作 者 ：邓仁菊,杨万勤*,张健,吴福忠
期 刊 ：生态学报 2010年 30卷 3期 页码：830~835
Keywords:seasonal freeze-thaw, litter quality, subalpine forest,
摘 要 ：凋落物质量是影响凋落物分解的重要生物因子，其在季节性冻融期间的变化可能对亚高山森林生态系统过程产生显著的影响。因此，采用凋落物分解袋法，研究了岷江冷杉(Abies faxoniana)和白桦 (Betula platyphylla)凋落物质量在一个季节性冻融期间(2006年10月至2007年4月)的变化。季节性冻融期间，岷江冷杉和白桦凋落物的木质素(L)和纤维素的降解率为全年降解的70%-75%，岷江冷杉和白桦凋落物的C/N、L/N和纤维素/N均显著增加，而纤维素/P均有所降低。岷江冷杉凋落物的C/P和L/P有所增加，但白桦凋落物的C/P和L/P有所降低。可见，季节性冻融期间，亚高山森林凋落物的质量发生了较为显著的变化，其显著影响了亚高山凋落物分解过程。
Abstract:Litter decomposition plays a key role in mass cycle and energy flow of the forest ecosystem, as a consequence of which more attentions have been given to the decomposition process of litters in different forest ecosystems around the world and their relations with biotic and abiotic factors over the past decades. As yet, far less information has been available on changes of litter quality in the subalpine forest over one freeze-thaw season, although seasonal freezing and thawing is a common natural phenomenon, which might give a strong influence on forest litter decomposition and then the forest ecosystem process. In order to understand the effects of seasonal freeze-thaw on the ecosystem process of the Subalpine forest, therefore, changes in litter quality as affected by seasonal freeze-thaw were studied in litters of fir (Abies faxoniana) and birch (Betula platyphylla) trees, which are the representative tree species in the subalpine forest of Western Sichuan, China, employing the method of litter bag. Litter bags were placed on the forest floor before soil freezing in October, 2006, and sampled after thawing in April and October, 2007. Concentrations of C, N, P, lignin and cellulose were also measured in litters, respectively. Lignin (L) in fir and birch litters degraded 14.4% and 16.7% over one freeze-thaw season, which accounted for 71.3% and 74.7% of the corresponding degradation rate over one year, respectively. Similarly, cellulose in fir and birch litters degraded 23.9% and 26.1% over one freeze-thaw season, which accounted for 73.6% and 75.4% of the corresponding degradation rates over one year, respectively. Consequently, as the indices of litter quality, the ratios of C/N, C/P, L/N, L/P, cellulose/N and cellulose/P in litters changed with the tree species during the freeze-thaw season. However, C/N, L/N and cellulose/N in both fir and birch litters increased significantly, whereas cellulose/P decreased significantly. In addition, the ratios of C/P and L/P increased in fir litter during the freeze-thaw season, while those decreased in birch litter. The findings showed that repeated freeze-thaw cycles during the freeze-thaw season had strong effects on litter quality in the subalpine forest, implying that seasonal freeze-thaw greatly influence the process of litter decomposition in the subalpine forest ecosystem.
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