Abstract:

A field experiment was performed in an 18-year-old Larix gmelinii plantation in Maoershan Forest Research Station of Northeast Forestry University to study the effects of N(NH₄NO₃,10 g·m^-2a^-1) addition on the contents of N,P,K,Ca and Mg in different tree components and leaf nutrient resorption efficiency in Larix gmelinii after five years of continuous N addition.The results showed that N addition had no significant influence on leaf nutrient contents,but significantly increased N and P contents in roots,branches and stems.N addition significantly increased N conctents and decreased C/N ratio in senesced leaves,and decreased leaf N resorption efficiency.The responses of leaf nutrient conctents and tree biomass to N addition suggested that soil N availability was not the limiting factor to tree growth in Larix gmelinii plantation.N addition resulted in the luxury consumption of N and P,made senesced leaves more decomposable,and accelerated N cycling.

Key words: N addition, Larix gmelinii, nutrient cycling, nutrient resorption, luxury consumption