Separate estimation of root respiration and rhizomicrobial respiration by means of δ~(13)C of soil microbial biomass

摘要

The total CO_2 efflux from planted soil (without plant remainders of previous crops) consists on three main sources: 1. CO_2 originated from microbial decomposition of soil organic matter (SOM) 2. Co_2 originated from microbial decomposition of rhizodeposits = rhizomicrobial respiration (RMR) 3. CO_2 originated from actual root respiration (RR) By using different tracer methods, important progress has been made during the last 10-20 years in the separation of the first CO_2 source from the sum of the two last sources (= root derived CO_2). However, there are still not any apropriable methods allowing the separation of RMR from RR in non-sterile soils. Accordingly to Killham and Yeomans (2001): "Discriminating between Co_2 which is directly derived from root respiration and that which is derived from mineralization of the components of C-flow is exceptionally difficult and has presented one of the greatest challenges to quantifying rhizosphere C-flow".