The occurrence of nitri?cation in some acidic forest soils is still a subject of debate.Identi?cation of main nitri?cation pathways in acidic forest soils is still largely unknown.Acidic yellow soil(Oxisol) samples were selected to test whether nitri?cation can occur or not in acidic subtropical pine forest ecosystems.Relative contributions of autotrophs and heterotrophs to nitri?cation were studied by adding selective nitri?cation inhibitor nitrapyrin.Soil NH~+_4-N concentrations decreased,but NO~-_3-N concentrations increased signi?cantly for the no-nitrapyrin control during the ?rst week of incubation,indicating that nitri?cation did occur in the acidic subtropical soil.The calculated net nitri?cation rate was 0.49 mg N kg~(-1)d~(-1)for the no-nitrapyrin control during the ?rst week of incubation.Nitrapyrin amendment resulted in a signi?cant reduction of NO~-_3-N concentration.Autotrophic nitri?cation rate averaged0.28 mg N kg~(-1)d~(-1)and the heterotrophic nitri?cation rate was 0.21 mg N kg~(-1)d~(-1)in the ?rst week.Ammonia-oxidizing bacteria(AOB) abundance increased slightly during incubation,but nitrapyrin amendment signi?cantly decreased AOB amo A gene copy numbers by about 80%.However,the ammonia-oxidizing archaea(AOA) abundance showed signi?cant increases only in the last 2weeks of incubation and it was also decreased by nitrapyrin amendment.Our results indicated that nitri?cation did occur in the present acidic subtropical pine forest soil,and autotrophic nitri?cation was the main nitri?cation pathway.Both AOA and AOB were the active biotic agents responsible for autotrophic nitri?cation in the acidic subtropical pine forest soil. The occurrence of nitri? Cation in some acidic forest soils is still a subject of debate. I denti cation of major nitriding pathways in acidic forest soils is still vital unknown. Acidic yellow soil (Oxisol) samples were selected to test whether nitri? Correlation contributions of autotrophs and heterotrophs to nitri? cation were studied by adding selective nitritonium cation inhibitors. Soil NH ~ + _4-N concentrations decreased, but NO ~ -_3-N concentrations increased signi? cantly for the no-nitrapyrin control during the rst week of incubation, indicating that nitrite did occur in the acidic subtropical soil. The calculated net nitrite rate was 0.49 mg N kg ~ (-1) d ~ (-1) for the no-nitrapyrin control during the rst week of incubation. Nitrification amendment was resulted in a reduction of NO ~ -_3-N concentration. Autotrophic nitrite rate averaged0.28 mg N kg ~ (-1) -1) d ~ (-1) and the heterotrophic nitrite rate was 0. 21 mg N kg -1 d -1 in the rst week. Ammonia-oxidizing bacteria (AOB) abundance increased slightly slightly during incubation, but nitrification amendment signal • cantly decreased AOB amo A gene copy numbers by about 80 % .However, the ammonia-oxidizing archaea (AOA) abundance showed signi? Cant increases only in the last 2weeks of incubation and it was also decreased decreased by nitrapyrin amendment.Our results indicated that nitri? Cation did occur in the present acidic subtropical pine forest soil, and autotrophic nitri? cation was the main nitri cation pathway.Both AOA and AOB were the active biotic agents responsible for autotrophic nitri? cation in the acidic subtropical pine forest soil.