沿河沙滩地杨树截根造林效果好

近几年来 ,老河口市经常发生春旱 ,而且早春地温偏低不利于杨树生根和成活 ,大面积造林的成活率不高。随着人民造林绿化意识的不断提高 ,我市杨树栽植面积逐渐扩大。为了有效地治理沙化土地 ,改善汉江生态环境 ,近几年来 ,在汉江沿岸沙滩上采取杨树截根苗深栽技术 ,栽植杨树面积已达2 33.3ｈｍ2 。仅 1 997年 ,老河口市林业局组织有关专家、技术员在市光华办事处西关村采取杨树截根造林技术 ,栽植杨树新品种 33.3ｈｍ2 ,成活率在97%以上。为了进一步推广此项造林技术 ,2 0 0 1年我市又在国有王甫洲林场采取杨树截根造林2 0 0ｈｍ2 。沿河滩…     

杨树叶锈病及其防治

杨树叶锈病 (Melampsoraspp)是一种危害杨树叶片、芽和嫩枝的病害 ,广泛分布于我国东北、华北、西北、中南的多数省区。该病在湖北石首市发病株率达 1 0 0 % ,主要危害杨树苗和中幼林。杨树得病后病叶上密生夏孢子堆 ,影响光合作用 ,使树体水分过量蒸发 ,导致叶片枯萎并提早脱落。发病严重时 ,在杨树生长期树叶即脱落殆尽 ,造成杨树在秋季二次萌叶及翌春放叶迟缓 ,削弱树势 ,对生长量有严重影响。为了控制该病的危害 ,我们在2 0 0 1～ 2 0 0 2年对该病的发生条件和防治技术作了初步研究 ,现将结果报道如下。1　症状石首市位于长江中游 ,地…     

Bt转基因杨树对杨树昆虫群落结构的影响

通过种植转基因杨树纯林和混交林 ,研究了Bt转基因杨树对杨树昆虫群落结构的影响。研究表明 1hm2的小面积的新疆转基因杨树和非转基因杨树之间群落结构和多样性差别不大 ;而对 6 7hm2 以上的转基因杨树纯林和 1∶1的转基因和非转基因杨树混交林中昆虫和蜘蛛群落结构的比较研究发现 ,Bt转基因杨树会改变其昆虫群落结构 ,在转基因纯林中杨叶蜂为优势种 ,而在混交林中杨扇舟蛾为优势种。为了避免其它非鳞翅目食叶害虫的危害 ,在转基因时应采用对非鳞翅目食叶害虫有抗性的种类或品系。转基因纯林的多样性和均匀性都较混交林高 ,有利于系统的稳定性 ,但转基因混交林中瓢虫的数量明显比转基因纯林高 ,分别为 0 2 1头·枝- 1 和 0 0 2 1头·枝 - 1 ,相差 1 0倍。蜘蛛的数量是纯林中较多 ,分别为 0 1 2 5头·枝 - 1 和 0 0 6 2 5头·枝 - 1 ,相差 1倍。转基因杨树对非目标昆虫和天敌的影响还需进行进一步详细的研究。转基因纯林和混交林的叶片被害率分别为 1 1 2 6 %和1 8 4 8% ,转基因纯林抑制目标食叶害虫的作用较好 ,但与混交林之间的差异不显著 ,两种林分的被害率都在不成灾的水平。     

晋西北不同植被类型土壤水分空间分异

采用土钻法对晋西北朔州地区杨树林、柳树林、草地3种植被类型0~600 cm土层土壤水分动态进行研究。结果表明:土壤平均含水量表现为草地杨树林地柳树林地。草地土壤平均含水量比杨树林地高1.25%,比柳树林地高1.9%。随着土壤深度的增加,土壤含水量先减小后上下波动,然后趋于稳定。0~100cm土层范围内,土壤水分变异系数大小为草地柳树林地杨树林地;在200~300 cm、400~500 cm土层范围内,变异系数表现为柳树林地草地杨树林地;300~400 cm、500~600 cm土层范围内,变异系数大小为柳树林地杨树林地草地。越靠近表层,土壤干化现象越严重,柳树林地干化现象最明显,含水量变化最剧烈,杨树林地次之,草地最稳定。     

杨树伐根嫁接河北杨

甘肃白银市是光肩星天牛[Anoplophoraglabripennis (Motsch) ]危害的重灾区。过去 10年由于该天牛危害不得不砍伐的杨树近 4 0 0 0万株 ,造成直接经济损失逾亿元。为了扭转光肩星天牛猖獗危害的局面 ,我市在西北率先成功应用杨树伐根嫁接毛白杨技术进行防护林的更新和天牛虫源林的改造。近年来又开展了杨树伐根嫁接河北杨的试验 ,并取得可喜的成果。利用杨树伐根嫁接抗旱、抗寒、抗天牛等性能优良的河北杨 ,可解决杨树蛀干天牛危害区清除虫害木后的更新及伐根不易清除的难题。在白银灌溉区嫁接的河北杨 1年生苗平均高3.8m ,平均地径 3.5cm …     

苹果卷叶象在杨树上的危害和防治

苹果卷叶象〔 Byctiscus princeps( Solsky)〕属于鞘翅目、象甲科 ,主要危害杨树、苹果、梨等。此虫在河北承德避暑山庄内对杨树的危害非常严重 ,我们对此虫进行了系统调查。1　发生与危害于 1 999年 4～ 9月在避暑山庄内采取1 2个样点 ,对上千株 2 0～ 4 0 a生杨树进行调查 ,杨树被害率达 1 0 0 % ,单株平均卷叶率为2 0 %～ 30 % ,最高卷叶率达 6 0 %。造成早期落叶 ,小枝枯死 ,树势衰弱 ,影响树体的生长。2　危害状越冬成虫于春季杨树展叶期将一片叶卷折 ,在其中产 1～ 3粒卵 ,以 2粒为多 ,以后将临近叶依次卷与其上 ,每卷一片叶产 1粒卵…     

大青杨、银中杨及三角叶杨的繁育技术

杨树以其生长快、成材早、适应性强、木材用途广 ,而成为我国的主要栽培树种。杨树品种繁多 ,根据适地适树的原则 ,我们对小兴安岭主要原料林造林树种大青杨、银中杨、三角叶杨进行了繁育试验 ,以便选育出适合朗乡地区的杨树新品种。1　试验地概况试验地选在黑龙江省朗乡林业局英山苗圃 ,地理坐标为 4 6°5 2′N ,12 8°4 8′E ,海拔高度为35 0m ,地下水位 1 6m ,土壤耕作层 2 5cm ,pH值为 5 6 ,年降水量 6 0 0～ 80 0mm ,无霜期为10 0天 ,≥ 10℃有效积温在 2 0 0 0～ 2 2 0 0℃之间 ,相对湿度在 70 %左右 ,年平均气温 - 0 5～0 5℃。…     

莱阳市几个黑杨品种的抗逆性调查与分析

杨树是我国北方的一个优良速生用材树种 ,近年来 ,莱阳市大力发展杨树速生丰产林 ,先后引进推广杂交杨新品种 40多个。 1999年莱阳市林业局与烟台市林业局种苗站合作建立杨树试验林 2hm2 ,2 0 0 2年下半年至 2 0 0 3年春 ,试验林内出现大量杨树整株死亡现象。我们对林内树木死亡情况进行了调查 ,对死亡原因进行了研究分析。1　调查地基本情况莱阳市杨树试验林位于龙旺庄办事处鹿格庄村南清水河北岸河滩 ,土壤为沙土 ,北沿为一防洪堤坝。林内地势平坦 ,排水良好 ,参试品种有I -10 7、I -2 14、中林 46、土耳其 6号、土耳其12号、土耳其 14号…     

杨树团状栽培模式为发展杨树兴利除弊(一)

杨树团状栽培模式是根据我国杨树主要产区——平原农区的社会经济和自然条件提出的一种创新的农林复合经营模式。它尽量缩小杨树的占地面积,由100%缩减到5%¹0%,减少杨树与农作物的接触和相互竞争,以农为主,使杨树对农作物的副作用降到最低,保证农作物高产。另一方面,杨树团具备了农田这样好的立地条件,能够长期分享农业对水、肥和土壤耕作的投入,杨树的优质、高产也能得到保证。有助于解决立地不合格、粗放经营和密度过大,这些长期困扰杨树发展的问题。与传统的行状造林方式比较,团状杨树栽培利多弊少,对农业影响小,农林长期和谐,达到双赢。在我国平原农区土地资源紧缺的条件下,在国家木材供不应求的情况下,杨树团状栽培模式对发展杨树有重要实用价值。     

不同林龄抑螺防病林林分内钉螺种群分布特点的研究——以安庆市大观区沿江滩地为例

运用不同调查方法对安庆沿江滩地杨树林地、江滩草地、芦苇丛等5个植被类型区的钉螺分布状况进行调查,研究了钉螺样本的形态指标和阳性率,以及对其与已采取的灭螺措施之间的相互关系进行了分析,结果表明：（1）成熟杨树林地、中龄杨树林地均无钉螺分布;杨树幼林地、江滩草地、芦苇丛螺口密度分别为4只／0．11m2、5只／0．11m2、7只／0．11m2。（2）杨树幼林地、江滩草地、芦苇丛所获钉螺样本的阴阳性检测,没有被血吸虫感染,均为阴性。（3）江滩营造抑螺防病林是改变钉螺孳生环境及人工控制钉螺种群密度的有效途径之一。     

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.