高产脂马尾松半同胞子代20年生测定林产脂力分析

以20年生高产脂马尾松半同胞家系子代林为材料进行产脂力分析,结果表明：马尾松半同胞家系间树高和产脂力均具显著差异;树高、胸径、产脂量和产脂力呈极显著的正相关;产脂力与温度呈正相关,与相对湿度及降雨量呈负相关,但均未达显著水平,可见马尾松产脂力受温度、降雨量与相对湿度3个气候因子的影响较小。采用双刀法采脂可明显提高产脂力。兼顾产脂力和生长量选出16个优良家系及22株优良单株。     

马尾松不同径级产脂量及松脂成分差异研究

采用长期定位观测,定时、定株收获的方法,研究了马尾松9种径级与产脂量以及6种径级与松脂成分之间的关系。分析结果表明:不同径级产脂量差异显著,随着径级的增大,产脂量也随之增加,呈正相关关系,初步认定马尾松产脂林采割起始径级不小于18 cm;不同径级的松脂主要成分一致,各成分含量存在一定差异,含油量有随着径级增大而增加的趋势,α-蒎烯含量高是马尾松松节油的特征。     

不同林龄马尾松人工林产脂量调查

对7年、10年、12年和15年生马尾松人工林的产脂量进行调查。结果表明:不同树龄的马尾松,单株采脂量均随着径级的增大而显著增加,但相同径级的马尾松,植株的产脂量并不会随着植株生理年龄的变化而产生显著变化;7年、10年、12年和15年生马尾松人工林产脂量分别为1.35、4.49、9.16和17.11 kg/(天·hm2),随着林龄的增大,单位面积可采脂植株数量和较大径级的植株数量以及单位面积产脂量均显著增加。     

马尾松产脂量密度效应的初步研究

对广西苍梧县国有天洪岭林场35年生的7种密度的马尾松林分进行采脂试验,结果表明:不同密度林分单位面积产脂量差异显著,低密度时,林分单位面积产脂量随着密度增大而增加,达到一定密度后,产脂量又随着密度的增加而减少;年平均单株产脂量则随着密度的增加而减少。在松脂主产区,进入成熟期的马尾松林分保留600~700株.hm-2的密度,产脂量高且经营效益好。     

马尾松产脂力、生长量和针叶中糖、淀粉含量的节律性变化

本文通过对不同龄级马尾松林分定点、定位、按月进行常法采脂和生长量调查，并测定针叶中可溶性糖及淀粉的含量，揭示了马尾松人工林林分的生长、发育以及内含物的变化规律。３５年生马尾松的产脂力和可溶性糖含量的相关性达到极显著水平，可溶性糖与淀粉含份呈负相关。产脂力和产脂量在年龄间和月份间都存在显著性差异，高产脂类型马尾松的产脂力和产脂量较普通马尾松有明显优势。经产脂力、生长量分析，初步确定马尾松的稳定采脂起始年龄，高产脂类型为２５年，普通马尾松为３０年。     

马尾松采脂林经济收益评估

马尾松(Pinus massoniana Lamb.)采脂林的经济收益一直倍受关注.该研究在广东信宜、河源和郁南3地建立了马尾松采脂试验林,分8个年度测定试验林的存活率、生长量及产脂力,并估算采脂林的经济收益.发现经济收益先逐年提高后缓慢下降,15a采脂林经济收益可达9583.5 元/hm2·a,经济收益与存活率和产脂...     

太岳林区油松采脂量及其与测树因子关系的研究

设置15块标地进行采脂试验,结果表明:太岳林区油松16 cm~32 cm径级林木年均采脂量为916.2 g,20 cm以上径级林木年均采脂量为1 042.5 g;每个径级林木采脂量与相邻3个高径级和3个低径级中任一径级林木采脂量间差异不显著,与相邻3个高径级和3个低径级以外的任一径级林木采脂量间差异均达显著或极显著水平;油松采脂量与采脂木胸径、活枝下高、冠幅、树冠因子呈一元线性回归关系,相关系数分别为0.993 6,0.705 1,0.765 6,0.911 6,相关关系显著或极显著。     

马尾松中龄林采脂效益分析

开展16年生马尾松(Pinus massoniana)人工林采脂与非采脂林分生长对比试验,并对连续5年的采脂效益和11年的马尾松松脂和原木市场进行分析。结果表明,采脂对马尾松中龄林生长的负面影响显著,采脂处理平均胸径、树高、单株材积增量只有非采脂的65.2%、56.6%、60.5%,因采脂导致林分蓄积生长量减少为32.014 9 m3/hm2,风害损失为6.325 m~3/hm~2。松脂原料收购价格波动较大,整体呈上升趋势。原木市场价格较为低迷,不利于促进林农种植马尾松的积极性。采脂对林分原木收益有一定的负面影响,但采脂林总体的经济效益比未采脂林经济效益显著,能有效提高马尾松商品林经济效益和缩短投资回收周期。     

马尾松天然林采脂试验分析

对马尾松天然林分进行产酯与其他生长量、气候、土壤因子的相关分析，结果表明：林分间及林分内的产脂力差异极大；产脂量与树高、树皮裂纹深度、胸径、树皮厚度、冠幅、侧枝基径呈显著或极显著的正相关；在气候因子中，月均温是影响产脂量的主要因素，而相对湿度和降水量则对产脂量影响不大；土壤的速磷及活性有机质含量高以及土壤酸性越强有利产脂力，而土壤全钾含量和速效钾含量高对产脂力可能有负面影响。     

桂东南马尾松采脂林配方施肥研究

为了提高采脂林经济效益,以此提高林农采脂积极性,缓解当前松脂产业发展的国内原料短缺问题,以桂东南地区马尾松土壤养分状况为基础,通过综合分析高产脂林分、低产脂林分土壤养分以及针叶养分动态关系,建立了相关模型,得出了适合桂东南马尾松采脂林施肥配方(N、P、K含量分别为8%、12%和10%,Mg+Ca+Si+有机质≥10%),并研究了不同施肥量对桂东南近熟马尾松林分生长和产脂的影响。研究结果表明:施配方肥可以有效促进马尾松生长和产脂,施肥2kg比施肥1kg可以提高胸径生长量90.9%,材积生长量38.6%,材积生长率12.7%,产脂量21%;施肥第一年可增加采脂林净利润8285元/hm~2。说明配方施肥可以有效提高采脂林经济收益,开展配方施肥技术推广,是解决当前国内松脂产业原料短缺问题的有效途径。     

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.