SOIL CO2 FLUX DATA (FIFE)

In the Soil Carbon Dioxide Flux study, a prototype gas exchange system and sensor were used to determine the soil surface flux of CO2 and associated parameters at the three FIFE supersites. The goal of this investigation was to characterize fluxes of carbon dioxide from the surface of the soil for a representative portion of the FIFE study area. These measurements are required to understand the carbon budget of the prairie and necessary for comparing vegetation models of photosynthesis with CO2 flux measurements by micrometeorological methods. The flux of the carbon dioxide from the surface of the soil is an important component of the carbon budget of a prairie ecosystem. The results from this study indicate that a soil chamber can be used to obtain reasonable estimates of soil surface carbon dioxide fluxes when operated in a closed system that is ported to the free atmosphere. Further, the flux of carbon dioxide from the soil surface of a grassland can be a large part of the carbon budget and should never be assumed to be negligible. Both soil temperature and soil water content are critical parameters for predicting soil surface CO2 flux, and leaf area index is a surrogate for the plant contribution through root respiration.

在本次土壤二氧化碳通量研究中，研究人员采用原型气体交换系统与传感器，对三个FIFE超级站点的土壤表面二氧化碳（CO₂）通量及相关参数开展测定。本次研究的目标是，针对FIFE研究区域的代表性样区，表征土壤表面二氧化碳通量的特征。此类测量是解析北美草原碳收支的必要基础，同时也是借助微气象法（micrometeorological methods）将光合作用植被模型与二氧化碳通量实测结果开展对比的必备条件。土壤表面二氧化碳通量是北美草原生态系统碳收支的核心组成部分之一。本研究结果表明，若将土壤箱（soil chamber）置于连通自由大气的封闭系统中运行，即可通过该装置获取精度可靠的土壤表面二氧化碳通量估算值。此外，草地土壤表面的二氧化碳通量可在生态系统碳收支中占据显著份额，绝不可被随意忽略。土壤温度与土壤含水量均为预测土壤表面二氧化碳通量的关键调控参数，而叶面积指数（leaf area index）则可作为根系呼吸所贡献的植物源通量的替代表征指标。