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Climatic Response Surfaces from Pollen Data for Some Eastern North American Taxa

1986; Wiley; Volume: 13; Issue: 1 Linguagem: Inglês

10.2307/2844848

1365-2699

Patrick J. Bartlein, I. Colin Prentice, Thompson Webb,

Geology and Paleoclimatology Research

Ecological response surfaces are nonlinear functions describing the way in which the abundances of taxa depend on the joint effects of two or more environmental variables. Continental-scale patterns in the relative abundances of plant taxa are dominated by the effects of macroclimate on the competitive balance among taxa. Pollen analyses record such regional variations for major vegetation components. Empirical ecological response surfaces were derived from high-resolution climate models to yield testable reconstructions of vegeta- eastern North America. The surfaces were obtained by second- or third-degree polynomial regression on two predictor variables, mean July temperature and annual precipitation, with various nonlinear transformations of variables to allow flexibility of shape. Response surface analysis consists of a remapping of abundance patterns from geographic space into climate space, and complements efforts to explain distri- butions in terms of biological processes. Each fitted surface is unique. The surfaces focus attention on the climatic location of range limits and optima, and on less obvious phenomena such as the spatial pattern in the relative sensitivity of different taxa to spatial variation in the climatic variables. Given certain assump- tions, response surfaces based directly on pollen data may be used collectively in a global nonlinear method for estimating past climates from postglacial pollen data. Such response surfaces may also be coupled to palaeoclimatic simulations from high-resolution climate models to yield testable reconstructions of vegeta- tional history.