Slow recovery in desert perennial vegetation following prolonged human disturbance

The study shows an exceptionally long-term recovery of perennial vegetation from prolonged heavy grazing and other human impacts. Since protection in 1906, overall species richness and habitat heterogeneity at the study site continued to increase until the 1960s when diversity, density and cover stabilized. During the same period, overall plant density and cover also increased. Species turnover increased gradually with time but no significant relation between any of the three community variables and precipitation or Palmer Drought Severity Index (PDSI) was detected. The increases in plant species richness, density, and cover of the perennial vegetation were mostly due to the increase of herbaceous species, especially palatable species. The lack of clear relationship between environment (e.g., precipitation) and community variables suggests that site history and plant life history must be taken into account in examining the nature of vegetation recovery process after disturbances.