赣南地区邓恩桉的种源生长比较

对江西省赣州市信丰九龙林场5年生的7个不同种源的邓恩桉进行生长性状调查与分析,结果表明：邓恩桉在赣南地区生长较为迅速,而且具有良好的抗寒能力,邓恩桉的不同种源间生长性状差异不显著,但通过对其个体的比较发现,种源17923、18264表现较好,具生长快、耐寒性好的特点,建议作为良种选择应用。     

柳桉种源试验小结

对澳大利亚的6个柳桉种源进行了比较试验,结果表明:低纬度低海拔种源的生长较低纬度高海拔和高纬度高海拔或低海拔的种源好,但6个种源在雷州的立地生长都较差。雷州地区不适宜柳桉生长。     

邓恩桉种源试验林生长性状遗传变异及选择

为筛选出邓恩桉(Eucalyptus dunnii)优良遗传材料,对6年生邓恩桉种源试验林的适应性及生长性状进行调查测定并统计分析。结果表明:试验林保存率为52.56%,各种源的整体适应能力差异显著;试验林平均树高为18.3 m,平均胸径为16.4 cm,平均单株材积为0.187 5 m3,各生长性状种源间差异极显著,3个生长性状在种源和单株水平上受中等强度以下遗传控制。构建多性状综合指数方程,按照标准选出3个优良种源及75个优良单株,其中优良种源树高、胸径、材积的遗传增益分别为2.89%、3.98%、9.11%,优良单株树高、胸径、材积的遗传增益分别为4.66%、8.56%、16.01%,选优效果明显。     

赣南耐寒桉树引种试验

选取种源来自于澳大利亚新南威尔士州、昆士兰州和维多利亚州的巨桉、邓恩桉、柳桉、亮果桉、史密斯桉、多利桉和巴吉桉共7个树种22个种源为试验材料,进行引种试验,34个月后对其生长指标与冻害等适应性指标进行调查。结果表明:参试材料中邓恩桉0612、邓恩桉99/01和多利桉97/06等3个种源的适应性较强,冻伤轻微,冻害等级为Ⅰ;邓恩桉0612、邓恩桉99/01适合赣南引种种植;但多利桉97/06生长量相对较低,应先进行引种驯化,再根据驯化情况及实际需要决定是否推广种植。     

福建省建瓯市丘陵山地引种邓恩桉的调查分析

对闽北的建瓯市3种不同坡位丘陵山地引种邓恩桉,结果表明:邓恩桉适应性和速生性较强,邓恩桉可耐-4℃的短暂低温严寒。造林当年的平均树高达3.1 m,8年生邓恩桉生长平均树高、胸径分别为9.5 m和10.3 cm,达到福建省一般产区桉树速丰林标准。3种试验处理的造林成活率均达到92.6%以上。8年生时,不同坡位对邓恩桉成活率与保存率的影响差异不显著,各处理的林分保存率达到85.7%~88.2%,不同海拔(坡位)造林对当年生邓恩桉树高、胸径及8年生胸径、蓄积量的影响差异极显著,对8年生树高的影响差异显著,海拔200m以下的中下坡引种邓恩桉较速生。     

巨桉种源早期生长对比及综合评价

对7个巨桉(Eucalyptus grandis)种源4a生时的生长性状进行测定分析,利用主成分分析结合模糊聚类法对各种源进行综合评价.结果显示:(1)7个种源间存在分化和差异,其中15508号种源平均树高及单株材积最大,分别为10.48 m、0.022 8 m3;13019号种源平均胸径和保存率表现最优,为8.09 cm和79％;种源16500号干形生长表现最优.(2)树高、胸径与单株材积三者与干形、保存率及海拔间均存在负相关;保存率与南纬、东经呈现显著正相关(P＜0.05),与海拔呈现负相关;干形与南纬、东经呈现负相关,与海拔间呈正相关.(3)基于主成分分析确定巨桉种源树高、胸径、单株材积、干形及保存率指标所占权重分别为:0.267 5,0.262 9,0.266 8,0.163 5和0.039 3.(4)根据综合评分及模糊聚类,第Ⅰ类种源(种源13019、15508、15875和16500)生长表现最优,适宜在引种地种植,其余种源可通过进一步测定选择优良个体作为世代育种材料.     

细叶桉和尾叶桉种源试验研究

尾叶桉与细叶桉8个种源生长性状与保存率的差异和遗传分析结果表明；种源间除高径比外各性状的差异极显著，种源层次各性状遗传力为43.25％～88.14％，单株层次各性状遗传力为16．00％～65．01％；树高、胸径、材积等生长性状间呈紧密的正相关，保存率与生长性状的相关不显著。3、5年生时尾叶桉14532种源和细叶桉13541种源在各自的树种中生长最优，平均单株材积分别这0.09636m^2时0.04516m^3。经综合评价，细叶桉13541、13544和尾叶桉14532、14531为优良种源。估算了参试种源各个性状的育种值。     

闽西北适栽桉树树种选择研究

自上个世纪90年代以来，闽西北进行了多批桉树树种引种或种源家系试验，结果表明：适宜闽西北地区推广种植的桉树有巨桉、邓恩桉、柳桉和赤桉，其中赤桉、邓恩桉最为耐寒。可以推广到闽西北大部份地区，巨桉、柳桉适宜闽西北较低海拔、绝对最低温度在-5℃以上的地区，但需要选择适宜的种源。树种内种源和家系间的生长性状、抗寒性存在显或极显差异，单株间的生长差异比家系间的生长差异大，而家系间又比种源间大。此外，桉树树种原产地的雨量分布情况对决定引种桉树极为重要。在高温潮湿的福建地区不适宜引进冬雨型桉树树种。     

湘南耐寒桉树种源试验研究

通过对４．５年生的赤桉、邓恩桉、多枝桉等３种类１１种源的种类种源试验林的生长调查、形质指标调查和选林保存率的调查,采用单因素方差分析和多目标决策理论等综合分析评定方法,来评判种源的优劣。研究结果表明：到目前试验研究阶段,仍以赤桉１５０２５、１５０２２和贵溪赤桉为最佳种源。多枝按１５２１３、邓恩桉１７３３３和祁阳赤桉为淘汰种源。在资兴市或类似资兴市气候的湘南各县（市）可以对赤桉１５０２５、１５０２２     

邓恩桉在福建南平不同海拔区的生长调查

对延平区三乡镇邓恩桉遭遇两次历史低温后生长情况进行调查分析,结果表明不同海拔高度对邓恩桉生长影响显著。邓恩桉新造林对持续的低温很敏感,成林后其耐寒能力大大增强,但海拔较高的地区种植邓恩桉其蓄积量小于当地杉木、马尾松的蓄积量,这与邓恩桉本身的生物学特性有关。邓恩桉在海拔≤260m、土层厚≥80cm的Ⅰ、Ⅱ类缓坡地生长状态好,4a生邓恩桉平均蓄积量达31.8m3·hm-2。     

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.