Evolutionary characteristics of biological soil crusts in grassland restoration in the Source Zone of the Yellow River

Abstract Biological soil crusts (BSCs) play an important ecological role in arid and semi-arid ecosystems. So far, most studies on BSCs have focused on deserts, while rarely examining the successional process of BSCs in artificial/restored grassland. This study aimed to explore the natural succession and characteristics of BSCs during the recovery process of an artificial grassland in the Source Zone of the Yellow River. Six sites in two grassland types, i.e. one healthy alpine meadow and five artificial grasslands, were selected in Maqin county, Qinghai Province. These artificial grasslands have been established for varying growth periods ranging from 1 to 18 years. We examined vegetation characteristics in relation to BSC types, BSC coverage and thickness at these six sites. Mosses appeared at the early stage of the natural succession of the grassland, and lichens and visible algal crusts followed. The dominant moss species was Barbula unguiculate . BSC coverage increased significantly with recovery period. BSC thickness increased initially in the early stage of recovery but decreased after 14 years of recovery. At an appropriate level (0~30%), an increase in litter coverage can increase BSCs thickness, but excessive litter (> 30%) can reduce BSCs coverage ( P < 0.05). Therefore, an increase in the total coverage of vegetation and maintenance of a suitable litter coverage (< 30%) are important to promote the establishment and succession of BSCs in recovered grasslands.