Degradation Process Of Salix Psammophila Sand Barrier And Action Mechanism Of Fungal Community

Salix psammophila sand barrier is one of the main measures to prevent and control sand in northwest China,and are effective in preventing wind-sand movement and fixing quicksand,improving water and soil,and promoting the recovery of vegetation.However,with the increase of setting years,different degrees of lodging damage occurred to S.psammophila sand barrier,which fundamentally affected the performance of its windproof and sand fixation.In this thesis,we use high-throughput sequencing technology,biological material structure and performance characterization,combined with chemometric analysis and other methods,to clarify the changes of sand barrier structure and performance during the degradation process,identify the main influencing factors with the surrounding soil environment,explore the distribution pattern of the fungal community of S.psammophila sand barrier in combination with the species composition and diversity characteristics of the fungal community,and predict the ecological function of the fungal community of S.psammophila sand barrier.The microenvironmental role of the fungal community in S.psammophila sand barrier.was explored,and the ecological functions of the fungal community in S.psammophila sand barrier were predicted on this basis.The main conclusions are as follows.(1)With the increase of setting years,S.psammophila sand barrier decays from the outside to the inside,the ducts and thin-walled cells and other tissues are broken and deformed,resulting in the collapse of cellular tissues and disintegration.After setting for five years,the loss of physical parameters such as mass loss rate,basic density,water content and dry shrinkage rate of S.psammophila sand barrier is less than 45%,while the loss of mechanical properties mainly based on modulus of elasticity is about 63%.When the setting years reaches seven years,the modulus of elasticity decreases by 77%,five years and seven years are important time inflection points in measuring the degradation process of the S.psammophila sand barrier;the degree of degradation at different slope positions is in descending order of lower slope > middle slope > top slope;the loss of water,loss of chemical composition,changes in chemical groups and changes in the internal anatomy of the Salix psammophila sand barrier lead to changes in its structure and properties,the mechanical strength is therefore affected and the properties are seriously degraded.(2)The degradation of the S.psammophila sand barrier caused a decrease in inter-perimeter soil moisture and soil p H,and the more severely the sand barrier was degraded,the higher the moisture content of the barricade and the lower its inter-perimeter soil moisture content;the changes in moisture and nutrient characteristics of the inter-perimeter soil of the S.psammophila sand barrier during the degradation process responded to microtopography to varying degrees,with small differences between slopes;the changes in inter-perimeter soil nutrient content of the S.psammophila sand barrier were related to the composition and diversity of the fungal community of sand barrier.(3)A total of 438 OTUs from 7 phyla,21 orders,54 families,110 families and177 genera of fungi were annotated of S.psammophila sand barrier of different setting years,Ascomycota and Basidiomycota were the dominant fungal community,and the species abundance of Ascomycota was greater than that of Basidiomycota;the distribution pattern of fungal species and community diversity The distribution patterns of fungal species and community diversity were significantly correlated with changes in the physical and mechanical properties of sand barrier,and their distribution was influenced by a combination of factors in the microenvironment of S.psammophila sand barrier.(4)The number of fungal species(OTUs)and community richness in the sand buried of the S.psammophila sand barrier at different slope positions were consistent,from large to small: down slope > middle slope > top slope;the Shannon index of fungal community diversity and the number of fungal communities of S.psammophila sand barrier showed an overall increasing trend;the dominant fungal groups of sand barrier at different slope positions were all Cysticerca and Strettaceous.The dominant fungal groups of sand barrier at different slope positions were Ascomycota and Basidiomycota;The main drivers of fungal communities at different slopes of the one years of S.psammophila sand barrier were the dry shrinkage rate and the soil p H.the main drivers of fungal communities at different slopes setting for three years of S.psammophila sand barrier were the soil p H and the basic density.The main drivers of fungal communities at different slope positions setting for five years of S.psammophila sand barrier were cellulose,lignin and modulus of elasticity.(5)The fungal communities of S.psammophila sand barrier of different setting years include three major types of trophic patterns: Sathotroph,Saprotroph and Symbiotroph.There are four mixed trophic modes: Pathotroph-saprotroph,Pathotroph-saprotroph-symbiotroph Saprotroph-symbiotroph and Pathotroph-symbiotroph,including 12 single ecological functional groups and 33 mixed ecological functional groups;The changes of microtopography have some influence on the ecological functions of the fungal communities of sand barrier;the ecological functions of the fungal communities of sand barrier vary greatly between different setting years,and changes in slope position have less influence on the fungal communities of sand barrier.The effect of slope changes on the ecological function of the fungal community of S.psammophila sand barrier is relatively small.