内蒙古磴口引黄灌溉对土壤影响的研究

内蒙古磴口河套地区４ａ灌溉试验表明：（１）采用目前生产上的１５０００－２２５００ｍ＾３／（ｈｍ＾２．ａ）灌溉量，使土壤表层的含盐量由灌溉前的０．５ｇ／ｋｇ上升到１．０ｇ／ｋｇ以上。（２）按合理灌水定额公式计算，年灌溉量以７５００ｍ＾３／ｈｍ＾２为宜；最佳含水率下限１９．９９％；在灌水期地下水位为１．９７－３．０２ｍ，变幅１ｍ左右（３）年灌水次数应控制在８－１２次。     

板栗树体结构与产量关系的研究

应用逐步回归和通径分析研究板栗树体结构与产量关系，结果表明，单位冠幅面积果枝量，单位冠幅面积强母枝量和叶果比是影响板栗产量的主导因子，其中单位冠幅面积果枝量与单位面积产量的关系最密切。树体结构为：树高３．２－４．２ｍ，枝下高１．０－１．５ｍ冠幅６．５－８．５ｍ＾２，树冠体积１５－１８ｍ＾３，单位冠幅面积强母枝量约２８条／ｍ＾２，单位冠幅面积强枝量约３０条／ｍ＾２，单位冠幅面积果枝量约１７条／ｍ＾２     

长白落叶松优良无性系造林增产效益研究

１９８５年选择长白落叶松种子园优良无性系进行芽接,于１９８７年营造丰产林０．４８ｈｍ＾２,以普通长白落叶松作对照。树龄８年生时,优良无性系树高,胸径,材积及每公顷蓄积量平均分别为３．９９ｍ,３．４８ｃｍ,２０．２×１０＾０－４ｍ＾３,和２．２４４ｍ＾３,分别和对照１０６．２％,１０３．３％,１２３．９％和１２３．８％;１３年生时上述各因子平均值为７．１８ｍ,７．９４ｃｍ,２２．６×１０＾－４ｍ＾３     

油麦吊云杉人工林生长量分析

油麦吊云杉，是四川盆地西缘山地主要优质用材造林树种之一，２８年生人工林主要林分因子胸径１３．４ｃｍ、树高１２．５ｍ、蓄积２８５．７９ｍ＾３／ｈｍ＾２，其林分胸径、树高和蓄积年平均生长量分别达到０．４８ｃｍ、０．４５ｃｍ和１０．２ｍ＾３／ｍ＾２．２８年生人工林林分养木层生物量为１７４．９６ｔ／ｈｍ＾２，平均净生产量达７８８０．８ｋｇ／ｈｍ＾２，ｙｅａｒ。这表明该树种人工林具有较高生产 在适生地区大力     

页岩红壤上湿地松幼林施肥效应

１９９２－１９９５年试验结果表明，在江西省分宜县页岩坡积物发育的红壤上，湿地松纪林施用Ｎ、Ｐ、Ｋ肥及其配合，使树高、胸径、蓄积等总生长量分别达到３．７２－４．０３ｍ、７．２０－７．９３ｃｍ、２７．６５－３４．１５８ｍ＾３／ｈｍ＾２，较对照显著增长５．１－１３．８％、７．０－１７．８％、１５．２－４２．４％。在各种施肥处理中，以Ｐ２Ｋ１配合的效果最佳；单施Ｎ、Ｐ、Ｋ肥均有效，但不同剂量间无明显差异。     

滩地柳树无性系人工林密度试验研究

长江滩地４年生苏柳１７２等无性系密度试验结果表明，造林密度对蓄积量生长和林木干形影响显著，１ｍ×１．５ｍ密度林分，蓄积年生长量达２７．５ｍ＾３／ｈｍ＾２，滩地柳林造林密度应不低于１６６７株／ｈｍ＾２。     

马尖相思造林技术研究

通过持续６年，面积达２３．６７ｈｍ＾２的造林试验，初步探索出适于云南引种区采用的马尖相思育苗、造林技术。在普文引种试区马尖相思生长迅速，６年生树高年均生长量达２．３１ｍ，胸径年龄生长量为２．９ｃｍ，活立木蓄积２８９．０４１４５ｍ＾３／ｈｍ＾２，年均生长量４８．１７３５７５ｍ＾３／ｈｍ＾２；４．５年生的马尖相思林，地上部分生物量达１０５．６ｔ／ｈｍ＾２，有效高的经济和生态效益。     

菇耳专用林定向培育：人工促进阔叶林伐后更新试验

对参试的３５．６ｈｍ＾２天然阔叶林伐后迹地进行菇耳专用林定向培育，通过树种选择，清杂，去高桩，补植，抚育，施肥等措施，４年后，幼树密度由２２５０株／ｈｍ＾２增加到７５００株／ｈｍ＾２以上；活立木蓄积由１．５ｍ＾３／ｈｍ＾２增加到４２ｍ＾３／ｈｍ＾２，平均生长量达１０．１ｍ＾３／ｈｍ＾２．ａ。     

巨尾桉人工林地上部分净生产力及养分循环的研究

对１．５－３．５年生巨尾桉扦插苗造林林分的生长、生物量增长、养分积累、凋物量及其分解、林下植物生物量及养分积累和林分养分循环的调研结果表明，安林木生长和生物量增长高峰期为２年生，３年生时开始下降。１．５，２．５和３．５年生林木地上部分生物量分别为１４．５，２８．５和３８．０ｔ／ｈｍ＾２，林下植物地上部分生物分别为２．６、３．４和６．３ｔ／ｈｍ＾２。林下植物地上部分的主要养分纱积累占２０－４０％。林     

塔拉生物生态学习性初步研究

１９９１－１９９５年在云南省昆明、景东、景洪、四川省布昆、新都等地对塔拉进行了引种试验研究，结果表明，３年生树开始开花、结实，一年２－３次，荚果单产６．０－７．５ｔ／ｈｍ＾２，树高３．７ｍ，地径５．５ｃｍ。它喜光、喜热、耐干旱，适宜在砂壤土和壤土上生长。     

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.     

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.     

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.     

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。     

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.