected that bird populations have undergone concomitant chan...

2002
JASON B. DUNHAM BRIAN S. CADE JAMES W. TERRELL

—We used regression quantiles to model potentially limiting relationships between the standing crop of cutthroat trout Oncorhynchus clarki and measures of stream channel morphology. Regression quantile models indicated that variation in fish density was inversely related to the width:depth ratio of streams but not to stream width or depth alone. The spatial and temporal stability of model predi...

2005
DAVID M. WALTERS MARY C. FREEMAN DAVID S. LEIGH CATHERINE M. PRINGLE

—We quantified the relationships among urban land cover, fishes, and habitat quality to determine how fish assemblages respond to urbanization and if a habitat index can be used as an indirect measure of urban effects on stream ecosystems. We sampled 30 wadeable streams along an urban gradient (5–37% urban land cover) in the Etowah River basin, Georgia. Fish assemblages, sampled by electrofishi...

Journal: :Ecology 2007
Darren W Johnson

For species that have an open population structure, local population size may be strongly influenced by a combination of propagule supply and post-settlement survival. While it is widely recognized that supply of larvae (or recruits) is variable and that variable recruitment may affect the relative contribution of pre- and post-settlement factors, less effort has been made to quantify how varia...

2015
Kendra L. Garner Michelle Y. Chang Matthew T. Fulda Jonathan A. Berlin Rachel E. Freed Melissa M. Soo-Hoo Dave L. Revell Makihiko Ikegami Lorraine E. Flint Alan L. Flint Bruce E. Kendall

Local increases in sea level caused by global climate change pose a significant threat to the persistence of many coastal plant species through exacerbating inundation, flooding, and erosion. In addition to sea level rise (SLR), climate changes in the form of air temperature and precipitation regimes will also alter habitats of coastal plant species. Although numerous studies have analyzed the ...

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