Literaturdatenbank
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Krzysik, A. J. (2002). A landscape sampling protocol for estimating distribution and density patterns of desert tortoises at multiple spatial scales. Chelonian Conservation and Biology, 4(2), 366–378.
Added by: Admin (14 Aug 2008 20:35:29 UTC) |
| Resource type: Journal Article BibTeX citation key: Krzysik2002 View all bibliographic details  |
Categories: General Keywords: Gopherus, Gopherus agassizii, Habitat = habitat, Nordamerika = North America, Schildkröten = turtles + tortoises, Testudinidae Creators: Krzysik Collection: Chelonian Conservation and Biology |
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| Abstract |
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Gopherus agassizii Testudinidae A sampling protocol was pilot-tested to estimate distribution and density patterns of desert tortoises (Gopherus agassizii) at multiple spatial scales. The value and uniqueness of the protocol is that it provides land managers with information on local small scale distribution and density patterns of tortoises, while concurrently monitoring long-term temporal density trends on landscape scales. The design is statistically rigorous and unbiased, and is valid at any population density or distribution in the landscape. The protocol is based on the integration of four design elements: defining the sampling universe(s), designing a landscape sampling frame, selecting a method for density estimation (distance sampling), and applying spatial modeling to develop a landscape distribution-density surface for the desert tortoise population of interest. Distance sampling is used to directly estimate tortoise density on a landscape scale. Small scale tortoise densities in this landscape are developed as a tortoise density surface by using unbiased estimates of burrow and scat densities at decreasing sampling scales to calibrate the overall tortoise density to local scales. The pilot study was conducted in the southcentral Mojave Desert at a lightly-used military training area and in a designated wilderness area in Joshua Tree National Park. Although tortoise density patterns were similar at the two sites, burrow/tortoise ratios, and other related parameters differed. Estimated tortoise densities were scale dependent and more variable at smaller spatial scales, indicating that tortoises were patchy in landscape distribution.
Added by: Admin |