元丰核桃实生苗建园需慎重选苗

元丰核桃是实生繁殖变异率较低的薄皮核桃品种。该品种易繁殖，结果早，果个大，出仁率高，品质好，丰产高产。栽植第2年即见果,第3年每667m^2产优质核桃25～35kg,第5年进入丰产期，每667m^2产量可达100～200kg，以后逐年递增。由于以上诸多优点，近年来，以元丰核桃实生苗建园的势头     

良种核桃丰产优质高效配套栽培技术研究

针对核桃良种低成本建园、整形修剪、施肥浇水、花期管理、晚霜预防、病虫防治等制约丰产优质的主要因素进行试验与探讨。结果表明,通过低龄幼树嫁接、整形修剪、合理肥水、花期管理及晚霜预防等综合配套技术措施的实施,2 a生实生砧苗嫁接香玲5 a生每667 m2产254.65 kg,元丰每667 m2产达342.54 kg,达到了良种核桃丰产优质高效目标。     

嫁接核桃的栽培与管理

核桃多用种子或嫁接繁殖,嫁接后2 a～3 a挂果,4 a～5 a进入丰产期,实生苗需8 a～10 a挂果,15 a进入丰产期.核桃营养丰富、用途广泛、价值高、需求量大,价格稳升,栽培前景十分好,栽培技术与管理是关键.     

早实新品系核桃采穗圃快速营建技术研究

对云南省林业科学院培育出的早实核桃新品系进行采穗圃快速营建技术的研究，通过种植密度，施肥，修剪，浇水4因素3水平的正交试验得出，快速营建早实新品系核桃采穗圃的方法为：选择具有深厚，疏松，湿润土壤的园地建圃，每666．6m^2种植嫁接苗330株，第2年开始，每年每株施厩肥10kg,复合肥0．2kg，旱季浇水8次以上；当新梢长5－8cm及时摘去生长点以促进当年2次分枝，此法，建圃第2年便可开始采穗，到第4年每666．6m^2所采接穗累计可供62000株核桃嫁接用，成本0．15元／个，4年后每年产接穗可供36000株以上核桃嫁接用，成本0．06元／个以下，采穗圃接穗的嫁接成活率达81．3％，该技术亦适用于其他核桃良种采穗圃建设。     

核桃根接试验

<正> 繁育核桃良种苗木应采用嫁接方法.但由于嫁接所用砧木为核桃实生苗,每株实生苗只能嫁接培育一株良种苗,所以良种苗木成本较高。为了降低成本,加快良种苗木繁殖速度,充分利用核桃室内嫁接和阳畦嫁接时剪掉的大量根系用实生苗根系发达,每株二年生实生苗可嫁接繁殖3至5株良种苗的特     

早实新品系核桃采穗圃快速营建技术研究

对云南省林业科学院培育出的早实核桃新品系进行采穗圃快速营建技术的研究.通过种植密度、施肥、修剪、浇水4因素3水平的正交试验得出,快速营建早实新品系核桃采穗圃的方法为选择具有深厚、疏松、湿润土壤的园地建圃,每666.6m2种植嫁接苗330株,第2年开始,每年每株施厩肥10kg、复合肥0.2kg,旱季浇水8次以上;当新梢长5～8cm及时摘去生长点以促进当年2次分枝.此法,建圃第2年便可开始采穗,到第4年每666.6m2所采接穗累计可供62000株核桃嫁接用,成本0.15元/个,4年后每年产接穗可供36000株以上核桃嫁接用,成本0.06元/个以下,采穗圃接穗的嫁接成活率达81.3%.该技术亦适用于其他核桃良种采穗圃建设.     

岷江上游干旱河谷理县新疆核桃引种调查

核桃是退耕还林工程中,理县干旱河谷地区引进的主要经济树种。对杂谷脑干旱河谷区域内引种的核桃进行了调查研究。结果表明:核桃在干旱河谷有较强的适应性,其成活率在90%以上。结果期的第2年产量,嫁接苗在420 kg.hm-2～450 kg.hm-2,产量年增长幅度在15%～20%,同时,结果时间早,栽培后第3年开始挂果,见效快;实生苗则表现在1 500 kg.hm-2～1 750 kg.hm-2,产量年增长幅度在10%左右,但结果时间晚,栽培后7 a和8 a开始挂果。     

野生铁核桃改造的锯干作砧嫁接技术

为改善传统野生铁核桃的嫁接技术，在玉溪市开展了野生核桃嫁接改造技术的研究。试验表明：在立春以后，以40－150cm高度锯干作砧，用1年生健壮穗条插皮接的方法嫁接，并预留抽水枝及锯口覆以消毒的干锯末嫁接最好，该技术使野生铁核桃嫁接成尖率从42．5％提高到87．9％。嫁接后的树木2－3年形成大的树冠，第3年开花结果，第5年进行盛,6年株产平均可达7－8kg。     

核桃低产林改造技术

宝鸡地区是较为理想的核桃生产基地 ,核桃生产居陕西省第 2位。但由于多年来形成了“鸟种、天管、人收”的粗放管理习惯 ,造成了树势衰弱 ,病虫害严重 ,产量连年减少 ,品质不断下降。单株产量仅 0 .37kg,出仁率2 8%～ 33%。我们在陇县、麟游推广低产林改造技术 3年 ,每公顷产量由 3.7kg提高到1 8.6 kg,投入产出比为 1∶ 42。现将改造技术介绍如下。1　垦复扩盘时间在春秋两季进行。一般大树垦复半径不小于 3m,小树同树冠投影面积 ,平地垦复成圆形 ,周围有蓄水堰 ,坡地垦复为鱼鳞坑形 ,树盘下坡做堰蓄水 ,上坡修成簸箕形收口。深度 1 0～ 2 5…     

特早熟甜柿西村早生栽培适应性观察

西村早生树势强，结果早，果形大，产量高。9月中旬果实开始成熟，较富有和禅寺丸早30天左右。定植后第2年开始挂果，第3年株产1．12kg最高株产9．65kg，第4年平均株产4－5kg，第5年为13.25kg最高单株产量26．35kg，每667m2产量平均为742kg。西村早生为甜柿中特早熟品种。果实扁圆形，单果重平均138g，最大单果重220g。果皮呈橙黄——橙红色，授粉后果实内种子达4粒以上，果肉有褐斑而自然脱涩，风味甜脆，品质中等，可溶性固形物含量14％，常温下存放10天左右，不易软化，商品性好。特早熟甜柿西村早生栽培适应性观察…     

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.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

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.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.