【作者】 刘洋；

【导师】 张健；

【作者基本信息】 四川农业大学 ， 水土保持与荒漠化防治， 2006， 硕士

【摘要】 森林凋落物是林地有机质的主要物质库和维持土壤肥力的基础，是森林生态系统物质循环和能量流动的主要途径，凋落物的养分归还对维持林地地力具有十分重要的意义。目前，桉树人工林已成为我国南方大面积造林的树种之一，通过对凋落物特性的研究可以深入了解森林生态系统的结构和功能，对桉树人工林的营造和经营管理有重要意义。试验自2004年7月起，选择四川洪雅1997年营造的巨桉人工林，对其凋落物数量、养分归还量、养分转移、分解速率及土壤养分动态变化等方面进行了一个生长周期的定位研究，结果表明： （1）巨桉人工林四个林分的年凋落量分别为8786、8112、5590、6011kg／hm²，年凋落量与林分密度成正相关，叶的凋落量随密度的增大而增大，枝和皮的凋落与林分密度没有显著的相关性。巨桉凋落物各组分量：落叶＞落枝＞落皮。巨桉人工林全年有一个明显的凋落物峰谷期，5月是全年凋落物的高峰期，1月凋落量达到最低，凋落总量的季节变化趋势是春＞夏＞秋＞冬。叶的凋落主要集中在春季，而枝、皮的凋落主要集中在夏季。 （2）巨桉人工林全年通过凋落物归还土壤的N、P、K、Ca、Mg五种大量元素总量分别为95.32、86.90、67.72、66.37kg／hm²，归还量大小依次为N＞K＞Ca＞Mg＞P。N的归还潜力E₃最高，E₁、E₂、E₄较接近，说明E₃的凋落物具有更高的改良土壤的效果，这也是E₃土壤养分含量最高的原因。凋落物各组分养分归还总量大小：落叶＞落枝＞落皮，落叶是巨桉凋落物养分归还的主体。各林分凋落物N、P、K、Ca、Mg的归还动态基本一致。养分归还总量春夏两季大，秋冬两季低，冬季1月养分归量最低。 （3）巨桉枝、叶在凋落前N、P普遍发生生理转移，而K、Ca、Mg的转移方向则不确定，有时为正有时为负。P的转移率是各元素中最高的，在叶中月平均转移率可达60.6％，枝中可达70.1％。巨桉人工林枝和叶在大量凋落前养分转移量都是最大的，养分内循环非常明显。养分年转移总量分别为145.96、118.10、70.72、78.26kg／hm²，大小依次为E₁＞E₂＞E₄＞E₃，即养分转移量与林分密度成正相关。叶的养分转移量比枝大数倍。叶中各元素转移量的大小为N＞K＞Ca＞P＞Mg，但枝中各元素的转移量大小在各林分表现不一致，E₁为K＞N＞Mg＞Ca＞P，E₂和E₃为N＞K＞Ca＞Mg＞P，E₄为N＞Ca＞K＞Mg＞P。 （4）巨桉枝、叶的分解系数都是E₃＞E₄＞E₁＞E₂，E₃凋落物的分解速度快于其更多还原

【Abstract】 Litter is major material pool of forest organic and the base of maintain the soil nutrient, and the major course of the material cycling and energy flow in forest ecosystem. It is very important for the nutrient to return to soil through litter to remain the sustainable productivity of the forest. Now, the Eucalyptus plantation is one of most tree species planted in south of our country. It is vital significance to plant and manage the Eucalyptus plantation through research the characteristic of litter to thoroughly understand the structure and the function of the forest ecosystem. From July 2004,the experiment choose the Eucalyptus grandis plantation planted in 1997 in YongYa SiChuan province, study on the litter production, nutrient return, nutrient retranslocation, litter decomposition and the soil nutrient change in a growth cycle, the result showed:（1） The annual litter production of four Eucalyptus grandis plantation were 8786 , 8112 , 5590, 6011 kg/hm² respectively, the annual litter production was connected with the forest density, leaf production was increased with the increase of the standing density, branches and barks had no remarkable relation with the density. The components of litter production was leaf> branches > barks. There was a peak and valley in the whole year, highest in May and lowest in January. The litter production of seasonal variation tendency in sequence of spring > summer > autumn > winter. Leaf mainly fell in spring while branches and barks fell main in summer.（2） The annual five macro-elements return to the soil through litter were 95. 32, 86.90, 67. 72, 66. 37 kg/hm² respectively, the sequence of nutrient return was N > K > Ca > Mg > P. E₃ was the highest in N potential return and E₁ E₂ E₄ were close, the litter of E₃ had the higher effect to improve the soil which was the reason that the soil nutrient content of E₃ was higher. The sequence of nutrient return of litter components was: leaf> branches > barks. Leaf was the main components of the nutrient return. The dynamic of N, P, K, Ca, Mg return in four Eucalyptus grandis plantation were basically similar. The nutrient return was higher in spring and summer than in autumn and winter, lowest in January..（3） Before falling, most of N, P in leaf and branches were transferred physiologically, while K, Ca, Mg transferred direction was uncertain, sometimes was positive and sometimes was negative. The transfer efficiency of P was the highest, reached 60.6% in leaf and 70.1更多还原