Desempeño y habilidad competitiva de la gramínea invasora Eragrostis plana en condiciones de estrés hídrico

Abstract

Eragrostis plana (capín Annoni) is an important invasive grass of the Río de la Plata grasslands, frequently associated with sites under high degree of abiotic stress (e.g., water stress). We performed two complementary experiments, in which we evaluated the relative effect of water stress on the performance and competitive ability of E. plana and two native grasses: Eragrostis bahiensis and Sporobolus indicus. In the first experiment, the performance of the species was studied in two treatments (n=5), with and without water stress. In the second, we evaluated the competitive ability by manipulating plant-plant interactions under water stress (n=5). Both experiments were carried out simultaneously in a greenhouse under controlled conditions. Different individual performance variables related to plant growth and resource acquisition/utilization strategies were measured (e.g., height, number of green and dry leaves, number of tillers, biomass). In the first experiment, the performance of each species with and without water stress was compared; while in the second, relative interaction intensity indices were calculated. Eragrostis plana was the most affected species by water stress, with lower leaf production, higher rate of leaf senescence and lower rate of height growth. In the competitive ability experiment, E. plana had a greater inhibitory effect on the growth of native plants, and its response was generally positive or neutral when interacting with them. We conclude that although water stress had a greater effect on E. plana than native grasses, the competitive ability of the invader is superior even under these conditions.