Vegetation Dynamics and Neighbour Associations in Pasture-Community Evolution

Abstract

Vegetation patterns and species assocations over 3 yr in 3 different-aged pasture communities with simiar management histories are analyzed. Relative abundances of species differed among the 3 pastures but there were no significant differences in species diversity or composition. Ordination of percentage-cover data from all surveys established a trend of increasing community stability, or constancy, with increasing pasture age. Soil analyses showed little correlation with species-over and no trends with pasture-age. Patterns of association in time between species were investigated with contact sampling. Four different patterns were identified. Between-species associations in younger communities were predominantly temporary, while older communities had more associations which were persistent over the study period. These data form the basis of a qualitative model of pasture-community evolution which attributes within-community changes in time to biotic interactions between neighbors. The model serves as a hypothesis for experimental studies.