[Response of Soil Microbial Diversity to Long-term Enclosure in Degraded Patches of Alpine Meadow in the Source Zone of the Yellow River].

The soil pH, water content, nutrients, and microbial community composition and diversity among one-year term (E1), short-term (E4), and long-term (E10) enclosures were analyzed for understanding the response of soil bacterial and fungal communities to long-term enclosure in degraded patches of alpine meadow in the source zone of the Yellow River, through determining the soil physicochemical properties and microbial diversity using high-throughput sequencing technology. The results showed that the E1 enclosure significantly decreased soil pH, whereas long-term and short-term enclosures increased soil pH. The long-term enclosure could significantly increase soil water content and total nitrogen content, and the short-term enclosure could significantly increase available phosphorus content. The long-term enclosure could significantly increase the bacterial Proteobacteria. The short-term enclosure could significantly increase the abundance of the bacteria Acidobacteriota. However, the abundance of the fungus Basidiomycota decreased in both long-term and short-term enclosures. With the extension of enclosure years, the Chao1 index and Shannon diversity index of bacteria showed an increasing trend, but there was no significant difference between long-term and short-term enclosures. The Chao1 index of fungi gradually increased, and the Shannon diversity index first increased and then decreased, but there was no significant difference between long-term and short-term enclosures. Redundancy analysis indicated that enclosure altered microbial community composition and structure mainly by changing soil pH and water content. Therefore, the E4 short-term enclosure could significantly improve the soil physicochemical properties and microbial diversity at the degraded patches of alpine meadow. The long-term enclosure is not necessary and will lead to the waste of grassland resources, reduction in biodiversity, and restriction of wildlife activities.

[Changes in Soil Bacterial Community Diversity in Degraded Patches of Alpine Meadow in the Source Area of the Yellow River].

MiSeq sequencing technology was used to investigate the bacterial compositions and diversities of active patch, non-active patch, recovered patch, and healthy alpine meadows so as to understand the changes in soil bacterial community diversity during altitude change and alpine meadow degradation. The relationship between bacterial diversity and environmental factors was analyzed using redundancy analysis (RDA). The results showed that the dominant bacterial phyla in the soil included Proteobacteria, Actinobacteriota, and Acidobacteriota in the study areas. The dominant bacterial genera that were identified via the MiSeq were RB41, Sphingomonas, and Bradyrhizobium. The relative abundance of these genera decreased with altitude increase and increased with the restoration progress of degraded patches but was significantly lower than that in the alpine meadow (P<0.05). The abundance of functional bacteria related to carbon fixation in degraded patches was higher than that in the healthy alpine meadow. The bacterial Chao1 index and species number in different types of degraded patches were significantly higher than those in the alpine meadow (P<0.05). The results of the RDA suggest that biological soil crust coverage and total nitrogen were the main influencing factors on dominant bacterial phyla at the altitude of 4013 m. Biomass, total nitrogen, and pH had a great influence on the dominant bacterial phyla at the altitude of 4224 m. Biomass and total potassium significantly affected the distribution of bacterial genera at the altitude of 4013 m. Sedge coverage and available nitrogen were the main influencing factors on bacterial dominant genera at the altitude of 4224 m. Biological soil crusts and pH had a great influence on bacterial diversities. The bacterial influence factors varied greatly at different altitude areas. Therefore, we should not only pay attention to the effect of alpine meadow degradation but also consider the effect of altitude in the study of bacterial diversity changes.