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Lanzhou University (2018)

Effect of Grassland Reclamation and Highway Traffic on Grassland Soil Degradation in Tibetan Plateau

关振寰;

Titre : Effect of Grassland Reclamation and Highway Traffic on Grassland Soil Degradation in Tibetan Plateau

Auteur : 关振寰;

Grade : Doctoral Dissertation 2018

Université : Lanzhou University

Résumé partiel
The cultivation of crops on grassland has a long history on the Tibetan Plateau,which has promoted the settlement of human beings on the plateau.The content of soil organic matter decreased significantly after reclamation,which is generally believed to be related to the decrease of organic carbon input and mineralization acceleration due to tillage disturbance.However,if the metabolic synthesis of soil microorganisms changes during this process,the decrease of soil organic matter content is related to the decrease of the accumulation of microbial synthetic materials,which has not been reported before.With the increase of economic activity since the reform and opening up,the transportation in Tibetan Plateau has been developing very fast,and there is little research on the effect of highway traffic on the accumulation of heavy metals in grassland soil.This thesis we take soil non-cellulosic hexoses(mainly by microbial synthesis)and pentose sugar(mainly plant sources)and the proportion of the content of amino sugars as the indicator,to study the grassland reclamation effects on soil microbial metabolism synthesis product accumulates.At the same time,we studied the accumulation of heavy metals in grassland soil and the influence of soil profile distribution on the high altitude and distance of highway.Conversion of grassland to cropland affects microbial transformation of plant derived organic substances and accumulation of microbially synthesized products in soil.We investigated long-term effects of agricultural use[more than 50 years’rotation with barley(Hordeum vulgare)and rapeseed(Brassica rapa)]after conversion from grasslands(grazed in the winter season)on the contents and composition of non-cellulose sugars and amino sugars in a broad range of soils on the Tibetan Plateau.Soils from two types of croplands(barley or rapeseed)were compared to reference grassland soil by detailed analyses of plant vs.microbial and bacterial vs.fungal bio-markers.The results show :(1)Long-term cultivation decreased total soil organic matter(SOM),light SOM,heavy SOM and total non-cellulose sugar contents in the 0–20 cm soil by 27%,60%,24%and 57%,respectively,reflecting decreased root biomass compared to grassland.(2)The ratios of(galactose+mannose)/(arabinose+xylose)and(rhamnose+fucose)/(arabinose+xylose)were both 26%smaller in cropland than in grassland soils,while these ratios of hemicelluloses in shoots or roots were similar between native and cultivated plants.(3)Consequently,net transformation of plant substances to microbially synthesized polysaccharides decreased in cultivated soils.The total amino sugars(muramic acid,glucosamine,mannosamine,galactosamine)in cropland soils decreased by 42%and their contribution to the SOM by 22%compared to grassland soils,but the ratio of glucosamine/muramic acid in cropland soils doubled compared to grassland soil.(4)All the above results were verified in the other seven extensive sampling points

Mots clés : Grassland ecosystem; Soil degradation; Amino sugar; Non-cellulosic sugar; Heavy metals; The background value; Enrichment characteristics; Pollution;

Présentation (CNKI)

Page publiée le 14 avril 2019