植被变化对气候的反馈机制及调节效应

Feedback mechanisms and regulatory effects of vegetation change on climate

植被通过光合作用固定大气中的CO_(2)来减缓温室效应,同时植被也通过改变地表能量收支影响温室效应。在过去的气候-植被研究中,大多关注气候变化对植被的影响,而植被对气候反馈的研究相对较少。植被通过调节地表能量收支、水通量等重要地气过程影响局地、区域乃至全球气候,在气候变化中的作用十分重要。因此,需要厘清植被对气候的反馈效应机制及其结果,并识别其地域差异。从生物地球物理和生物地球化学过程两方面分析植被与气候之间的作用机制,对全球及关键区域内植被变化对局地、区域乃至全球的气候反馈效应进行了系统总结:(1)生物地球物理反馈的区域特征明显,生物地球化学反馈则表现在全球尺度上,二者相互作用但难以统一;(2)植被破坏带来的气候影响在气温效应方面与生态系统的类型及地理分布相关:热带森林破坏带来增温效应,北方森林破坏带来降温效应,温带森林破坏则会通过增加森林反照率抵消丢失的固碳降温效应,气温效应表现不明显;(3)当前研究对关键过程机制考虑不够完善,不同研究方法的结果差异较大,且缺乏高质量观测数据的验证;同时考虑生物地球物理和生物地球化学的净气候反馈研究尚无法支撑植树造林对气候变化单一减缓作用的常规理解。本文可为科学评估植树造林对气候变化作用的方向与强度提供理论依据。

Vegetation mitigates the greenhouse effect by fixing atmospheric CO_(2)through photosynthesis,while vegetation also affects the greenhouse effect by altering the surface energy balance.In the past climate-vegetation studies,most of them focused on the effects of climate change on vegetation,while relatively few studies on vegetation feedback on climate.Vegetation affects local,regional and even global climate by regulating surface energy balance and water fluxes,and its role in climate change is vital.Therefore,it is extremely important to clarify the mechanisms of vegetation feedback effects on climate and their outcomes and to identify their geographical differences.In this paper,we analyze the mechanisms between vegetation and climate in terms of biogeophysical and biogeochemical processes,and systematically summarize the feedback effects of vegetation restoration/destruction on local,regional,and even global climate in global and key regions.show that:(1)the regional characteristics of biogeophysical feedback are obvious,while biogeochemical feedback is manifested at the global scale,and the two interact with each other but are difficult to be unified;(2)The climate effects of vegetation destruction is related to the type and geographical distribution of forest ecosystems in terms of temperature effect:tropical forest destruction brings warming effect,temperate forest destruction will offset the lost carbon sequestration and cooling effect by increasing forest albedo,and boreal forest destruction brings cooling effect;(3)The current study does not consider the critical process mechanisms well enough,the results of different research methods vary widely,and the results lack the validation of high-quality observation data from multiple sources,while the net climate feedback studies considering biogeophysical and biogeochemical are not yet able to support the conventional understanding of the single mitigation effect of afforestation on climate change.It has been widely recognized that afforestation mitigates climate warming by increasing the carbon sink function,but the net climate effect of afforestation depends not only on the carbon cycle process,but also on the surface albedo,evapotranspiration,soil water cycle,heat absorption process by water evaporation and aerosol concentration and process,so the study of the climate feedback effect of afforestation still has many problems to be solved.In this paper,we summarized the problems of the current research on the effect of vegetation on climate feedback,and proposed the future direction of related research,providing a theoretical basis for scientific assessment of the direction and intensity of the effect of afforestation on climate change.