寒温带地区非生长季典型森林群落凋落物分解及养分释放

  目的  研究寒温带森林凋落物在非生长季的分解及养分释放特征，可为寒温带地区森林养分循环及森林生产力评价提供理论依据。  方法  选取寒温带地区 4 种典型森林（白桦林、山杨林、兴安落叶松林和樟子松林）为研究对象，采用埋袋法进行分解试验，分析秋季、冬季和春季冻融期凋落物分解和养分释放动态变化。  结果  秋季是非生长季凋落物质量损失率和养分释放最高的时期，4种林型凋落物质量损失率在17.50% ~ 30.60%之间，白桦林凋落物分解最快，兴安落叶松林分解最慢。冬季凋落物质量损失率在0.52% ~ 5.12%之间，春季冻融期在3.12% ~ 7.65%之间。非生长季白桦林分解最快，分解速率达1.37 g/(kg·d)，兴安落叶松林最慢，为0.87 g/(kg·d)。4种林型秋季凋落物中C、P、K元素均处于释放状态，且释放率在17.45% ~ 65.90%之间，其中白桦林C、P释放率最大，分别为28.14%、65.90%，山杨林K释放率最大为58.19%。冬季4种林型凋落物中C、P、K释放率大幅降低，N呈现累积状态，累积率在1.44% ~ 51.54%之间。春季冻融期间，凋落物养分释放率有所回升，但不同林型受土壤温湿度影响，波动性较大。  结论  寒温带4种林型在非生长季凋落物质量损失率在21.60% ~ 42.37%之间，除山杨林N整体上呈现累积状态外，其他林型凋落物C、N、P、K元素均表现为释放，凋落物质量损失率、元素C、P、K释放均以秋季为主，而N释放则以春季为主。 

Litter decomposition and nutrient release of typical forest communities in non-growing season in cold temperate zone

  Objective   Studying the decomposition and nutrient release characteristics of forest litter during the non-growing season aims to provide theoretical basis for forest nutrient cycling and productivity evaluation in cold temperate zone.   Method  Four typical forests (Betula platyphylla forest, Populus davidiana forest, Larix gmelinii forest and Pinus sylvestris var. mongolica forest) in cold-temperate regions were selected to conduct the decomposition experiment using bagging method and analyze the decomposition and nutrient release dynamic of litter during autumn, winter and freezing-thawing in spring, respectively.  Result  The highest mass loss rate and nutrient release of litter was found in autumn. The litter mass loss rate of the four forest types ranged from 17.50% to 30.60%, in which the fastest and slowest litter decomposition were found in the Betula platyphylla and Larix gmelinii forest, respectively. In particularly, the mass loss rate of litter in winter ranged from 0.52% to 5.12%, while the range from 3.12% to 7.65% was found in freezing-thawing period of spring. In the non-growing season, the fastest decomposition rate 1.37 g/(kg·d) occurred in Betula platyphylla, while the slowest was found in Larix gmelinii forest with 0.87 g/(kg·d). Both C, P, and K in the litter of the four forest types exhibited the released state, in which the range of release rate ranged from 17.45% to 65.90%. The release rates of C and P in Betula platyphylla forest were the highest, 8.14% and 65.90%, respectively, and the release rate of K in Populus davidiana forest was the highest, being 58.19%. In contrary, N showed a cumulative state in all forest communities. The release rates of C, P, and K in the four forest communities litter in winter were greatly reduced, while N showed a cumulative state, with the cumulative rate ranged from 1.44% to 51.54%. During the freezing-thawing period in spring, the nutrient release rate of litter increased, but different forest types fluctuated greatly due to the influence of soil temperature and humidity.  Conclusion  In the non-growing season, the litter mass loss rate of the four forest types in the cold temperate zone ranges from 21.60% to 42.37%. Except for the overall accumulation of N in Populus davidiana forest, the C, N, P and K elements in the litter of other forest types are released. The litter mass loss rate and the release of C, P and K elements are mainly in autumn, while the N release is mainly in spring.