18年生尾巨桉无性系木材纤维形态和基本密度变异研究

对18年生尾巨桉（Eucalyptus urophlla×E．grandis）无性系木材纤维特征与基本密度进行研究,通过测定木材的纤维长度、宽度、壁厚、腔径、木材基本密度,分析结果表明：木材基本密度、纤维长度、纤维长宽比、壁厚、壁腔比在树干径向方向由髓心向外有逐渐增大的规律。纤维长度与基本密度之间呈显著的负相关,纤维宽...     

杨树无性系生长和材性的遗传变异及多性状选择

以７年生２５个杨树无性系为材料研究了生长和材质性状的遗传变异及性状之间的相关．６个性状纤维长、纤维宽、长宽比、木材密度、树高、胸径在无性系间均存在极显著的差异。生长和材质性状受中等更强度的遗传控制．６个性状的重复力分别为８１．９％，７３．３％，７０．５２％。６４．３％．６８．８％，７０．５４％．胸径和树高之间、纤维长度与纤维长宽比、胸径之间、木材密度与胸径之间都呈现出较高的遗传正相关．宜接选择效果优于间接选择，指数选择优于直接选择。由４性状树高、胸径、纤维长度与基本密度配合的选择指数对本实验群体比较合适。利用选择指数评选出４个生长和材质兼优的优良无性系。     

竹柳等4个柳树无性系造纸材性测定分析

对3年生竹柳、苏柳172、苏柳795、苏柳799进行造纸材性测定,结果表明:4个柳树无性系的木材基本密度在0.324~0.368 g/cm3之间,纤维长度在0.866 9~0.928 8 mm之间,纤维宽度在21.349~22.683μm之间。4个柳树无性系木材纤维的长宽比、壁腔比及腔径比等指标均符合造纸原料要求,而且纤维长度、宽度均分布比较均匀。     

21年生杉木优良无性系生长与材质性状研究

对来源于湖南省的38个杉木无性系在江西省分宜县大岗山年珠林场21年生试验林各生长性状进行了调查与分析,选出4个杉木优良无性系43、68、88、300和大岗山杉木一般生产用种ck进行生长性状和材性性状对比研究。结果表明:4个优良无性系总体胸径与木材基本密度之间存在极显著负相关关系(r=-0.331),优良无性系43胸径生长量、单株材积生长量和木材基本密度均优于对照,可作为生长和材性性状联合选择的建筑材无性系;各优良无性系纤维长宽比均高于对照,优良无性系300长宽比最大且长纤维最多,最适宜用作纸桨材;各无性系不同林龄间纤维长度的差异较为明显,为杉木优良纸桨材无性系最佳采伐时间的确定提供了理论基础。     

杨树无性系生长与材性遗传变异及综合选择研究

以6年生18个杨树无性系为材料，研究其生长与材性性状的遗传变异及性状问的相关性，结果表明：除纤维含量、纤维长度外，树高、胸径、材积、纤维宽度、长宽比、木材基本密度6性状在无性系间均存在显著差异，各性状重复力在0．6109～0．9053之间，生长性状受高度遗传控制，纤维宽度、长宽比、木材基本密度受中等至强度遗传控制；生长与材性性状遗传具有相对独立性，就杨树纸浆材而言，材性改良应以生长性状的改良为前提；利用灰色关联度分析法评选出XL-90、XL-77、XL-101、XL-75、XL-92共5个综合性状优异的美洲黑杨杂交新无性系，其中XL-90、XL-77表现尤为突出，与I-69比较，其单株材积生长量分别提高60．71％、46．45％，单株纤维产量分别提高51．43％、44．13％。     

不同林分密度对桉树幼林木材材性的影响

对两种桉树无性系(巨细桉DH201-2和尾巨桉DH32-29)在5种不同林分密度下(1250、1657、2500、5000和6667株.hm-2)的木材材性(包括木材基本密度和纤维形态特征)进行了测量和研究分析(纤维形态特征分两种不同材型分析:心材与边材)。结果表明:无性系DH201-2的林分密度3(2 500株.hm-2)木材基本密度最大,为452 kg.m-3,DH32-29以林分密度2(1657株.hm-2)的木材密度最大,为436 kg.m-3;相同无性系相同林分密度下,边材纤维长度比心材纤维长度长,边材长宽比一般比心材长宽比要大,纤维宽度则无显著差异;无性系DH201-2的林分密度3(2500株.hm-2)和林分密度5(6667株.hm-2)是符合林分蓄积量、木材基本密度和纤维长度最大值的组合。     

南方型黑杨无性系木材材性的研究

在48个7—8年生南方型黑杨无性系对比试验林中,选择生长量达中等以上水平的19个新、老无性系,开展木材基本密度、纤维素含量、纤维形态的分析研究。纤维素含量和纤维长度在19个无性系中无显著差异,基本密度只在中汉17等几个无性系间有显著差异。基本密度和纤维长度在不同年龄间都存在显著差异。1～3年生的纤维长度在0．9mm以下,属短纤维;4—7年生的纤维长度在0．91mm以上,达到中级纤维长度标准。因此,杨树纸浆材超短轮伐期可以确定为3a或3a以上。     

9个桉树无性系木纤维径向变异研究

为研究不同无性系桉树的木纤维特性和变异规律,采用木材解剖技术,测定9个尾叶桉×巨桉无性系的纤维长度、纤维宽度、纤维双壁厚、长宽比、壁腔比和腔径比等纤维特性指标,分析这些特征在径向上的变异规律。结果显示：9个无性系的纤维长度、宽度、双壁厚、长宽比、壁腔比和腔径比的变异范围分别为899.74～1 038.08μm, 17.41～20.77μm, 8.07～12.13μm, 44.15～60.07,0.96～2.04,0.41～0.57;综合分析各纤维指标,DH33-9、LEI9、DH32-22综合指标达到优质纸浆材原料的要求;其中无性系DH33-9还具有长宽比>35,壁腔比<1的特征,可作为优质的纤维原料。研究结果为桉树有针对性的培育以及木材的合理加工利用提供参考和依据。     

两个桉树无性系木材材性的年龄效应

以桉树主栽区雷州林业局的2个桉树无性系为研究对象,研究其木材材性的年龄效应.结果发现:尾细桉LH1和ZU6无性系,其纤维长度、宽度和长宽比均随林龄呈增加趋势,纤维长度在0.6 ～ 0.8 mm之间,长宽比在34.4 ～ 42.4之间,同龄LH1的长宽比高于ZU6;随林龄增加木材质量和制浆造纸性能提高.     

杨树抗云斑天牛新品种选育材性性状遗传分析

格性直接影响木材的用途及其经济价值。材性育种已成为现代林木育种的一个重要内容。世界各国都非常重视。木材密度和纤维长度是主要的两个材性特征,往往是林木材性改良的两个性状。木材密度直接影响木材物理力学性质,木材纤维长度和长宽比直接影响纸浆和纸的质量。研究木材密度和木材纤维特性的遗传变异规律,有助于指导林木材性育种工作。本文报道I-69杨×I-63杨F1杂种无性系木材性状遗传变异的研究结果。     

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.     

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。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.