毛竹不同营林类型技术经济效果分析

对毛竹不同经营类型的技术经济效果分析表明：不同松土深度的产值间具有极显著差异，松土以２５ｃｍ为最好，纯收入高；不同氮肥用量的产值间具极显著差异，每３３３ｍ２施用５ｋｇ、１０ｋｇ、１５ｋｇ、２０ｋｇ尿素，增值幅度分别为３２．５５％、７８．２５％、１０２．４６％和１３６．５６％，边际投入产出比分别为１：７．６、１：１．０８、１：５．６、１：８．０，这个施肥范围属于施肥量－产值曲线的快速上升期；５种营林模式的△ＮＰＶ均大于零，劈山、松土、伐桩施肥、松土施尿素１０ｋｇ、松土施ＮＰＫ（５：２：３）配合肥的增值幅度分别是５５．２９％、９７．７１％、４２．３４％、１００％、１６２．８６％。     

土壤本底与毛白杨幼林施肥效应间关系的研究

通过对定州市毛白杨幼林施肥试区土壤本底分析及４年的施肥效应调查,结果表明：该区土壤肥力低下,富钾、少磷、氮素尤缺;施肥效应与土壤本底密切相关;单施氮肥,林木材积随着施氮量的增加而增加,即Ｎ１＜Ｎ２＜Ｎ３,材积分别为对照的１２６．５％、１４９．０％、１７１．４％;单施磷肥,材积随着施磷量的增加而增加,即Ｐ１＜Ｐ２,材积分别是对照的１４２．９％和１５７．１％;单施钾肥无效;氮磷配合差异显著,Ｎ１·Ｐ１和Ｎ２·Ｐ１处理,毛白杨材积分别为对照的１４６．９％和１４９．０％;氮钾配合等同单施氮肥效果。     

施钾对沟叶结缕草生长和营养成分的影响

沟叶结缕草施钾试验，采用每株施钾量为０．２５ｇ、０．５ｇ、１ｇ和２ｇ４种，另不施钾为对照。施钾水平的提高促进了河叶结缕草的生长，当施钾量为２ｇ／株时，处理株的株高、分蘖数、地上部鲜重和根鲜重分别为对照的１．２倍、１．９倍、２．６倍和２．５倍，与对照间的差异均达极显著水平。施钾还使沟叶结缕草地上部分钾、锰含量和全株总糖量增加，但地上部分氮、钙含量和蛋白质含量减少。     

应用DRIS法对1年生苗木土壤营养诊断及对策

应用ＤＲＩＳ方法对１年生刺槐（Ｒｏｂｉｎｉａｐｓｅｕｄｏ－ａｃａｃｉａＬ．）苗木、土壤营养程度进行了诊断。采用ＤＲＩＳ诊断图，确定叶片氮指标为－７．０～６．７、磷－７．８～７．１、钾－６．７～７．３，营养最平衡，生长最好。同时对土壤施肥诊断得知，氮、磷、钾比近似１４∶１∶４最合理。试验表明，施尿素５．０ｇ／盆、磷肥１０．０ｇ／盆，钾肥２．０ｇ／盆苗木营养最平衡，地径生长达１．４２ｃｍ，诊断合理，符合实际。认为，刺槐林地土壤磷、钾严重不足，特别是集约经营，施用适量的磷肥、钾肥定会促进生长。     

黄土高原油松刺槐人工林对土壤肥力影响的研究

研究了黄土高原油松、刺槐人工林对土壤的培肥效应，结果表明：油松、刺槐人工林能显著提高土壤肥力水平，降低土壤ＰＨ，１８龄油松１．２ｍ＾２及３３龄刺槐１．６ｍ＾２根区土壤断面的有机质，全氮、有效氮、有效钾、ＣＥＣ均值无林对照分别提高５７．８％、６８．６％、１０９．３％、２８．９％、５４．５％及７４．３％，１２３．６％、２８５．３％、４２．４％、６３．７％，ｐＨ降低１４．４％及２．９％，油松，刺槐林对土     

应用DRIS法对1年生苗木壤营养诊断及对策

应有ＤＲＩＳ方法对１年生长刺槐（Ｒｏｂｉｎｉａｐｓｅｕｄｏ－０ａｃａｃｉａＬ．）苗木，土壤营养程度进行了诊断，采用ＤＲＩＳ诊断图，确定叶片氮指标为－７．０～６．７，磷－７．８～７．１，钾－６．７～７．３，营养最平衡，生长最好，同时对土壤施肥诊断得知，氮，磷，钾比近似１４：１：４最合理，试验表明，施水素５．０ｇ／盆，磷肥１０．０ｇ／盆，钾肥２．０ｇ／盆苗木营养最平衡，地径生长达１．４２ｃｍ，诊断合理     

芹菜施用锌肥效果好

江苏省东台市土肥站对芹菜施锌连续３年研究结果表明，锌肥能显著提高产量，增产率达１１．５％～１２．１％；植株含锌量和根的锰含量、叶的铁含量均有不同程度提高；维生素Ｃ含量提高１２．６％～３１．４％；基施锌肥总糖含量叶柄部分增加１０４％，根部增加３８％，叶面喷施则降低总糖含量；纤维素含量下降８．９％～１３．７％；施锌方式以基施效果最好，用量以硫酸锌４公斤／６６７米２效果最佳芹菜施用锌肥效果好     

肥料对山地芒果树生长、产量及质量的影响

１９９３年６月至１９９５年６月，在元江海拔８１０米的西北灌区进行为期２年的试验表明：氮、钾对“三年芒”果树有显著的增产效果，而磷则不显著，但磷对树干和技条的增粗作用较氮、钾明显；就可溶性固形物含量而言，本试验中最佳Ｎ、Ｐ、Ｋ比例为１：０．５：０．５。     

黑枣苗氮磷营养及经济施肥的研究

试验采用苗床施肥，结果表明，肥料用量适宜促进营养元素吸收利用，７～８月份苗木叶片含氮量３．５％～４．０％、含磷量０．２％～０．３％、含钾量１．０％或稍高时，苗木生长良好。在该试验条件下，施Ｐ２Ｏ５１２０ｋｇ／ｈａ、施纯氮１８０ｋｇ／ｈａ左右，幼苗产量、质量及施肥利润均达到较高水平。     

梯形整地桉松混交林模式的水文生态功能

１９８２～１９９１年，对广西宜山县庆远林场不同整地方式及其不同植被类型的水文要素进行对比观测研究。结果表明，梯形整地桉松混交林模式具有显著的涵养水源、保持水土功能；与其他植被类型相比较，具有以下几点显著的差异：ａ．森林群落冠层的年截留水量为２３０．１ｍｍ，占降水量的１８．４％，比其他森林群落增加截留量１２．０％～５７．１％。ｂ．枯枝落叶层贮量及其最大持水量分别为７．７ｔ／ｈｍ２和２３．０ｔ／ｈｍ２，是其他植被类型的１．４～６．４倍。ｃ．土壤层的最大贮水量为５１１．５ｍｍ，比其他植被类型增加贮水６．６％～１１．８％。ｄ．林地水、土流失量分别为４．６ｍ３／（ｈｍ２·ａ）和０．６３ｋｇ／（ｈｍ２·ａ），比其他植被类型减少７９．０％～９７．９％。     

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.     

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.     

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.     

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.     

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.     

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。