The structure and function of the rhizosphere microbial communities of Carex praeclara and Leymus secalinus in a Zoige alpine grassland

Rhizosphere microorganisms are thought to play a crucial role in the promotion of plant growth and health. Carex praeclara and Leymus secalinus are dominant plant species that have colonized the desertification land of Alpine wetland grasslands in Zoige. There is a lack of comprehensive research on their rhizosphere microbes. In this study, we used deep shotgun metagenomic sequencing to analyze the microbial community and functional composition of the rhizosphere and corresponding non-rhizosphere soils of C. praeclara and L. secalinus. The microbial diversity and structure exhibited a remarkable difference among the rhizosphere and non-rhizosphere samples, and the predominant taxa included Actinobacteria, Proteobacteria, Acidobacteria and Chloroflexi in all the samples. Genes that were over-represented include those involved in the acquisition of nutrients, stress responses, transposable elements and plant growth promotion suggest that the interactions between microbe-plant and microbe-microbe are more intense in the rhizosphere soil. The relative abundances of pivotal genes that participate in microbial nitrogen (N) and phosphorus (P) transformation were higher in the rhizosphere soil than in the non-rhizosphere soil, indicating the enhancement of potential soil N- and P-cycling in the plant rhizosphere. Our findings provide valuable information on the structure and function of the microbial communities of the C. praeclara and L. secalinus rhizospheres and lay a foundation for the further use of C. praeclara and L. secalinus to increase vegetation coverage, improve soil properties and restore the ecological function of degraded alpine sandy land.

Tree fine roots productivity and turnover rates estimation in alpine sandy land

Sequential coring method was used to collect the data of fine roots from June to August in alpine sandy land. Turnover rates were calculated by maximum or mean biomass during the growing season in 2015 using Decision Matrix (DM) or Maximum-Minimum (MM) method. Results show that biomass in June is lower than that in July and August. Turnover rates of Artemisia desertorum are higher than that of Caragana intermedia and Caragana korshinskii. Turnover rates of mixed forest are higher than that of pure forest. Soil gravimetric water content is highly related to root biomass/ length in the depth of 40 - 60 cm for Caragana intermedia and Caragana korshinskii. But soil gravimetric water content and root biomass/ length have no obvious regularity in the depth of 40 ~ 60 cm for Artemisia desertorum. The minimum water requirement threshold of around 0.02 can be acquired for Caragana intermedia and Caragana korshinskii in the arid region. In alpine sandy land, it is suitable to plant Artemisia desertorum compared to Caragana intermedia and Caragana korshinskii; mixed forest has more advantages compared to pure forest.