高坡地板栗低产林改造与丰产技术

通过对比试验，对山区高坡地板栗低产林的丰产技术措施进行了初步探讨，并对板栗高接换种技术进行了重点研究，结果表明，高接换种和合理施肥，能明显提高高坡地板栗林的产量和经济效益，板栗高接换种能否成功的关键是选优，换冠，科学管理。     

实生劣质杏树高接换种技术

高接换种坚现有劣质低产杏树进行丰产改良的有效途径，本项研究通过对不同高接技术和接后配套措施的接口愈合程度，家接成活率，新枝生长量，树冠恢复状况，产量及经济效益的对比试验，结果表明：杏树高接换种采用改良皮下接法，同时做好接穗蜡封和接口处理是提高杏树高接中成活率最佳配套技术，成活率、新枝生长量比对照提高８．９％和６５．６％，接后第４ａ经济效益是高楼前的９．６倍。     

实生劣质杏树高接换种技术

高接换种是对现有劣质低产杏树进行丰产改良的有效途径,本项研究通过对不同高接技术和接后配套措施的接口愈合程度,嫁接成活率,新枝生长量,树冠恢复状况,产量及经济效益的对比试验,结果表明：杏树高接换种采用改良皮下接法,同时做好接穗蜡封和接口处理是提高杏树高接换种成活率最佳配套技术,成活率、新枝生长量比对照提高８９％和６５６％,接后第４ａ经济效益是高接前的９６倍。     

核桃低产园改造技术

一、高接换种、改劣换优1、芽接换种核桃高接换种应首选芽接，因为芽接部位结合紧密，不会劈叉，较枝接减少了为防止刮风吹断新梢的绑缚支撑工作，大大节省了人力物力。     

推广果树高接换种技术提高果园经济效益

1果树高接换种的必要性果树高接换种是将生长多年的果树在适当部位改接成新品种的一项技术。其优点是：1．1改造低质低产果园党的十一届三中全会以来，我市的果树生产发展迅速，规模不断扩大。目前已建果园4257个，面积754万亩。栽植各类果树300万株。但由于追求速度，忽视了优良品种的选择，特别是老果园栽植的品种多是小、酸、硬、涩，产量低而不稳，经济效益甚微。据调查，这类果园占总面积的11％，这部分果园急需改造，提高经营者的收入，而改造的捷经是高接换种。1．2充分开发利用本地野生果树资源九台是半山区，野生果树资源十分丰富…     

乌桕高接换种技术

乌桕是重要的木本油料和生物质能源树种,同时也是贵州省的乡土树种,用高接换种技术对现有产量不高及品种低劣的乌桕树进行品种改良,可提高其产量及经济效益。     

桃树高接换优配套技术

桃树高接换优配套技术郭宝林，杨俊霞（河北农业大学林学院，保定，０７１０００）针对桃树的生长结果习性及枝接不易成活的问题，对桃树进行了高接换头套袋技术的探讨，取得了当年嫁接、当年成活及形成花芽的良好效果。现将高接换头套袋技术报道如下。１高接时期和方法高...     

成龄低产枣树高接换种技术及效果

自1991年起在稠城镇西张、大王和下骆宅镇江村等地,开展了成龄低产枣树的高接换种工作,先后嫁接300余株。达到当年挂果、3年投产、4年略有增产、6年显著增产的效果。现将试验情况介绍如下。l高接换种技术1）高接品种。高接砧木选择品质差,产量低而生长旺盛的野生枣,劣种枣等成龄枣树。接穗选用品质好、产量高、生长健壮的义乌大枣。2．）高接时间。以春季枣树萌芽抽梢期间为宜,日平均气温在16℃以上即可进行嫁接。最佳时期是4月上旬,如气温低可延至中旬。3）接穗采集。选自生长势强、品性优良、丰产性能好的义乌大枣或马枣树。采集生…     

板栗大砧低接换种试验初报

在板栗低产林改造和品种改良中，一般采用高接换优。我们开展了大砧低接换种试验，使树体矮化，便于早期管理。     

2次结实板栗高接换种试验初报

选用优良板栗新品系－２次结实板栗对５年生低产栗园进行多头高接改造，采取造时抹芽摘心，病虫防治，深翻改土，合理修剪等综合技术措施，其嫁接茬成活率达１００％，接穗成活率达９６％，高接换种后栗园，当年改接当年挂果，每公顷产量第１年达２０６．２５ｋｇ，第２年则高达９８１ｋｇ，是原栗园（末改接）的５．１倍，且２次坚果商品价值均较高，经济效益显著。     

‘关山’樱花高接换种技术研究

为培养新品种大苗,研究‘关山’樱花高接换种技术。本试验以8 a生‘关山’樱花为砧木,分别进行高接换头的嫁接时间、嫁接接穗的保湿方法、不同品种对嫁接成活率影响方面的研究。结果表明:‘红花高盆樱’在12月和3月嫁接成活率最高,可达到82.60%,嫁接后的保湿方式以套袋保湿和蜡封成活率较高,在试验的几个品种中,‘染井吉野’和‘椿寒樱’成活率最高,达到83.33%,91.11%。可在生产中推广应用。     

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.     

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.     

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.