Responses to defoliation in Holcus lanatus, Lolium perenne, and Trifolium repens from three different-aged pastures

Abstract

The effects of defoliation on biomass distribution were studied in plants of Holcus lanatus L., Lolium perenne L., and Trifolium repens L. collected from three different-aged pastures. Individual plants were cloned and ramets from each clone were subjected to clipped and unclipped treatments over a period of 1 year. In the unclipped treatment for each species, plants from the three pastures showed no differences in the extent of clonal growth (i.e., tiller or stolon production). In the clipped treatment, however, plants from the oldest pasture displayed significantly more extensive clonal growth than plants from the younger pastures. With increasing pasture age, there was a significant trend of increasing compensatory clonal growth in response to defoliation for all three species. This may be interpreted as a consequence of selection pressure from grazing. However, the data do not suggest that the grass–grazer relationship is a mutualism. Alternative interpretations are considered.