油脂嫩枝扦插育苗试验

用油松嫩枝作插穗，在粗河沙中扦插育苗，插后先形成愈合组织，后从愈合组织处生根，皮部不生根，以浓度１０００μｇ／ｇ萘乙酸处理生根率最高，为５７．７％，移栽成活率为９４．９％。     

长白落叶松嫩枝扦插技术研究

利用全光雾插技术对长白落叶松半木质化插穗扦插育苗研究表明：夏插３０ｄ后开始生根，从扦插至大部分插穗生根（７２．７％）需要７２ｄ时间。２．５ａ生插穗未经激素处理生根率达７０．８％，利用２００ｇ／ＬＩＢＡ溶液浸泡２０ｍｉｎ后，插穗生根率提高到８０％；不同采穗母株间插穗生根率变异幅度为３２％～９５．３％，差异达到极显著水平；不同年龄插穗经２００ｇ／ＬＩＢＡ溶液处理后生根率随母株年龄的增大而降低。     

ABT生根粉在龙眼和荔枝扦插育苗中应用技术研究

龙眼和荔枝为我国特产优质果品，是公认的扦插难生根成活的树种。近年来，我们通过用流水、ＡｇＮＯ３或乙醇等溶液浸泡处理先去除枝条内部抑制生根的物质，然后用ＡＢＴ１号生根粉处理枝条基部，通过认真管护，龙眼扦插愈合率达８７．６％，生根率达７８．２％，成活率达７４．５％；荔枝扦插愈合率达５６．１％，生根率达４７．６％，成活率达４６．３％。苗木移栽后生长良好     

ABT生根粉在龙眼和荔枝扦插育苗中应用技术研究

龙眼和荔枝对我国持产优势果品，是公认的扦插难生根成尖的树种。近年来，我们通过用流水，ＡｇＮＯ３或乙醇等溶液浸泡处理先去除枝条内部抑制生根的物质，然后用ＡＢＴ１号生根粉处理枝条基部，通过认真管护，有扦插愈合率达８７．６％，生根率达７８．２％，成活率达７４．５％；荔枝扦插愈合率达５６．１％，生根率达４７．６％，成活率达４６．３％。苗木移栽后生长良好。     

植物生长素对东北红豆杉嫩枝扦插生根的响

以ABT-1^#、2．4-D、IAA、IBA、NAA5种植物生长素处理东北红豆杉当年生半木质化嫩枝，进行扦插生根试验，结果表明：嫩枝插穗扦插40-60d后在形态下端形成愈合瘤，并逐渐长出不定根，属于愈合组织生根型；在激素配比均为100×10^-6的条件下，经2．4-D处理的插穗生根率达到68％以上，经ABT—1^#和IBA处理的达到52％以上；采自幼龄植株的嫩枝插穗生根率高于老龄植株。     

西伯利亚落叶松嫩枝扦插育苗技术研究

西伯利亚落叶松扦插较难生根，１９９２～１９９３年在哈密林木良种基地进行了全光喷雾嫩枝扦插育苗试验。结果表明，以锯末为扦插基质，用１．５ａ生西伯利亚落叶松嫩枝扦插，平均生根率达到８０．３９％；平均生根数量５．８６条，每穗平均根长１．７８１ｃｍ。初步认为，提高西伯利亚落叶松幼龄母树嫩枝扦插生根效果的最佳组合是：锯末（基质），扦插密度２ｃｍ×４ｃｍ，生根粉（ＡＢＴ）５００μｇ／ｇ，插条长度８～１０ｃｍ。     

杂种松扦插繁殖试验初报

通过近３年的杂种松扦插繁殖试验结果表明,选用黄泥心土基质、穗条采下后浸于５０ｍｇ／ｋｇ的台化牌植物生根促进剂溶液或１ｇ／ｋｇ多菌灵溶液各０．５ｈ或浸于１ｇ／ｋｇ多菌灵溶液０．５ｈ后蘸黄泥浆扦插等处理、在冬春季节光照充足的圃地、穗条长６～１４．５ｃｍ、顶端次生叶长５．５～１３ｃｍ等条件下扦插生根率高;并且在穗条、管理措施、扦插季节等条件合适的情况下,部分家系的扦插生根率较稳定,可达到７５％,最高达１００％。大规模扦插试验平均生根率达９１％。     

朝鲜荚莲扦插试验研究

对不同扦插基质生根情况、不同生根剂处理的效果进行了试验分析，结果表明：以草炭土为基质时，扦插生根率最高为64．34％，其次是河沙、珍珠岩为53．88％、42．36％，园田土最差，为23．68％。朝鲜荚莲扦插经生根剂处理后生根率明显提高，而不同生根剂之间插穗生根率有差异，ABT、IBA、NAA处理插穗对生根有显著影响（P〈0．05），GA对插穗生根影响不显著（P〉0．05），1mol／LABT处理10rain效果最好，生根率达到了82．43％。     

柳桉组织培养与工厂化育苗技术研究

以柳桉带腋芽的幼嫩茎段为外植体进行组培快繁，其启动培养、增殖培养、生根培养的最佳培养基依次为MS＋6-BA2＋NAA1、改良MS＋6-BA0．2＋NAA0．2＋IBA0．8、改良MS＋NAA0．2＋IBA0．8，繁殖系数可达3以上，生根率可达85％以上；试管苗移栽前需炼苗10—15d，移栽时间选在3、4、10、11月份移栽成活率最高，可达90％以上；柳桉萌发力强，试管苗移栽成活后长到一定高度经过采穗可促使腋芽不断；蒡发，生产上可利用此原理建立田间采穗圃，1株试管苗6个月内可供采穗10—12根；试管苗移栽前必须经过一个炼苗阶段，炼苟时间为10—15d，移栽成活率可达90％以上；气温与柳桉扦稳的愈合、生根关系十分密切，在气温18—25℃时扦插，有利于插穗愈合生根；使用50mg／LGGR溶液处理插穗，可使插穗生根提早5d左右，同时可使生根率提高10％。     

马尖相思离体培养再生植株的研究

用马尖相思（Ａｃａｃｉａ ｍ ａｎｇｉｕｍ ）１０ 年龄树芽器官为外植体,通过组织培养直接诱导不定芽产生,并获得根茎叶齐全的试管苗。剪取当年枝条的自顶芽往下依次带节的茎段培养,以第二、第三节茎段诱导芽萌动率高而快;芽诱导培养基为改良ＭＳ＋ ６－ＢＡ ２ ｍ ｇ／Ｌ＋ ＮＡＡ ０．５ ｍ ｇ／Ｌ,芽诱导率９０％ ;芽增殖培养基为改良ＭＳ＋ ６－ＢＡ ０．５ ｍ ｇ／Ｌ＋ ＮＡＡ ０．２５ ｍ ｇ／Ｌ＋ ＶＢ２ ５ ｍ ｇ／Ｌ＋ Ｖｃ ４ ｍ ｇ／Ｌ,芽增殖倍数４．８ 倍;生根培养基为１／２ ＭＳ＋ ＡＢＴ ２ ｍ ｇ／Ｌ＋ ＩＢＡ ０．２ ｍ ｇ／Ｌ＋Ａｃ ０．１％ ,生根率９７．０％ ;黄心土为试管苗最佳移栽基质,成活率达到８５％ 。     

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.     

Boron in forest trees and forest ecosystems

This review critically examines the role of boron (B) in forests in view of recent findings on B nutrition and the continuing occurrence of B deficiency. Many perceptions about the role of B in plants and its uptake and mobility have been altered since the last review on B in forest trees in 1990. Now there is evidence for a fundamental role of B in the formation of the pectic structure in primary cell walls in plants, and further roles in membrane function are being explored. In plants, channel-mediated B uptake, active B uptake and B uptake by mycorrhizas have been shown, B transporters have been identified, and B retranslocation has been shown. We explore these findings and their consequences on forest trees and on ecosystems that they dominate. Particular emphasis is placed on B retranslocation and B in mycorrhizal symbiosis, given their importance in trees.     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.     

Development of Pinus sylvestris Main Stems Following Three Different Precommercial Thinning Methods in a Mixed Stand

Reducing competition by point cleaning may be an attractive alternative to conventional precommercial thinning in forestry. In this study, survival and development of main stems of Scots pine (Pinus sylvestris L.) following point cleaning were examined in a mixed stand of mainly Scots pine and birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Sweden. Treatments studied were: no precommercial thinning, conventional precommercial thinning, point cleaning of all secondary stems, and point cleaning of only the secondary stems that were higher than the main stem, within a radius of 0.8 m from the main stem, respectively. A randomised complete block design with three replicates was used. Measurements taken 13 growing seasons after these treatments showed that conventional precommercial thinning was the best treatment for retaining Scots pines as main stems. However, conventional precommercial thinning resulted in the poorest timber quality of the remaining Scots pines in terms of stem taper, thickest branch diameter and relative live crown height. In conclusion, point cleaning has to be followed by a complementary cleaning operation if the objective is to retain Scots pines as main stems in such mixed stands.