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The ecological mechanisms hypothesized to structure species-rich communities range from strict local determinism to neutral ecological drift. We assessed the degree of ecological determinism in tropical plant community structure by analyses of published demographic data; a broad range of spatial, historical, and environmental variables; and the distributions of 33 herbaceous species (plot size = 0.02 ha) and 61 woody species (plot size = 0.09 ha) among 350 plots in a 16-km2 forest landscape (Barro Colorado Island, Panamá). We found a strong degree of cross-landscape dominance by a subset of species whose identities were predictable from sapling survivorship rates under shade. Using canonical ordination we found...
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Geochemical mass balances were computed for water years 1992–1997 (October 1991 through September 1997) for the five watersheds of the U.S. Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) Program to determine the primary regional controls on yields of the major dissolved inorganic solutes. The sites, which vary markedly with respect to climate, geology, physiography, and ecology, are: Allequash Creek, Wisconsin (low-relief, humid continental forest); Andrews Creek, Colorado (cold alpine, taiga/tundra, and subalpine boreal forest); Río Icacos, Puerto Rico (lower montane, wet tropical forest); Panola Mountain, Georgia (humid subtropical piedmont forest); and Sleepers River, Vermont (humid northern...
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