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.

Plant community characteristics, soil nutrients and their interactions in artificial grassland with different establishment years in the Three Rivers Headwater Region

“…The total nitrogen, total phosphorus and total potassium in the artificial grassland showed an increasing trend with the increase in establishment years, but the trends of available nitrogen, available phosphorus and available potassium were opposite. Other studies have shown that the contents of total nitrogen, available nitrogen, available potassium and organic matter in artificial grassland soils increase with the increase in establishment years (Sun et al, 2019), which is not consistent with the results of this study. This is due to the different vegetation characteristics and the different utilization of nutrients, resulting in the heterogeneity of soil in different years of artificial grassland.…”

“…With the increase in establishment years, the pH of artificial grassland decreases gradually, and the water content and organic carbon increase gradually. This is because the alpine artificial grassland has a large underground root system to adapt to the cold environment; as the accumulation of underground roots increases, they are rapidly converted to organic carbon and other soil nutrients (Sun et al, 2019; Xing et al, 2020). The change in the aboveground plant community driven by soil is an important driving factor of artificial grassland succession, which determines the succession direction of artificial grassland to some extent (Wang et al, 2012).…”