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Ningxia University (2022)

The Response of Ningxia Desert Grassland Vegetation-soil-Microbial to Precipitation Change and Warming

张翼

Titre : The Response of Ningxia Desert Grassland Vegetation-soil-Microbial to Precipitation Change and Warming

Auteur : 张翼

Grade : Doctoral Dissertation 2022

Université : Ningxia University

Résumé partiel
The extremely important strategic ecological position of desert grassland ecosystem,and its sensitivity and inevitability to climate change determine that it is very important to study the response of desert grassland ecosystem to climate change.Therefore,in this experiment,the desert grassland in Yanchi County,Ningxia,on the southern edge of Mu Us Sandy Land,was taken as the research object,and five precipitation gradients and two temperature gradients were simulated by using the precipitation shelter technology and the OTC(Open-Top Chamber).The five precipitation gradients were 33%,66%,100%,133%,and 166%of the normal precipitation(R33,R66,RCK,RCK).The temperature gradient is natural temperature,and non-directional warming(X,X+1.5℃),and the interaction of precipitation and warming is TR33,TR66,TRCK,TR133,and TR166.The ecological response of vegetation,soil,microorganism and their coupling relationship to precipitation change and warming in desert steppe was studied(2018-2021),and the main results were as follows :(1)Under the precipitation change,increasing precipitation(R166)will significantly increase the diversity,evenness,and richness of vegetation,and increase the density and frequency of Agropyron mongolicum,Lespeseza bicolor,and Polygala tenuifolia ;Precipitation has significant effects on the contents of organic carbon,total nitrogen and total phosphorus in leaves and roots of Agropyron mongolicum,Lespeseza bicolor and Polygala tenuifolia.Increasing precipitation is beneficial to the enrichment of organic carbon,total nitrogen,and total phosphorus in the litter,and promotes the increase of vegetation biomass.Reducing the nitrogen content in plant leaves inhibited the net photosynthetic rate of vegetation.There is a significant positive correlation between precipitation and vegetation biomass,litter organic carbon,litter total phosphorus,and the vegetation diversity index.The soil water content in 0-40cm soil layer is the fastest and most sensitive to the precipitation change.Under RCK treatment,the soil water content in this soil layer is higher than in other treatments,and the soil water retention capacity is relatively stable.Meanwhile,the increase in precipitation promotes soil respiration and carbon emission.There was a significant positive correlation with soil respiration,soil organic carbon,total nitrogen,total phosphorus and their stoichiometric ratio.The response of microbial diversity to precipitation changes slightly in 1-2 years,and the β diversity of soil fungi was significant increased by R166 treatment in the third year of precipitation increase.The precipitation is mainly negative correlated with the abundance and coverage of bacteria.(2)Under the warming,warming by 1.5℃(the average warming measured by OTC is 1.5℃)can improve the diversity,richness and evenness of vegetation ;Warming reduced the coverage and density of Lespeseza bicolor and Agropyron mongolicum,but increased the density and height of Polygala tenuifolia.Warming increased the accumulation of organic carbon content in leaves and roots ofAgropyron mongolicum,Lespeseza bicolor,and Polygala tenuifolia,and decreased the total nitrogen content in leaves,roots of Lespeseza bicolor,and Polygala tenuifolia.Warming makes the aboveground biomass of vegetation decrease year by year,while the root biomass of vegetation increases significantly.There was a significant negative correlation between temperature,litter organic carbon,and litter total phosphorus.Warming reduces the fractal dimension of soil,promotes the accumulation of organic carbon in 20-30cm soil,and reduces the ratio of soil organic carbon to total nitrogen and soil respiration ;Warming is negative correlated with soil total nitrogen and soil respiration.Grassland soil microbes are extremely sensitive to temperature changes,and warming significantly improves the richness and evenness of soil fungal communities,and promotes the bacterial β diversity.

Mots clés : Desert grasslands ;Precipitation change ;Warming;Soil characteristic ;Plant characteristic ;Soil microbial diversity ;

Présentation (CNKI)

Page publiée le 15 octobre 2022