海拔和郁闭度对祁连山青海云杉林叶凋落物分解的影响

为了探究海拔和郁闭度对青海云杉林叶凋落物分解的影响，本文选择海拔为2850 m，3050 m，3250 m和3450 m四个梯度和高、中、低三个林分郁闭度，采用分解网袋法，研究青海云杉叶凋落物分解速率及分解过程中N、P元素变化。结果表明，质量损失率随时间在波动增大。分解速率先减小后增大，不同海拔下分解速率为K₃₄₅₀ > K₃₀₅₀ > K₃₂₅₀ > K₂₈₅₀，不同郁闭度下分解速率为K_低 > K_中 > K_高，青海云杉叶枯落物分解50%和95%所需时间约为5.3 a和22.7 a。枯落物分解过程中，N、P含量和累积系数在不同海拔和郁闭度下的变化不同，与季节变化有关。研究结果为祁连山森林生态系统地球化学循环奠定基础。

Decomposition and its nutrients dynamic of Qinghai spruce leaf litter with elevation gradient in Qilian Mountains

In order to explore the effects of different altitudes and canopy closures on the decomposition of leaf litter of Qinghai spruce (Picea crassifolia), four altitudes (i.e. 2850 m, 3050 m, 3250 m, and 3450 m) and three kinds of canopy closure (high, medium, and low) were selected in this study. Field decomposition net bags were used to study the litter decomposition rate (K), nitrogen (N), and phosphorus (P) content changes of leaf litter during decomposition. The results showed that the rate of mass loss increased with time. The decomposition rate decreased first and then increased with time. The sequence of decomposition rate at different altitudes was K₃₄₅₀ > K₃₀₅₀ > K₃₂₅₀> K₂₈₅₀, and the order of decomposition rate at different canopy closure was K_low > K_medium > K_high. Qinghai spruce leaf litter decomposition time needed for 50% and 95% mass loss was about 5.3 year and 22.7 year. During the decomposition of the leaf litter, the changes of N and P content and accumulation coefficient at different altitudes and canopy closure were different, and were related to seasonal changes. Results obtained in the study would lay the foundation for geochemical cycle in the forest ecosystem of Qilian Mountains.