Spatial and temporal composition of herbaceous vegetation in Geoffroea decorticans (Gill. Ex Hook. & Arn.) Burkart. thickets

In the Central Semiarid Region of Argentina, the native woody species Geoffroea decorticans has increased in range and density, probably due to overgrazing. The aim of this work was to evaluate the floristic and functional composition of the herbaceous vegetation along time in grazed sites, within thickets of G. decorticans, and compared to grasslands. We registered the cover of each herbaceous species in different locations within thickets and in the natural grassland, at each season for two years, from autumn 2021 to summer 2023. Indicator species of grasslands were found to be mostly palatable native perennials, resulting more homogeneous than those of thickets. Moreover, the mean cover of palatable species was higher in grasslands than in thickets. Consequently, grasslands confer stability and food resource for livestock. Woody thickets would exhibit a decreased stratification from the center to the edge, that would give rise to niche opportunities and biodiversity reservoirs. Temporal variability in floristic composition indicated differences between grasslands and thickets over time, which decreased in spring, probably by homogenization by grazing in winter. The temporal variability of functional composition showed a cyclical variability in all locations that decreased in spring in all cases.