造林密度对不同马尾松种源生长和木材基本密度的影响

利用设置在福建武平的12年生马尾松种源与初植密度互作试验林,研究5个优良种源生长、形质和木材基本密度对初植密度的反应及其互作效应.结果表明:马尾松不同种源对初植密度的反应存在较大的差异,并因性状而异.种源胸径和活枝下高对初植密度反应最为敏感,树高次之,树干通直度和木材基本密度反应最小.广西岑溪、广东信宜、江西崇义和福建武平属于胸径对初植密度敏感的种源,皆表现在2.5 m×2.0 m初植密度下生长量最大,广东高州种源胸径生长对初植密度的敏感性则较小;5个参试种源活枝下高的初植密度效应差异显著,皆随着初植密度增加而升高;除发现江西崇义种源树干通直度和福建武平种源木材基本密度在不同初植密度间存在一定差异外,马尾松种源树干通直度和木材基本密度的初植密度效应不显著.初植密度对胸径、活枝下高、树干通直度和木材基本密度的种源分化影响不显著,仅树高生长在1.5 m×2.0 m和2.5 m×2.0 m 2种初植密度下种源差异明显.统计分析可知:马尾松生长、形质和木材基本密度的种源和初植密度互作效应较小,初植密度不影响种源生长和材质材性的相对表现,然而因区组×种源×初植密度互作效应明显,应在给定初植密度下为不同优良种源确定适宜的立地条件.     

初植密度对白桦食用菌原料林生长的影响

在黑龙江省铁力林业局退耕还林迹地进行白桦食用菌原料林试验,初植密度分别为2 500、3 300、4 400和5 500株/hm2,营造白桦与落叶松混交林作为对比试验林分,研究不同初植密度和造林方式对白桦生长的影响。结果表明:2 500株/hm2栽植密度林木生长最快,各生长性状表现较好;初植密度与树高、胸径的相关程度不明显;初植密度与树高、胸径的拟合方程均为3次方程,拟合程度一般;白桦与落叶松混交林较白桦纯林生长性状表现更好。     

马尾松优良种源对初植密度的早期生长反应

在马尾松中心产区之一的闽西地区,利用5个马尾松优良种源在肥力中等立地上设置的种源与密度互作9年生试验林测定材料,初步研究优良种源生长对初植密度的反应式样和互作效应.结果表明,5个参试优良种源对初植密度的反应差异很大,江西崇义和福建武平种源生长对初植密度反应敏感,广西岑溪和广东高州种源生长对初植密度反应较小,而广东信宜种源的生长反应则一般.比较分析发现,广西岑溪、广东高州、广东信宜3个南部种源在1.5 m×2.0 m初植密度下树高和胸径生长量大、单位面积蓄积量高,适宜较高初植密度短周期经营,但也可在2.0 m×2.5 m较稀初植密度下实现大径材培育目标.江西崇义和福建武平两个中部种源在2.0 m×2.0 m中等初植密度下生长表现最好.马尾松种源生长分化与初植密度有关,在较密和较稀初植密度下种源生长分化较大,密植似可提高早期选择效果.研究还发现,种源×初植密度、区组×种源×密度互作显著,应针对不同立地和种源设计不同的初植密度,实现优良种源与初植密度的优化配置.     

杉木幼龄林分断面积生长的良种与密度效应研究

[目的]探讨不同良种和初植密度对杉木幼龄期断面积生长的影响及其互作效应,以揭示在这两个控制因子下杉木林断面积生长发育规律。[方法]以2012年春在福建省邵武卫闽国有林场营造的杉木良种和初植密度互作试验林为研究对象,根据8年的逐年定位观测资料,分析2个杉木种子园良种(第1代种子园良种和第3代种子园良种)和4种初植密度(1 667、3 333、5 000、6 667株·hm~(-2))控制下的林分断面积生长动态效应。[结果]初植密度对林分断面积生长具有极显著影响,同一林龄下,初植密度越高,林分断面积生长愈大。林分断面积生长的良种效应差异不显著,但低初植密度下(1 667和3 333株·hm~(-2)),第3世代良种的断面积生长要高于第1世代良种,且随林龄增长这种现象愈明显。方差分析结果表明良种和初植密度间交互效应不显著,多重比较结果表明:低初植密度下,良种对断面积生长的正效应和密度对断面积生长的正效应具有叠加效应,且随林龄增长这种叠加效应愈明显,而高初植密度下(5 000和6 667株·hm~(-2)),不同良种和密度组合下的断面积生长差异不显著。[结论]低初植密度下,杉木幼龄林分断面积生长的良种和密度效应具有叠加效应,第3世代良种初植密度为3 333株·hm~(-2)的断面积生长显著高于第1世代良种初植密度为1 667株·hm~(-2),随初植密度增大,良种对林分断面积生长的影响程度逐渐减弱。     

初植密度对中国沙棘林木生长特征的影响

为探讨初植密度对中国沙棘林的林木生长过程及主要生长特征的影响,在毛乌素沙地布设了初植密度为2 500株/hm2、4 444株/hm2、10 000株/hm2、40 000株/hm2的中国沙棘林田间观测试验。根据测定结果,分析了中国沙棘林的林木生长过程及主要生长特征(生长量上限、生长量增长率、速生期迟早、速生期长短)与其初植密度的关系。结果表明:(1)初植密度的变化没有改变林木树高、地径、冠幅的"慢-快-慢"生长节律,采用Logistic方程回归结果可分别解释其变异的99%、98%、93%。(2)初植密度的变化改变了林木生长过程的主要特征。其中,树高生长量上限及树高生长量增长率随其初植密度的增大呈现先上升后稳定的态势,地径生长量上限、地径生长量增长率、冠幅生长量上限随其初植密度的增大呈下降的态势,冠幅生长量增长率随其初植密度的增大呈现先升后降的态势。(3)初植密度变化对林木冠幅生长特征的影响最大,对地径生长特征影响次之,对树高生长特征影响最小。且在不同初植密度下均是林木的冠幅首先进入速生期,其次是树高,最后是地径。     

辽东山区不同密度落叶松人工幼龄林林木生长和土壤养分特性

[目的]探究落叶松人工林生长和土壤特性与初植密度的关系,为辽东山区落叶松人工林的合理经营提供科学依据.[方法]以辽宁省清原大孤家林场内3种初植密度(1600、2500、3300株/hm2)的15年生落叶松人工林为研究对象,基于林木生长指标和土壤养分指标等数据,分析初植密度对林木生长和土壤特性的影响.[结果]林分平均胸径...     

伊克昭盟黄河冲积平原区杨树造林适宜的初植密度和成材密度的探讨

伊盟地区人工林中主要造林树种以杨树为主。特别是在黄河冲积平原上,因杨树比其它树种生长迅速,所以无论用材林或防护林,都以杨树为主。但在不同立地条件下,初植密度和成材密度多大合适,向来没有确定下一个有科学依据的指标。五十年代,搬用苏联经验,初植密度采取每亩666株的高密度,而且成活后没有做到适时地抚育间伐,以后形成“小老头树”为多。到了六十、七十年代,人们逐步觉得初植密度过大,不便机械作业,且生长不良,也浪费种苗。所以有些地方将初植密度改为:1×2米、     

广林9号桉幼林的施肥效应

将磷肥、尿素和桉树专用肥3种肥料分为3个水平,对4个不同初植密度广林9号桉树幼林进行施肥处理。采用方差分析方法分析了不同施肥处理及不同初植密度对桉树幼林生长的影响。结果表明：不同施肥种类及施肥量对广林9号桉幼林生长差异显著,桉树专用肥的影响极显著,尿素影响显著,磷肥影响不显著,其中尿素随施用量的增加对苗木生长存在抑制作用;桉树专用肥随施用量的增加对苗木生长有明显促进作用。不同初植密度的1年生广林9号桉幼林生长差异不显著。     

灰木莲不同造林密度的幼林生长及形质性状效应研究

为探寻闽南山地灰木莲的合理种植密度,以促进林分高效生长,在闽南山地开展灰木莲6种不同初植密度试验,分析比较不同初植密度对5 a生幼林生长及形质性状的影响效应,结果表明：种植密度对灰木莲的幼林生长和形质性状存在显著性影响,种植密度越大,树高、胸径、枝下高、主干分叉性、侧枝密度、侧枝角度等性状表现越好,而种植密度对冠幅、主干通直度、侧枝粗细等性状无显著性影响。综合各项生长指标效应,灰木莲适宜的初植密度为1 667～3 333株·hm^-2(株行距1.5 m×2.0 m和2.0 m×3.0 m),能有效促进灰木莲快速生长以及形成较好的形质性状。     

湿地松纸浆林密度试验初报

采取不同的初植密度处理 ,对湿地松纸浆林树高、胸径生长量进行了方差分析 ,3年生以下 ,初植密度对树高和胸径均无显著差异 ,随着年龄增长 ,树高、胸径生长差异呈增加趋势。树高 5年生、胸径 4年生时各密度处理有显著性差异。密度越小 ,树高、胸径生长量越大     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.