遮荫对弗吉尼亚栎苗木生长及光合-荧光参数的影响

[目的]揭示美国引进树种弗吉尼亚栎幼苗对光照强度的响应特征,为弗吉尼亚栎的引种驯化和高效栽培提供科学依据。[方法]采用人工遮荫法,研究3种光环境下(全光——100%自然光、中度遮荫——50%自然光和强度遮荫——25%自然光)弗吉尼亚栎苗木生长、光合作用以及叶绿素荧光参数的变化。[结果]表明:中度遮荫明显促进弗吉尼亚栎苗高生长(P0.05),但对地径生长影响不明显;而强度遮荫条件下,地径生长受到明显抑制(P0.05),苗高虽有所下降,但与对照相比差异不明显。对弗吉尼亚栎光响应曲线的观测表明:与全光条件相比,中度遮荫条件下,弗吉尼亚栎叶片暗呼吸速率(Rd)、光饱和点(LSP)以及光补偿点(LCP)均明显下降(P0.05),说明适度的遮荫有助于提高弗吉尼亚栎对光的利用效率,促进干物质的积累;而强度遮荫条件下,光补偿点和光饱和点明显上升,暗呼吸速率明显增加(P0.05)。遮荫并未对表观量子效率(α)和最大净光合速率(P_(max))产生明显的影响。进一步对叶绿素荧光参数分析发现,遮荫条件下,PSⅡ最大光化学量子产量(F_v/F_m)和实际光量子产量(Yield)有所增加,但均在正常范围,说明遮荫对PSⅡ活性并未产生胁迫。[结论]弗吉尼亚栎幼苗对遮荫均具有一定的耐受性,中度遮荫有利于苗高生长;而强度遮荫不利于干物质的积累。因此,建议在营林以及人工栽培过程中维持50%以上的自然光照。     

3树种在海防林建设中的适应性评价

通过对弗吉尼亚栎(Quercus virginiana)、木麻黄(Casuarina equisetifolia L.)、紫花海棠(Malus‘ Purple’)3个树种在萧山区海防林建设的适应性试验,结果表明:弗吉尼亚栎和木麻黄这2个树种生长良好,保存率分别为95%和94.5%,可以在萧山围垦地区作为营造沿海防护林的新优树种加以推广;紫花海棠成活率(保存率)仅为40%,缺乏良好的耐旱抗涝习性,不能盲目引进造林,还有待进一步试种而定。     

辽东栎种子生命力的试验研究

<正> 辽东栎(Quercus Iiaotungensis koidz)是壳斗科落叶乔木,生长迅速、材质坚硬,喜凉爽气候,耐干旱瘠薄,是一个很好的水源涵养,水土保持和薪炭树种。辽东栎在我区主要分布在六盘山次生林区,由于它天然更新繁殖比较容易,现有林分主要是萌芽林,因此直播造林或育苗造林开展很少。主要是辽东栎直播苗早期生长慢,特别是对辽东栎种子的     

弗吉尼亚栎种子育苗和无性繁育技术

随着杭州湾跨海大桥和杭州湾新区的建设,在沿海防护林和新区绿化过程中极缺优良常绿耐盐碱树种.为此,2003年从美国引进弗吉尼亚栎(简称弗栎)种子播种育苗,2006年进行扦插繁苗试验,并通过一系列的试验以求形成苗木规模化生产技术体系.结果发现,弗栎种子易受象鼻虫危害,新引进种子必须进行杀虫处理;由于弗栎种子发芽和出苗不整齐,最好采取催芽播种和加温育苗,以提高出苗率,防止烂种;弗栎实生幼苗生长具有明显的抽梢-停梢生长阶段,春季有3次抽梢,秋季有1次明显抽梢期;在整个生长过程中,温度在30℃以下,生长速度随温度的升高而加快,大于32℃后,生长速度下降,在夏季高温会出现长时间的停梢现象.弗栎可采用扦插繁苗,扦插时间以秋季9月上、中旬为宜,插穗应选择当年生粗度3 mm以上、节间紧的枝条下部为宜,插穗以留3叶为好,插穗处理以15 000～20 000 mg/kg萘乙酸沾根处理为宜.     

几种国外栎属树种引种育苗试验

栎属植物是亚热带常绿阔叶林的主要建群种.在湖南长沙中南林业科技大学植物园引种8个国外栎属树种,观察其种子发芽情况及苗木生长表现.结果表明,8个树种露地栽培均能发芽,其中弗吉尼亚栎、柳栎、南方红栎和娜塔栎在发芽率、生长发育和观赏性状等方面均优于其他4个树种,有望在城市绿化中推广应用.     

宜兴市引乐属种源和杂交松试验初报

于１９９９年３月在宜兴市林场建立美国栎属（包括柳叶栎５个种源、红栎２个种源）,杂交松（杂种Ｆ１代,父本、母本）以及对对种青冈、麻栎、小叶栎和马尾松等共１４个处理的引种试验林。通过１ａ观测,其生长和保存率存在显著变异。（１）美国栎属生长变异极显著,树种间比较是柳叶栎〉红栎〉青冈。在柳叶栎中以９８１８号最大,９８２２号最小。红栎种源间无差异。造林成活率由于是采用容器苗造林,达９５．００％～１０．００％     

盐城粉沙淤泥质海岸立地条件及造林试验

以盐城粉沙淤泥质海岸射阳幸福大道和大丰市王竹海堤内侧两个试验样地立地条件分析为基础,对其造林树木生长情况作了野外调查。根据土壤含盐量和pH值,将盐城5县(市)8个试验样地划分成轻、中、重度盐渍土造林区,选取美国白蜡、弗吉尼亚栎、苏柳、七叶树等20多个树种进行造林。调查数据表明,盐城5县(市)造林平均成活率为81%,但不同立地条件树种生长情况和成活率也不同。     

弗吉尼亚栎引种研究与应用

正中国林科院亚热带林业研究所陈益泰研究员2001年首次从美国引种弗吉尼亚栎,开展了弗吉尼亚栎引种研究和应用。研究解决了弗吉尼亚栎规模化栽培技术,突破了无性繁殖技术,在国内建成了弗吉尼亚栎良种母树林,彻底摆脱了苗木市场对进口种子的依赖。近20年的引种研究和栽培实践证明,弗吉尼亚栎是一个适宜在我国长江中下游及其以南沿海地区推广的优良树种。它的突出优点是:生态幅较宽,对气温、光照、     

宜兴市引种美国栎属种源和杂交松试验初报

于 1999年 3月在宜兴市林场建立美国栎属 (包括柳叶栎 5个种源、红栎 2个种源 ) ,杂交松(杂种F1代 ,父本、母本 )以及对照树种青冈、麻栎、小叶栎和马尾松等共 14个处理的引种试验林。通过 1a观测 ,其生长和保存率存在显著变异。 (1)美国栎属生长变异极显著 ,树种间比较是柳叶栎 >红栎 >青冈。在柳叶栎中以 9818号最大 ,982 2号最小。红栎种源间无差异。造林成活率由于是采用容器苗造林 ,达 95 0 0 %～ 10 0 0 0 % ,种间和种源间变异不显著。但保存率变异显著 ,以柳叶栎 9816号和青冈最高 ,为 98 0 0 %～ 90 0 0 % ,红栎 982 1号和柳叶栎 982 3号最低 ,为 6 5 70 %～6 5 80 % ,比造林成活率有很大降低。 (2 )杂交松F1代最大 ,父本次之 ,母本最小。造林成活率和保存率差异均不显著 ,一直保持在平均 99 0 0 %     

弗吉尼亚栎不定芽增殖及试管苗再生影响因子研究

[目的]探析弗吉尼亚栎组织培养中不定芽增殖和生根的关键影响因子,建立弗吉尼亚栎试管苗再生体系,为弗吉尼亚栎无性系选育提供技术支撑。[方法]以弗吉尼亚栎带芽茎段为外植体,采用不定芽增殖途径,研究弗吉尼亚栎组织培养过程中外植体选择、褐化控制以及培养基选择、激素配比对不定芽增殖和生根的影响。[结果]表明:向培养基中添加抗坏血酸、硫代硫酸钠和活性炭均显著降低外植体的褐化半径(p<0.05),其中,外植体在含有3.00、5.00 g·L^-1活性碳的培养基中褐化半径最小。基本培养基筛选试验表明:以1/4MS或WPM为基本培养基时,平均芽长和芽数明显优于MS培养基。不定芽增殖最佳培养基为1/4MS+1.20 mg·L^-1 6-BA,培养周期40 d,增殖倍数可达6.6。最佳生根培养基为1/4MS+0.50 mg·L^-1 IBA+0.50 mg·L^-1NAA,生根率达53.33%,且根粗壮,木质化程度较高。组培苗移植到灭菌河沙中,平均成活率达57.78%。[结论]培养基成分和激素配比是影响弗吉尼亚栎不定芽增殖和试管苗再生的主要因子,低盐培养基(1/4MS或WPM)不仅可以促进不定芽增殖,且能够减轻外植体褐化;还发现野外取材的外植体极易褐化,而来源于无菌苗的外植体,褐化程度明显低于野外取材的外植体。     

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.     

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.