柳杉半同胞子代遗传变异与优良遗传型选择

对40个柳杉半同胞子代的生长、木材品质和形质等性状的遗传变异规律和相关性进行了比较系统地研究,结果表明:2年生树高及26年生树高、胸径和材积等生长性状在家系间存在显著差异;木材品质和形质性状中的髓心偏心率和木材心材比率在家系间存在显著差异,而树皮率和木材基本密度在家系间的差异不明显;2年生树高与26年生胸径、材积间呈显著正相关,心材比率与26年生树高、胸径和材积间呈显著正相关;树皮率与2年生树高相关性不明显,而与26年生树高、胸径和材积等呈显著负相关;髓心偏心率、木材基本密度与生长性状相关性不明显。通过综合比较,评选出生长量大、木材品质好的优良家系12个,树高、胸径和材积的平均遗传增益分别为1.21%、4.77%和8.02%,木材偏心率的平均值为0.3%,木材基本密度的平均值为0.341 g/m3,这些优良家系具有广阔的推广应用前景。     

长白落叶松优良家系选择的研究

对黑龙江省宁安县省林科院所属的江山娇实验林场23年生长白落叶松自由授粉家系子代测定林的研究结果表明,树高、胸径、材积都存在较大的变异,9年生变异系数分别为5.5%、8.2%、18.0%;23年生变异系数分别为12.0%、18.0%、38.9%.家系间变异幅度树高、胸径及材积分别为7.9%～14.2%、12.6%～21.9%、28.0%～45.2%.树高、胸径、材积3个性状在家系间都存在显著差异,23年生时树高、胸径、材积的家系遗传力分别为0.696、0.492、0.608,生长性状受中等强度的遗传控制.通过对17个家系的生长性状分析,筛选出了226、96、251三个生长性状优良的家系.     

火炬松引种家系遗传变异及速生家系选择

对10年生火炬松半同胞家系的生长性状测定表明:火炬松的树高、胸径和材积在家系间差异显著,火炬松家系的生长形状主要受中等遗传力所控制,参试家系性状在各试验点的变异系数差异明显,材积的变异系数在7.90%～17.13%。通过育种值法最终筛选出5、16、18、6和8号等5个速生家系。     

巨桉引种试验及优良遗传型选择

对8年生巨桉种源、家系试验林进行全面调查分析表明：生长性状在不同种源、家系间存在显著或极显著差异;形质性状在不同种源间差异不显著,在不同家系间存在极显著差异;耐寒能力在不同种源间存在极显著差异,在不同家系间差并不显著。通过综合评价和比较,选出适应福建省永安地区种植的巨按优良家系10个,树高、胸径、材积和耐寒指数平均值分别为14．80m、16．6om、0．1749m^3和4．42,树高、胸径和材积的遗传增益分别为18．96％、加．44％、67．17％;优良个体15株,其树高、胸径、材积和耐寒指数平均值分别为17．91m、20．63cm、0．2976m^3和4．85,树高、胸径和材积的遗传增益分别为44．9％、48．8％和184．1％。这些优良材料可以通过无性繁殖进行推广应用。     

杉木第二代种子园子代遗传变异及优良家系选择研究

来自广东省龙山林场杉木第二代种子园的39个自由授粉家系参加了1998年多点子代测定和2001年单点子代测定试验,结果表明：11年生子代测定林的树高、胸径、单株材积在家系和地点间差异达到极显著水平（P〈0．01）,8年生子代测定林生长性状的差异较小;家系平均树高、胸径、材积遗传力分别为0．24、0．26、0．30,主要生长性状受中等偏下的遗传力控制;第二代种子园材积遗传增益在1．88％～5．85％．其遗传增益和现实增产效果高于1．5代种子园,也高于初级种子园。对11年生多点子代测定林家系进行了丰产稳定性分析,选择出广谱丰产稳定家系5、8、17、19、23、26、28号,平均单株材积比群体均值提高3．39％;丰产家系3、7、15、21号和家系20、22、25号,分别适合龙山林场和曲江林场及相似立地条件地区限制性推广利用,平均单株材积比群体均值分别提高9．91％和4．89％;8年生单点子代测定林,以单株材积高于群体均值作为入选标准,有1、2、4、6、7、8、10、11、12、14、15、19等12个家系入选,平均单株材积比群体均值提高6．76％。     

长白落叶松优良家系选择的研究

对24年生长白落叶松自由授粉家系子代测定林的研究结果表明，胸径、树高、材积3个性状在家系间都存在显著差异，通过对17个家系的生长性状分析，筛选出了170、120、501、322、153、274六个生长性状优良的家系，其胸径、树高、材积平均大于对照3．83％、7．23％、11．67％。     

Productivitv evaluation and family selection of 25-year old plus tree progeny in Pinus massoniana

对25年生马尾松优树子代测定林调查分析,结果表明马尾松子代树高、胸径、材积在家系间存在显著的遗传变异,其家系遗传力分别为0.428、0.565和0.610.利用以树高、胸径、材积构建的指数选择方程从参试家系中选择出20个速生优良家系,平均材积遗传增益为26.0％.从入选的优良家系中选择出100株优良单株,平均材积比群体均值大122.21％.     

邓恩桉生长、木材密度和树皮厚度的遗传变异研究

以广西桂林和柳州的邓恩桉种源/家系(6个种源53个家系)试验林为材料,对8.5年生胸径以及10.5年生胸径、树高、材积、木材密度和树皮厚度的遗传变异进行了研究,结果表明:10.5年生时,邓恩桉在桂林和柳州的平均单株材积分别为0.218、0.189 m~3,平均木材密度分别为521.0、483.7 kg·m~3,树皮厚度分别为1.15、1.26 cm;10.5年生材积性状和木材密度在种源间差异不显著(P＞0.10),10.5年生木材密度在家系间差异显著(P＜0.05);树皮厚度在种源间、家系间差异均不显著(P＞0.10).除8.5年生胸径外,其他性状的试验地点与种源间交互作用不显著(P＞0.10);8.5年生胸径、10.5年生树高、木材密度均存在显著的试验地点与家系间交互作用(P＜0.05);10.5年生树皮厚在种源、家系水平上和地点均不存在显著的交互作用.8.5年生胸径、10.5年生胸径与树高的遗传力在0.128 9～0.234 5间,木材密度的遗传力为0.700 0～0.962 9,树皮厚度的遗传力为0.105 3～0.335 7.     

龙泉杉木三代种子园子代林主要生长性状变异研究

对营造在浙江省龙泉市林科院6年生杉木三代种子园家系(36个家系,1个对照)子代林的树高、胸径和材积进行测定与分析.结果表明:6年生杉木的树高、胸径和材积3个生长性状在家系间差异达极显著,且有相对较高的广义遗传力,而材积有中等以上的遗传变异系数.杉木三代种子园有较好的群体改良效果,6年生时材积的遗传增益比对照提高了14.89％.以材积为依据,采用对比法选择出9个早期速生型杉木优良家系,其群体的树高、胸径和材积平均值分别大于对照10.04％、15.99％和45.69％.     

高脂马尾松扦插苗与实生苗造林早期生长比较

通过对高脂马尾松扦插苗、实生苗进行造林试验，结果表明：造林后2～5年，两种林分平均保存率均达到95％以上；3、4年生时树高、胸径、单株材积差异极显著，4年生时扦插苗的幼林树高、胸径、冠幅、单株材积平均分别高于同龄实生苗的13．11％、24．95％、18．53％和69．81％，说明利用优良无性系繁殖扦插苗进行造林是可行的。     

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.