Net ecosystem CO_2 exchange and controlling factors in a steppe——Kobresia meadow on the Tibetan Plateau

作     者：SHI Peili, SUN Xiaomin, XU Lingling, ZHANG Xianzhou, HE Yongtao, ZHANG Dongqiu & YU Guirui Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China Graduate University of Chinese Academy of Sciences, Beijing 100039, China 

作者机构：1. Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China2. Graduate University of Chinese Academy of Sciences Beijing 100039 China 

出 版 物：《Science China Earth Sciences》 (中国科学（地球科学英文版）)

年 卷 期：2006年第49卷第S2期

页      面：207-218页

核心收录：

学科分类：090503[农学-草业科学] 0909[农学-草学] 0905[农学-畜牧学] 09[农学] 0903[农学-农业资源与环境] 

基　　金：This study was performed under the auspice of the National Key Project for Basic Research (Grant No. 2002CB412501) the National Natural Science Foundation of China (Grant no. 30470280) Knowledge Innovation Program of Chinese Academy of Sciences (KZCX3-SW-339) Damxung Grassland Station of Tibetan Autonomous Region provided observation site and person-nel. Special thanks are extended to Mr Guo Wanjun, Suo- lang Ciren, Huang Qingyi and Yang Junping for their help in data collecting 

主　　题：Tibetan Plateau alpine steppe--Kobresia meadow NEE ecosystem respiration PAR soil moisture temperature response LAI eddy covariance. 

摘      要：Knowledge of seasonal variation of net ecosystem CO2 exchange (NEE) and its biotic and abiotic controllers will further our understanding of carbon cycling process, mechanism and large-scale modelling. Eddy covariance technique was used to measure NEE, biotic and abiotic factors for nearly 3 years in the hinterland alpine steppe--Korbresia meadow grassland on the Tibetan Plateau, the present highest fluxnet station in the world. The main objectives are to investigate dynamics of NEE and its components and to determine the major controlling factors. Maximum carbon assimilation took place in August and maximum carbon loss occurred in November. In June, rainfall amount due to monsoon climate played a great role in grass greening and consequently influenced interannual variation of ecosystem carbon gain. From July through September, monthly NEE presented net carbon assimilation. In other months, ecosystem exhibited carbon loss. In growing season, daytime NEE was mainly controlled by photosynthetically active radiation (PAR). In addition, leaf area index (LAI) interacted with PAR and together modulated NEE rates. Ecosystem respiration was controlled mainly by soil temperature and simultaneously by soil moisture. Q10 was negatively correlated with soil temperature but positively correlated with soil moisture. Large daily range of air temperature is not necessary to enhance carbon gain. Standard respiration rate at referenced 10℃(R10) was positively correlated with soil moisture, soil temperature, LAI and aboveground biomass. Rainfall patterns in growing season markedly influenced soil moisture and therefore soil moisture controlled seasonal change of ecosystem respiration. Pulse rainfall in the beginning and at the end of growing season induced great ecosystem respiration and consequently a great amount of carbon was lost. Short growing season and relative low temperature restrained alpine grass vegetation development. The results suggested that LAI be usually in a low le