Abstract: Effects of external nitrogen(N) on the decomposition of early stage of Pinus koraiensis needle litter were studied in a 13 weeks laboratory incubation experiment.Three doses of external N(equal to 0,30 and 50 kg N/(hm²·year,respectively,as NH₄NO₃) were added to two types of P.koraiensis litter collected along elevation gradient in the Changbaishan Mountains,northeastern China.The results showed that the addition of external N increased the decomposition rate significantly(P<0.05).High external N treated samples showed greater weight loss and respiration rate than low N treated one and the control.Internal N was not an overriding constraint on litter decomposition,and lignin content controlled the decomposition rate of litters.The releases of dissolved organic carbon(DOC) were not significantly affected by external N input.The effect of N addition on dissolved organic nitrogen(DON) leaching is uncertain.In spite of part of inorganic N leaching,the litter still immobilized 40%-55% external N.The retention of inorganic N generally increases along the external N gradient.