Effects Of Grassland Utilization Modes On Leymus Chinensis And Its Photosynthetic Carbon Transformation Microorganisms

Grassland ecosystems are an important part of the terrestrial ecosystem and store 10%to 30%of soil carbon in the world.Carbon stocks of grassland are relatively stable and have an important impact on the global carbon cycle,but the transformation of grassland carbon and the active microbes driving the carbon cycle are not well understood.Therefore,in this paper,the soils of the two different types of grasslands used as enclosures and grazing as carriers in typical grassland in inner Mongolia,We tried to explore the effect of the absence of soil nutrients on the growth of Leymus chinensis and studied the release and transformation of photosynthetic carbon in the rhizosphere area of Leymus chinensis during the vegetative growth stage and the related active microbial community structure with RNA-SIP and high throughput sequencing technology.The decomposition of different parts of Leymus chinensis in the enclosing and grazing soil and its related active microbial community structure were analyzed.Based on the above research,the main findings of this paper are as follows:(1)The grasses are planted in greenhouse conditions in enclosed and grazing soils with different nutrient deficiency.We find the lack of phosphorus in enclosed and grazing soil limits the growth of pasture in different time;the loss of nitrogen partially affected the regeneration of late grasses,especially in grazing soils;the lack of copper in the grazing soil limits the growth of gresses to a certain extent.(2)We cultivate the Leymus chinensis at vegetative stage with 13CO2 in greenhouse for 14 days,and find that when photosynthetic carbon of Leymus chinensis transforms from root to soil,its active bacteria and eukaryotic community differ with the distance from the root.RNA-SIP results show that Gaiella,Rubrobacter from Actinobacteria and Microvirga,Massillia,and Shinella from Proteobacteria are the main active bacteria that act as photosynthetic carbons in the rhizosphere and rhizosplne soil and Leptomyxa,Hamigera,and Cladosporium are the major active eukaryotic microorganisms in the rhizosphere and rhizosplane soil in enclosed grassland,respectively.(3)Different parts of 13C-Leymus chinensis were applied to enclosed and grazing soils and cultured for 56 days.The Leymus chinensis residues are effectively decomposed in the enclosing soil,which significantly increases the soil organic carbon content and causes a positive priming effect of the original organic matter in the soil.However,different parts of Leymus chinensis caused different priming effects of grazing soil.(4)The soils of enclosed and grazing grasslands result in different active bacterial community structures in decomposition of different parts of Leymus chinensis.Billicus dominated during the decomposition of stems and leaves of Leymus chinensis in enclosing soil,and Escherichia-Shigella is a key bacterium that decomposes the root in grazing soils.Eukaryotes are mainly involved in the decomposition of the root,in which Euglypha plays a leading role in the degradation of the root system in the enclosed grassland soil.