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This study aimed to determine the influence of tree species on soil labile organic matter pools and microbial characteristics 1 9 years after reforestation of Chinese fir(Cunninghamia lanceolata(Lamb.)Hook)woodland with itself or a native broadleaf species,Mytilaria laosensis.The results showed that tree species transition had a significant impact on soil dissolved organic carbon(C)and nitrogen(N)pools.Water,hot water and KC1 extractable organic C pools were greater in all three layers(0-5,5-10,10-20 cm)in M.laosensis soil than in C.lanceolata soil.In the 0-5 and 5-10 cm layers,the concentrations of dissolved organic N extracted by water and hot water in M.laosensis plantation were significantly higher than that in C.lanceolata plantation.The sizes of soil dissolved organic C and N pools in different solvents generally followed the same order: KCl>hot water> water.In the top 5-cm soil layer,M.laosensis plots also had greater concentrations of light fraction organic C and N than C.lanceolata plots.The fumigation extraction method and phospholipid fatty acids(PLFA)analysis indicated that there was significantly greater microbial biomass in M.laosensis soil than in C.lanceolata soil.The mass of fungal PLFAs,bacterial PLFAs and total PLFAs were positively correlated with soil dissolved organic C and N extracted by hot water.This demonstrated that hot water extracted organic matter may contains some microbial biomass.Soil labile organic matter and microbial biomass can be used as indicators of soil quality,our results therefore indicated that the transition of land use change from C.lanceolata to M.laosensis can improve soil fertility in the plantation.