Well-drained upland soils generally have stronger microbial catabolism during organic C transformation than water-logged paddy soils. However, the intensity of microbial anabolism and necromass formation processes in these contrasting agricultural soils is unclear. To quantify these processes, 40 pairs of adjacent upland and paddy soils collected from four climates (mid-temperate, warm temperate, subtropics, and tropics) across eastern China were incubated with 13C-labeled root exudates under simulated field water conditions for 50 days. Upland...