基于稳定碳同位素技术研究大气CO_2浓度升高对植物-土壤系统碳循环的影响

Investigation on effects of elevated atmospheric CO_2 concentration on plant-soil system carbon cycling:Based on stable isotopic technique

大气CO_2浓度升高影响植物光合作用过程和生物量积累,改变植物地上和地下生物量的动态分配.土壤有机质的形成和周转依赖于植物组分的输入,因此,CO_2浓度升高所造成的植物生理和代谢的变化对土壤碳库收支平衡具有重要影响.采用稳定碳同位素(^(13)C)技术研究土壤-植物系统的碳循环可阐明大气CO_2浓度升高条件下光合碳在植物各器官的分配特征和时间动态,明确光合碳在土壤中的积累、分解与迁移转化过程以及对土壤有机碳库周转的影响.本文综述了基于^(13)C自然丰度法或^(13)C示踪技术研究大气CO_2浓度升高对土壤-植物系统碳循环的影响,主要包括:1)对植物光合作用的同位素分馏的影响;2)对植物光合碳(新碳)分配动态的影响;3)对土壤有机碳新老碳库动态以及微生物转化过程的影响.明确上述过程及其调控机制可为预测CO_2浓度升高对陆地生态系统碳循环及源汇效应的长期影响奠定基础.

Elevated atmospheric CO2 affects plant photosynthesis process and biomass accumula- tion, furthermore alters the distribution of photosynthetic carbon （C） above- and below-ground. The formation and turnover of soil organic carbon （SOC） depends on the input of photosynthetic C, so the change of plant physiology and metabolism caused by increasing CO2 concentration will further affect the balance of SOC pool. Therefore, stable isotope 13 C technique is powerful for clarifying the influence of elevated atmospheric CO2 on C cycling in plant-soil system, including the distribution of photosynthetic C among plant organs, and the transformation and accumulation of photosynthetic C in soil. This review summarized research focused on the effects of elevated atmospheric CO2 on C cycling in terrestrial ecosystems based on 13C natural abundance or 13C tracing technique, inclu- ding： 1 ） isotopic fractionation effect in plant photosynthesis; 2） the distribution of photosynthetic C in plant organs ; 3） the transformation and stabilization of photosynthetic C in SOC driven by micro- bial process. Clarifying the above processes and controlling mechanisms is essential to predict long- term influence of elevated CO2 on C cycling and evaluate the source-sink function of SOC in terres- trial ecosystems.