森林土壤有机碳分解对模拟增温的响应

Responses of soil organic carbon decomposition to experimental warming in forest ecosystems

由化石燃料燃烧和土地利用变化引起的全球气候变暖是地球上最严重的人为干扰之一,对陆地生态系统结构和功能产生重要的影响。土壤有机碳(SOC)是陆地生态系统最大的碳库,其微小变化都会影响全球碳平衡和气候变化。近30年来,国内外学者在不同森林生态系统相继开展了野外模拟增温对SOC分解的影响及其调控机制研究。基于在全球建立的26个野外模拟气候变暖实验平台,系统分析增温对森林生态系统SOC分解的影响格局和潜在机制,发现增温通常促进森林SOC的分解,对气候变暖产生正反馈作用。然而,因增温方式和持续时间、土壤微生物群落结构和功能的多样性、SOC结构和组成的复杂性、植物-土壤-微生物之间相互作用以及森林类型等不同而存在差异,导致人们对森林SOC分解响应气候变暖的程度及时空格局变化缺乏统一的认识,且各类生物和非生物因子的相对贡献尚不清楚。基于已有研究,从土壤微生物群落结构和功能、有机碳组分以及植物-土壤-微生物互作3个方面构建了气候变暖影响SOC分解的概念框架,并进一步阐述了今后的重点研究方向,以期深入理解森林生态系统碳-气候反馈效应,为制定森林生态系统管理措施和实现“碳中和”提供科学依据。1)加强模拟增温对不同森林生态系统(特别是热带亚热带森林生态系统)SOC分解的长期观测研究,查明SOC分解的时空动态特征;2)加强土壤微生物功能群与SOC分解之间关系的研究,揭示SOC分解对增温响应的微生物学机制;3)形成统一的SOC组分研究方法,揭示不同碳组分对增温的响应特征和机制;4)加强森林生态系统植物-土壤-微生物间相互作用对模拟增温的响应及其对SOC分解调控的研究;5)加强模拟增温与其他全球变化因子(例如降水格局变化、土地利用变化、大气氮沉降)对SOC分解的交互作用,为更好评估未来全球变化背景下森林土壤碳动态及碳汇功能的维持提供理论基础。

Global climate warming,which arises from increased greenhouse gases because of fossil fuel combustion and land use change,is one of the most profound anthropogenic disturbances to our planet,seriously impacting the structure and function of terrestrial ecosystems.Soil organic carbon(SOC)is the largest carbon pool in terrestrial ecosystems,and its small changes will affect global carbon balance and climate changes.In the past 30 years,the mechanisms of increasing temperature on SOC decomposition have been studied in different forest ecosystems.In this study,we systematically analyzed the influence patterns and mechanisms of warming on SOC decomposition through 26 field warming experiments established in forest ecosystems worldwide.We found that warming generally promoted the decomposition of forest SOC and had a positive feedback effect on climate warming.However,due to the differences in warming types and durations,diversity of soil microbial community structure and function,the structure and composition of the SOC,plant-soilmicroorganism interactions,and forest types,we still lack a comprehensive and mechanistic understanding of the extent and spatial-temporal pattern of forest SOC decomposition in response to climate warming.The relative contributions of these biological and abiotic factors are unclear.We developed a conceptual framework of SOC decomposition under the warming context and considered microbial community composition and function,SOC fractions,and plant-soil-microorganism interactions.To improve our understanding of the carbon-climate feedback of forest ecosystems under warming and provide the scientific basis for formulating forest ecosystem management practices and realizing“carbon neutrality”,we further proposed future research directions on SOC decomposition.1)Investigate the long-term effects of warming on the SOC decomposition in different forest ecosystems,mainly tropical and subtropical forest ecosystems,to identify the spatialtemporal dynamic characteristics of SOC decomposition;2)probe into relationships between SOC decomposition and microbial functional community and their adaptation to long-term warming,to reveal the microbial mechanisms of SOC decomposition in response to warming;3)form a unified method of SOC fraction to reveal the response characteristics and mechanisms of different soil carbon components to warming;4)clarify the responses of plant-soil-microorganism interactions to the simulated warming and their regulations on SOC decomposition in forest ecosystems;5)explore the interactions of warming and other global change factors(e.g.,precipitation regime changes,land use changes,and atmospheric nitrogen deposition)on SOC decomposition to provide a theoretical basis for better assessment of forest soil carbon dynamics and maintenance of carbon sink function under future global changes.