A combination of competition and resistance strategies explain the invasive success of Nassella trichotoma

Abstract

This work aims to describe the two mechanisms, competition and tolerance, that may explain the process of invasion of N. trichotoma in the natural grassland communities of the Ventania mountain system and elsewhere. The specific objectives are (1) to determine the competition relationships between N. trichotoma and palatable species under different levels of frequency, intensity and defoliation selectivity (mechanism of direct and apparent competition); and (2) to evaluate the above-ground biomass production of standing biomass of N. trichotoma and Chascolytrum subaristatum (a common palatable grass species) under different levels of intensity and frequency of defoliation (mechanism of tolerance). The working hypotheses are that (a) selective defoliation on palatable species reduce their competitive ability favoring individuals of non-defoliated N. trichotoma growing next to them and (b) N. trichotoma and C. subaristatum have equal tolerance to defoliation.