【作者】 吕瑞恒；

【导师】 刘勇；

【作者基本信息】 北京林业大学 ， 森林培育， 2010， 博士

【摘要】 本论文以华北地区常见针叶树种油松、华北落叶松为研究对象,探讨2树种凋落物分解动态变化以及间伐强度对凋落物分解过程的影响,为提高人工林林分质量,丰富和完善抚育间伐理论提供参考。本研究在北京延庆县营盘村周边山地设置样地,在同一龄级4种密度下交互放置凋落袋,测定油松、华北落叶松有机、无机养分动态变化过程,了解间伐对针叶凋落物分解速率的影响,同时调查间伐通过改变林下地被、土壤性质的情况及其对凋落物分解的影响。通过主成分分析等统计方法,综合分析影响凋落物分解的主导因子,以及调控凋落物分解的密度效应。结果表明：(1)油松针叶凋落物分解周期为11.77-17.69年,华北落叶松针叶凋落物分解周期为9.01-13.25年。针叶凋落物在秋季分解率最大,初始N含量、C／N比是制约2树种针叶凋落物前期分解速率的主导因子。(2)通过轮置分解法,研究同一凋落物质量在不同间伐强度下无机养分释放的差异性。凋落物初始养分含量越高,能够缩短凋落物养分积累释放的时间,尤以氮元素最为明显。间伐对凋落物分解的影响表现为随着间伐强度的增大,养分积累释放波动幅度很大,其中以夏季-秋季表现最为显著。(3)针叶凋落物分解速率与林下灌草多样性、养分积累量均有不同程度的显著相关性,灌木层作用尤为突出。林下凋落层厚度与分解速率呈极显著负相关,相关系数油松为-0.621,华北落叶松为-0.758。(4)4种土壤酶活性均以夏季活性最高,凋落物分解过程中5种无机养分的释放与不同土壤酶活性呈现不同程度的相关性。同时,养分之间的积累和释放也相互影响相互制约,尤其以Ca元素最为突出,与N、P、K元素呈极显著正相关。(5)对不同间伐强度下影响凋落物分解因子进行主成分分析可知,24、32年油松凋落物质量(初始C、N含量)、灌草多样性及林下死地被层对凋落物分解影响较大。40年油松则以凋落物质量因子、草本层多样性指数影响最大。立地条件为Ⅲ的华北落叶松,粗脂肪、粗蛋白、全氮、C／N、灌木层Simpson(?)旨数、土壤含水率对其凋落物分解影响较大。立地条件为Ⅳ的华北落叶松,第一主成分主要综合了木质素、灌木层Shannon-Wiener指数、灌木层Simpson指数、灌木层Gleason指数、凋落层厚度的信息。(6)对各间伐强度下影响凋落物分解因子进行分析评判,来反映各间伐林分对林下凋落物分解作用的综合水平。24、32年油松,以间伐Ⅲ为最优,密度分别为1700株／hm2、1325株／hm2,40年油松则以间伐Ⅳ最优,密度为1050株／hm2。华北落叶松2种立地条件下均以间伐Ⅳ为最优,间伐Ⅰ最小。最优密度分别为1325株／hm2、1150株／hm2,说明适当的间伐强度对针叶人工林凋落物的分解有促进作用。更多还原

【Abstract】 ABSTRACTTwo main conifers in North China, Pinus tabulaeformis Carr and Larix principis-rupprechtii Mayr,, were used as the objects of the study. Litter decomposition dynamics of these two coniferous, as well as effects of different precommercial thinning (PCT) intensities on the decomposition process were explored. The study used the litterbag technique to quantify the dynamics of organic and inorganic nutrients in leaves of same-age-class Pinus tabulaeformis and Larix principis-rupprechtii plantations under four different PCT treatments with plots allocated in the middle hilly lands of Yingpan, Yanqing County, Bejing. Comprehensively, the effects of PCT and understorey vegetation (shrubs and herbs) & soil properties changed by PCT on decomposition rate were analyzed and evaluated by Principal Components Analysis (PCA) to find the dominant factor controlling the coniferous litter decomposition, as well as the optimal density of coniferous plantations for the litter decomposition. The results showed that:(1) Decomposition cycle of coniferous litter for Pinus tabulaeformis was 11.77-17.69 years and for Larix principis-rupprechtii was 9.01-13.25 years. The decomposition rate reached the peak value in the autumn. The initial N content and initial C:N ratio were the main factors influence litter decomposition rates in early stage.(2) The effects of four different PCT intensities were different in the initial quality of the coniferous litter. The more initial litter nutrient content can shorten the time of elements release, especially nitrogen. Thinning effects on litter decomposition showed that with thinning intensity increase, the accumulation and release of nutrient fluctuations was more obvious, which in summer-autumn performance was the most significant.(3) Correlated analysis showed that the decomposition rate was significantly correlated with biodiversity of understory vegetation (shrubs and herbs) and the retained amount of nutrients. The layer of forest litter and decomposition rate was significantly negatively correlated, the correlation coefficient was-0.621 in the Pinus tabulaeformis plantations, and was-0.758 in the Larix principis-rupprechtii plantations.(4) The activities of four soil enzymes were most active in summer. Different degrees of correlations (positive or negative) were discovered between the returned amount of five nutrients and the activities of soil enzymes in the process of litter decomposition. At the same time, the retained amounts and returned amounts of five nutrients also interacted with each other.(5) The PCA was used among all shaping factors in the data process, the results showed the quality of coniferous litter (initial C and N content) of 24-year-old and 32-year-old Pinus tabulaeformis plantations, biodiversity of understory vegetation and undergrowth dead litter played stronger role in the decomposition of coniferous litter. In contrast, the highest contributing ratio of 40-year-old Pinus tabulaeformis plantations was the factor of litter quality, Larix principis-rupprechtii (index III)summarized the effects of coarse fat, coarse protein, total nitrogen content, C/N in leaves of Larix principis-rupprechtii, Simpon index of shurb and soil moisture content on the litter decomposition. Larix principis-rupprechtii (indexⅣ)mainly integrated the information of lignin content in leaves, indexes of shrub layer and depth of litter layer.(6) The shaping factors on litter decomposition were analyzed and determined to reveal the total role played by plantations under different PCT treatments. It was observed that PCT treatment III was the optimal density for 24-year-old and 32-year-old Pinus tabulaeformis plantations, while PCT treatmentⅣwas the best for 40-year-old Pinus tabulaeformis plantations. For Larix principis-rupprechtii plantations in two kinds of site conditions, PCT treatmentⅣplayed the strongest role but PCT treatment I poorly worked on the coniferous litter decomposition. It might suggest that appropriate PCT intensities accelerate and promote the coniferous litter decomposition in conifer plantations.更多还原