大气CO_(2)浓度和温度升高对农田土壤碳库及微生物群落结构的影响

Effects of Elevated CO_(2) Concentration and Warming on Soil Carbon Pools and Microbial Community Composition in Farming Soil

大气CO_(2)浓度和温度升高会通过影响作物的光合作用,从而影响光合碳向土壤中的输送。输入到土壤中光合碳含量的变化势必会对土壤外源碳的主要分解者--微生物的群落结构产生影响。土壤微生物在土壤有机质的转化过程中发挥着重要的作用,是土壤碳循环的主要驱动者,其群落结构和功能的改变会影响土壤有机质的动态变化,而这些变化会进一步增加或者降低大气中的CO_(2)浓度,从而对气候变化产生反馈作用。未来土壤的碳平衡取决于大气CO_(2)浓度和全球变暖对土壤中碳的输入、输出以及碳在土壤中的驻留时间。因此,只有全面了解大气CO_(2)浓度和温度升高将对土壤碳库及土壤微生物群落结构产生何种影响,才能明确地揭示陆地生态系统对气候变化的反馈机制,对未来农田土壤有机碳库的管理和生产力的维持有重要意义。文章综述了大气CO_(2)浓度和温度升高及其交互作用对土壤碳库和土壤微生物群落结构的影响。主要结论为:(1)大气CO_(2)浓度和温度升高对土壤碳库的影响可以相互抵消,但是土壤碳库是否成为碳“源”与温度升高的幅度密切相关;(2)大气CO_(2)浓度升高增加了光合碳在玉米、小麦等植株各部分的分配,温度升高同样对光合碳的分配规律产生影响,但对不同部位的影响不一致,多呈降低或无显著影响;(3)大气CO_(2)浓度和温度升高可能对土壤微生物活性及其群落结构产生交互影响,且对不同微生物(细菌、真菌和古菌)群落的影响程度不同,进一步对土壤有机碳的转化产生影响。最后提出未来的研究方向:(1)从气候变化影响植物-土壤互作角度解析根系分泌物的转化过程及其对微生物的影响;(2)通过DNA-SIP进一步研究大气CO_(2)浓度和温度升高条件下土壤微生物对不同植物来源碳的选择性利用与碳循环的关系,从而阐明气候变化条件下微生物底物利用策略以及微生物群落结构的变化。

Elevated atmospheric CO_(2) concentration(eCO_(2))and warming may affect the crop photosynthesis,and consequently alter the translocation of photosynthetic carbon to soil.Under climate change,the change of photosynthetic carbon retained in soil may shape the structure of microbial community involved in photosynthetic carbon transformation.As a major driver of soil carbon cycle,soil microorganism plays an important role in the transformation of soil organic matter.The changes of microbial community structure and function under climate change are likely to affect the turnover of soil organic matter,resulting in an increase or decrease in the concentration of atmosphere CO_(2) as a feedback to climate change.Soil carbon balance depends on the input and output of carbon in the soil and its retention in the soil.However,it is unclear that how climate change may affect the stability of the soil carbon pool.Therefore,the change of the soil carbon pool corresponding with soil microbial community structure is the core mechanism of terrestrial ecosystem in response to climate change,which is important to the management of soil organic carbon and the maintenance of soil productivity on farmland in the future.This paper reviewed the responses of soil carbon pool and soil microbial community structure to global climate change(eCO_(2) and warming).The main conclusions were as follows:(1)Elevated CO_(2) and warming exhibited the tradeoff effect on soil carbon pools,but whether soil carbon pool became carbon source depended on the extent of warming;(2)Elevated CO_(2) increased the accumulation of photosynthetic carbon in plant parts of corn and wheat.Warming also posed an impact on the accumulation of photosynthetic carbon,but the impact varied among different parts with negative or no effect;(3)Warming and eCO_(2) showed a cumulative effect on soil microbial activity and community diversity,but different microbial kingdoms(bacteria,fungi and archaea)had different roles to affect carbon turnover.Finally,it was proposed that the future research directions included:(1)in-depth study on the impact of climate change on the turnover of root exudates considering the plant-soil interaction and its influence on microbial properties;(2)DNA-SIP being applied to explore the relationship between different plant-carbon sources utilized by soil microorganisms and carbon cycling under eCO_(2) and warming.Thus,these proposed studies might clarify substrate-utilizing strategies by microbes and the response of microbial community to climate change.