¹³C Labelling of Litter Added to Tea (<i>Camellia sinensis</i> L.) Plantation Soil Reveals a Significant Positive Priming Effect That Leads to Less Soil Organic Carbon Accumulation

Abstract

Although annual return of litter occurs in tea (Camellia sinensis L.) plantations, the level of soil organic carbon (SOC) therein remains relatively low. The exact impacts of pruned litter on soil and its association with SOC accumulation in tea plantations remain unclear. In this study, we prepared 13C-labeled tea plant material and incubated it with soils collected at a tea plantation. Carbon dioxide (CO2) efflux and its sources were measured and distinguished based on the 13C isotopic method. Soil microbial community and the utilization of litter C were assessed by phospholipid fatty acid (PLFA) analysis combined with a stable isotope probing (SIP) technique. Litter incorporation initially significantly increased CO2 efflux. The majority of CO2 production (>90%) arose from native SOC mineralization, which was reflected by a strong positive priming effect (PE) that decreased over time. During the incubation period, β-glucosidase activity significantly decreased in both the control and litter-amended soil. A significant difference in the microbial community was observed between control and litter-amended soil, in which litter incorporation significantly increased the biomass of each microbial group relative to control soil. Based on PLFA-SIP, 78% of the C incorporated into individual microbes was derived from native SOC, while only 22% was derived from litter. Additionally, partial least squares regression path modeling (PLS-PM) revealed that the microbes associated with native SOC mineralization directly affected the changes in SOC (ΔCSOC+litter), whereas microbes related to litter degradation exhibited an indirect effect on ΔCSOC+litter by affecting β-glucosidase activity under litter incorporation. Taken together, SOC accumulated less in the tea plantation system despite the annual return of pruned litter to the field.

Keywords

• tea litter
• native SOC
• priming effect
• ¹³C-PLFA-SIP
• microbial community
• PLS-PM