开路与闭路涡度相关系统对森林生态系统甲烷通量观测的比较

doi:10.3969/j.issn.1000-6362.2019.11.001

摘要/Abstract

摘要： 作为涡度相关技术观测的两种主要技术手段，开路（OPEC）和闭路（CPEC）两种涡度相关系统在观测森林生态系统CH4通量过程中存在较大的不确定性，本研究利用OPEC和CPEC两种涡度相关系统，对黄河小浪底人工混交林CH4通量进行连续观测，选取生长旺季2016年7月24日-8月5日连续14d数据，对比两种观测系统的功率谱和协谱，估算闭路涡度相关系统的延迟时间，并分析其在连续晴天和连续雨天的通量观测结果。结果表明：CPEC系统的功率谱和协谱在所有频率上与OPEC系统基本一致，在惯性副区功率谱符合-5/3相似规律，协谱符合-4/3相似规律；以OPEC系统为“准”标准，CPEC系统观测CH4通量的延迟时间合适流速范围内的5个不同流速（40、37.5、35.5、33.5、31.5L·min-1）分别为4.6、7.7、5.3、10.8和14.3s，平均延迟时间为8～9s；与OPEC观测系统测定的CH4通量相比，CPEC系统观测结果晴天偏低12%；雨天高出32%。OPEC观测系统适用于晴天CH4通量观测。经校正，消除延迟影响后的CPEC观测系统可用于测定雨天CH4通量，以弥补OPEC观测系统缺测的值。两种系统并行观测、相互弥补，可望获得更完整、更高质量的CH4通量数据。

Abstract: The eddy covariance technique provides a useful tool to directly measure CH4 exchange between the vegetation and the atmosphere. The open-path (OPEC) and close-path (CPEC) systems have uncertainties in measuring methane flux in forests. Therefore, it is necessary to compare the measured CH4 flux obtained from the OPEC and CPEC systems. In this study, CH4 flux was measured using the OPEC and CPEC systems in a mixed plantation in the Xiaolangdi area during the growing season of 2016 (July 24th to August 5th). The (co)spectra were analyzed and the time lag was estimated. Moreover, CH4 flux from the OPEC and CPEC systems was discussed. The results showed that the (co)spectra showed a good agreement with the -5/3 for spectra and -4/3 for co-spectra. Under different sampling flow rate (40, 37.5, 35.5, 33.5 and 31.5L·min-1) conditions, the time lag was 4.6, 7.7, 5.3, 10.8 and14.3s, respectively, and the average lag time was 8-9 s. CH4 flux derived from the CPEC system was 12% lower than that measured by the OPEC system in sunny days, while CH4 flux obtained by the CPEC system was 32% higher than that measured by the OPEC in rainy days. The OPEC system was more suitable measuring CH4 flux in comparison with the CPEC system in sunny days. The lag time should be corrected for the CPEC system in rainy days since it can be used for compensate for missing values in the OPEC system. Higher quality data of CH4 flux can be obtained by using the CPEC and OPEC systems together.

Key words: Eddy covariance, Lag time, Spectrum analysis, Methane flux, Forest ecosystem

原文文，张劲松，孟平，同小娟，潘庆梅，何方杰，李剑侠. 开路与闭路涡度相关系统对森林生态系统甲烷通量观测的比较[J]. 中国农业气象, 2019, 40(11): 669-677.

YUAN Wen-wen，ZHANG Jin-song，MENG Ping，TONG Xiao-juan，PAN Qing-mei，HE Fang-jie，LI Jian-xia. Comparison of CH4 Flux Measurement by Open- and Close- Path Eddy Covariance System[J]. Chinese Journal of Agrometeorology, 2019, 40(11): 669-677.

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