由植物和微生物在地下所产生并释放到大气中去的二氧化碳（这个过程被称为“土壤呼吸”），构成第二大“陆地碳通量”。 来自美国University of Maryland，College Park 的Ben Bond-Lamberty 和Allison Thomson利用一个20年（1989-2008）的土壤呼吸测量结果数据库发现，不仅土壤呼吸在随时间增加，而且这种增加与温度变化强相关。他们估计，全球土壤呼吸总量在以每年约0.1%的速度增加，说明它对气温有一定敏感度。这与最近几十年陆地碳循环的加速是一致的。
参考文献：Nature 464, 579 (2010). doi:10.1038/nature08930
Temperature-associated increases in the global soil respiration record
Authors: Ben Bond-Lamberty & Allison Thomson
Soil respiration, RS, the flux of microbially and plant-respired carbon dioxide (CO2) from the soil surface to the atmosphere, is the second-largest terrestrial carbon flux. However, the dynamics of RS are not well understood and the global flux remains poorly constrained. Ecosystem warming experiments, modelling analyses and fundamental biokinetics all suggest that RS should change with climate. This has been difficult to confirm observationally because of the high spatial variability of RS, inaccessibility of the soil medium and the inability of remote-sensing instruments to measure RS on large scales. Despite these constraints, it may be possible to discern climate-driven changes in regional or global RS values in the extant four-decade record of RS chamber measurements. Here we construct a database of worldwide RS observations matched with high-resolution historical climate data and find a previously unknown temporal trend in the RS record after accounting for mean annual climate, leaf area, nitrogen deposition and changes in CO2 measurement technique. We find that the air temperature anomaly (the deviation from the 1961–1990 mean) is significantly and positively correlated with changes in RS. We estimate that the global RS in 2008 (that is, the flux integrated over the Earth’s land surface over 2008) was 98 ± 12 Pg C and that it increased by 0.1 Pg C yr-1 between 1989 and 2008, implying a global RS response to air temperature (Q10) of 1.5. An increasing global RS value does not necessarily constitute a positive feedback to the atmosphere, as it could be driven by higher carbon inputs to soil rather than by mobilization of stored older carbon. The available data are, however, consistent with an acceleration of the terrestrial carbon cycle in response to global climate change.