Porcupine diggings as a unique ecological system in a desert environment.

The influence of porcupine diggings upon annual vegetation on a north-facing hillslope in the Negev Desert, Israel, has been observed for some 10 years. It was found that within the porcupine diggins there are changes over time in terms of species richness, plant density and plant biomass, and that such changes take place in three stages. During the initial growing season (stage 1), species richness, plant density and plant biomass are lower than in the surrounding non-disturbed area, followed by progressive plant succession. Subsequently, a maximum level is attained when a dig becomes 50-60% filled in (stage 2). As the extent of filling exceeds 60%, a decrease in species richness, plant density and plant biomass is observed (stage 3). This process concurs with models derived in other ecosystems with animals that create surface disturbances. The role of porcupine diggings as a model of disturbance and recovery is discussed.