Review on the Approaches of Separ ating Autotrophic and Heterotrophic Components of Soil Respir ation
综论土壤呼吸各组分区分方法

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.