干湿交替对土壤呼吸和土壤有机碳矿化的影响述评

土壤干湿交替循环对土壤呼吸的“激发效应”被证实在干旱、半干旱和地中海气候区普遍存在。土壤干湿交替被认为是影响土壤呼吸的重要因素。土壤物理、化学、生物性状会在干湿交替过程中发生一系列变化,引发土壤CO₂排放量显著激增而引起“Birch效应”。随着未来气候变化下极端降水天气事件发生频率的增加,降雨强度和频率的改变将导致部分地区的土壤经受更广泛和频繁的干湿交替作用,加剧土壤干湿循环,影响土壤呼吸。重点论述了干湿交替对土壤碳素循环各个关键过程(尤其是土壤呼吸和SOC矿化)的影响效应,归纳总结了干湿交替对土壤碳素循环的影响机制,从土壤团聚体、根系呼吸、微生物呼吸等方面阐述了干湿交替对土壤呼吸和土壤有机碳(SOC)矿化激发效应的影响及其机理。综合生理学说与物理学说观点,认为干湿交替主要通过土壤结构、SOC的分解速率、土壤微生物群落的结构与稳定性等的改变来影响土壤呼吸和SOC矿化过程。目前,关于干湿交替对土壤碳素循环关键过程影响的研究结果还不尽一致,其影响机制尚不明晰,研究方法也还有一些不足之处。简要指出了目前研究过程中存在的一些不足,并对未来研究中值得深入研究的科学问题进行了探讨与展望。

Review on the Effects of Soil Alternate Drying-Rewetting Cycle on Soil Respiration and Soil Organic Carbon Mineralization

Soil respiration priming effect caused by alternate drying-rewetting cycle is proved to commonly existe in arid,semi-arid and Mediterranean climate zones.Soil alternate drying-rewetting cycle is regarded as an important factor that influences soil respiration.During the soil alternate drying-rewetting process,a series of physical,chemical and biological changes happened,which leads to the‘Birch effect’caused by the significant increase of soil CO₂ emission.Under the future climate change,increasing frequency and intensity of extreme rainfall events is expected to happen,the extension and frequency of soil alternate drying-rewetting cycle may be enhanced in some regions,which will lead to the changes in soil moisture,intensify the soil drying-rewetting cycle,and in turn lead to soil respiration changes.We summarized the research progresses and underlying mechanisms of the effects of soil alternate drying-rewetting cycle on key processes of soil C cycling(especially soil respiration and priming effect of soil organic matter mineralization)from the aspects of soil aggregate,root respiration,and microbial respiration.Based on the comprehensive understanding of the theories of physiology and physics,it is concluded that soil alternate drying-rewetting mainly affects soil respiration and soil organic carbon mineralization by changes of soil structure,soil organic carbon decomposition rate,and structure and stability of soil microbial community.At present,available results of the effects of soil alternate drying-rewetting cycle on the key processes of soil carbon cycling(soil respiration and soil organic carbon mineralization)remain not consistent.The underlying mechanism is still not clear and some research methodological deficiencies need to be further explored and improved.In the end,some deficiencies in current research and possible key topics in the future study are proposed and pointed out.