草地土壤呼吸对全球变化的响应

Respondence of Grassland Soil Respiration to Global Change

草地是陆地生态系统主体生态类型之一,其土壤呼吸是全球碳循环的重要过程之一,草地土壤呼吸的动态变化将直接影响全球碳平衡。相对于其他陆地生态系统,草地对全球变化的响应更为迅速。因此,在全球变化的趋势下,草地土壤呼吸将首先受到影响。本文综述了全球变化下CO2浓度上升、全球气温升高、全球降水增多、放牧、草地农垦以及土地利用管理措施(施肥、灌溉)的草地土壤呼吸响应。土壤呼吸对大气CO2浓度上升和全球气温升高的响应都存在增加、减少和无显著变化3种情况,这与大气CO2浓度上升和全球气温升高引起的土壤含水量、土壤N的可利用性等因素的改变与否有关。土壤呼吸Q10受到土壤温度、土壤含水量、降水、土壤深度、土壤有机碳、海拔高度、土地利用方式和时间尺度等因素的影响。降水增多一般可以促进土壤呼吸,但降水引起的温度以及土壤通透性的降低也会导致土壤呼吸的降低。因放牧强度、频度和方式的差异,放牧对土壤呼吸的影响出现增加、减少和无显著影响的不同结果;人工剪草对土壤呼吸及其各组分的影响也存在差异。草地农垦后,土壤呼吸增强,土壤碳损失约为20%～50%。施肥对土壤呼吸的影响有增加、减少和无显著影响,因肥料种类和施用剂量等而异。在干旱和半干旱地区,灌溉会促进草地土壤呼吸。但是,目前全球变化对草地土壤呼吸的综合影响尚不清楚,因此深入探讨草地土壤呼吸对全球气候变化和土地利用变化的响应等仍是今后努力的主要方向。

Grassland is one of the main terrestrial ecotypes and the dynamic change of its soil respiration can directly affect the global C cycle.Grassland responses more rapidly to global C cycle than other terrestrial ecosystems.Therefore,grassland soil respiration could be firstly affected by global climate change and land use change.The objective of this paper is to provide a scientific review on grassland soil respiration response to global change and human activities.The elevated atmospheric CO 2 and rising temperature can both stimulate, suppress or show no significant effect on grassland soil respiration,depending on whether changes of soil moisture,soil available N and other related factors occur or not.The Q 10 ,which is the temperature sensitivity index of soil respiration,of grassland soil respiration is affected by soil temperature,soil moisture,precipitation,soil depth,soil organic carbon,altitude,land use patterns,time scales and other related factors.This implies that the relationships between grassland soil respiration and soil temperature is affected by other factors and grassland soil respiration is actually affected by the combined effects of multiple factors.Increasing precipitation will generally stimulate grassland soil respiration.However,the decrease of soil temperature and soil permeability which are caused by precipitation will reduce soil respiration amount.Due to grazing intensity,grazing frequency and grazing forms,the impact of grazing on soil respiration appears to increase,decrease or show no significant effect.The effects of clipping on soil respiration and its components（soil heterotrophic respiration and root respi-ration）are different.When agricultural reclamation occurs in grassland,soil respiration could enhance and the soil carbon will lose approximately 20%-50%.Fertilization might increase,decrease or show no significant effect on grassland soil respiration,according to fertilizer type,loading levels and so on.In the arid and semi-arid regions,irrigation might promote grassland soil respiration.However,the integrated effects of these global changes,i.e.,elevated atmospheric CO 2 ,rising temperature,increasing precipitation,grazing,land reclamation, fertilization and irrigation,are unclear.Therefore,the research on the respondence of soil respiration to global climate change and land use change should be enhanced in the future.