Rehabilitation of Semi-Arid Grasslands through the Perennialization of Lots by Implementing Perennial Forage Exotic Grass

Abstract

Argentina is the country with the highest proportion of arid and semi-arid ecosystems in Latin America. In the rangelands of Southwestern Buenos Aires (Patagones Department), there is a clear advancement of the agricultural frontier to the detriment of the native forest in this region. Due to rainfall variation and seed acquisition, Thinopyrum ponticum is cultivated as a forage perennial crop in this region. Our objective was to evaluate the performance of T. ponticum as a facilitating crop for the medium-term rehabilitation of natural grasslands in semi-arid areas. The working hypotheses were that: 1) native perennial grass cover increases over the years and 2) diversity and specific richness of the vegetation are enhanced by the duration of Tall Wheatgrass implantation. Data were collected from commercial plots where T. ponticum was shown: recent implantation (5–8 years, RI); medium implantation (13–15 years, MI); and old implantation (20–22 years, OI). Thirty-four species were identified and classified into seven functional groups: Annual grasses, annual herbs, perennial herbs, exotic perennial herbs, perennial forage grasses, exotic perennial forage grasses, perennial forage exotic grasses, and non-forage perennial grasses. Thinopyrum ponticum’s total cover was between RI and OI. Total cover, species richness, and Shannon-Weaver diversity index showed no differences among treatments. Perennial forage grasses exhibited higher cover values in sites with greater implantation age and annual grasses showed the opposite response. Our results indicated that T. ponticum does not invade the sampled plots and enhances the colonization of the planted plots by perennial forage native species. However, even though the herbaceous cover had been recovered, the woody layer which could provide environmental services and specific values for conservation was not.