The Effects of Grazing on Abiotic and Biotic Parameters in a Semiarid Ecosystem: A Case Study from the Northern Negev Desert, Israel

Abstract

Livestock grazing is considered a disturbance of both biotic and abiotic parameters that may lead to degradation of rangelands and desertification. We report a case in which grazing was used as a management tool in a rehabilitation project. The aim of this study was to quantify the effects of grazing on a managed ecological system. To do so, we monitored the diversity and composition of the plant community, herbaceous biomass, soil moisture, soil organic matter, habitat structure and quality of the vegetation for grazers (protein content and digestion). These parameters were monitored on the south and the north slopes, because of the differences in the radiation, which affect the water regime and the vegetation. Monitoring was in grazed plots and in plots ungrazed for three years. Our results showed that grazing had immediate effects on the plant community and habitat structure. The densities of plant species decreased (∼20%), vegetation community composition was affected (∼50-61%) and exposed soil surface increased (∼50%). A significant decrease was found in total protein content in plants over time: from 17-19% in beginning of the grazing season to 5-6% at the peak of the season. Digestible material was significantly more at the peak of the growing season in the grazed plots (63.7%) compared to the ungrazed plots (57.4%) in the north-facing slope, but not in the south-facing slope. When plant diversity, soil fertility, and soil moisture were considered, no correlation was found in relation to grazing. The significance of the research was that it demonstrated that livestock grazing can be effective as a management tool while imposing limited damage to the ecosystem.