外源氮输入对长白山红松凋落物早期分解的影响

该文研究了外源氮对长白山红松凋落物早期分解的影响，并对不同海拔红松凋落物分解过程对外源氮输入的响应进行了比较.实验共包括3个外源氮梯度（0、30和50 kg/(hm2·a)，NH4NO3）.13周的培养实验后，研究结果表明，在红松凋落物分解的初期阶段，外源氮输入促进了其分解过程（P0.05），接受高外源氮输入样品的分解量和呼吸速率显著高于低外源氮和对照样品；内源氮并不是影响不同海拔红松凋落物分解的主要因素, 木质素含量才是控制其分解的主要因子；外源氮对凋落物可溶性有机碳(DOC)的淋失都没有显著影响，而对可溶性有机氮(DON)淋失量的影响存在很大的不确定性.研究发现，尽管有部分外源氮淋失，但凋落物仍可以通过固持作用截留40%～55%外源氮，随着外源氮输入的增加其截留量也随之增加. 

Effects of nitrogen addition on the early stage decomposition of Korean pine litter in the Changbaishan Mountains, northeastern China.

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/(hm²·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.