Influences Of Vegetation Restoration Methods On Alpine Steppe Soil Microorganisms

The Qinghai-Tibet Plateau is a very unique and fragile alpine ecosystem, where the permaforst degradation and loss of vegetation are becoming more and more serious due to the increasing human activities and global warming. To effectively restore the disturbed ecosystem on the Qinghai-Tibet Plateau, the government and researchers have conducted a series of revegetation programs and restoration studies. To date, the restoration dynamics of aboveground vegetation in this region is well studied, but little is known about the restoration of below-ground microorganisms, which are essential for nutrient cycling and ecosystem stability. Filling this knowledge gap will greatly contribute to our guidance and evaluation of the ecological restoration on the Qinghai-Tibet Plateau.This study was conducted in an artificial vegetation restoration site, which is located in Tuotuohe of frozen soil engineering corridor of Qinghai-Tibet Plateau. Vegetation restoration was conducted in 2002 by planting single species of Elymus nutans, Leymus secalinus, Roegneria thoroldiana, Poa crymophila in separate plots in the pit, or mixed sowing of Elymus nutans+Poa crymophila, and natural recovery plots (no seeding) and native plots (without vegetation destruction) were set at the same time (7 treatments in total). In 2013, the vegetation properties, soil characteristics, and the community structure and function of soil microbes under different treatments were analyzed using 454 sequencing and other state-of-the-art techniques. The main findings are as follows:1. Most plant and soil variables were significantly different among our treat-ments. Compared with the natural recovery plots, all the artificial vegetation restoration methods significantly increased vegetation coverage and soil aggre-gate stability. Among the five artificial restoration treatments, it seemed that the revegetation with Roegneria thoroldiana was better than others, because most of the plant and soil variables in this treatment showed highest similarities to that of native plots, indicating that revegetation with Roegneria thoroldiana was better.2. Natural recovery plots and native plots had less bacteria than that of the artificial. From 454 high-throughput sequencing of each soil samples,4092 bac-terial OTUs (mainly Actinobacteria and Proteobacteria) and 720 fungal OTUs (mainly Ascomycota) were identified. Compared with natural recovery plots, two artificial restoration methods, planting single species of Roegneria thoroldiana and mixed sowing of Elymus nutans+Poa crymophila, significantly increased bacterial and fungal OTU richness; NMDS analysis showed that there was a sig-nificant difference in soil bacterial community composition among treatments, which were related to soil organic carbon, pH value and content of soil phospho-rous; fungal community composition of plots planted Roegneria thoroldiana is most similar to that of native plots, and plots planted Elymus nutans or Leymus secalinus showed highest bacterial community composition similarity to that of the native.3. Arbuscular mycorrhizal(AM) fungal colonisation rate and spore commu-nities showed significant difference among varied restoration plots. Roegneria thoroldiana seeding led to highest AM fungal colonisation rate, indicating that this recovery method is beneficial to symbiotic relationship between plants and AM fungi. Twenty phylotypes of AM fungi were identified from all root samples (5 families,6 genera). Native plots showed the highest number of phylotypes while plots planted Poa crymophila showed the lowest. Although diversity in-dex and species composition of AM fungi showed no significant differences among treatments, relatively community structure of AM fungi in Roegneria thoroldiana plots is most similar to native plots.4. Biolog analysis showed that microbial functional diversity differed among treatments, and artificial restoration increased functional diversity significantly, compared with natural recovery plots and native plots. Especially in Roegneria thoroldiana plots, microbial functional richness and dominance index were the highest.Our results showed that artificial vegetation restoration, which is an effective method to restore vegetation disturbed regions of the Qinghai-Tibet Plateau, can rapidly and effectively increased vegetation coverage and diversity, improved soil stability, and improved soil microbial richness and functional diversity. Compre-hensively, vegetation characteristics, soil physical and chemical properties, and soil microbial community characteristics of artificial planted Roegneria thoroldiana plots were more similar to native plots, indicating that planting Roegneria thoroldiana might be more effective than planting other species in the process of ecological restoration in this region.