Thinning shelter forest reduced the soil priming effect and soil microbial respiration by altering the contribution of soil organic carbon from different sources

Abstract

Thinning affects the understorey microclimate and the material input into the shelter forest soil, and it alters the contribution of the plant-derived and microbial-derived carbon (C). This difference effects the utilization of C by soil microbes and ultimately soil C emission. There is still no adequate characterization for the contribution of plant-derived and microbial-derived C to soil organic C (SOC) under thinning. Moreover, how this difference affects microbially driven C emissions (soil microbial respiration, SMR) and the contribution to the soil priming effect in this process are still unknown. The contribution of plant-derived and microbial-derived C to SOC were quantified by comparing lignin phenols and amino sugars under thinning and control treatments. Meanwhile, a 30-day indoor cultivation experiment was conducted. Soil priming effect and SMR were tested by adding 13C-labelled glucose to the soil of the thinning and control treatments. The purpose was to investigate the contribution of C from different sources to SOC, as well as its influence mechanism on soil priming effect and SMR.The results indicate that thinning significantly increased the fungal-derived (10.19 and 7.34 g kg−1) and microbial-derived C (11.05 and 8.19 g kg−1) of Quercus acutissima Carruth (QAC) and Pinus thunbergii Parl (PTP). However, the bacterial-derived C (0.86 and 0.85 g kg−1) decreased. Compared to the control treatment, the plant-derived, fungal-derived and microbial-derived C increased by 6.6 % and 1.1 %, 17.9 % and 12.2 %, and 16.6 % and 10.1 %, respectively, while bacterial-derived C decreased by 1.3 % and 2.1 %. Thinning reduced the soil priming effect of QAC by lowering the pH and increasing F/B and fungal-derived C. At the same time, this phenomenon was not evident in PTP, mainly attributed to the content of SOC and vanillyl and syringyl monomers. Thinning reduced the SMR, which was mainly related to the suppression of soil priming effect. In summary, this study has demonstrated that thinning reduced the soil priming effect and SMR of shelter forests by altering the contribution of plant-derived and microbial-derived C to SOC.