Restoration of Degraded Grassland Significantly Improves Water Storage in Alpine Grasslands in the Qinghai-Tibet Plateau

Alpine grassland has very important water conservation function. Grassland degradation seriously affects the water conservation function; moreover, there is little understanding of the change of water state during grassland restoration. Our study aims to bridge this gap and improve our understanding of changes in soil moisture during the restoration process. In this study, the water storage, vegetation, and meteorology of a non-degradation grassland (grazing intensity of 7.5 sheep/ha) and a severely degraded grassland (grazing intensity of 12–18 sheep/ha) were monitored in the Qinghai-Tibet Plateau for seven consecutive years. We used correlation, stepwise regression, and the boosted regression trees (BRT) model analyses, five environmental factors were considered to be the most important factors affecting water storage. The severely degraded grassland recovered by light grazing treatment for 7 years, with increases in biomass, litter, and vegetation cover, and a soil-water storage capacity 41.9% higher in 2018 compared to that in 2012. This increase in soil-water storage was primarily due to the increase in surface soil moisture content. The key factors that influenced water storage were listed in a decreasing order: air temperature, litter, soil heat flux, precipitation, and wind speed. Their percentage contributions to soil-water storage were 50.52, 24.02, 10.86, 7.82, and 6.77%, respectively. Current and future climate change threatens soil-water conservation in alpine grasslands; however, grassland restoration is an effective solution to improve the soil-water retention capacity in degraded grassland soils.

Soil multifunctionality is negatively related to microbial community stochasticity in restored grasslands

It is generally assumed that there is a relationship between microbial diversity and multiple ecosystem functions. Although it is indisputable that microbial diversity is controlled by stochastic and deterministic ecological assembly processes, the relationship between these processes and soil multifunctionality (SMF) remains less clear. In this study, we examined how different grassland restoration treatments, namely harvest only, topsoil removal and topsoil removal plus propagule addition, affected i) soil bacterial and fungal community stochasticity, ii) SMF, and iii) the relationship between community stochasticity and SMF. Results showed that soil microbial community stochasticity decreased in all the three restoration treatments, while SMF increased. Soil multifunctionality was found to be significantly and negatively correlated with soil microbial community stochasticity. Plant diversity and plant C/N indirectly influenced SMF by regulating the microbial community stochasticity. Our findings provide empirical evidence that when deterministic community assembly processes dominate in soils, then higher microbial functioning is expected.

Relationships between plant community productivity and diversity vary with trampling disturbance in an Inner-Mongolian steppe

The relationship between diversity and productivity of plant communities is an important issue in grassland restoration. However, the degree to which this relationship varies during the restoration stage after trampling disturbance is not clear. Here, we conducted a five-year study in a steppe after 4-year trampling to detect restoration patterns of plant community and investigate variation in diversity-productivity relationships. Our results showed that community cover, abundance, height, and productivity recovered quickly after the trampling disturbance ceased. However, the recovery of diversity was slower than biomass in the steppe. In addition, grass, annual, and biennial recovery was more rapidly than the recovery of forbs in the steppe. Moreover, following the restoration process, the positive correlation between productivity and diversity was decoupled, and a negative correlation between productivity and diversity developed. Our finding provides the key evidence for the asynchronous relation between productivity and diversity, and reveals that grass restored more rapidly than forbs in plant community restoration after disturbance. This study indicates that the trade-off between plant community structure and function can vary with the restoration process, and implicates that future modeling and experimental studies should focus on the different responses of productivity and diversity in plant community restoration.