造林密度对1—63杨木材密度的影响

本文研究了４×４ｍ，５×５ｍ，６×６ｍ和７×７ｍ４种不同株行距对Ｉ－６３杨木材基本密度株内变异的影响。方差分析表明，不同造林密度、离地不同高度和不同树龄之间木材密度存在极显著差异，不同方位间无差异。胸高处木材密度与全树木材密度间存在的明显的线性正相关。     

马尾松纸浆林造林密度对木材性质的影响

本文研究了龙里林场5种造林密度，15年生马尾松纸浆林木材基干密度和管胞形态。结果表明：造林密度对木材基本密度影响不大，但具明显的趋势，即一定造林密度条件下，木材基本密度随造林密度增加而增加，造林密度对管胞形态的影响，表现出因年龄而异，不同造林密度马尾松管胞形态总平均值变化不大，但管胞长度随树龄的增大而增加的趋势，受到造林密度影响，较低的造林密度各生长轮管胞形态差异不显著。管胞长度频率分布具一定的规律，中等长度（2501－3500um)管胞长度频率分布最大，占总频率的45％－74．19％，随着造林密度加大，中等长度的管胞增加，较短管胞长度（≤2500um)减少。     

造林密度对马尾松木材主要性质影响的研究

本文对贵州省龙里林场马尾松密度试验林 ,5种造林密度 ,15年生马尾松木材基本密度、生长轮宽度、晚材率和解剖特性进行研究。结果表明 :造林密度对马尾松生长轮宽度、晚材率和管胞列数影响较大 ,方差分析达到显著水平。造林密度大 ,则生长轮变窄 ,管胞列数减少 ,晚材率增加。造林密度对马尾松木材基本密度的影响不显著 ,但具明显的规律性 ,即随着造林密度加大木材基本密度增加 ,造林密度过大反而下降。造林密度对管胞形态的影响表现出因树龄而异 ,不同造林密度马尾松管胞形态总平均值变化不大 ,但管胞长度随树龄的增大而增加的趋势受到造林密度影响。较低的造林密度各生长轮管胞长度差异不显著。组织比量不受造林密度影响。     

造林密度对马尾松林分生长木材造纸特性及经济效益的影响

贵州省龙里林场松造林密度试验林１５年的试验结果表明,密度对树高生长无明显影响;平均胸径、单株材积随密度的增加而减小,高径比和蓄积量则随密度的增大而增加,不同处理间的差异从６￣８年起达到显著或极显著水平。小径原木出材率随密度的增大明显降低,短小原木和薪材的出材率及出材量均随密度的增大而增加,各处理间的差异达到极显著水平。木材生长轮宽度随造林密度的增加而减小,晚材率和木材基本密度大体上随密度的增高而增     

造林密度对杨树木材性质的影响

合理的造林密度是科学的营林措施中一项重要而容易操作的措施,造林密度的大小影响林木生长、林分的郁闭、林木树冠大小和激素分化等,因而直接影响木材的材质。本文简要综述了造林密度对杨树木材密度、纤维形态、纤维素含量和物理力学性质的影响规律,强调在选择造林密度时不仅要考虑单位面积上规格材的生产率,也要充分注意其对木材性质的影响,才能兼顾杨树人工林的丰产与优质。     

刺楸木材基本密度的变异研究

本文以安徽琅琊山天然林内的三株刺楸木材为材料，详尽研究其基本密度的径向变异、轴向变异以及影响基本密度变化的主要因子，结果发现：发现为木材基本密度的径向变化趋势为自髓心向外以曲线形式降低，到一定年限后保持平缓或略有下降，用幂池数模拟，相关系烤在０．８以上；轴向变化趋势为自树干基部向上渐增大，到５．３米处达最大值，再向上到树冠基部又变小．方差分析表明株间变异大于株内变异；从解剖分予组织比量来看，基本密     

杉木木材基本密度变异的研究

利用设置在分布区北缘江苏宁镇丘陵（句容、江宁）的各种试验测定林所收集的２４个种源、５０个江苏当地种源优树半同胞子代、１７个产地间杂交组合子代４９０株平均木选择材料,以及融水种源山洼、山谷、山坡３种栽植立地,３０００、４９５０、６０００株·ｈｍ－２３种栽植密度,以及６、８、１０、１５、１８ａ等５个年龄组林分２７５株样木材料研究杉木木材的基本密度变异规律。结果表明,杉木全分布区试验不同种源,江苏种源优树自由受粉子代家系,江苏江宁×四川德昌种源产地杂交组合子代间有显著的遗传变异（依次为：Ｆ＝６．７１＊＊＞Ｆ０．０１＝２．４０;Ｆ＝３．８７＊＊＞Ｆ０．０１＝２．１９;Ｆ＝２．６３＊＞Ｆ０．０５＝２．３６）,具有选择改良潜力。栽植立地对融水种源幼龄材基本密度没有明显影响;林龄与栽植密度是引起木材基本密度变异的重要因素。供试测定材料基本密度与材积生长没有统计置信的负相关关系,性状间影响弱。杉木材性改良及生长与材性联合改良,可按“生长（材积）、材性（基本密度）两阶段独立选择法”进行改良。     

浅谈造林密度对树木的影响

造林密度是指单位面积上栽植的株数，林分的产量是由单位面积总株数决定的，只有合理的株数，用材林单位面积的木材产量才能提高。     

杉木材性株内变异的研究Ⅰ.木材力学性质和木材密度

对１５株浙江产杉木株内不同高度和圆周不同方位上木材的抗弯强度、抗弯弹性模量、顺纹抗压强度和木材密度的差异，木材密度的径向变异模式和木材力学性质与木材密度的相关关系进行了测定和分析。主要结果是：抗弯强度和抗弯弹性模量在株内不同高度上差异特别显著；顺纹抗压强度和木材密度未表现出显著差异；在圆周不同方位上，三项力学性质和木材密度均为南北向高于东西向，差异不显著；木材密度径向变异模式在不同高度和不同方位上均为接近水平有一定波动的直线；三项力学性质与木材密度的相关关系在不同高度和不同方位上均特别显著，但不同力学性质与木材密度的相关系数有明显差异，不同高度上和圆周不同方位上，亦有差异。     

造林密度对杂种落叶松生长与材性的影响

采用SAS、SPSS等软件分析了4种造林密度(2 500、3 300、4 400、6 600株/hm2)对杂种落叶松的生长、木材密度、纤维长度、纤维宽度及纤维素含量的影响。结果表明:造林密度对杂种落叶松的生长影响非常显著,对纤维长度、宽度影响显著(P<0.05),对木材密度和纤维素含量影响不显著。11年生杂种落叶松的平均纤维长度为2.52 mm,平均宽度为40.56μm,长宽比平均值为64.88,纤维素的平均含量为50.41%。     

EFFECT OF TIMBER DENSITY ON RETENTION OF WOOD PRESERVATIVES

The amount of CCA fixed in the southern pine treated with CCA have been eval-uated.The conclusions from these experiments are:with the timber density increases,the reten-tion based on weight/weight will decrease,but the retention based on weight/volume will bealmost constant.Retention by weight would be more influential than by volume.     

栽培密度对喜树(Camptotheca acuminata Descne)幼苗生物量及喜树碱含量的影响

栽培密度是植物生长的重要影响因子,能够显著影响植物的生长.2004年5月,将温室培养的喜树(Camptotheca acuminata Descne)幼苗按照5种栽培密度(11、16、25、44、100株·m-2)移栽到田间,并于2004年9月中旬采收.我们对喜树幼苗的生长(包括株高和冠幅)、生物量分配、喜树碱含量和产量进行了研究.就5种栽培密度而言,喜树幼苗生物量、株高、冠幅及总叶面积均在密度为25株·m-2时最大.嫩叶喜树碱含量高于喜树幼苗其它各器官的喜树碱含量并且随栽培密度的改变有明显变化,在100株·m-2时达到最大,但其它器官喜树碱含量随栽培密度的变化不显著.栽培密度为25株·m-2时,喜树碱积累显著增强.结果显示,为得到较高喜树碱含量的喜树原料,喜树幼苗的最适栽培密度应为25株·m-2.     

Effect of planting density on plant growth and camptothecin content of Camptotheca acuminata seedlings

C. acuminata seedlings cultivated in greenhouse were transplanted into the fields with 5 designed planting densities (11, 16, 25, 44 and 100 plants·m⁻²) in May of 2004 and were harvested in the middle of September of 2004. The seedling growth indexes including plant height and crown width, biomass allocation, camptothecin (CPT) content and CPT yield of different organs (young leaf, old leaf, stem, and root) were studied. For the 5 selected planting densities, the plant biomass, height, crown width, and total leaf area ofC. acuminata seedlings all showed highest values at the planting density of 25 plants·m⁻². CPT content in young leaves was higher than that in other organs of seedlings and presented an obvious change with the variation of planting densities and with the highest value at density of 100 plants·m⁻², while for other organs no significant variation in CPT content was found with change of planting density. The accumulation of CPT was enhanced significantly at the planting density of 25 plants·m⁻². It is concluded that for the purpose to get raw materials with more CPT fromC. acuminata, the optimal planting density ofC. acuminata seedlings should be designed as 25 plants·m⁻². Foundation item: This paper was supported by the National Natural Science Foundation of China (No. 3970086) and Heilongjiang Province Foundation for Distinguished Youth Scholars (JC-02-11) Biography: Wei Huan-yong (1978-), male, Graduate in College of Life Sciences, Northeast Forestry University, Harbin 150040, P. R. China. Responsible editor: Zhu Hong     

Snag density varies with intensity of timber harvest and human access

Many species of vertebrates depend on snags (standing dead trees) for persistence, and limited research suggests that snag density is lower in areas of intensive timber harvest and increased human access. While intensive timber harvest is one source of potential snag loss, ease of human access to forest stands may also facilitate loss via firewood cutting of snags. Accordingly, we hypothesized that density of snags (number of snags/ha) would decline in forest stands with increasing intensity of timber harvest and increasing ease of human access. We tested our hypothesis by sampling stands under varying levels of timber harvest and access on National Forest land in the northwestern United States. Stands with no history of timber harvest had 3 times the density of snags as stands selectively harvested, and 19 times the density as stands having undergone complete harvest. Stands not adjacent to roads had almost 3 times the density of snags as stands adjacent to roads. Unharvested stands adjacent to non-federal lands and closer to towns had lower snag density, as did stands with flat terrain in relation to nearest road. Our findings demonstrate that timber harvest and human access can have substantial effects on snag density. Meeting snag objectives for wildlife will require careful planning and effective mitigations as part of management of timber harvest and human access.     

杨树新无性系丹红杨引种试验

作者通过对潜江地区丹红杨品比试验林与推广示范林的调查,从造林类型、栽植密度、土壤条件等方面进行生长量、抗性分析,结果表明:丹红杨在潜江的引种栽培初步成功,推广示范区丹红杨单株材积生长量是中潜3号的132.5%～163.9%,表现出速生、丰产、抗性强等特点,可以作为杨树工业原料林的优良品种在江汉平原及类似地区推广应用。     

丹红杨等几个杨树品种引种试验初报

为了选育适合平原地区生长的杨树新品种,湖北省潜江市林科所引进丹红杨Populus deltoides.CL.Dan Hong.等杨树新品种进行生长、抗性试验,以中潜3号为对照,通过对参试品种胸径、树高、材积、抗虫性、抗病性调查,分析了各品种间的生长量差异和抗性差异,丹红杨在所有参试品种中表现出生长快、抗性强、综合性状优良的特性,值得在江汉平原等适生区域推广。     

造林密度和修枝对‘欧美107杨’生长量的影响

以3种造林密度‘欧美107杨’为研究对象,通过测定不同年份胸径、树高、枝下高等,来分析造林密度及修枝对‘欧美107杨’生长量的影响.结果表明,‘欧美107杨’胸径和单株材积生长量随着造林密度的增大而减小,即3种造林密度‘欧美107杨’2a胸径和单株材积生长量由高到低依次为株行距3m×12m、5m×6m、3m×6m,而树高生长量变化趋势正好相反.修枝在一定程度上能促进树高生长和提高枝下高,有利于提高杨树木材质量.     

35杨等黑杨派杨树无性系区域化试验

在江苏沿海、沿江和里下河地区10个市（县）,对35杨等8个黑杨派无性系进行了区域化试验。通过对7年生树干解析数据分析表明,品种间和试点间的产量水平都达显著或极显著差异。其中,35杨与7号杨各试点平均产量极显著高于其余品种（α=0.01）,苏杨18号产量显著高于72杨（α=0.05）;位于长江圩区的江宁试点产量显著高于其他试点（α=0.05）,金湖林场试点产量显著低于其余试点（α=0.05）。通过区域产量多重比较（邓肯法）结果得出各品种适栽地区：35杨在江苏各栽培区均速生高产,生长稳定性高,可在江苏全省广泛应用;苏杨7号丰产性显著优于69杨与72杨,在沿海轻度盐碱地和沿江平原地区适应性强,可在类似地推广;74杨和17号杨平均丰产性低于72杨和69杨,但74杨平均造林成活率高,在徐州地区表现出一定的生长优势,而17号杨分枝角度小,树干通直,高生长优势明显,是营建农田防护林和公路绿化的优良品种,因此可以控制推广。     

杉木生长,材性兼优种源选择的研究

经对杉木中心产区优良种源的中间试验研究表明,种源间生长与木材基本密度性状有一定差异,根据对１２年木材基本密度性状和９年材积生长性状的测定结果,初步选出广西那坡,贵州锦屏,贵州榕江等生长,材性兼优的种源。其木材基本密度与广西融水优良种源相近,材积生长比融水种源增加４７．０％￣８３．６％,遗传增益达１３．４１％￣２３．８６％。     

Effect of Poplar (Populus deltoides) shelterbelt on the growth and yield of wheat in Punjab, India

A study was conducted around Chandigarh (Punjab), India to assess the effect of Populus deltoides shelterbelt on wheat. Crop density, root and shoot length, biomass and grain yield of wheat at crop maturity were significantly lower, up to 12 ± 1 m in the fields sheltered by P. deltoides than in unsheltered plots. The reduction of biomass and grain yield of wheat were comparatively more than that of other parameters. The observed reduction in the growth and yield of wheat could be attributed to phytotoxic interference of the phenolics from the tree with the crop. This revised version was published online in August 2006 with corrections to the Cover Date.