The Community And Functional Diversity Of Soil Microbes In The Rhizosphere Of Hedysarum Scoparium In Northwestern Desert

Global climate change has affected desert ecosystems,leading to the changes in desert vegetation on large-scale spatial scales.How to improve the utilization of water resources,the reconstruction of vegetation and the sustainable development of ecosystem is a key issue under the change of desert environment.The changes of the vegetation originate from adaptation to desert ecosystems,and this adaptation depends on the response of soil microbial communities to a large extent.Soil microbial communities have a decisive influence on the ecosystem because of the rich diversity.They affect the growth and diversity of plants by decomposing soil organic matter,assimilation of inorganic nutrients,and driving the circulation of soil nutrients.Therefore,determining the spatial response of desert soil microbial community to vegetation cover is conducive to elucidating the adaptation of soil microbial community and plant to desert environment,and predicting the change of desert ecosystem function.Hedysarum scoparium(Leguminosae),a regnant species in desert environments,is endemic to Asian deserts and is primarily distributed in desert areas of Northwest China.H.scoparium has a strong adaptability(e.g.,developed roots and resistance to infertility)that is particularly suitable for the renovation of degraded lands,making it an effective afforestation pioneer species in northwestern China.In addition,this species can be foraged for food and used as a woody oil and fibre plant source.In this dissertation,we studied the spatial distribution characteristics of soil microbial community structure and metabolic function diversity and the soil variables in the rhizosphere of H.scoparium in Northwestern China through phospholipid fatty acids(PLFA)and BIOLOG methods.The ecological effect explores the response characteristics of soil microbes to plants and soil factors on large-scale spatial scales and provides an accurate theoretical basis for vegetation restoration and scientific management of desert ecosystems.The main results are as follows:1.The spatial distribution of microbial community structure and catabolic function diversity in the rhizosphere soil of H.scoparium was significant.The contents of Gram-positive and Gram-negative bacteria,fungi,AM fungi,and actinomycetes were the highest at Ordos,while the Wuhai and Dengkou were smaller.The catabolism of carbohydrates,polymers,carboxylic acids,amino acids,and phenolic carbon sources were the most at Ordos.The catabolism of polymers at Shapotou and Minqin was the lowest.The catabolism of carboxylic acids was the lowest at Shapotou.In addition,the diversity of microbial community composition and catabolic function in the rhizosphere soil of H.scoparium was significantly higher than that in the bulk soil.It showed that H.scoparium could adapt to the harsh environment of arid desert,and promoted the activities of soil microorganisms.2.The composition of microbial communities in the rhizosphere of H.scoparium was dominated by bacteria,including bacteria > actinomyces> fungi > AM fungi,and the characteristic microorganisms PLFA were respectively Gram-positive bacteria(i15:1?6c,i14:0,i15:0,a15:0,i16:0,and a17:0),Gram-negative(16:1?9c,16:1?7c,17:1?8c,and 18:1?7c),actinomycetes(17:1 ?7c10Me,17:0(10 Me and 18:1?7c 10Me),fungi(18:2?6c),anaerobic bacteria(15:0 DMA);The AWCD values that characterize soil microbial carbon catabolism all increased with incubation time in different sites.The main carbon sources were carbohydrates,polymers,carboxylic acids,and amino acids.The main single carbon sources are carbohydrates(D-cellobiose,?-D-lactose,i-erythritol.Alcohol,D-glucuronide,glucose-1-phosphate,D-galactonic acid ?-lactone,D-galacturonic acid),amino acids(L-arginine,L-asparagine,L-serine and L-threonine),carboxylic acids(alpha-butyric acid),polymers(Tween 40).3.The rhizosphere soils of the H.scoparium are generally alkaline in the Northwestern Desert,and the soil moisture was low.RDA analysis showed that soil moisture,pH,SOC,ammonia N,available phosphorus,urease and alkaline phosphatase activity affected the composition and catabolic function of soil microbial communities.Ammonia nitrogen,urease,pH and SOC were the main soil variables affecting the composition of soil microbial community structure;ammonia N,pH and phosphatase were the main soil variables affecting the carbon source catabolic function of soil microbial communities.The soil physicochemical properties and soil enzymes were important soil factors that affected the spatiotemporal change of microbial community diversity.4.Based on the characteristics of desert soil microbes,breeding beneficial microorganism species in arid environments and comprehensive providing different substrate carbon sources is very meaningful in the ecological restoration of desert environment microorganisms.At the same time,the biotechnology to rehabilitate desert soil ecological environment is of great significance for arid desert vegetation restoration and ecological environment protection.