土壤呼吸对温度升高的适应

Acclimatization of soil respiration to warming

土壤呼吸是陆地生态系统碳循环的重要环节之一 ,其对温度升高的敏感程度在相当大的程度上决定着全球气候变化与碳循环之间的反馈关系。土壤呼吸对温度升高的适应是个比较普遍的现象 ,其表现形式主要为随着温度的持续升高和升温时间的延长 ,土壤呼吸对温度升高反应的敏感程度下降。产生这一现象的机制包括影响因子主导地位的转移和温度以外其他因子的协同变化。土壤呼吸对温度升高的适应可以视为碳循环对全球变暖的负反馈效应 ,它可能会在一定程度上缓和陆地生态系统对全球气候系统之间的耦合作用 ,并且导致土壤呼吸对全球温度升高响应的时空差异。由于目前生态系统模型多数没有考虑土壤呼吸的对温度升高的适应性 ,而采用统一的 Q1 0 值 。

Soil respiration is an important component of carbon cycle of terrestrial ecosystem, and is usually driven by temperature. Feedback between carbon cycle and global climate change is mostly determined by the sensitivity of soil respiration to warming.. The sensitivity of soil respiration to warming declines when temperature continually increases, or warming keeps much longer, which is a common phenomenon known as acclimatization. Main mechanisms involve transfer between dominant factors and change of other factors with temperature. There are many factors other than temperature that could impose different effects on soil respiration under certain temperatures, such as water content, soil nutrient, roots, soil microorganism, etc.,, which could play dominant roles when temperature is high enough. Those factors usually change with temperature, e.g. when temperature increases or warming continues for a prolonged time, soil might become dryer, labile carbon might be decreased, activity of enzyme related to respiration of soil microorganism and roots might be reduced, allocation of photosynthetic production to belowground might be depressed. Acclimatization of soil respiration is a negative feedback of carbon cycle to global warming, which could mitigate the coupling of terrestrial ecosystem and global climate, i.e., CO_2 efflux from soil stimulated by warming would be restricted by the acclimatization in some degree. Because of acclimatization of soil respiration to warming, CO_2 flux from soil responding to global climate change is likely to be complex and highly variable spatially and temporally. Modeling is a necessary approach for predicting or simulating how ecosystem responds to climate change, but most of the currently used models do not take into account of the sensitivity of soil respiration to temperature. A fixed Q_(10) might result in large errors or biases when predicting CO_2 flux from soil and future climate conditions.