Effects of disturbances on aboveground biomass of alpine meadow in the Yellow River Source Zone, Western China

A bibliometric analysis of research trends and hotspots in alpine grassland degradation on the Qinghai-Tibet Plateau

A bibliometric analysis of current research, hotspots, and development trends was used to develop an overall framework of mechanisms of alpine grassland degradation on the Qinghai-Tibet Plateau. This investigation includes data from 1,330 articles on alpine grassland degradation on the Qinghai-Tibet Plateau, acquired from the Chinese Science Citation Database (CSCD) and Web of Science Core Collection (WOS). Research was divided into three themes: spatial scope and management of typical grassland degradation problems, dynamic mechanisms of grassland degradation and effects of ecological engineering, and grassland degradation risk based on remote sensing technology. The results of the analysis showed that the research can be summarized into three aspects: typical grassland degradation identification, dynamic mechanism analysis of grassland degradation, and grassland ecosystem stability strategy. The main findings can summarized, as follows: (1) Ecological analyses using the river source as a typical region defined the formation of "black soil beach" type degraded grasslands in the region, and promoted the ecological environment management and protection of the alpine grassland by discussing the causes of regional ecological environment changes; (2) Dynamic mechanism analyses of climate change and characteristics analyses of grassland vegetation-soil degradation revealed that alpine grassland degradation is the result of multiple main factors; and (3) Risk prediction methods for grassland degradation, methods of grassland management and sustainable countermeasures for agriculture and animal husbandry development, and the development of a comprehensive index of influencing factors on grassland degradation all indicate that selecting the right grassland restoration measures is the key to grassland restoration. Remote sensing monitoring and high-throughput sequencing technology should be used in future research on grassland ecosystems. In addition, multiscale, multidimensional, and multidisciplinary systematic research methods and long-term series data mining could help identify the characteristics and causes of alpine grassland system degradation. These findings can help identify a more effective coordination of landscape, water, lake, field, forest, grass, and sand management for the prevention of alpine grassland degradation.

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

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.