Autotrophic and heterotrophic components of soil respiration caused by rhizosphere priming effects in a plantation

Abstract

Root-exudate inputs can stimulate the decomposition of soil organic carbon by priming microbial activity, but its ecological significance is still not fully understood. This study evaluated autotrophic respiration and heterotrophic respiration driven by roots using the13C natural abundance method in a Robinia pseudoacacia plantation. The results showed that the priming effect existed in deep soil of the plantation. The proportions of autotrophic respiration and heterotrophic respiration deriving from priming effect to total soil respiration varied with soil depth. Rhizomicrobial respiration (RMR) accounted for about 15% of the total soil respiration, and the rate of priming decomposition of soil organic matter (PSOM) was only about 5% of the total soil respiration. RMR was significantly positively correlated with PSOM. Heterotrophic respiration derived by the priming effect was too weak to have a positive impact on atmospheric CO2.