Management regimes underpin soil carbon accrual following forest conversion to tea plantations across China

Forest conversion to tea plantations, a land use change type widely practiced in China due to the high economic value of tea plantations, is thought to reduce soil organic C (SOC) levels. However, changes in SOC following the conversion at the national scale and the mechanisms involved are not well understood. Here, we conducted a large-scale pairwise (tea plantation versus adjacent forest plots) soil sampling involving 176 plots (88 pairs) across China. Forest conversion had divergent effects on SOC, with significant increases in 47 pairs and significant decreases in other pairs. Changes in SOC, particulate organic C (POC), and mineral-associated organic C (MAOC) following conversion to tea plantations were mainly associated with changes in amino sugars rather than lignin phenols and proteins. More specifically, the allocation of amino sugars, lignin phenols, and proteins to POC and amino sugars and proteins to MAOC was closely linked to changes in SOC. Combined organic-chemical fertilizer applications and furrow and split fertilizer applications facilitated the allocation of microbial- and plant-derived C to POC and MAOC, ultimately enhancing SOC accumulation in tea plantations, particularly in soils with decreasing pH and low initial SOC. Our findings provide novel data for designing management regimes to increase soil C sinks in tea plantations following forest conversion.