741杨几个重要栽培生理特性的研究

以７４１杨嫩枝扦插苗为材料，采用盆栽沙培、土培或溶液培养法，研究了７４１杨的抗旱性；适宜生长的介质ｐＨ值和培养液浓度，Ｎ，Ｐ，Ｋ施肥量和配比；用人工遮阴法研究了７４１杨的耐阴性。７４１杨不耐旱，在中等水分胁迫条件下（基质含水量日变幅为田间持水量的４８％～６５％）没有表现出明显的渗透调节、降低蒸腾速率等作用，生物量只达到对照（充分供水）的６０．５％．但在严重水分胁迫下（相对含水量日变幅２５％～３５％）能通过自身调节机制并继续存活。７４１杨生匕的最适ｐＨ值为５．０～７．５，只有当介质ｐＨ＞９．５时才强烈抑制生物量增长。７４１杨溶液培养时，盐浓度体积百分数以０．２３２％最好，浓度达到０．４６４％时，不仅抑制生长，而且出现水分胁迫症状。７４１杨Ｎ，Ｐ，Ｋ的适宜施肥浓度分别为３０ｍｍｏｌ·Ｌ－１，３ｍｍｏｌ·Ｌ－１，６．６ｍｍｏｌ·１－１，，最适配比为１０：ｌ：４．５。７４１杨是一个喜光树种，在全日照下生长最好，在较弱光（全日照的２４．５％）表现出很强的适应性。它不能长期生活在２．５％日照条件下。     

遮荫对红松、红皮云杉苗木生长的影响

研究不同年龄红松，红皮云杉在全日照、70％、40％、30％及10％光照条件下的生长情况，结果表明，红松、红皮云杉苗木均在相对照度70％的条件下，树高生长量最大。全日照不利于苗木高生长。地径生长随着光照强度的增大而增大。相对照度70％条件下，红松、红皮云杉（小）平均单株生物量最高。红皮云杉（大）在全日照下平均株生物量最高。随着苗龄的增长对光的需要量增大。     

马蹄金的建植与管理

马蹄金（ＤｉＣｈｏｎｄｒａｒｅｐｅｎｓ）为旋花科马蹄金属多年生匍匐性草本植物。叶肾形，互生，直径１～３厘米。叶面光滑，叶柄、叶背及匍匐茎上密生白色绒毛；花小，直径２～４毫米，白色，花期４～５月。果实成熟期７月，能自播；草层高５～１５厘米。因其适应性强、生长迅速、管理方便等，被广泛应用于园林、绿化中。马蹄金的栽培管理应注意以下四点：一、园地选择　马蹄金既喜阳又耐阴，在全日照条件下生长迅速，即使在建筑物北侧、疏林及郁闭度０７的林冠下也能生长良好；既可种植于平整的场地又适应坡地条件；土壤ｐＨ值在６…     

沙生饲用灌木树种的适应性评价

试验对５个沙生灌木树种的引种、生物量、抗旱性、饲料成分及营养价值作了测试和分析，并与乌兰布和沙漠传统饲用灌木、牧草、农副产品饲料进行了比较。结果表明：花棒、梭梭和乔木状沙拐枣不同产地间在高生长、地径生长两个性状上差异显著；乔木状沙拐枣和杨柴的地上生物量低于多枝怪柳（对照）１０．６９％和１８．８７％，花棒、梭梭、毛条分别高于对照１６．９８％、２７．０４％和２．６４％。所选５个树种７项生态生理综合指标反映的抗旱性均高于对照树种二白杨和小叶杨；适于在乌兰布和干旱环境中生长；粗脂肪、租纤维和无氮浸出物高于传统饲料汤、柳、榆树叶；饲料成分及营养价值高于玉米秸和小麦秸；１１种氨基酸总含量分别为：毛条１２．５３％，花棒１０．９１％，传统饲料多枝栓柳为７．８％，紫花苜蓿１．１８％，沙打旺１．２４％，玉米秸０．８２％，小麦秸１．０５％．栽培沙生饲用灌木是沙区发展畜牧业的一条有利途径。     

桉树薪炭林混交试验──Ⅳ尾叶桉和大叶相思或肯氏相思混交试验

试验结果表明：尾叶桉和大叶相思或肯氏相思施行行间混交是可行的，３年生尾叶按混交林林分蓄积量和生物量比尾叶按纯林分别增长１８．７％～２３．３％和１６％～２４．３％，且以两行尾叶桉加一行大叶相思混交效果较好；其次为一行尾叶桉加一行大叶相思或肯氏相思。通过混交不仅能促进木木生长而且能提高尾叶桉于材生物量所占的比重，能改良土壤，提高林地有机质的含量。     

辽西低山丘陵荒坡营造水保林工程整地措施试验研究

为提高辽西半干旱地区营造水土保持林的成活率与质量，进行了工程整地措施试验。认为，造林前一年采取工程整地措施．能拦截坡面径充、拦蓄泥土、积存枯草（枝）落叶。较荒坡土壤含水量提高，土层厚０～１５ｃｍ为４．２％～７．５％，１５～３０ｃｍ为４．６％～８．５％；土壤有机质含量增加０．０３％～１．３７％；全氮增加　０．０１６％～０．０３１％，全磷提高０．００６％～０．０１４％；阳离子代换量高５．３０～　８．２４ｍｇ／１００ｇ土。土壤机械组成较荒坡粗沙比例降低，粘粒比例增高，物理性沙粒比例减少，物理性粘粒比例升高。给树木生长提供了良好的生态环境条件。造林成活率提高１０％～２５％，树木径粗增加０．１０～０．２８ｃｍ，树高增加１５．３％～９２．１％，树木长势显著好于荒坡造林。     

桉树薪林混交试验—IV尾叶桉和大叶相思或肯氏相思混交试验

试验结果表明：尾叶桉和大叶相思或肯氏相思施行行间辊交是可行的３年生尾叶桉混交林林分蓄积量和生物量比尾叶桉纯林分别增长１８．７％～２３．３％和１６％～２４．３％，且以两行尾叶桉加一行大叶相思混交效果较好，其次为一行尾叶桉加一行大叶相思或肯氏相思。通过混交不仅能促进木木生长而且能提高尾叶桉干材生物量所占的比重，能改良土壤，提高林地有机质的含量。     

国槐截形叶螨的生物学特性及防治

北京地区国槐普遍受截形叶螨（ＴｅｔｒａｎｙｃｈｕｓｔｒｕｎｃａｔｕｓＥｈａｒａ）危害，从５月下旬至１１月上旬均有发生，危害盛期在７—８月份，有螨叶率市区达７０％，近郊区可达９０％以上。根据有效积温及气象资料推算，截形叶螨在北京地区每年发生１５—１７代。在２８℃、ＲＨ６７℃条件下，室内饲养，发育一代平均６．７天，在２７℃、Ｒｈ７２％条件下，雄成螨平均寿命７．５天，雌成螨１０．７天。截形叶螨以成螨越冬，其场所主要在树干及粗枝树皮裂缝内，极少部分在小校、树冠下草地及根际土壤中。早春用生物制剂—２．５％日光霉素１０００倍，１０％增效浏阳霉素２０００倍７３％克螨特乳油２０００倍及洗衣粉４００倍，碳酸氢铵颗粒剂１００倍防治，均能取得很好的效果。     

落羽杉属种源研究∶生长和生物量变异

对落羽杉属不同种源、家系和树种苗期、幼林期生长量（高、胸径、冠幅）、保存率和生物量及其分配（总生物量，干、枝、叶、根生物量及其比值）进行了５年研究。发现落羽杉不同种源、家系间、内均存在显著的性状变异。变异系数以种源、家系间最大，个体间其次。生物量的变异系数大于生长量。未发现不同种源、家系在不同地点存在明显互作。采用多性状综合选择法评选出７个优良种源、家系或树种（１６００、４０１、中山杉、３０４、５０２、鸡公山落羽杉和７０１），它们的生长量、生物量大，叶生物量较大，地上部分生物量／根生物量比值大。其综合选择指数值比平均值大１３．９７％～３５．３３％，树高比平均值大１１．２２％～２４．４９％，比本地近似树种（江宁池杉）大３４．５４％～４６．１８％；胸径比平均值大１２．８１％～４８．２８％，比江宁池杉大３８．７９％～８２．４２％；总生物量比平均值大５４．５９％～１１０．６７％；保存率一般也高于平均值及本省江宁池杉。这些优良种源、家系或树种可以在江苏全省及国内类似地区作用材、防护和观赏树种推广应用。     

桉属树种与种源、家系比较试验

以９个桉属树种，其中８个种泊来自原产地，７个家系和７个杂种后代来自国内次生资源进行混合比较，５年生评价结果表明：树种、种源、家系呈极显著差异；尾叶桉及其两个种源、尾巨桉杂交种细叶桉的１３５４４种源适合本试验区戒严和格短轮伐期经营，可获得适应性和生长指标平均值超过平均水平３５％的选择效应。其中最优为１４５３４号尾叶桉种源，５年生单株材积０．０５０．６１ｍ＾３／株（８９．０３ｍ＾３／ｈｍ＾２）。种子采     

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.     

qPCR quantification of Ophiognomonia clavigignenti‐juglandacearum from infected butternut trees under different release treatments

The use of a molecular assay for quantifying conidia of Ophiognomonia clavigignenti‐juglandacearum, the fungal pathogen responsible of butternut canker, was investigated. Purified DNA from conidia collected on glass fibre filters of a passive rain collectors was quantified using a TaqMan real‐time quantitative polymerase chain reaction (qPCR) assay. The qPCR assay could specifically discriminate the target species from all other North American known species of Ophiognomonia, and it was sensitive enough to repeatedly detect one conidium. A linear relationship between numbers of conidia and qPCR C_t values was determined, and used to assess the sporulation of the pathogen under trees that were released to promote their vigour. In total, 977 samples of field‐captured conidia from 49 trees, at two locations, and from two successive growing seasons were analysed. No significant difference of sporulation was observed under control and release treatments. However, our results demonstrated that qPCR assay was reliable for detecting and quantifying O. clavigignenti‐juglandacearum from environmental samples, which will be useful to assess further control methods for this disease.     

The potential of alley cropping in improvement of cultivation systems in the high rainfall areas of Zambia I. Chitemene and Fundikila

Three trials investigating the potential of alley cropping to improve the traditional systems of cultivation, chitemene and fundikila, in the Northern Province of Zambia are described. Flemingia congesta, Tephrosia vogelii, and Sesbania sesban, were grown in association with finger millet, groundnut, cowpea, and maize in various traditional cropping sequences. The indigenous species Tephrosia vogelii and Sesbania sesban were not able to withstand repeated pruning and the long following dry season, and were replaced with Calliandra calothyrsus, and Cassia spectabilis.Over a four year period, there was no benefit by alley cropping with any of the tree species on crop yields, and yields in alley crop treatments even dropped significantly below the control treatments in the fourth year, casting doubt on the potential of alley cropping for sustainable production. There was also no consistent effect on soil chemical characteristics in any of the trials. It was suggested that this lack of beneficial response to alley cropping was due to low tree biomass production low quality of prunings, and an inappropriate cropping sequence. There was no evidence that alley cropping contributed to enhanced nutrient recycling, despite substantial localised pools of soil nutrients, particularly in the chitemene, with which recycling could potentially occur.     

Toxicity of biocide GCSC-BtA on arthropod pests under different temperature conditions

The present research dealt with the toxicity of GCSC-BtA (Germany–China Scientific Cooperation-Bacillus thuringiensis-Abamectin), a new type biocide developed by conjugating a toxin from Bacillus thuringiensis (B.t.) with Abamectin from Streptomyces avermitilis, on arthropod pests under different temperature conditions. The results showed that GCSC-BtA possessed higher toxicity than B.t. crystal, Abamectin or Cypermethrin, with pest mortalities of 97.9, 93.7, 96.4, 82.3 and 96.7% for Tetranychus cinnabarinus (Boisd.) (Acari, Tetranychidae), Frankliniella occidentalis Pergande (Thys., Thripidae), Aphis fabae Scopoli (Hom., Aphididae), Plutella xylostella (L.) (Lep., Plutellidae) and Cameraria ohridella Deschka et Dimić (Lep., Gracillariidae), respectively. Toxicities of GCSC-BtA to T. cinnabarinus and P. xylostella decreased significantly at the older developmental stage with an exception that egg stage had the highest tolerance, in which LC₅₀s of GCSC-BtA were 0.0001, 0.0019 and 0.0708 mg/ml for nymph, adult and egg of T. cinnabarinus, and that 0.0399, 0.2035 and 0.9033 mg/ml for the 2nd instar larvae, 4th instar larvae and egg of P. xylostella, respectively. Also, the biocide was more effective to the lower stage of A. fabae than the higher one with LC₅₀s of 0.0023, 0.0086 and 0.0171 mg/ml against 1st instar nymph, 3rd instar nymph and adult, respectively. In general, toxicity of the new type of biocide was positively related to temperature against all the tested pests, except against T. cinnabarinus, where it was almost similar at the three temperature conditions. GCSC-BtA displayed significantly lower toxicities at 15/20°C than 20/25°C or 25/30°C against F. occidentalis, A. fabae, P. xylostella and C. ohridella. However, no significant difference was found in the toxicities against F. occidentalis, A. fabae and C. ohridella above 20°C, whereas toxicity against P. xylostella increased as temperature raised. Therefore, to achieve higher efficacy in the field, application rate and time should be devised according to these factors.