Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Ecosystem Carbon Exchange in A Desert Steppe in Ningxia under Precipitation Change and Nitrogen Addition

Auteur : 朱湾湾

Grade : Master 2021

Université : Ningxia University

Résumé partiel
As the consequence of global change,the change of precipitation pattern and increase in atmospheric nitrogen deposition directly affect soil moisture and nutrient contents,and thus affect plant community structure and the migration and transformation of soil-microbial elements.Both plant community structure and soil-microbial element balance could directly or indirectly affect the capacity of carbon fixation through plant photosynthesis,resulting in the changes in ecosystem carbon exchange.Desert steppe is characterized by low precipitation,high evaporation,low critical load of nitrogen deposition and the total amount of acceptable nitrogen deposition,so they are sensitive to the change in precipitation and the increase of nitrogen deposition.However,there still lacks a better understanding on how precipitation,nitrogen deposition and their interactions affect ecosystem carbon exchange in desert steppe,especially under extreme precipitation conditions.To deeply understand the response mechanisms of the ecosystem carbon exchanges in desert steppes under changing precipitation and increasing nitrogen deposition,a field experiment involving five precipitation treatments（50%reduction,30%reduction,natural,30%increase,and 50%increase）and two nitrogen addition treatments（0 and 5 g·m-2·yr-1）was conducted in a desert steppe of Ningxia in 2017.The temporal dynamics of net ecosystem carbon exchange（NEE）,ecosystem respiration（ER）,and gross ecosystem productivity（GEP）were monitored from May to October of 2019.Together with the changes in plant biomass,plant diversity,soil and microbial C:N:P ecological stoichiometry,and other key soil properties,the main influencing factors of ecosystem carbon exchange were analyzed too.The main findings are as follows:1)Changing precipitation did not clearly change the temporal dynamics of ecosystem carbon exchange.Under 0 and 5 g·m-2·yr-1 of nitrogen addition,monthly dynamics of NEE,ER,and GEP increased first and then decreased,with the peak values appearing in late August or early September.Ecosystem carbon exchange changed from carbon source to carbon sink during the growing season

Mots clés : changing precipitation pattern ;atmospheric nitrogen deposition ;ecosystem carbon exchange ;plant community structure ;soil property ;

Présentation (CNKI)