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sur le développement des zones arides et semi-arides

Titre : Study on Energy Balance and Water and Carbon Flux of Jujube Forest Ecosystem under Drip Irrigation in Arid Area

Auteur : 乔英

Grade : Doctoral Dissertation 2022

Université : Xinjiang Agricultural University

Résumé partiel
Ziziphus jujuba Mill.（jujube）is a tree species that provides both ecological and economic benefits.Jujube trees have been successfully introduced to Xinjiang Uygur Autonomous Region,China over the last two decades,with the planted area reaching 500,000 ha.The increasing area of jujube forests in arid zones has aggravated the challenge of water scarcity.However,few studies have explored the carbon balance of jujube forests during either the reproductive period or entire year.An in-depth study of the processes and energy-driven mechanisms regulating water-carbon flux cycles in jujube forest ecosystems in arid zones is needed to develop approaches for managing the local greenhouse effect,alleviating water scarcity,and improving water use efficiency（WUE）in arid zones.This study conducted continuous flux observations in drip-irrigated jujube forests in the arid zone for two years using an eddy correlation system and auxiliary observation equipment.Missing flux data were interpolated using the R language“REddy Proc”package.The terms of thermal storage in the energy balance were also corrected to analyze the energy balance closure of jujube forests and the trend of each energy component.Management of forest water consumption in arid zones requires estimations of evapotranspiration.This study simulated evapotranspiration using the SIMDual-Kc model and improved S-W model.The relationships between evapotranspiration in jujube orchards and driving factors were analyzed using the structural equation model（SEM）.The R language“REddy Proc”package was used to split net ecosystem CO2 exchange（NEE）into total ecosystem respiration(Reco)and total primary productivity（GPP）to analyze the characteristics of carbon flux changes and water use efficiency WUE.The results showed the following.（1）The REddy Proc package could interpolate the data better with the error statistic parameters of b=0.86-0.99,R 2=0.86-0.95,d=0.96-0.98,EF=0.84-0.92,and RSR=0.28-0.40.After conducting the R package interpolation,the energy balance closures of the jujube date forests were 73.45%and 73.11%,respectively.R 2 of the 2-year effective energy（H+LE）and available energy（Rn-G）was 0.97.After adding the thermal storage terms,the energy balance closures increased to 77.17%（by 3.72%）and 75.86%（by 2.75%）,respectively.R 2 of the effective energy（H+LE）and the available energy（Rn-G-S）was 0.97,respectively.The daily-averaged variation pattern of each energy component was similar during the fertility and dormancy with a single-peaked daily variation according to the variation pattern of the net radiation.The annual energy balance closures of the jujube date forests were 73.45%and 73.11%,respectively.The thermal storage terms had some influences on the improvement in the energy balance closure of jujube date forests.

Mots clés : arid area ;Ziziphus jujuba Mill.（jujube） forest ;Eddy covariance technique ;energy balance ;model simulation ;evapotranspiration;carbon flux ;

Présentation (CNKI)