Determination of ecological scale |
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Authors: | David W Carlile John R Skalski John E Batker John M Thomas V I Cullinan |
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Institution: | (1) Pacific Northwest Laboratory, 99352 Richland, WA, USA;(2) Alaska Department of Fish and Game, P.O. Box 3-2000, 99802-2000 Juneau, AK, USA;(3) Center for Quantitative Sciences, University of Washington, HR-20, 3737 15th Avenue NE, 98195 Seattle, WA, USA;(4) 14409 Duryea, 98444 Tacoma, WA, USA;(5) Pacific Northwest Laboratory, 99352 Richland, WA, USA |
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Abstract: | We suggest that ecological processes and physical characteristics possess an inherent scale at which the processes or characteristics occur over the landscape. We propose a conceptual spatial response model that describes the nature of this ecological scale. Based on the proposed spatial model, we suggest methods for estimating the size of study plots or transects and the distance between replicate plots needed to approach statistical independence. Using data on percent cover for Agropyron spicatum, a common arid-land bunchgrass, we demonstrated four relationships that should hold if the spatial response model is appropriate. These relationships are sample variance increases as functions of (1) transect segment length and (2) intersegment length (transect segment dispersal), and correlation decreases as functions of (3) intersegment length and (4) transect segment length. Based on evaluation of these four relationships, cover for A. spicatum is correlated over the landscape on a scale of 400 to 700 m, and a segment length of 64 to 128 m is most appropriate for measuring cover for this species. |
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Keywords: | spatial correlation ecological scale line-intercept transects Agropyron spicatum spatial pattern segment length dispersal landscape ecology |
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