Regulating effects of mixed-cultivated grasslands in surface water conservation and soil erosion reduction along with restoration of alpine degraded hillsides

Abstract

Abstract. Vegetation restoration is among the most effective measures for controlling runoff and soil erosion resulting from human activity. Nevertheless, few studies have been undertaken to analyze the effects of plant restoration on maintaining the stability of the hydrological cycle, especially, in alpine degraded hillsides where mixed-cultivated grasslands predominate in the landscape. In this research, we conducted in situ monitoring using runoff plots to investigate the impact of three strategies, each combining two grass species per plot (three species in total), on a 20-degree slope, assessing the activation and volume of surface runoff and soil loss in alpine degraded hillsides over three years (2019, 2020 and 2022). A severely degraded meadow plot was used as control. The findings indicated that mixed-cultivated grasslands can effectively manage runoff and reduce soil loss as planting ages increase. Between 2019 and 2022, the values of the runoff reduction ratio decreased for Deschampsia cespitosa and Elymus nutans (DE), Poa pratensis L.cv. Qinghai and Elymus nutans (PE), and Poa pratensis L.cv. Qinghai and Deschampsia cespitosa and (PD) from -79.3 % to -115.4 %, from -130.4 % to -156.1 %, and from -48.5 % to -87.6 %, respectively. On the contrary, the mean sediment concentration reduction ratio increased from -120.9 to 55.8 % (in DE), from 112.4 to 59.7 % (in PE), and from -94.3 to 62.1 % (in PD). This implies that protective measures should be prioritized during the initial planting stage of cultivated grasslands in alpine degraded hillsides. The key factors affecting soil loss and runoff were rainfall amount, duration and intensity (60-min intensity). We conclude that the results of this study can serve as scientific guides to design efficient policy decisions for planning the most effective vegetation restoration in the severely degraded hillside alpine meadows.