Retention of harvest residues promotes the accumulation of topsoil organic carbon by increasing particulate organic carbon in a Chinese fir plantation

Background:As commonly used harvest residue management practices in subtropical plantations,stem only harvesting (SOH) and whole tree harvesting (WTH) are expected to affect soil organic carbon (SOC) content.However,knowledge on how SOC and its fractions (POC:particulate organic carbon;MAOC:mineral-associated organic carbon) respond to different harvest residue managements is limited.Methods:In this study,a randomized block experiment containing SOH and WTH was conducted in a Chinese fir(Cunninghamia lanceolata) plantation.The effect of harvest residue management on SOC and its fractions in topsoil(0-10 cm) and subsoil (20-40 cm) was determined.Plant inputs (harvest residue retaining mass and fine root biomass) and microbial and mineral properties were also measured.Results:The responses of SOC and its fractions to different harvest residue managements varied with soil depth.Specifically,SOH enhanced the content of SOC and POC in topsoil with increases of 15.9%and 29.8%,respectively,compared with WTH.However,SOH had no significant effects on MAOC in topsoil and SOC and its fractions in subsoil.These results indicated that the increase in POC induced by the retention of harvest residue was the primary contributor to SOC accumulation,especially in topsoil.The harvest residue managements affected SOC and its fractions through different pathways in topsoil and subsoil.The plant inputs (the increase in fine root biomass induced by SOH) exerted a principal role in the SOC accumulation in topsoil,whereas mineral and microbial properties played a more important role in regulating SOC dynamics than plants inputs in subsoil.Conclusion:The retention of harvest residues can promote SOC accumulation by increasing POC,and is thus suggested as an effective technology to enhance the soil carbon sink for mitigating climate change in plantation management.