杉木火力楠混交林养分归还与生产力

通过对野外试验和室内测试数据的整理分析．比较研究了杉木火力楠混交林和 杉木纯林养分归还、吸收等生态过程的特征以及生产力结果表明混交促进了养分归还过 程．可提高土壤肥力和系统生产力．１５年生混交林技和叶凋落物分别是纯林的２倍和３ 倍，其中容易分解的火力楠凋落物占 ６４％．混交林通过凋落物分解所归还的养分是纯林 的 ２～ ３倍．相当年凋落量 ６５． ９％的混交林根系年死亡量是纯林的 ２倍，在整个系统养分 归还中占有很大的份额．混交林土壤全 Ｎ、 ＮＨ＋４－Ｎ和有效 Ｋ分别比纯林提高 ６４． ３％。 ８２． ３ ％和 ６３． １％．与此同时土壤孔隙组成和水分过程也大为改善．混交林生产力较纯林 提高５２．７％．混交林５种大量元素的归还／吸收比率是纯林的２倍，表明混交林养分循环 效率较高，较少的人为维持可以保持较高的生产力水平．

Nutrient return and productivity of mixed Cunninghamia lanceolata and Michelia macclurei plantations

Baed on the field experiment and laboratory analysis, characteristics of ecological processes, such as nutrient return, uptake, and of productivity of mixed Cunninghamia lanceolata and Michelia mncclurei plantations was investigated in comparison with pure C. lanceolata plantations. The results show that in the mixed plantations, the process of nutrient return was greatly enhanced, and the soil fertility and the productivity were raised significantly. For example, in a 15 years old mixed plantation. the branch and leaf litters were respectively twice and triple that in the pure one with the same age, and the litter was mainly corn- of fallen leaf of M' macclurei, which decomposes much easier. As a result, the amount of nutrients returned to the soil in the mixed plantation was 2~3 times as much as that in the pure. The annual mortality of fine roots Of the mixed plantation. corresponding to 65. 9% of aboveground litter fall, was about twice as much as that in the pure. Tile soil total N, NH 4 -N and available K contents of mixed plantation were increased by 64. 3, 82. 3 and 63. 1 % respectively against the pure, soil porosity and water status were also improved. The productivity, measured as annual net production, of mixed plantation was increased by 52. 7%. The ratio of return/uptake of five major elements in mixed plantation is twice as big a, that in the pure, indicating that the mixed plantation cycles its nutrients more efficiently, and sustains ifs productivity at a higher level with a minimal human support.