Response Of Microorganisms Associated With Soil Phosphorus Transformation To Different Vegetation Restoration Types In Mu Su Sandy Land

Vegetation restoration is an effective way to control desertification.After revegetation in the Mu Us Sandy Land,the soil organic carbon and total nitrogen content increased,but with the accumulation of nitrogen,the problem of soil phosphorus restriction became increasingly prominent.As a nutrient necessary for plant growth,phosphorus（P）is a limiting factor for plant growth in terrestrial systems,which will affect the effect of sandy ecological restoration.Soil microorganisms are important regulators of soil organophosphate mineralization and inorganic phosphorus dissolution.However,there are few studies on the response of microbial communities associated with phosphorus transformation in sandy soils to vegetation restoration.Therefore,in this study,soil with different vegetation restoration types in Mu Su Sandy Land including grassland（GL）,shrub land（SL）,grass-shrub land（GSL）and forest land（FL）0-20 cm was used as the research object,and bare sand land（CK）was used as the control,the soil phosphorus fractions were graded by Tinessen’s improved continuous grading method,and high-throughput sequencing technology were used to analyze the microbial community structure and diversity encoded by pho D and gcd,the key functional genes of soil phosphorus transformation.This paper provides a theoretical basis for in-depth understanding of soil phosphorus fractions changes and microbial response mechanisms of different vegetation restoration types in Mu Su Sandy Land.The main results of this study are as follows:（1）Different vegetation restoration types significantly affected soil nutrient content.Vegetation revegetation significantly reduced soil p H,while soil organic carbon,total nitrogen,available phosphorus,microbial biomass and soil enzyme activity increased,among which the nutrient content of grass-shrub land（GSL）and forest land（FL）was significantly increased,the soil total phosphorus content of bare sand land（CK）was second only to forest land（FL）,and the planting of the other 3 vegetation types reduced the soil total phosphorus content.（2）Vegetation restoration is conducive to increasing the phosphorus fractions in the soil that are easily used by plants,and in this study,soil phosphorus mainly existed in the form of poorly soluble inorganic phosphorus HCl-Pi,and the content was between 108.41-197.35mg·kg^-1.Vegetation regeneration increased the contents of Resin-Pi,Na HCO₃-Pi and Na HCO₃-Po in soil,and the changes of forest land（FL）and grass-shrub Land（GSL）compared with bare sand land（CK）increased by 97.73%and 81.82%,Na HCO₃-Pi increased by 3.12mg·kg^-1 and 3.36 mg·kg^-1,respectively,and Na HCO₃-Po increased by 6.93 mg·kg^-1 and 7.35mg·kg^-1;The contents of Na OH-Pi and Na OH-Po,which are medium-stable phosphorus fractions increased significantly in grass-shrub land（GSL）and grass land（GL）.At the same time,vegetation restoration reduced the content of highly stable phosphorus fractions HCl-Pi,which decreased by 64.02-89.0%.（3）The relative abundance of pho D and gcd,the key functional genes of soil phosphorus transformation,was not significantly affected by vegetation restoration,and the ratio of pho D to gcd relative abundance was between 1.24～2.73,which varied with the different types of vegetation restoration.The dominant microbial phylums encoded by different vegetation restoration types of pho D include Actinobacteria,Proteobacteria,Acidobacteria,Cyanobacteria,Bacteroidetes,Candidatus-Rokubacteria and Chloroflexi,with Bradyrhizobium and Kribbella are the dominant genus.Soil p H and total phosphorus content are important factors affecting the microbial communities encoded by pho D,and the relative abundance of pho D is significantly correlated with soil organic carbon（SOC）content.（4）The dominant microbial phylums coded by gcd for different vegetation restoration types include Acidobacteria,Proteobacteria,Actinobacteria,Bacteroidetes and Gemmatimonadetes.The dominant genus are Bradyrhizobium and Steroidobacter.Soil p H,soil dehydrogenase activity（DEA）,and available phosphorus（AP）content are important factors affecting the microbial communities encoded by gcd.At the same time,the relative abundance of gcd was significantly correlated with the content of Na OH-Pi of medium-stable inorganic phosphorus,and the content of available phosphorus（AP）in soil.This study shows that the available phosphorus（AP）that can be directly absorbed and utilized by plants in different vegetation restoration types in the Mu Su Sandy Land mainly comes from the dissolution of inorganic phosphate in soil by gcd-coded microbial communities.With the revegetation process,the role of soil pho D-encoded microbial communities in soil phosphorus transformation increased,and was affected by the total phosphorus（TP）content of soil.Vegetation restoration significantly affected the relative abundance of microbial dominant taxa in the key process of phosphorus transformation,and had little effect on the relative abundance of soil pho D and gcd functional genes.It is proposed that the two vegetation restoration models of forest planting and grass shrub mixed planting in Mu Su Sandy Land can improve the use efficiency of inorganic phosphorus in sandy soil and better restore the vegetation of Mu Su Sandy Land.