【作者】 张群；

【导师】 范少辉；

【作者基本信息】 中国林业科学研究院 ， 森林培育， 2011， 博士

【摘要】 科学地集约经营人工用材林,通过合理营林措施,有效地控制木材形成,提高人工林木材产品质量,实现高产优质的森林培育目标是当前林业生产及森林培育学科发展的方向。本项研究以我国南方造林面积最大的杉木人工林为研究对象,以培育高品质的杉木无节大径材为研究目标,研究密度控制和人工修枝等营林措施对杉木人工林木材质量的影响,探讨提高杉木木材质量和加工利用率的森林培育方法。在福建省洋口国有林场1996年营造的杉木人工纯林进行试验,按3种林分密度:900株?hm-2、1 200株?hm-2、1 800株?hm-2和4级修枝强度:6 cm、8 cm、10 cm、12 cm(修枝处的最小直径)对杉木进行密度和修枝处理,以不修枝杉木为对照。系统地研究人工修枝对杉木生长和生产力、木材的物理力学性质和主要缺陷,以及林下植被和林地土壤等林分环境的影响作用。最后综合木材生产的数量、质量和利用等多项指标,确定了对提高杉木木材质量有利的合理林分密度和适合采取的修枝强度,以及人工修枝的起始时间、修枝次数和时间间隔,林地土壤管理等具体森林栽培措施,为杉木无节大径材培育提供科学依据。试验结果表明,人工修枝对杉木优质材培育具有积极作用。在合理密度下,人工修枝对杉木生长有一定促进作用,杉木的胸径生长提高20%,树高生长和林分蓄积提高4%,缩短杉木数量成熟的时间,生产力提高50%以上。人工修枝还能有效地控制木材中节子的长度,提高杉木无节材比例,同时减小尖削度,提高枝下高,使杉木干形更趋近于通直圆满。杉木修枝10年后,无节材比例可达20%~25%,比不修枝的杉木提高了近5倍。修枝后杉木人工林的林下植被盖度、种类丰富度和多样性大大提高,人工修枝对提高杉木人工林的林分稳定性和物种优势种的更迭起到一定作用。在木材性质方面,人工修枝还可以降低幼龄材比例,从而提高杉木木材的尺寸稳定性。木材幼龄材比例下降了近一倍。然而,人工修枝也带来一些不利影响。在密度较大的林分内进行修枝,会抑制杉木的树高、胸径和材积生长,延缓杉木的数量成熟时间。此外,人工修枝还会降低杉木木材密度和冲击韧性等木材物理力学性能,且修枝强度越大,对木材物理力学性能的影响越大。林地土壤肥力消耗加大,应加强人工抚育措施,维持地力保证以获得最大材积生长量。采用工业CT扫描获取杉木木材内部结构信息,有效地解决了传统解剖方法无法确定无节材内部缺陷的难题,为工业CT扫描技术在木材利用科学上的应用研究做了有益的尝试。单位长度范围内,杉木木材的节子轮数为4~5轮,平均间距为0.22 m,节子数量20个左右。杉木每一轮枝上的节子数量约为4~5个,呈均匀对称分布。随着在树干上着生位置的上移,节子的数量逐渐减少,节子尺寸则是长度逐渐缩短而直径增大。而利用植物生长模型对杉木分枝结构的模拟,直观地表达了杉木无节材的内部缺陷结构与分布,为木材加工利用提供有效信息,大大提高木材利用率。试验证明,杉木无节大径材的培育方案为在林分密度1 200株?hm-2条件下,采用修枝强度为10 cm对5年生的杉木进行人工修枝最为合适。采用树干直径作为修枝强度的度量值,能够有效地控制木材缺陷的范围,不受林木生长状况影响,同时与树高控制法相比,还具有操作性强的优势。修枝10年后,杉木树高接近15 m,胸径可达22 cm以上,平均材积0.24 m3。4~10年为杉木速生期,7~9年时杉木生长速度最快。15年生时,杉木还未达到数量成熟年龄。杉木木材的含水率为8%,气干密度0.34 g?cm-3,抗弯弹性模量11.9 MPa,抗弯强度65.8 MPa,冲击韧性15.58 kJ?m-2。林下植被主要有五节芒、渐尖毛蕨、芒萁等草本和粗叶榕、杜茎山、苦竹等灌木,还有三叶青、大头艾纳香、玉叶金花等藤本植物。林下植被的盖度达40%以上,而未修枝杉木林下植被盖度仅为2%。更多还原

【Abstract】 The development trends of current forest silviculture are to intensively manage plantation, adopt reasonable cultivation measures, effectively control the wood formation and improve the quality of timber, and achieve the goal of high yielding and quality. For the purpose of producing high-quality large-diameter clear wood, the author studied the effects of density control and green-pruning on the wood quality of Chinese fir (Cunninghamia lanceolata) and the measures to improve the timber quality and productivity of Chinese fir which planted the largest area in South China.The sample site is at the Chinese fir pure plantation established in 1996 located at the Yangkou State-owned Forest Farm in Fujian Province. The Chinese fir trees were pruned artificially with 4 intensities :6 cm, 8 cm, 10 cm and 12 cm, and 3 stand densities:900 tree?hm-2, 1 200 tree?hm-2 and 1 800 tree?hm-2 with non-pruned Chinese fir trees as the contract. The influences of green-pruning on tree growth and productivity, wood physical properties and defects, and on the forest environment conditions, such as understory vegetation and forest soil, were studied. By integrating the wood quantity, quality and utilization and other indicators, the reasonable stand density and pruning intensity beneficial to improving the timber quality of Chinese fir were determined. Some silviculture measures about initial time, frequency and time interval of pruning, and stand soil management were suggested so as to provide a scientific basis for produce large-diameter clear wood of Chinese fir.The results of the study showed that green-pruning played a positive role in improving Chinese fir’s wood quality. 10 years after pruning, the DBH of Chinese fir increased by 20%, the height and stand volume increased by 4%, the wood quantity maturity came earlier, the productivity increased by more than 50%. Green-pruning could also effectively control the length of knots on wood, reduce tree taper, improve the proportion of clear wood and the under branch height, so that to improve the stem form and quality. The proportion of clear wood increased to 20% to 25%, nearly 5 times that of non-pruned Chinese fir tree. The coverage, species richness and diversity of understory vegetation were greatly improved after pruning. Green-pruning played a positive role in improving the forest stability and helping the dominant species’change. Green-pruning could also improve the wood properties by reducing the proportion of juvenile wood, and improve wood dimensional stability. After pruning, the proportion of juvenile wood of Chinese fir dropped by 40% or more. However,green-pruning could also bring some negative impacts. Pruning in the dense stands and using heavier intensity would restrict the increments of tree height, diameter and volume, delay the quantity maturation. In addition, pruning would degrade some physical and mechanical properties of wood such as density and bending strength. And more soil fertility will also be consumed. So it was necessary to strength artificial tending and to maintain the site quality to yield the maximum volume increment.The study showed that, for cultivating knot-free,large-diameter Chinese fir wood with stand density of 1 200 tree?hm-2, it was appropriate to prune the 5-year-old young Chinese fir stands with pruning intensity of 10 cm. Using tree diameter as a measure of pruning intensity could effectively control the wood defects and could be free from the influences of tree growth conditions. Also, it was more operational compared with the method of tree height controlling. 10-years after pruning, the tree height of Chinese fir was close to 15 m, DBH up to 22 cm, the average volume up to 0.24 m3. The fourth to tenth year was the fast growth period for Chinese fir trees, when the trees were 7 to 9 years-old, the growth rate was the fastest. Chinese fir could not reach the quantity maturity until 16-years-old. 10 years after pruning, the moisture content of wood was 8%, air-dry density was 0.34 g?cm-3, MOE was 11.9 MPa, bending strength was 65.8 MPa, and the toughness was 15.58 kJ?m-2. The coverage of understory vegetation of pruned Chinese fir plantation was more than 40% while that without pruning was only 2%. The dominant understory herb, shrub and liana species were Miscanthus floridulus, Cyclosorus acuminatus, Dicranopteris linearis, Ficus hirta, Maesa japonica, Pleioblastus amarus, Tetrastlgma hemsleyanum, Blumea riparia var. megacephala and Mussaenda pubescens.By CT scanning, the internal structure information of wood was obtained. It effectively solved the problem that the traditional dissection methods could not determine the internal defects of wood. The results of CT scanning showed that the whorled branches of Chinese fir were 4 to 5 rounds with round spacing of 0.22 m, and the knots number was 20 per meter. The knot number of each round was about 4-5 and was symmetrical distributed. For the knots on the trunk, the higher they locate, the less the number was, the length became shorter while the diameter became larger. Plant growth model was used to simulate the structure of branches, which could provide effective informations for wood processing and utilization by visually presenting the structure and distribution of internal wood defects, so the timber utilization would be greatly improved.更多还原