Comparison of eddy covariance and static chamber/gas chromatogram methods in measuring ecosystem respiration

ZHENG Ze-mei1,2,YU Gui-rui1,SUN Xiao-min1,CAO Guang-min3,WANG Yue-si4,DU Ming-yuan5,LI Jun1,LI Ying-nian3(1Synthesis Research Center of Chinese Ecosystem Research Network,Key Laboratory of Ecosystem Network Observation and Modeling,Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing 100101,China;2Graduate University of Chinese Academy of Sciences,Beijing 100039,China;3Northwest Institute of Plateau Biology,Chinese Academy of Sciences,Xining 810001,China;4Institue of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029,China;5National Institute for Agro-Environmental Sciences,Tsukuba 3058604,Japan)

static chamber/gas chromatogram;eddy covariance;ecosystem respiration

Based on the measurement of carbon flux by the methods of eddy covariance and static chamber/gas chromatogram,a comparison was made between the two methods in evaluating ecosystem respiration over winter wheat(Triticum aestivum)-summer maize(Zea mays) double cropland and Kobresia humilis alpine meadow.The results showed that under the conditions of obtained data having good quality,nighttime ecosystem respiration from eddy covariance measurement was significantly agreed with that from static chamber/gas chromatogram measurement,with the correlation coefficients ranging from 0.95 to 0.98,and the daytime ecosystem respiration from these two measurements also had a good consistency though the static chamber/gas chromatogram measurement often produced higher values.The daily mean value of ecosystem respiration was significantly different between these two measurements,but the seasonal pattern was similar.For winter wheat-summer maize double cropland,the difference of mean air temperature inside and outside the chamber was 1.8 ℃,and the daily mean value of ecosystem respiration across the whole study period was 30.3% lower in eddy covariance measurement than in static chamber/gas chromatogram measurement;while for alpine meadow,the difference of the mean air temperature was 1.9 ℃,and the daily mean value of ecosystem respiration was 31.4% lower in eddy covariance measurement than in static chamber/gas chromatogram measurement.The variance between the daily mean values of ecosystem respiration obtained from the two measurements was higher in growing season than in dormant season.