Influence of Simulated Grazing (Clipping) on Pinegrass Growth

Abstract

Pinegrass (Calamagrostis rubescens) was clipped at several frequencies and intensities at three sites in the Douglasfir (Pseudotsuga menziesii) zone of British Columbia. The effect of herbage removal on pinegrass vigor could be assesed by measuring tiller height, tiller number/m2, or yield/m2 the year following clipping. Variability in pinegrass cover at a site necessitated measuring initial plot cover so than an analysis of covariance could be done to statistically isolate its effect. Initial pine grass cover did not affect the tiller height measurement however. Plant vigor decrease due to herbage removal depended upon the degree and time of herbage removal and either the environmental conditions during the year of clipping or plant history before herbage removal or both. Pinegrass vigor was most sensitive to clipping during the last half of July and early in August. This is the time when pinegrass growth is slowing down and summer dormancy is settling in. It is recommended that pinegrass be grazed for a short time while it is actively growing (early in June) and then later when mid-summer dormancy is well established (August) to maintain its vigor. If pinegrass must be grazed during July, then it should be rested durying July the following year. Further work is required to establish grazing schemes that will maximize animal production and maintain adequate pinegrass vigor.