Enhancing Semi-Arid Ecosystem Resilience in Jordan Using Controlled Grazing – A Short and Long-Term Assessment

Abstract

Grazing management strategies in arid ecosystems are of critical importance to regulate plant regeneration, improve forage quality, and ensure sustainable utilization of rangelands. This study examines the impacts of controlled grazing management on vegetation dynamics (gain/loss) and land cover changes over a 17-year period (2006-2022) at the Royal Botanic Garden, Jordan. Climatic factors, including precipitation and temperature, were analyzed alongside the Normalized Difference Vegetation Index (NDVI) to assess vegetation health and greenness. Autoregression models were used to investigate annual temporal trends between vegetation biodiversity indices and climatic factors. To assess controlled grazing's impact on vegetation biodiversity, the study period was divided into four periods: the initial period (period0: 2006-2007) which represented the pre-dating-controlled grazing period, followed by three subsequent periods: period1 (2008-2012), period2 (2013-2017), and period3 (2018-2022). Land cover analysis using yearly averaged NDVI values was assessed, including five distinct classes: water body, barren soil, herbaceous and shrub, open forest, and closed forest. The study identifies short-term changes during period1 and long-term changes during periods 2and3. The results revealed a significant annual temporal trend only in the NDVI index (P<0.001), indicating dynamic changes in vegetation health over the whole study period. A positive influence of controlled grazing on vegetation dynamics and biomass production was observed. During period3, controlled grazing has led to a significant (P<0.05) increase in vegetation biomass compared to earlier periods (214.4ton in period3 compared to 97.1 and 106.8ton in periods1 and2 respectively). The NDVI index also showed significantly higher values during the later periods of controlled grazing, emphasizing its positive impact on long-term vegetation health. Furthermore, the study showed interesting trends in plant groups and species, with short-term controlled grazing leading to increased species richness and significant changes in vegetation indices. Over the study period, controlled grazing influenced land cover dynamics, with significant decreases in barren soil (from 66.7% to 9.8%) and increases in herbaceous and shrubland areas (33.2% to 89.6%). The study concludes that controlled grazing significantly shapes plant communities, fostering dynamic changes in species and groups over time. The study provides valuable insights into the ecological impact of controlled grazing management. Findings revealed vegetation resilience to short-term climate variations, with sustained vegetation health under grazing.

Keywords

• plant biodiversity indices
• ndvi
• vegetation cover
• vegetation health