综论土壤呼吸各组分区分方法

Review on the Approaches of Separating Autotrophic and Heterotrophic Components of Soil Respiration

研究土壤呼吸各个组分对土壤总呼吸的贡献是定量评价植物和土壤碳平衡及能量平衡的重要基础。目前区分土壤有机质分解呼吸和根呼吸的方法主要有成分综合法、壕沟法、根分离法、林隙法、根生物量外推法、同位素法,区分纯根呼吸和根际微生物呼吸的方法有同位素稀释法、模拟根际沉降物法1、4CO2动态法、根系分泌物洗涤法、1δ3C微生物量法及一些非同位素法的联合。土壤呼吸各组分区分研究中,区分纯根呼吸和根际微生物呼吸将是未来研究的一个重大课题,区分方法的改进、完善和创新,不同区分方法间的比较研究将是未来研究的一个重要方向。

Soil respiration is an important part of global carbon cycle, which accounts for about 25% of the global carbon dioxide exchange. Estimating the contribution of soil organic material （ SOM-derived ） respiration, root respiration and rhizomicrobial respiration to total soil CO2 efflux and the carbon distribution between actual root respiration and rhizodeposits is crucial in determining the carbon and energy balance of plant and soil. Up to date a large amount of the researches have been done on partitioning total soil respiration into autotrophic and heterotrphic components and great progress has been achieved. But it is still very difficult to discriminate between the CO2 directly derived from actual root respiration and that derived from mineralization of rhizodeposits, and this has presented one of the greatest challenges to quantifying rhizosphere C-flow. Several methods have been suggested to separate SOM-derived respiration and root-derived respiration （including actual root respiration and rhizomicrobial respiration）： （1） integration of component method, （2） trenching method, （3） root-excising method, （4） gap formation method, （5） root mass extrapolation method, and （6） isotope method. Also there are several methods to separate actual root respiration and rhizomicrobial respiraton： （1） isotope dilution method, （2） model rhizodeposition method, （3） 14CO2 dynamics method, （4） exudate elution method, （5） 13C of CO2 and microbial biomass and （6） combination of some no-isotopic methods. This review has described the basic principles and assumptions of these methods and compared the results obtained in the original research papers.