LI-COR产品测得涡度协方差数据助力科学家发重要文章

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近日，美国科学家M. A. Rawlins等人发表了一篇题为《Assessment of model estimates of land-atmosphere CO₂ exchange across Northern Eurasia》的文章，文中用到了横跨欧亚大陆北部流域4个研究区域的6个通量塔获取的涡度协方差数据，对净生态系统生产力（NEP）及其组分总初级生产力（GPP）、生态系统呼吸（ER）和土壤碳的滞留时间进行了系统分析，从而使用涡度协方差的测量方法对多种陆地-大气层CO₂交换的模型进行了有效的评估。该项研究在通量观测领域一经问世便获得了大量的关注，其中通量塔的数据均由LI-7500A CO₂/H₂O分析仪，LI-7200 CO₂/H₂O分析仪，和LI-7700开路式CH₄分析仪测量得到。

文章原文摘要：

Abstract. A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO₂) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary roductivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960–2009 at 0.5_ resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO₂ fluxes derived from sitebased eddy covariance measurements as well as regionalscale GPP estimates based on satellite remote-sensing data.

The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g Cm^-2 yr^-2, equivalent to 3 to 340% of the respective model means, over the analysis period. For the multimodel average the increase is 135% of the mean from the first to last 10 years of record (1960–1969 vs. 2000–2009), with a weakening CO₂ sink over the latter decades. Vegetation net primary productivity increased by 8 to 30% from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO₂ sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model elements controlling vegetation productivity and soil respiration as being needed for reducing uncertainty in landatmosphere CO₂ exchange. These advances will require collection of new field data on vegetation and soil dynamics, the development of benchmarking data sets from measurements and remote-sensing observations, and investments in future model development and intercomparison studies.

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http://www.biogeosciences.net/12/4385/2015/bg-12-4385-2015.pdf

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