MODELING SMALL-SCALE SPATIAL INTERACTION OF SHORTGRASS PRAIRIE SPECIES

Native grasses interact spatially with themselves and their environmen t and can therefore be thought of as a system of dependent random vari ables. One method of modeling the spatial dependence of a multi-specie s population is a Gibbsian pairwise potential model. Since natural !;e lection operates at the level of individual plants, the information ob tained from such a model should provide a greater understanding of the intraspecific interactions in plant populations, while providing a th eoretical basis for determining a plants' 'competitive zone' of influe nce. In this paper we fit a pairwise potential model to describe the s patial dependency of dominant grasses and forbs measured on a 1.5 x 1. 5 m study plot located on a shortgrass prairie site near Fort Collins, Colorado. Dominant grasses included blue grama (Bouteloua gracilis), western wheatgrass (Agropyron smithii), Indian ricegrass (Oryzopsis hy menoides), and needle-and-thread grass (Stipa comata). Procedures for introducing spatial heterogeneity in the model is also discussed. (C) 1997 Elsevier Science B.V.