齐心协力忙造林

2003年，我省林业生产走过了不平凡的一年。林业工作在国家林业局和省委、省政府的关心下，在各级党政领导的支持下，经过全省广大林业干部职工的共同努力，林业建设取得了硕果累累的成绩。全省森林覆盖率达到53．67％，拥有立木蓄积量3．23亿立方米，实现林业总产值362亿元，完成人工造林41．47万公顷，义务植树1．2亿株，是我省历史上造林任务最多、资金投入最大的1年。在国家林业局组织的全国营造林实绩综合核查中，综合得分99．53分，造林质量居全国第一，赢得了造林质量“七连冠”的美誉。     

实施中德合作造林项目促进延安林业可持续发展

中德合作陕西二期延安造林项目，从2001年正式启动实施至今，已完成人工造林15519．69公顷。完成计划任务18000公顷的86．2％。经省、市项目监测中心监测，合格面积累计达15205．86公顷，合格率为97．9％。中德合作造林项目的建设。填补了延安林业史上利用外资的空白，对延安的林业机制、管理模式的转变，技术刨新以及可持续发展，产生了深刻的影响。     

水保工程是提高内蒙古黄土丘陵造林质量的有效途径

内蒙古的黄土丘陵分布区，降水量少，蒸发量大，植被稀疏矮小，水土流失严重，土壤含水率为５％，造林成活困难，成活率在４０％以下，造林质量差，若不配以水保工程措施，则不易成功。因此，必须进行水保工程设计。现将水保工程设计的方法及造林应注意的问题作以介绍。造林配以水保工程后，提高了造林质量，经调查，１９９１、１９９２、１９９３年的造林成活率均为８５％。工程措施、生物措施完成后的第五年，林草覆盖率可达７０％以上，基本上改变了生态环境，经济效益有明显提高。以凉城县双古城乡小夭沟行政村为例，全村总面积２２８８公顷，其中造林面积４１２公顷，森林覆盖率为１８％，１９８３年林业收入近万元、人均纯收入３１９元，而１９９３年林业收入达到１１万元、人均纯收入７００元，人民生活有显著改善。     

耀州区林业生态工程建设初显成效

1998年以来，耀州区委、区政府抓住国家实施西部大开发战略和山川秀美工程的机遇，以林业生态工程建设为重点，精心组织，强化管理，讲求质量，注重效益，六年人工造林保存面积31万亩，占全区人工造林保存总面积的56．9％，森林覆盖率由九十年代初的28．4％提高到38．2％，境内的漆水河、沮河、赵氏河、清峪河、浊峪河五大流域内林草覆盖面积达到75％以上，水土流失得到有效控制，一个山川秀美的新耀州展示在人们眼前。     

浅析影响造林质量的社会因素

随着我国大规模植树造林活动的开展，特别是《中共中央国务院关于进一步加快林业发展的决定》的出台，如何提高造林质量、确保工程建设的有效实施，已成为各级政府和林业主管部门首要解决的问题。作根据多年来从事造林工作的实践，主要针对影响造林质量的思想观念、造林机制、苗木的选择供应、效益补偿机制、林业产业链、质量监管体系等社会因素进行了阐述和分析。     

我国首个碳汇项目造林工程全面完成

2005年底，赤峰市林业对外项目管理办公室组织技术人员，对敖汉旗实施的“碳汇”国际合作“中国东北部敖汉旗防治荒漠化青年造林项目”工程进行实地监测，结果表明：2005年春季营造的2万亩杨树、踏郎混交林合格率为100％。同时，对秋季完成的2．5万亩造林项目进行实测，结果显录造林地块、模式、树种均符合项目设计要求，至此，该项目已全面完成造林任务。     

让世行贷款造林成为窗口工程

新邵县从1995年开始实施世界银行贷款造林项目。通年5年来卓有成效的工作，取得了令人瞩目的成绩。累计完成营造林1750．4公顷，为计划面积的175％；完成总投资525万元。经过多层次严格检查，历年新造林成活率均在95％以上，造林面积保存率100％，达到了速生丰产林标准，项目营造林质量在全省名列前茅。据专家测算，项目建成后，可新增森林蓄积量20．2万立方米，楠竹115万根，实现产值7210万元，投入与产出之比为1∶13．7，且有力地促进了全县科技兴林和林业管理水平的提高，产生了很好的示范和辐射作用。世行贷款造林是迄今新邵林业投资最…     

2004年我国林业建设发展势态良好

最新统计资料显示，2004年我国共完成营造林面积716．7万hm^2，为年计划的96％；实现林业产业总产值6076．77亿元：林业投资完成额348．22亿元。六大林业工程实施顺利，2004年完成的造林面积为510．71万hm^2，占全部造林面积的84．18％。     

河南省世行造林项目管理的主要措施

1990年以来,河南省先后利用世界银行贷款实施了4个大型林业外资造林项目,利用世界银行资金达4．6亿元人民币。20年的实践积累中,不断总结项目实施管理过程的经验,形成了项目管理的鲜明特点,对提高林业造林项目的整体实施质量起到了重要的推动作用。     

影响我国人工造林质量的因素及技术措施

随着重大林业工程的实施和国家对造林的投入迅速增加,造林质量倍受关注。文章分析和总结了我国造林质量中存在的问题,提出相应的对策措施。     

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.