陆地生态系统土壤呼吸、氮矿化对气候变暖的响应

土壤呼吸和氮矿化对气候变暖的响应是影响陆地生态系统碳收支的主要因素之一,也是当前全球变化研究的主要内容之一。短期内温度升高能明显提高土壤呼吸速率,随着温度的进一步升高和升温时间的延长,土壤呼吸速率对温度升高的敏感性可能逐渐降低。由于土壤呼吸的温度敏感性与土壤水分含量、气候、植被、凋落物等多种因素有关,并随时间和空间的变化而变化,因此,用一个固定的Q10（土壤呼吸的温度敏感系数）来计算土壤呼吸对温度升高响应的量,会给研究结果带来很大的不确定性。生态系统对气候变暖的响应除了直接的反应外,还具有复杂的适应性。尽管模拟研究表明未来气候变暖将使土壤呼吸增加,但是有关土壤呼吸对气候变化适应性的试验数据比较少,对未来气候变化背景下土壤呼吸的模拟仍有很大的不确定性。气候变暖将促进土壤氮素的矿化速率,其影响程度的强弱不仅与温度有关,而且与土壤基质的质量与数量、土壤水分、升温持续的时间等有关,这使目前有关研究结果出现了很大的不确定性。针对上述研究中存在的问题,今后应统一土壤呼吸的测定方法,区分土壤呼吸各组分对温度升高的响应,在研究土壤呼吸和氮矿化对温度升高的响应时结合考虑其它因素能在一定程度上减少研究结果的不确定性。

The Responses of Soil Respiration and Nitrogen Mineralization to Global Warming in Terrestrial Ecosystems

Study on the responses of soil respiration and nitrogen mineralization to global warming is very important to understand the balance of the terrestrial carbon budget. Soil respiration will increase as temperature increase in short-term. However, it would have no sensitivity to wanning or acclimation in long-term. The temperature sensitivity of soil respiration is heterogeneous temporally and spatially since it is controlled by environmental factors such as soil water content, climate, vegetation, litters and so on. Therefore, many uncertainties will be unavoidable when a fixed Q10 is used to calculate the variations of soil respiration. The responses of terrestrial ecosystems to warming have complex acclimations besides direct reactions. Although the results of modeling suggest that soil respiration would increase due to global warming, big uncertainties still exists in modeling soil respiration due to lacking of measurements about acclimation of soil respiration to warming. Soil nitrogen mineralization rates are promoted by the global wanning. The extents of effects are related to not only temperature, but also soil substrate quality and quantity, soil water, the duration time of increasing temperature and so on. Due to the integrated effects of these factors, many uncertainties appear. The problems above will be solved by use of uniform methods, distinguishing of the responses of different components of soil respiration to wanning, and consideration of other factors such as both increases and decreases in the quantity and distribution of region precipitation, increased N deposition and elevated atmospheric CO2 concentration.