Patterns and Determinants of Microbial- and Plant-Derived Carbon Contributions to Soil Organic Carbon in Tea Plantation Chronosequence

Tea plantation soils have great potential for carbon (C) sequestration because of the perennial nature of tea plants. Long-term tea plantations can lead to soil acidification. However, how the dynamics of soil organic carbon (SOC) stocks and its molecular composition respond to tea plantation establishment remains unclear. Amino sugars and lignin phenols were used as biomarkers for microbial necromass and plant lignin components to investigate the changes in their distribution to SOC across a tea plantation chronosequence (1-, 7-, 16-, 25-, and 42-year old), thus providing a holistic perspective of SOC formation and stabilization. Long-term tea plantation increased SOC content and the levels of amino sugars and lignin phenols, but reduced microbial biomass C despite an increase in dissolved organic C. Comparatively, the contribution of microbial-derived C to SOC was lower than that of plant-derived C. Despite the increased levels of amino sugars over the time-course, the proportion of bacterial-derived C in the SOC decreased, reflecting diluted contributions of bacterial residues to the SOC pool. Further, the decrease in soil pH and microbial biomass C over time resulted in shifts in the contribution of bacterial and fungal residues the pool, with an increase in the contribution of fungal residues. These findings provide new insights into changes in SOC accumulation in long-term tea plantations, highlighting an increase in soil C sequestration associated primarily by the presence of lignin phenols. This build up is affected by abiotic (physical and chemical protection) and biotic factors including increased dominance of fungal residues inputs.