Soil gross nitrogen (N) transformation rates are highly sensitive to land use change. However, understanding the efect of land use change on internal N cycling patterns and its underlying mechanisms in tropical soils remains elusive. Here, four typical land uses including forest (> 400 years), eucalyptus (15 years), rubber (35 years), and paddy feld (40 years) plantations in tropical region of China were investigated. The technique of 15N tracing was used to quantify soil gross N transformation rates. We also measured soil biochemical properties as well as carbon (C) and N fractions to evaluate the controls on any changes in soil N cycling processes. We found that converting natural tropical forests to managed ecosystems shifts the soil N dynamics from nitrate-dominated N forms towards ammonium-dominated N forms, suggesting that managed ecosystems becoming conservative (i.e., lower ratio of autotrophic nitrifcation (ONH4) to ammonium immobilization (INH4) and nitrous oxide (N2O) emissions and higher nitrate immobilization) than the natural tropical forest. The higher tendency of N loss (i.e., higher ONH4/INH4 and N2O emissions) of the natural tropical forest was mainly due to the higher concentrations of soil total N and hydrolysable ammonium N and microbial biomass, which stimulated ONH4. Lower microbial biomass, hydrolysable ammonium N, particulate organic C, and gross N mineralization, however, signifcantly decreased ONH4 in managed ecosystems. Our study also showed a pivotal role of soil C and N fractions in controlling soil heterotrophic nitrifcation, which enhanced signifcantly with decreasing amino sugar N, amino acid N, dissolved organic C, easily oxidizable organic C, and light fraction organic C. Our fndings highlighted the pivotal role of soil C and N fractions in regulating soil N cycling under future land use chang