Separation of soil respiration; a site-specific comparison of
partition methods
Abstract. Without accurate data on soil heterotrophic respiration (Rh), assessments of soil carbon (C) sequestration rate and C balance are challenging to produce. Accordingly, it is essential to determine the contribution of the different sources of the total soil CO2 efflux (Rs) in different ecosystems, but to date, there are still many uncertainties and unknown regarding the soil respiration partitioning procedures currently available. This study compared the suitability and accuracy of five different Rh/Rs partitioning methods in a subtropical forest: (1) regression between root mass and root derived CO2; (2) root exclusion bags with intact soil blocks; (3) root exclusion bags with hand-sorted roots; (4) lab incubations with minimally disturbed soil microcosm cores; and (5) soil δ13C-CO2 natural abundance. The relationship between Rh and soil moisture and temperature was also investigated. A qualitative evaluation table of the partition methods with five performance parameters was produced. The Rs was measured weekly from February 3rd to April 19th 2017 and found to average 6.1 ± 0.3 Mg C ha−1 y−1. During this period, the Rh measured with the in-situ mesh bags with intact soil blocks and hand-sorted roots were estimated to contribute 49 ± 7 % and 79 ± 3 % of Rs respectively. The Rh percentage estimated with the root mass regression, microcosm incubation and δ13C-CO2 natural abundance were 54 ± 41 %, 8–17 % and 61 ± 39 % respectively. Overall, no systematically superior or inferior Rh/Rs partition method was found. The paper discusses the strengths and weaknesses of each technique with the conclusion that combining two or more methods optimizes Rh assessment reliability.