陆地生态系统碳通量面临的挑战与机遇--基于涡度协方差测定

Challenges and opportunities for measuring carbon fluxes in terrestrial ecosystems by eddy covariance

区域和全球涡度协方差网络提供了基于陆地-大气生态系统间最大的综合性原位碳通量观测数据集。这些数据目前已成为自下而上核算陆地生态系统碳平衡的基础,但部分测量数据合理性问题引起通量界广泛关注。通过梳理近40年研究进展,总结了涡度协方差测量原理,系统地分析了仪器局限性和环境因素潜在影响,讨论了不同碳通量组分填补存在的争议、生态系统冬季休眠期的净碳吸现象违背生理学知识、夜间湍流发展不充分对生态系统呼吸的低估等,并由此产生数据偏移和测量滞后时间等。通过阐述涡度协方差测量原理和数据处理存在的缺陷与争议,提出了适当的改进措施以限制(或降低)数据测量产生的不确定性,旨在为后续监测精度提升和探究陆地生态系统碳循环及其对环境因子的响应提供理论支撑。

Regional and global eddy covariance networks provide the largest comprehensive in situ dataset on carbon fluxes between terrestrial and atmospheric ecosystems.Carbon balance in terrestrial ecosystems can be accounted for bottom-up by these flux data.However,the plausibility of some measurement data has aroused widespread concern from the flux community.This study reviews the research progress over the past four decades,summarizes the principles of eddy covariance measurement,and systematically analyzes the limitations of the instrument and the potential impact of environmental factors.Subsequently,we discuss the controversy over the filling of different carbon flux components,the net carbon uptake phenomenon of ecosystem dormancy in winter against physiological knowledge,the underestimation of ecosystem respiration by insufficient development of nighttime turbulence,and the phenomenon of data offset and measurement lag time due to the above factors.By focusing on the defects and disputes in the measurement principle of eddy covariance and data processing,appropriate improvement measures are proposed to limit(or reduce)the uncertainty of data measurement.This study aims to provide theoretical support for improving monitoring accuracy in the future as well as exploring the carbon cycle of terrestrial ecosystems and its response to environmental factors.