Field occurrence, recovery, and simulated trampling resistance and recovery of two grasses

Abstract

A field survey of subtropical trampled grasslands showed that some species of grass such as Cynodon dactylon were present in sites subject to all degrees of trampling impact and some, particularly Eragrostis tenuifolia, were only present in trampled sites. Cynodon dactylon had the greatest recovery in an exclosure plot and when isolated in the glasshouse. Eragrostis tenuifolia recovered well when isolated in the glasshouse but its growth declined in the exclosure plot as the cover neared 100%. Cynodon dactylon and Eragrostis tenuifolia were used in a simulated trampling experiment carried out in the glasshouse. Biomass was measured and resistance and recovery indices were calculated. Cynodon dactylon lost a steadily greater proportion of its biomass over successive trampling experiments while the proportional loss of biomass sustained by Eragrostis tenuifolia declined. The proportional rise in biomass between trampling treatments was increasingly greater in Cynodon dactylon than in Eragrostis tenuifolia. Cynodon dactylon had the highest recovery index and Eragrostis tenuifolia had the highest resistance index. We conclude that the resistance strategy is more useful when plants are frequently trampled throughout the growing season and the recovery strategy is more useful when plants remain untrampled for a relatively longer time.