Selection of Grasses With Different Carbon Assimilation Pathways Under Different Sheep Stocking Pressures.

Abstract

The path of carbon assimilation was noted for 30 common grasses from unfertilized sheep pastures of the Northern Tablelands of New South Wales. These grasses were then grouped according to their susceptibility to stocking pressure and the frequency and relative frequency of 16 of these related to apparent intensity of stocking about a sheep camp. C₃ grass frequency was independent of stocking pressure, but under heavy stocking introduced C₃ species replaced native C₃ species. C₄ NADME species showed an increase in occurrence under high stocking rates, whereas C₄ NADPME species showed a decrease in occurrence under high stocking intensity. It is suggested that response to grazing may have been a factor in the evolution of different pathways of carbon assimilation.