Patchiness in patterns of growth and survival of two grasses.

Individuals of two perennial bunch grasses, Bouteloua rigidiseta and Aristida longiseta, were transplanted into otherwise undisturbed natural short-grass vegetation in which these species are dominants. Significant differences in survivorship and growth rate were found among quadrats for both species. The relative favorability of quadrats for Bouteloua, but not for Aristida, changed during the course of the two year study. For neither species was a consistent relationship between pre-existing density and transplant performance found. However, one patch type was identified in which Bouteloua transplants grow well, although this species is not naturally present there, apparently because it cannot establish. Microsite differences, created by different soil in transplanted peat pots, were also found to be important. Bouteloua had a higher survivorship the first year, Aristida the second, which suggests that Aristida is the more tolerant of drier years.