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Lanzhou University (2021)

Study on Carbon Budget Process of Grape Farmland in Arid Oasis Region

张扬

Titre : Study on Carbon Budget Process of Grape Farmland in Arid Oasis Region

Auteur : 张扬

Grade : Master 2021

Université : Lanzhou University

Résumé partiel
The fragile ecological environment makes the process of ecosystem carbon budget extremely sensitive to the interference of natural factors and human activities in the arid area of Northwest China,especially the oasis farmland ecosystem is strongly disturbed by human production activities.Therefore,it is of great significance to deeply understand the dynamics of productivity and respiration process of the vineyard ecosystem in this region for accurately evaluating the process of farmland carbon budget in arid oasis region of China.Taking the vineyard in Nanhu Oasis of Dunhuang as the research object,the net ecosystem exchange and soil respiration of the vineyard were measured by combining the vorticity covariance system with soil carbon flux measurement system in 2019.Gross primary productivity(GPP),net ecosystem productivity(NEP)and ecosystem respiration(Re)were obtained by the net ecosystem exchange.Soil respiration(Rt)was divided into below-ground autotrophic respiration(Rab)and heterotrophic respiration(Rh)by root exclusion method,above-ground autotrophic respiration(Raa)and total autotrophic respiration(Ra)were calculated.Based on this,the dynamics of productivity and respiration process of the vineyard in arid oasis area were explored,and the comprehensive effects of various environmental factors on them were determined by using correlation analysis and structural equation model.Finally,the process of carbon budget in grape farmland was quantitatively evaluated.The main results are as follows :(1)The diurnal and seasonal variation of gross primary productivity(GPP)and net ecosystem productivity(NEP)of grape fields in the oasis in 2019 showed unimodal characteristics,but there were some fluctuations in different weather condition.The correlation analysis showed that the main influencing factors of the two were leaf area index(LAI),air temperature(Ta),photosynthetic effective radiation(PAR),soil water content(SWC),water vapor pressure deficit(VPD),etc.The structural equation models between GPP,NEP and environmental factors were established to quantify the direct and indirect effects of various factors.The final model could explain 67%and60%of the changes of the two factors.The models showed that the most important factor was VPD,whose standardized total effect coefficients for GPP and NEP were-0.63 and-0.71,respectively.In addition,the enhancement of Taand PAR could promote photosynthesis and improve farmland productivity to a certain extent.Although the total effects of SWC on GPP and NEP were lower,the coefficients of effect were only0.15 and 0.22,it would affect GPP and NEP through the negative effect on VPD.Finally,we focused on the response of NEP to the main environmental factors.PAR,as the direct driving force of photosynthesis,could explain 27~54%of NEP changes with the right-angle hyperbolic model,but high Ta,high VPD and low SWC will weaken the response of NEP to PAR.

Mots clés : grape farmland ;productivity;respiratory process ;carbon budget ;influencing factors ;

Présentation (CNKI)

Page publiée le 14 novembre 2021