THE EFFECTS OF COMPETITION AND ENVIRONMENTAL HETEROGENEITY ON 3 COEXISTING GRASSES

The effects of competition and spatial heterogeneity in the environment on Aristida longiseta, Bouteloua rigidiseta and Stipa leucotricha were investigated by transplanting small plants of each species into undisturbed vegetation and into quadrats from which the herbaceous vegetation had been removed. While transplants planted in pairs did not perform as well as those planted single, the species of the neighbour had no effect. The positive effect of the removal of pre-existing herbaceous vegetation upon the transplants was generally greater in "rocky' than in "grassy' quadrats, suggesting that the total competition experienced by these grasses was more intense in "rocky' quadrats, despite their lower cover. Both A. longiseta and B. rigidiseta could survive, and even reproduce, under the caniopies of woody plants, suggesting that these species are excluded from this micro-environment by the inability of their seedlings to establish there. The 3 species differed in their response to 3 types of micro-environment, and to different plots within those micro-environments. These differences may promote the coexistence of these three species. -from Author