Exploring the Jordanian rangeland status transition merging the restoration experiment with modeling

Abstract

Due to recurring droughts and severe overgrazing, Jordan’s dry rangelands are exceptionally prone to degradation. Establishing both restoration and sustainable rangeland management practices are crucial to reverse the negative impacts on the ecosystem. However, a primary estimate of the native baseline’s water and sediment fluxes is essential to properly target a sustainable transition from degraded to a potentially revegetated landscape status. In Jordan, a widely applied restoration technique is the mechanized micro-Water Harvesting basin (WH) approach on sloping, degraded, and hard-crusted rangelands. Small basins (6m long by 0.6 cm deep) are scooped out of the soil along the contour with the spoils piled on the down slope side of the basin. Within the micro-pit basins native shrubs are planted supporting the development of shrub islands. This technique captures overland flow and reduces soil erosion. The Rangeland Hydrology and Erosion Model (RHEM) was used to explore three different rangeland ecological states and their implications on water and soil fluxes: i) the supposed historical vegetation condition (baseline), using literature review and scientist and community questionnaire data, ii) the actual degraded status, and iii) micro-WH based restored equilibrium scenario, based on field monitoring and modeling. Rangeland experimental site near Amman, Jordan, provided diverse monitoring and validation data for RHEM modeling. RHEM was applied to evaluate 1) long-term stability of the 3 different ecological states of the hillslopes (i-iii), and 2) event based spatially distributed watershed modeling to estimate how the different scenarios of landscape vegetation patterns would alter hydrologic processes. The spatial-temporal assessment of water and sediment transport in baseline, degraded, and restored Jordanian rangelands provide information on the sustainability of the WH restoration approach to different rainfall events (i.e., 10 year runoff event) and allow us to approximate resilient equilibrium water and soil dynamics that is available to support the restored vegetation.