Scenario-based modelling of soil conservation function by rangeland vegetation cover in northeastern Iran

Soil conservation is one of the most important regulative functions of natural ecosystems. Vegetation cover significantly contributes to soil conservation. This study aims at investigating changes in erosion and sedimentation and the annual economic value of soil conservation by vegetation cover in northeastern Iran, by application of Revised Universal Soil Loss Equation (RUSLE), Sediment Delivery Distributed models (SEDD) and replacement cost method. The results demonstrated that the topography factor (LS-factor) was the most important factor contributing to soil erosion in the region. Also the mean soil erosion and the Specific Sediment Yield (SSY) were 14.84 and 2.82 ton ha⁻¹ yr⁻¹ in rangeland areas. More than half of the basin’s area (62%) was characterised as negligible and slight soil erosion class (0–10 ton ha⁻¹ yr⁻¹), and 18% as severe and very severe (25–100 ton ha⁻¹ yr⁻¹). Soil conservation function by vegetation cover was equal to 356,893 m³ yr⁻¹, with the economic value of US$ 55,335 yr⁻¹. According to the SEDD results, the amount of sediment trapped by the rangeland vegetation cover was 200,763 ton yr⁻¹, with annual economic value of US$ 5,347,500 yr⁻¹ By increasing vegetation cover, the annual soil erosion and sedimentation will extremely decrease and a larger part of the study area would experience slight to moderate erosion. Our findings showed that RUSLE/SEDD model provides a robust spatially-explicit platform to quantify the amount and distribution pattern of soil erosion and sedimentation to management and conservation practices, if the calibration and localization of the model are accomplished.