共查询到20条相似文献，搜索用时 78 毫秒
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水土保持林的密度调控 总被引：3，自引：1，他引：3
以长江中上游地区的马尾松水土保持林为对象 ,从林分结构、林分生物产量的角度出发 ,通过研究马尾松水土保持林乔木层中枝叶生物量、林下植被生物量和枯枝落叶层生物量与林分密度 (株数密度或郁闭度 )之间的数学模型 ,提出了水土保持林经营的最适郁闭度为 0 .6 8,并编制出了马尾松水土保护林的最适经营密度数表。 相似文献
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南方型杨树工业原料林培育目标与培育年限的定量化研究 总被引：2，自引：0，他引：2
根据湖北省10个县、市31块标准地林分的调查资料,在对杨树所处立地条件和林分密度类型进行分级组合的基础上,对南方型杨树工业原料林的培育目标与培育年限进行了定量化研究。研究结果表明:各组合类型培育小径材、中径材、大径材的平均年限分别为6,7～9a,10～11a以上;各种立地条件下,中密度林分培育各种规格的工业原料林的年限最短;Ⅰ类立地中密度类型培育不同用途林分的年限最短,Ⅲ类立地低密度类型最长;Ⅰ类立地中密度和低密度组合类型较好,培育大、中、小径材均较理想,Ⅱ类立地中密度类型林分不宜培育大径材,Ⅲ类立地各种密度类型差别不大,以中密度林分最好。 相似文献
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马尾松人工林密度与枯枝落叶量的关系 总被引：2，自引：0，他引：2
对14年生马尾松人工林生态系统4个密度林分的枯枝落叶量及养分含量测定表明,林分枯枝落叶的年凋落物量和林地上枯枝落叶层的总贮量均随林分密度增大而增加。在枯枝落叶层中已经分解的物质量及其养分释放量,以密度为3210株/公顷的松林最高。 相似文献
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江西省丘陵区湿地松多效益经营模式最适立地类型的研究 总被引：3，自引：1，他引：2
研究森林经营模式首先要研究立地类型。利用树干解析材料,采用模糊聚类进行分析,按照立地等级划分建模单元,分别建模单元利用Richards生长函数模拟现实林分树高生长,结合江西省林业用地实际情况,编制了江西省丘陵区湿地松多效益经营模式的最适立地类型表。 相似文献
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思茅松天然次生林林分生长模型的研究 总被引：3，自引：0，他引：3
从影响林分生长的立地、年龄、密度3个主要因素出发，利用优势高生长与密度关系相对较小的这一特点，在不同立地条件、林分密度、林龄的思茅松天然林次生林中设立98块标准地，依据标准地测定的数据，以Logistic和Richards理论方程为基本模型，在模型中引入立地质量，林分密度，林分年龄构建了思茅松天然次生林林分的生长模型系统。研究表明Logistic模型不仅具有良好的预测性，而且具有广泛的适用性，用它作为描述思茅松天然次生林林分生长的基本模型，能很好地表达其生长过程。 相似文献
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杉木建筑材林密度管理技术与生长效应的研究 总被引：1，自引：0，他引：1
根据杉木人工林现有林调查材料、固定样地材料及密度管理试验林材料，分析了不同立地类型、不同密度的杉木林分生长效应，在建立数学模型的基础上，提出了杉木建筑材林合理密度管理技术。 相似文献
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通过对泾川刺槐人工林调查 ,用数理统计原理 ,建立林分树高、冠幅相关数学模型及各不同立地类型林分树高、年龄相关数学模型 ;根据数学模型编制经营密度预测表 ,以此确定间伐强度 ,使林分达到最佳合理经营密度。 相似文献
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为了系统地研究杉木人工林的栽培营养，对５、１０、１５、１９上生不同地位指数（１４、１６、１８）的杉木枯损枝叶的生物量培养、养分含量、养分积累和分布进行研究，结果表明：杉木枯损枝叶包括保留在树体上的未凋落和在地面上的已凋落两个部分，在研究杉木林分枯损枝叶时不可忽视未凋落部分。枝叶总枯损量随地位指数的提高而增加，随林龄的变化是在１０年生时最大，１５年生以后随林龄增加又有一定增加。杉木枯损枝叶中养分的总 相似文献
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以固定样地观测和临时样地调查相结合的办法收集林分现实生长与经间伐或间伐设计后所保留群体的生长资料;以固定样地观测资料为依据,以林分平均胸径连年生长量及胸径度离散度的指标,确定不同地位指数林分间伐的起始年龄;采用Ｒｉｃｈａｒｄｓ函数模拟合理密度与生长水平下的林分平均树高及胸径生长;并采用间伐或间伐设计前,后林分生长标准的调查资料,以地位级指数,林林分平均胸径及胸径离散度为自变量建立起人工速生丰产林的 相似文献
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西藏自治区森林枯落物碳储量估算 总被引：1，自引：0，他引：1
利用典型样地采样,建立了枯落物碳密度与厚度关系方程,并结合森林资源连续清查的样地坡度与枯落物厚度因子,估算出西藏自治区森林枯落物碳储量.结果表明,西藏自治区丰富的森林植被生产了巨大的枯落物层碳库,有机碳分解和碳库消耗缓慢.研究该部分碳库状况,为估算和评价陆地生态系统碳储量并据此制定相应的对策提供了基础数据. 相似文献
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Decomposition dynamics were compared among green tree leaves, partially decomposed tree leaf litter (i.e., decayed tree leaf litter on forest floor) and a mixture of the two in a warm temperate forest ecosystem in central China to test the influence of litter chemical quality on the degree of decomposition. The study was conducted in situ at two contrasting forest sites, an oak forest dominated by Quercus aliena var. acuteserrata Maxim., and a mixed pine and oak forest dominated by Pinus armandii Franch. and Q. aliena var. acuteserrata. We found marked differences in the rate of decomposition among litter types at both forest sites; the litter decomposition constant, k, was about 39 % greater at the oak forest site and more than 70 % greater at the pine-oak forest site, for green leaves than for partially decomposed leaf litter. The decomposition dynamics and temporal changes in litter chemistry of the three litter types also greatly differed between the two forest sites. At both forest sites, the higher rate of decomposition for the green leaves was associated with a higher nitrogen (N) content and lower carbon to N ratio (C/N) and acid-unhydrolyzable residue to N ratio (AUR/N). We did not find any non-additive effects when mixing green leaves and partially decomposed leaf litter. Our findings support the contention that litter chemical quality is one of the most important determinants of litter decomposition in forest ecosystems at the local or regional scale, but the effect of litter chemical quality on decomposition differs between the contrasting forest types and may vary with the stage of decomposition. 相似文献
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不同立地条件下华北落叶松叶凋落物的分解特性 总被引：1，自引：0，他引：1
采用凋落袋法,研究2种立地条件下不同林分密度华北落叶松人工林叶凋落物基质质量、分解速率的差异。结果表明:海拔与坡度是造成2种立地(地位级Ⅲ,Ⅳ)差异的主要因子,华北落叶松叶凋落物季节失质量率均表现出双峰曲线,且在秋季失质量率最高。2种立地条件下,叶凋落物半衰期分别为2.57,2.67年,完全分解分别需要11.09,11.24年。叶凋落物年平均失质量率、分解速率及初始无机养分含量均表现出立地Ⅲ高于立地Ⅳ。与立地Ⅳ相比,在立地Ⅲ下,C/N均值、木质素含量均值更有利于凋落物分解。经t检验分析,2种立地条件下叶凋落物初始无机养分含量之间并无显著差异性,而有机养分中木质素含量、有机碳含量之间差异显著(P<0.05)。相关分析表明:凋落物分解速率与全碳、C/N、凋落物层厚度呈极显著负相关,相关系数分别为-0.735,-0.569,-0.758。叶凋落物质量指标表明:在立地Ⅲ条件下,林分密度为1675株·hm-2最为有利于凋落物分解;在立地Ⅳ条件下,则以林分密度1300株·hm-2最为有利于叶凋落物分解。 相似文献
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在孟加拉吉大港丘陵地区,调查了热带季风气候条件下的3种人工林(7年生大叶相思(Acacia auriculiformis)林、15年生大叶相思林和18年生混交林)和1种天然林的森林凋落物及其对土壤性质的作用.结果表明,总的有机质积累随人工林树龄增加而增加,但是年积累量随之降低.在同一植被类型内,不同坡位新鲜或部分分解的凋落物有机质累计量变化较大,坡底部有机质积累量最高,沿着山坡向上逐渐减少.在15年生大叶相思人工林内,土壤整合有机物积累量变化趋势与新鲜或部分分解有机质积累量变化趋势相反.在7年生和15年生的大叶相思林以及18年龄的阔叶混交人工林内,新鲜、部分分解和完全分解(含土壤整合有机质)有机质总生产速率分别是2554.31、705.79和1028.01kg.ha-1·a-1,新鲜凋落物有机质在3种林分中的生产速率分别是38.23,19.40和30.48 kg·ha-1·a-1.3种人工林和自然林内,平均新鲜凋落物的有机质积累占有机质产出总量的32.45%,部分分解凋落物占13.50%,而全分解整合土壤有机质占54.56%.森林土壤酸度随凋落物分解阶段的深入而增加. 相似文献
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土壤水分梯度对阔叶红松林结构的影响 总被引：2，自引：0，他引：2
2002年8月,在吉林省白河林业局红石林场(12755E,4230N),沿着一个山坡设置了一个长宽为112m8m、包含14个样方的样带。调查了群落结构、0-10cm和10-20cm的土壤含水量、枯落物现存量及其C、N、P含量,主要树种的叶片和枝条的C、N、P含量。沿着山坡的不同位置土壤含水量的不同导致阔叶红松林的群落结构发生变化。蒙古栎的比例随着土壤含水量的下降而逐渐升高,而其他主要阔叶树种则逐渐减少乃至消失。枯落物的水分变化趋势与土壤一致。在不同坡位枯落物的分解状况不同,干重差异显著。坡下枯落物含量较坡上的丰富,部分原因在于群落结构的变化。水分和养分含量的变化影响了枯落物的成分、降解及其养分的释放,进一步影响了林木的生长速度和林分结构并最终影响整个生态系统。图7表2参14。 相似文献
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It is important to study the effect of tree density on the substrate quality and decomposition rate of leaf litter in plantations. In 2002, an experiment of the effects of thinning intensities at four different levels (i.e., 0 (I), 35.7% (II), 49.2% (III), and 64.2% (IV)) on undergrowth were carried out in an 18-year-old Pinus tabulaeformis plantation at an initial density of 3130 trees/hm2 in the middle of the hills of Yingpan, Yanqing County, Beijing. Three years later, the rates of decomposition, the amount of nutrients returned, and the characteristics of leaf litter were compared by a litter bag method. The results show that the annual loss of dry matter of leaf litter in plots I, II, III, and IV was 25.81%, 26.25%, 27.68%, and 25.96%, respectively. The turnover of leaf litter was 10.04, 9.84, 9.24, and 9.97 years, respectively. Therefore, it is feasible and convenient to evaluate the effect of thinning on the rate of decomposition. In the first two months, the N, P, K, and Mg nutrients were released quickly. During the entire observation period of 14 months, the return of both N and Mg nutrients in the four plots exhibited a release-accumulation type of cycle. The return of P and K indicated a trend of release-accumulation and a relative balance. However, the return of Ca was far different from that of the other nutrients in the four plots. The total nutrient return of the four elements N, P, K, and Mg in the plots was 10.806, 31.016, 31.798, and 39.365 g/kg, respectively. Specifically, the quality of leaf litter in plot I was the worst in that N and Ca accumulated only 2.567 and 0.767 g/kg, respectively. Thinning did decrease the ratios of lignin to N and C to N and accelerated the rate of decomposition of leaf litter. The content of crude ash in leaf litter was enhanced by thinning, which prevented acid material, such as tannins and resins, from returning to the soil. The effect of thinning intensity was evaluated by the ratio of lignin to N, the ratio of C to N, and the ash content in leaf litter. 相似文献
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Klaus Lorenz Caroline M. Preston Susan Krumrei Karl-Heinz Feger 《European Journal of Forest Research》2004,123(3):177-188
Litter decomposition was studied for 2 years in a mixed forest serving as a water protection area (Rhine-Neckar conurbation, SW Germany). Two experiments differing in initial dry weight equivalent in litterbags were set up: one to compare decomposition of European beech leaves (Fagus sylvatica) with common oak leaves (Quercus robur), and the other comparing decomposition of Scots pine needles (Pinus sylvestris) with black cherry leaves (Prunus serotina Ehrh.), respectively. Mass losses were greater for oak litter than for beech (75.0 versus 34.6%), and for cherry litter than for pine (94.6 versus 68.3%). In both experiments, a strong initial loss of soluble compounds occurred. The changes in litter N and P concentrations and the decrease in C-to-N ratio coincided with changes in residual mass. However, neither tannin and phenolic concentrations nor NMR could explain the pronounced variation in mass loss after 2 years. Differences in litter palatability and toughness, nutrient contents and other organic compounds may be responsible for the considerable differences in residual mass between litter types. The fast decay of black cherry leaves appears to play a major role in the present humus dynamics at the studied site. Since black cherry has a high N demand, which is mainly met by root uptake from the forest floor, this species is crucial for internal N cycling at this conurbation forest site. These effects together may significantly contribute to prevent nitrate leaching from the forest ecosystem which is subject to a continuous N deposition on an elevated level. 相似文献