土壤呼吸温度敏感性(Q₁₀)是模拟全球变暖背景下生态系统碳释放强度的一个重要参数，实验研究表明Q₁₀受多种环境因素的影响，因而具有显著的空间异质性。目前大多数生物地球化学模型采用的是一个简化的常数值，这无疑增大了未来气候变化预测的不确定性。地表过程与资源生态国家重点实验室周涛与史培军等人，在生态系统碳循环过程模型和土壤有机碳观测资料的基础上，反演了Q₁₀的全球分布格局，并探讨了其分布对碳－气候反馈的潜在影响。

研究结果表明：土壤有机碳与土壤呼吸等观测资料能够有效反演Q₁₀值的空间分布；反演的Q₁₀值具有很高的空间异质性。与常数值相比，Q₁₀值的空间分布格局能够更有效地模拟不同空间格点的土壤呼吸，从而提高其模拟精度。Q₁₀值的空间分布格局对全球碳－气候反馈的影响显著，当模型考虑Q₁₀值的空间差异时，全球变暖与碳释放之间的反馈强度远大于采用常数值时的模拟结果。

 

 

Figure. Spatial pattern of the optimal Q₁₀ values. In general, tundra, C₃ and C₄ grasslands, shrublands, and croplands have higher Q₁₀ values than deserts, bare grounds, broadleaf deciduous forests, and woodlands

Global pattern of temperature sensitivity of soil heterotrophic respiration (Q₁₀) and its implications for carbon-climate feedback

Tao Zhou, Peijun Shi, Dafeng Hui, and Yiqi Luo

 

Temperature sensitivity of soil respiration (Q₁₀) is an important parameter in modeling effects of global warming on ecosystem carbon release. Experimental studies of soil respiration have ubiquitously indicated that Q₁₀ has high spatial heterogeneity. However, most biogeochemical models still use a globally constant Q₁₀ in projecting future climate change, partly because no spatial pattern of Q₁₀ values has been derived. In this study, an inverse analysis was conducted to retrieve a global pattern of spatially heterogeneous Q₁₀ values by assimilating data of soil organic carbon into a process-based terrestrial carbon model. The estimated Q₁₀ values were, in turn, incorporated into soil respiration models to evaluate their impacts on global respiratory carbon release from soil (i.e., total soil respiration is equal to microbial and root respiration) and from microbial decomposition (i.e., heterotrophic respiration). The results show that the observed soil organic carbon content and soil respiration offer good constraints on estimation of Q₁₀ values in different spatial grids. Estimated Q₁₀ values have a high spatial heterogeneity and are regulated by many spatially heterogeneous environmental factors. Q₁₀ values vary with biome types and, in general, are higher at high-latitudinal bands. The derived spatially heterogeneous Q₁₀ values result in better soil respiration estimation at different sites than the globally invariant Q₁₀. The feedback intensity of total soil respiration and heterotrophic respiration to climate warming would be underestimated by about 40% and 25%, respectively, if a globally invariant Q₁₀ rather than spatially heterogeneous Q₁₀ values are used in models.

 

 

 

 

 

 

 

Journal of Geophysical Research,2009

http://www.agu.org/pubs/crossref/2009/2008JG000850.shtml