毛竹林地垦复有利于增产增收

毛竹林地经过垦复后,可使地下鞭分布加深、数量增加、鞭径增粗、节间增长、健壮芽比例增加,有利于竹林的增产增收。为了解不同经营措施对毛竹林地下鞭系统生长的影响,我们在2004年11月对垦复与非垦复毛竹林地的地下鞭系统的生长状况进行了调查,现将调查情况分析如下:毛竹林地的基本情况被调查的毛竹林两块相互毗连,位于山坡下部,坡向西南坡,土壤为山地黄泥沙土,土层厚度在70-100厘米之间。其中一块从1996年开始深挖垦复,垦复深度25-30厘米。在垦复过程中,挖除老鞭、死鞭、竹蔸、树(柴)桩、石块等。以后主要通过施肥、挖笋等经营措施,到2004…     

毛竹垦复扩鞭试验初报

毛竹造林后,其竹鞭范围不断扩大。在肥沃疏松的土壤条件下,毛竹竹鞭生长快,竹鞭质量也高。潜山县在实施世行贷款林业持续发展项目进行竹林垦复时,通过试验发现,深翻垦复能使单鞭变短,鞭段数增加;竹蔸施肥能促进竹鞭的长度生长,有利于竹鞭范围的扩展;垦复扩鞭对新竹株数、扩展范围的影响极显著。     

毛竹垦复影响竹鞭生长效果分析

毛竹不仅是我国重要的用材树种之一，也是重要的经济栽培竹种，在竹类资源中占有最大的面积。为了解垦复对毛竹竹鞭生长的影响，笔者在2007年11月对垦复毛竹林竹鞭的生长状况进行了调查，毛竹经过垦复后，可使竹鞭分布加深、数量增加、鞭径增粗、节间增长、健壮芽比例增加，有利于毛竹的丰产增收。     

毛竹扩鞭成林新竹生长效果研究

对毛竹林周边扩鞭成林试验表明，不同扩鞭成林措施对扩展区域内新竹的数量和质量指标均有一定的影响，其中，不同措施对新竹株数、扩展范围的影响极显著，对退笋率、胸径的影响显著，对新竹高的影响不显著。施肥措施的新竹扩展范围大、退笋率低；深翻垦复措施的新竹株数多；复合措施的效果更好。随着坡位的降低，毛竹扩鞭成林的新竹数量指标和质量指标均呈变好的趋势。研究结果可为毛竹扩鞭成林提供参考。     

方竹林垦复前后生物量结构变化的研究

方竹林垦复前总生物量1 496.34 g.m-2,垦复后2 959.59 g.m-2,垦复后笋产量是垦复前的2.31倍。垦复后1龄、3龄竹各构件的生物量均有提高,2龄竹的生物量变化不大,说明竹林年龄结构调整尚未完成。垦复后0-20 cm土层的生物量是垦复前的3.54倍,说明垦复措施主要改善了0-20 cm层的鞭根系统结构。垦复后地上部总含水率略有下降,地下部总含水率比垦复前略有提高。天然方竹林的垦复改造对竹林的生物量结构和产量有明显的影响。     

浅谈挖掘毛竹鞭笋的意义及提高鞭笋产量的技术措施

本文初步论述了挖掘毛竹鞭笋的意义和通过深翻垦复、施肥等技术措施,提高了鞭笋产量,并对新罗区目前鞭笋生产的现状及存在问题进行了分析。     

撩壕施肥影响毛竹林鞭系结构分析

为探讨撩壕施肥对毛竹林地下鞭系结构的影响,历时10年试验,结果表明:组成竹林地下鞭系结构的竹鞭长度、鞭节数量、鞭段数量、鞭质量、鞭根质量、鞭芽数量,分别比对照竹林增多97.6%、86.2%、74.4%、1.24倍、1.55倍、59.4%;平均节间长、平均鞭段长、平均岔鞭长、平均鞭量、平均鞭根量、平均鞭径、平均鞭芽长度、平均鞭芽粗度,分别比对照竹林增加6.8%、12.9%、13.3%、10.5%、28.9%、8.8%、9.4%、12.1%;幼龄鞭、壮龄鞭、老龄鞭的生长量分别占竹林总生长量的6.3%、66.4%、27.3%。撩壕施肥的竹林其鞭系结构数量和质量均优于对照。     

笋竹两用林de培育

竹林清理砍去竹林中的杂草灌木，挖除树蔸、竹蔸和老竹鞭，不伤活鞭、鞭芽，保留少量落叶阔叶树。垦复近蔸宜浅，远蔸宜深，陡坡宜浅，缓坡宜深。垦复深度为20~30厘米，不伤走竹鞭及鞭芽。林内的石块分堆集中，并将林地清理所造成的穴填平。在6~8月或冬季进行。挖竹节沟沿等高线挖竹节沟，上下间隔15~20米，沟宽0.4米，深0.4米，沟与沟间隔1米，用于蓄水保土。科学施肥①肥料种类：以施有机肥为主，无机肥为辅。有机肥主要有厩肥、饼肥、人粪尿和青草等。无机肥主要是化肥。②施肥量：一般每增产100公斤竹材需施尿素、过磷酸钙各1.5公斤，氯…     

红壳竹笋用林竹鞭的生长结构及其分布

通过对红壳竹不同年龄竹鞭长度、重量、鞭段长度、鞭径、侧芽 (笋芽、壮芽、弱芽、空芽节 )数量及其在不同土层中的分布状况、竹鞭的分岔和延伸方向等进行分析。认为壮龄鞭所占比例最大 ,其次为幼龄鞭 ;壮龄鞭在 10～ 2 0cm土层分布最多 ,幼龄鞭在 0～ 10cm土层分布最多。竹鞭大多数为平行生长。为红壳竹笋用林的土壤管理提供科学依据     

北亚热带毛竹鞭笋高产培育研究

通过对南京市江宁区东善桥林场毛竹林地的调查,进行毛竹鞭笋高产培育研究.结果表明:(1)试验地在垦复、施肥、开设采集带集约管理的培育措施条件下,毛竹鞭笋产量有所提高.(2)通过设置采集带既可以解决鞭笋采集困难的问题,又可促使林分的稳定与改善.     

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。