针叶矿质营养元素与松材线虫病感病的关系

用ＩＣＰ仪测定１０个有代表性种源的马尾松针叶的矿质营养元素,同时对这１０个种源接种松材线虫,结果发现不同种源的抗性差异显著。马尾松不同时期的矿质元素含量与马尾松对松材线虫的抗性关系不一样,其中休眠期针叶内的Ｍｎ,Ｆｅ,Ｃｏ含量与抗性呈正相关,而Ｎｉ含量与抗性呈负相关。     

不同营林措施对马尾松针叶养分的影响

对设置在贵州龙里、台江以及广西热带林业实验中心的不同施肥、不同密度、不同抚育措施、不同整地方式和不同种源马尾松人工林试验样地内针叶样品的Ｎ、Ｐ、Ｋ、Ｃa、Ｍg含量进行分析研究，结果表明，除广西施肥５年后，不同处理间针叶Ｎ、Ｍg两元素含量具有极显著差异外，其余措施对马尾松针叶养分含量的影响均未达到显著差异水平。因此，施肥具有调节马尾松针叶养分含量的作用；而不同造林密度林地内马尾松个体吸收养分的能力相同，则高密度易造成地力的快速衰退，对长期高密度造林的林地，应加以施肥，以维护土壤的持续利用；抚育措施并不影响林木养分的吸收；整地也未对马尾松吸收养分有多大影响；不同种源吸收养分的特点差异不大，因而优良种源加速林地地力的衰退。     

华山松针叶中矿质元素含量的地理变异

以１２年生的种源林为取材对象，在１９９１年４月３０日、７月３０日、１０月３０日及１９９２年１月３０日同时采当年和１年生针叶，测定Ｎ、Ｐ、Ｋ、Ｃａ和Ｍｇ浓度。结果表明，除Ｋ外，其它矿质元素浓度种源间存在极显著差异。地理变异呈纬向渐变型。极端温度与元素地理差异有密切关系，并构成主导自然选择压。元素浓度的季节动态与针叶生长节律循环相伴。南、北华山松已分化成两个营养能力显著不同的地理种群，但动态模式基本相似。     

引种针叶树种矿质元素浓度及季节变化的比较研究

以８～１０年生的引种试验林为取材对象,分别在１９９２年４月３０日、７月３０日、１０月３０日及１９９３年１月３０日,同时采１５个树种当年和１年生针叶,测定Ｎ、Ｐ、Ｋ、Ｃａ和Ｍｇ浓度。结果表明,矿质元素浓度种间存在极显著差异。各元素浓度高低总趋势为Ｎ＞Ｋ＞Ｃａ＞Ｐ＞Ｍｇ。松属中单维管束亚属和双维管束亚属分别表现为富Ｎ、Ｍｇ和Ｋ、Ｐ两种元素含量型。树种间Ｍｇ元素季节动态存在显著多样性,Ｎ、Ｐ、Ｋ、Ｃａ动态模式松类树种具有极大的相似性。     

湿地松营养元素含量变化与生长关系的研究

以湖南省湘潭县湿地松不同配方施肥试验为研究对象，于不同生长季节分别在施肥区和对照区采集针叶进行Ｎ，Ｐ，Ｋ，Ｃａ，Ｍｇ养分动态分析，并将各生长季节元素含量与树高、胸径进行相关性统计分析。结果表明：营养元素Ｎ、Ｐ、Ｋ、Ｃａ、Ｍｇ含量在不同生长季节变化是不同的。Ｎ、Ｐ、Ｋ、Ｃａ、Ｍｇ含量在生长初期最高，Ｎ、Ｐ９月最低，Ｋ、Ｃａ、Ｍｇ速生期最低，Ｃａ生长末期最高。ＮＰ、Ｋ、Ｍｇ含量在生长季节逐渐减少，Ｃａ则逐渐递增。叶片中Ｎ、Ｐ、Ｍｇ含量在生长初期，速生期，末期与湿地松树高，胸径生长显著相关。     

不同产地香椿苗期营养元素吸收力研究

为探讨香椿不同种湖间在营养元素吸收力上的差异，以北纬２４°４０′－３３°４８′，东经１０１°３１′－１１９°５４′间的３２个产地种源为对象，研究了不同苗龄苗木根、茎、叶中Ｋ、Ｃａ、Ｍｇ、Ｐ、Ｎ５种营养元素的吸收力。结果表明，营养元素百分含量及重量在各种源不同器官中波动较大，香椿种源在对５种元素吸收力上有明显的选择性，除７个月苗龄叶中Ｐ、根中Ｎ、Ｋ，茎中Ｎ、Ｋ、Ｍｇ和一个月苗龄苗木根中Ｎ与纬度显著相     

湿地松营养元素含量变化与生长关系的研究

以湖南省湘潭县湿地松不同配方施肥试验为研究对象，于不同生长季节分别在施肥区和对照区采集针叶进行Ｎ，Ｐ，Ｋ，Ｃａ，Ｍｇ，养分动态分析，并将各生长季节元素含量与树高，胸径进行相关性统计分析。结果表明：营养元素Ｎ，Ｐ，Ｋ，Ｃａ，Ｍｇ含量在不同生长季节变化是不同的，Ｎ，Ｐ，Ｋ，Ｃａ，Ｍｇ含量在生长初期最高，Ｎ，Ｐ９月最低，Ｋ，Ｃａ，Ｍｇ速生期最低，Ｃａ生长末期最高，Ｎ，Ｐ，Ｋ，Ｍｇ含量在生长季节逐渐减少，     

蓝桉幼林不同生长期的叶片营养元素含量分析

１９９２－１９９６年对不同年龄蓝图桉幼林各生长季节叶片的５处主要营养元素含量进行了分析研究。结果显示，蓝图桉幼林叶片中Ｎ、Ｐ元素的含量夏季高于冬季；Ｎ含量第１、２年较高，各的间差异不显著；Ｐ一各年间差异显著，第３年含量最高。元素Ｋ、Ｃａ、Ｍｇ的含量各年间差异显著，含量随林龄增加而增加，２．５年以后达到高峰，之后由于“组织稀释”，浓度有所下降。施肥能提高叶片中Ｎ、Ｋ、Ｃａ元素的含量；由于施肥使蓝桉生     

青冈常绿阔叶林死地被层和土壤性质特征的研究

１９９０年至今对浙江建德青冈常绿阔叶林生态系统的养分循环进行了研究。报道了死地被层现存量，死地被层（包括Ｌ、Ｆ、Ｈ三亚层）和土壤（包括Ａ、Ｅ、Ｂ三层）中Ｃ和８种养分元素的分布，以及植物对养分元素的累积特征。结果表明：死地被层现存量为１４．１４１ｔ／ｈｍ２，其中Ｈ＞Ｆ＞Ｌ．死地被物中９种元素含量和贮量大小依次为Ｃ＞Ｎ＞Ｃａ＞Ｍｎ＞Ｋ＞Ｍｇ＞Ｐ＞Ｚｎ＞Ｃｕ，而土壤中为Ｃ＞Ｎ（Ｋ）＞Ｋ（Ｎ）＞Ｍｇ＞Ｍｎ＞Ｃａ＞Ｐ＞Ｚｎ＞Ｃｕ。与其它地区相比，本区土壤中Ｍｎ和Ｎ的含量较高而Ｐ和Ｃａ较低．不同元素具有不同的层次分布和季节变化特征。自表层至深层，Ｃ、Ｎ、Ｃａ、Ｍｎ的含量呈下降趋势；而Ｋ、Ｍｇ的含量均在表层较低，并在深层有较高的含量；而Ｐ、Ｃｕ和Ｚｎ则以Ｈ与Ａ层的含量为最高．植物对元素的累积特征因元素和层次（种类）而异。各元素中以Ｃａ的富集系数最高，Ｎ次之，Ｃｕ和Ｚｎ最低；一般而言，藤本、草本和下木层植物对元素的累积程度比乔木层和亚乔木层要高。     

杉木地理种源矿质分析及变异规律的研究

研究了杉木地理种源间矿质元素（杉木种源针叶灰分中氮、钾、铁、磷、钙、钩等元素百分含量）代谢的差异，及其与地理分布的关系，作为选择优良种源的科学依据。试验测定结果：生长快的种源钾含量高于生长慢的种源，钾、铁两元素百分含量高值区和杉木生长好的中心区基本一致。     

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.     

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.     

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.     

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.     

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。