杉木育苗密度对苗木质量的影响

通过对西畴，麻栗坡、马关三县９个杉木山地苗辅不同苗木密度的苗高，地径，根幅、根长、地上部份鲜重，地下部份鲜重及长度大于５ｃｍ一级侧根数量等项指标的调查表明，苗木七质量成反比关系。密度为１００￣１４０株／ｍ＾２时，合格苗率达８５％以上。     

黄樟Pt菌剂育苗对比试验

对比常规育苗,对比Pt菌剂应用于黄樟(Cinnamomum parthenoxylum)育苗的效果。通过调查苗木的苗高、地径、主根长、Ⅰ级侧根数、Ⅰ级侧根长、地上部份鲜重和地下部份鲜重,对数据进行分析,对比二者苗木的生长情况。结果表明:采用Pt菌剂培育黄樟苗木,苗木多项质量指标得到提高,苗木高径比未失衡,反而促进了苗高和地径的协调生长。与对照比较,极显著的缩短主根长度,缩短55.39%,苗高差异达到极显著水平,提高39.08%;地径、Ⅰ级侧根数、地上部份鲜重和地下部份鲜重差异达到显著水平,分别提高42.11%、183.33%、32.29%、131.58%;Ⅰ级侧根长差异不显著,但也提高3.59%。     

樟子松苗移植密度试验

樟子松１年生苗采用２０×２０ｃｍ、２０×１０ｃｍ、２０×７５ｃｍ、２０×５０ｃｍ、２０×４０ｃｍ、２０×３３ｃｍ６种移植密度试验结果表明，苗木高生长差异不明显，地径差异达到了１％的显著水平。苗木径高比、单株生物量随着移植密度的减小而增大。一级苗百分率随密度的增大而减小，经济效益随密度的增大而上升，最大密度与最小密度的单位产值相差４倍以上。从综合质量指标和经济效益两方面考虑，以２０×４０ｃｍ和２０×５０ｃｍ两种移植密度最佳。     

关于杂交杨W－14合理密度的研究──密度对苗木产量、质量的作用

通过对杂交杨ｗ－１４密度试验所产种条、苗木的生物量测算、内含物（还原糖、全氮等）测定、育苗、造林试验，确定了生产种条的合理密度为７～１４株／ｍ２，平茬苗（Ⅰ（２）－０）的合理密度为３～６株／ｍ２；合格种条的标准是地径（离地５ｃｍ）、Ｄ５＞１ｃｍ，Ｄ５／Ｈ＞０．００６，全条皮干重（Ｗ）在（Ｗ）ｄ１１．７ｇ以上，还原糖含量在４４ｍｇ／ｇ左右，合格苗木的标准是：地径（离地６ｃｍ）Ｄ６＞１．５－２．０ｃｍ，地上部皮干重为３１ｇ或３９ｇ以上，上段皮还原糖含量在４５．８ｍｇ／ｇ以上。     

山白兰苗木移植密度试验

对山白兰苗木移植密度的试验进行分析研究，结果表明，最适宜的苗木移植密度（株行距）为２５ｃｍ×２０ｃｍ，该密度的苗木生长表现好，苗圃产苗量较高，公顷产量１３．５万株。     

香椿苗木管理技术

香椿苗木与其它树种的苗木相比 ,有其特殊性。一是香椿经营方式多样 ,二是苗木秋季贪青生长。经营方式不同则需不同规格的苗木 ,不同规格的苗木需要不同的管理技术。1　培养不同规格的苗木栽培目的不同要求不同的经营方式 ,不同的经营方式需要不同的苗木规格。1.1　大田、地边栽植苗木规格大田、地边栽植用苗木一般需 1年生大苗 ,苗高 1.0～ 1.5ｍ ,地径 1.0～ 1.5ｃｍ以上 ,根系完整 ,顶芽饱满 ,圃地苗木密度为株行距 0 .3ｍ× 0 .4ｍ。1.2　密植园苗干规格要求苗高一般为 0 .8～ 1.2ｍ ,地径 1.2ｃｍ以上 ,需培养多侧枝树形。根系完整 ,顶…     

枫香苗期密度试验及苗木分级指标探讨

通过对枫香苗期苗木密度与地经、高、根系、叶面积、生物量等的方差分析，得出枫香苗期最适密度为９０株／ｍ＾２。采用逐步聚类法对苗木分级指标进行了探讨，提出枫香苗木分级指标为：Ｉ级苗Ｈ≥５０．９ｃｍ，Ｄ≥０．４９ｃｍ；Ⅱ级苗３７．７ｃｍ≤Ｈ≤５０．８ｃｍ，０．３０ｃｍ≤Ｄ≤０．４８ｃｍ；Ⅲ级苗Ｈ≤３７．６ｃｍ，Ｄ≤０．２９ｃｍ。     

香椿育苗密度的研究

５种密度（４、７．９、１４．３、１６．９、３０株／ｍ２）香椿播种苗密度试验表明，香椿苗木对密度的生态对策与一般树种不同。高密度只对地径生长有明显的抑制作用，在４～３０株／ｍ２的范围内，地径随着密度的增加而减小，而苗高则随着密度增加有增有减。高径比是合格苗的重要指标，其值不得超过６０。在试验密度范围内，苗茎生物量是渐增的，但有效生物量以７．９株／ｍ２为最高。育苗合理密度为８株／ｍ２左右。在合理密度、合理生产管理条件下，可保证８０％的苗木合格。     

樟子松苗木培育方法的研究

经３年试验表明．樟子松１—１苗木的地径、苗高生长均达到了辽宁省林木育苗技术规程标准，造林平均成活率在８４％，应以株行距５～８×１０～１５ｃｍ移植，比培育３年生苗木提高圃地利用率，是培育造林苗木的主要方法。从５种密度切根不移植培育２年生苗木的试验看出，造林平均成活率达８８．８％，最高为９５％，以１２５～１５０株／ｍ２密度培育．转培育１一１苗省移植工序．是培育造林苗较理想方法。比１年生苗剪根保留１５ｃｍ和２０ｃｍ根长，培育１—１苗木为佳。     

银杏环形密度试验初报

１　材料与方法环形密度试验示意图　　１９９７年我们在富阳亚林所圃地内安排了环形密度试验。试验地土壤属山地红壤，含全氮、全磷、速效氮、速效磷、速效钾、有机质、肥力中等偏低，质地较粘重。我们选用同一批苗木中的粗壮１年生苗，按离中心点１０ｃｍ，３０ｃｍ，７０ｃｍ，１５０ｃｍ，２７０ｃｍ，幅射状安排了１２次重复（见示意图）。使４圈栽植树苗木的株行距，分别代表１５ｃｍ，３０ｃｍ，６０ｃｍ，１００ｃｍ，第５圈作为保护行。种植前，按照每苗施厩肥５千ｇ的标准，施基肥。连续２年测定了苗木高度，地径粗。第２年，还观…     

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。     

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.     

Key Habitats in the Norwegian Production Forest: A Case Study

This study investigated the forest history, structural characteristics, the presence of fungal species suggested to indicate ecological continuity in old-growth forest, and the species composition of saproxylic beetles in 30 old forest ''woodland key habitats'' (WKHs), and compared them with production forest in the same age-class in south-eastern Norway. No statistically significant differences in forest characteristics, community of saproxylic beetles or number of red-listed beetles were found between the WKHs and the production forest, probably owing to a combination of profound long-term logging and a lack of will to delineate sufficiently large WKHs in the one area with significantly less forestry impact. The study indicates the advantage of including forest history information in WKH selection where such data exist, and the importance of restoring habitats in heavily exploited forest landscapes.