春风又绿树芽菜

春风吹绿嫩树芽。我国有不少木本蔬菜，如香椿芽、柳树芽、枸杞芽、树头菜、桑叶芽、漆树芽、槐树芽等等，它们以芽为主体，有的还带了嫩绿的短枝，不仅味道鲜美，而且大多对人体健康大有裨益。这些树上佳蔬，才是最佳的纯天然的绿色食品。 香椿芽　　为椿科乔木，香椿的嫩芽，常带有短嫩枝。香椿芽有一种特殊的香味，是营养价值很高的蔬菜，它含有丰富的蛋白质、维生素Ｃ、钙、磷、铁等矿物质。我国人民食用香椿芽开始于汉代，已有２０００多年的历史了。香椿芽食用方法方便，可以单吃，也可以生拌豆腐，配炒鸡蛋、或油炸香椿鱼、腌咸菜等…     

香椿生物学起点温度的研究

通过对香椿的休眠期、生物学起点温度及解除休眠的试验研究发现:香椿落叶后有17天的生理低温休眠期;生物学起点温度为8.3℃;顶芽解除休眠完成芽萌动需要的有效积温为234℃,从芽萌动到采芽需要的有效积温为165℃。根据这一结果进行栽培,可以提高香椿芽的产量。     

采芽长度和采芽期对香椿芽品质的影响

研究了矮化香椿园中采芽时期和采芽长度对香椿品质的影响。为便于分析，将测定结果归纳为３类指标：外观、口感和其他营养成分。研究表明，春季（４～７月）采芽，各项指标均优于秋季（９月）。春季第１茬芽的品质最好，但第２、３茬芽的品质降低较少。从品质和产量综合考虑，春季采芽长度以１０～１５ｃｍ为宜。秋季（９月），各项指标急剧降低，为确保枝条安全越冬，已不适于采芽。     

日光温室栽培香椿芽新技术

日光温室栽培香椿芽新技术韩鸿声，孙蕾（山东省林科所，济南，２５００１４）山东省林科所研究成功的“日光温室栽培香椿新技术”，严冬依靠太阳热增温生产香椿芽，每平方米生产鲜椿芽４．５～６．１５ｋｇ，纯收入９０～１６０元，投入产出比约为１：５～７。鲜椿芽元旦...     

矮化香椿园密度、整形和采芽技术研究

在保定郊区建立４种密度的香椿矮化密植园，根据４年的研究，１～４年内以最高密度（３．８株／ｍ２）和高密度（２．５株／ｍ２）的产芽量最高，第４年采完芽后，对最高密度应进行疏伐，保留２．５株／ｍ２；中密度（１．７４株／ｍ２）和低密度（０．８３株／ｍ２）５～１０年内可以不疏伐。结合采芽进行两种方式的整形，即矮干多侧枝型和灌丛型。前者的总产量较高，且可提早１年采芽。采芽３年后，两种整形方式的年产量已无显著差异。采芽与整形相结合，可以促进侧枝和树冠的形成。但是，高密度严重抑制侧枝形成和存活，以至不能形成树冠。矮化密植香椿园第３年的产芽量最高可达５２００ｋｇ／ｈｍ２，年均纯收益为３８９４０元／ｈｍ２。     

1995年林业部科技推广项目选介

日光温室栽培香椿新技术依据树木生理学和栽培学原理，设计并建造了新型日光温室，在室内建造酿热温床和海绵田，进行了香椿教培试验。总结出了一整套香椿密植、促进侧芽生长、提高香椿芽产量的配合技术措施。采用水技术栽植香椿生产香椿芽，平均每平方米温室面积可采收香椿芽1．8～6．15kg，最高可达7.43kg/m2，投入产出比为1：4.97～7．2O。完成单位：山东省林科所北方地区大棚工厂化容器育苗配套换术该成果研制出容器苗生产主要作业工序所需的配套设备。实现了基质粉碎、搅拌、填装、播种、复上的机械化苗木生态环境调控的自动化，容器…     

香椿芽蔬菜培育技术

香椿芽蔬菜培育技术张发（河南省卢氏县潘河镇尤里卡特种繁育场４７２２４４）香椿是我国特有的树种，其嫩芽芳香味美，鲜食、炒食、腌制均清香可口。芽紫红色者称紫椿，芽绿色者，称绿椿。香椿芽及嫩叶，有收敛止血、去湿止痛、开窍止痢等功效，常食对人体健康有益，是地...     

香椿栽培及效益分析

香椿（Toona sisesis（A．Juss）Roem．）别名香椿头和香椿芽,原产于中国,已有二千多年的栽培历史。《本草纲目》中指出香椿的叶、芽、根、皮和果实均可人药,我国民间有“食用香椿不染杂病”的说法。香椿全身是宝,具有很高的材用价值、食用价值和药用价值。     

苹果自由纺锤形树冠成形技术

苹果自由纺锤形树冠成形技术定植时采用一级苗，定干高度７０～８０ｃｍ。当年萌头后在树干４０ｃｍ以上整形带内按主枝选留方位刻芽（或涂抽枝宝）５～６个。夏剪时选留３～４个新梢作主枝，拉枝呈７０～８０度，７月在当年主枝上刻芽（或涂抽枝宝），每枝刻１２～１５个...     

塑料大棚培育香椿技术

香椿芽味美,营养丰富,为名贵佳肴,是人们喜爱的绿色木本蔬菜。近年来利用塑料大棚培育香椿使香椿提前采芽,多茬收获,在产量和经济效益上有较大幅度的提高。根据我们在华县辛庄乡几年的试验和调查研究,现将培育香椿技术介绍给大家。 育苗技术     

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.