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sur le développement des zones arides et semi-arides

Titre : The Effects of Grazing and Mowing on Soil Phosphorus Pools and Microbes Related to Phosphorus Transformation in Inner Mongolia Grassland

Auteur : 张梅

Grade : Doctoral Dissertation 2022

Université : Xinjiang Agricultural University

Résumé partiel
Grassland degradation is becoming increasingly serious due to inappropriate grassland management practices,including the loss of vegetation diversity and the reduced soil fertility.Phosphorus（P）is an important component of soil fertility,and its availability plays an important role in the productivity and sustainable development of grassland ecosystems.Previous studies reported that overgrazing and mowing,as common grassland management practices,could significantly decrease soil P content in grassland ecosystem.However,it is not clear how soil microbes are involved in the process of soil P transformation and the mechanisms of affecting soil bio-available phosphorus under different grazing intensities and mowing in grassland ecosystems.In this study,soil samples were selected in July 2019 from Inner Mongolia grassland,and the experiments of different grazing intensities and mowing were conducted based on three long-term locational research stations.In typical steppe and desert steppe,four grazing treatments included:i)non-grazing（UG） ;ii)lightly grazing（LG） ;iii)moderately grazing（MG） ;iv)heavily grazing（HG）.In mowing experiment,soil samples were selected from three sites（i.e.the second team of Shertala Town,the twelfth team of Shertala Town,and Baiyinxile Ranch）,and the mowing treatments included:control and mowing,respectively.The effects of different grazing intensities and mowing on the abundance,diversity and structure of functional genes community（organic phosphorus mineralisation,pho D ;inorganic phosphorus mobilization,pqq C）related to soil phosphorus transformation were investigated using fluorescence quantitative PCR and high-throughput sequencing.Meawhile,changes in soil phosphorus pools and phosphorus transformation-related enzyme activities were determined by soil chemical sequential extraction and enzymatic methods.The results of the study were as follows.（1）In typical steppe,the soil H2O-Pi,Na OH-Pi,Na OH-Po,D.HCl-Pi,C.HCl-Pi and residual-P contents were significantly higher in the treatments of UG and LG than that in the treatments of MG and HG,and the highe value of these items were always observed in the LG treatment.In desert steppe,no significant difference was observed for soil total phosphorus content among all the treatments,and grazing reduced soil total organic phosphorus but increased total inorganic phosphorus ;the contens of soil C.HCl-Pi and Residual-P were significantly lower in the UG tretment than those in the tretments of LG,MG and HG ;the HG treatment significantly decreased soil H2O-Pi contents compared to the UG treatment.In addition,grazing had no effect on soil acid phosphatase activity in typical steppe,but soil acid phosphatase activity was decreased with increasing grazing intensity in desert steppe.In typical steppe,compared to the UG treatment,soil alkaline phosphatase was significantly increased by 21.46%in the LG treatment,and decreased by22.89%in the HG treatment.In desert steppe,alkaline phosphatase activity was decreased with increasing grazing intensity,ranging from 6.94%to 68.17%compared to the UG treatment.

Mots clés : Grassland ;Grazing;Mowing ;Phosphorus transformation microbes ;Community composition ;

Présentation (CNKI)