Pinus contorta growth in northern Sweden as affected by soil scarification

The aim of this study was to quantify the effects of different soil scarification methods on tree growth. Soil scarification influenced stem volume and stem biomass yield of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) in a 17-year-old field trial in boreal Sweden. Soil scarification (disc trenching, mounding and ploughing) resulted in an average stem volume yield of 3.1 and 34.2 m³ ha^–1 on the poor and intermediate sites, respectively, while corresponding values for no soil scarification were 0.9 and 16.7 m³ ha^–1. In comparison to no scarification, ploughing increased volume yields by 500% on the poor site and by 200% on the intermediate sites. The ranking according to stem volume yield was ploughing > disc trenching = mounding no soil scarification. Averaged over the two sites, the mean annual increment of stem biomass was 219% and 145% higher (in d.w., 0.26 kg and 0.34 kg per sample tree) after ploughing compared with no soil scarification, for the average and dominant sample trees, respectively. Although not significant, the increased growth rate after soil scarification decreased the average stem basic wood density of the sample trees with 1.6% and 5.3%, at the poor and intermediate sites, respectively. In conclusion, soil scarification significantly increased the 17-year stem volume yield compared with no scarification. The results also indicate that the difference in stem biomass yield between ploughing and the other methods, especially no soil scarification, will increase even more in the near future.     

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.     

基于树高和树冠因子的立木材积模型研究

[目的]由于激光雷达技术已经能准确测定立木树高及相关树冠因子,应用该技术建立基于树高和树冠因子的立木材积模型,为激光技术在森林蓄积估计中提供技术支撑.[方法]利用云杉、冷杉、栎树、桦树4个树种组的3 010株实测样木数据,分析了立木材积与胸径、树高、树冠因子之间的相关关系;并通过对数回归方法构建了基于树高和树冠因子的立木材积模型,用确定系数R²和平均预估误差MPE等6项指标对模型进行评价.[结果]表明,立木材积与单一因子之间的相关,以胸径最为紧密,其次是树高,再次是冠长和冠幅.基于树高和树冠因子的立木材积模型中,以树高和冠幅作为解释变量的二元模型效果较好,再增加冠长因子的三元模型改进不大.云杉、冷杉、栎树、桦树4个树种组基于树高冠幅的立木材积模型,其R²分别为0.81、0.80、0.76和0.77,MPE分别为4.7%、5.3%、5.4%和5.3%,模型预估精度均能达到95%左右.[结论]本文对材积与林木因子之间相关关系的定量分析,建立了云杉、冷杉、栎树、桦树4个树种的立木材积模型,模型预估精度高.为激光雷达技术定量估测森林参数提供了依据.     

Aboveground biomass of three conifers in the Qianyanzhou plantation, Jiangxi Province, China

Regressive models of the aboveground biomass for three conifers in subtropical China—slash pine (Pinus elliottii), Masson pine (P. massoniana) and Chinese fir (Cunninghamia lanceolata)—were established. Regression analysis of leaf biomass and total biomass of each branch against branch diameter (d), branch length (L), d ³ and d ² L was conducted with functions of linear, power and exponent. A power law equation with a single parameter (d) was proved to be better than the rest for Masson pine and Chinese fir, and a linear equation with parameter (d ³) is better for slash pine. The canopy biomass was derived by adopting the regression equations to all branches of each individual tree. These kinds of equations were also used to fit the relationship between total tree biomass, branch biomass, foliage biomass and tree diameter at breast height (D), tree height (H), D ³ and D ² H, respectively. D ² H was found to be the best parameter for estimating total biomass. However, for foliage biomass and branch biomass, both parameters and equation forms showed some differences among species. Correlations were highly significant (P<0.001) for foliage biomass, branch biomass and total biomass, among which the equation of the total biomass was the highest. With these equations, the aboveground biomass of Masson pine forest, slash pine forest and Chinese fir forest were estimated, in addition to the allocation of aboveground biomass. The above-ground biomass of Masson pine forest, slash pine forest and Chinese fir forest was 83.6, 72.1 and 59 t/hm² respectively, and the stem biomass was more than the foliage biomass and the branch biomass. The underground biomass of these three forests which estimated with others’ research were 10.44, 9.42 and 11.48 t/hm², and the amount of carbon-fixed were 47.94, 45.14 and 37.52 t/hm², respectively. __________ Translated from Chinese Journal of Applied Ecology, 2006, 17(8): 1382–1388 [译自: 应用生态学报]     

25年生大花序桉种源生长与形质性状的遗传变异及选择

[目的]研究广西国有东门林场25年生大花序桉种源生长与形质性状的遗传变异,筛选优良种源及单株,为大花序桉良种繁育及中大径材培育提供优质遗传材料。[方法]采用方差分析、构建性状选择指数方程综合分析等方法,对11个大花序桉种源进行生长与形质性状遗传变异分析及选择。[结果]表明:大花序桉胸径(DBH)、树高(H)、单株材积(V)、树干通直度(ST)和树干圆满度(SF)在种源间呈极显著差异;上述5个主要性状的种源遗传力(H2)为0.634 0.895,单株遗传力(h2)为0.136 0.342;以DBH、H、V、ST和SF 5个性状指标构建大花序桉种源/单株选择指数方程,按标准选择出4个优良种源和13株优良单株,优良种源平均材积遗传增益达11.2%,优良单株平均材积遗传增益达29.7%,选择效果尚好。[结论]大花序桉5个主要性状遗传变异在种源水平受中度至较强遗传控制,在单株水平受弱度遗传控制。优良种源D47、S14127、B47和S12195生长材性兼优,可用作培育优质中大径材。     

Pine needle consumption and bark stripping by sheep grazing annual pastures in young stands of widely spaced Pinus radiata and P. pinaster

The consumption of the pine needles and the stripping of bark by sheep grazing annual pastures in three open stands of P. radiata and one of P. pinaster were measured. The P. radiata were four years old and the densities were 250, 500 and 750 trees ha^-1. The P. pinaster included two, three and four year-old trees and the density was 440 trees ha^–1.Needles were eaten immediately after the sheep were admitted and this continued throughout the year. Within ten weeks of the start of winter grazing, sheep stocked at 7–10 ha^–1 had eaten about half of the accessible needles on both species where densities were less than500 trees ha^–1. The estimated consumption was about 260 g sheep^–1 day^–1 for the P. radiata. Bark stripping then commenced and continued throughout spring and summer on most plots. In some plots at low tree density, bark was stripped from more than 35% of the trees. In denser stands, needle consumption per tree was less and bark was stripped from less than 5% of the trees.Bark damage was most common on the smaller trees, and severity of stripping was negatively correlated with tree size. Of all the trees with bark damage, 22% of the P. pinaster and 14% of the P. radiata had more than half of the stem circumference stripped. A number of these will probably suffer both stem distortion and growth retardation, and some may die.Methods of reducing the incidence of bark damage are discussed.     

C2H2-reduction byErythrina poeppigiana in a Costa Rican coffee plantation

Acetylene reduction activity by root nodules of the legumeErythrina poeppigiana, growing as shade tree in a Costa Rican coffee plantation, was estimated. The mean activity found was 15.7 nmole C₂H₄ · mg (dry weight)^–1 · h^–1. Root nodules collected at different distances from theErythrina stem showed the same activity per dry weight unit. However, as the biomass of the nodules was highest near the stem, was the acetylene reduction activity (expressed per soil volume) maximal near theErythrina stem and declined with distance.     

Modelling agroforestry systems of cacao (Theobroma cacao) with laurel (Cordia alliodora) or poro (Erythrina poeppigiana) in Costa Rica

Predictive models were developed for Cordia alliodora branch and Theobroma cacao branch or leaf biomass,based on branch basal areas (r² 0.79) but the model of C. alliodora leaf biomass, although significant, was of very low accuracy (r² = 0.09) due to annual leaf fall. At age 10 years, shade tree stem biomass accounted for 80% of the total above-ground biomass of either tree. However, between the ages of 6 and 10 years, the biomass increment of T. cacao branches (3–4t.ha^–1.a^–1) was similar to that of the shade tree stems. During the same period, the net primary productivity was 35 and 28 t.ha^–1.a^–1, for the Erythrina poepigiana and and C. alliodora systems, respectively.Cocoa production under either of the shade trees C. alliodora or E. poeppigiana was 1000 kg.ha^–1.a^–1 (oven-dry; ages 6–10 yr). During the same period, C. alliodora timber production was 9 m³.ha^–1.a^–1 whilst the leguminous shade tree E. poeppigiana does not produce timber. Litterfall over the same 5 years, including crop and/or shade tree pruning residues, averages 11 and 23 t.ha^–1.a^–1, respectively. The main difference was due to E. poeppigiana pruning residues (10t.ha^–1.a^–1).Soil organic material reserves (0–45 cm) increased over 10 years from 198 to 240 t.ha^–1 in the E. poeppigiana plots and from 168–184 t.ha^–1 in the C. alliodora plots. These values, together with the productivity indices presented, provide evidence that the systems are sustainable.For economic reasons, the use of C. alliodora is recommended under the experimental conditions. however, on less fertile soils without fertilization, the greater biomass and hence nutrient return to the soil surface under E. poeppigiana, might make this the preferable shade tree.     

Modelling the influence of site and weed competition on juvenile modulus of elasticity in Pinus radiata across broad environmental gradients

Data from a nationwide set of Pinus radiata D. Don plots established at a range of conventional stand densities were analysed at age 6 to (i) determine how environment and competition from weeds influence dynamic modulus of elasticity (E) of the lower stem base, (ii) develop a predictive multiple regression model of E for basal stemwood and (iii) identify significant direct and indirect environmental influences (through stem slenderness) on E using path analysis.Site had a highly significant (P < 0.001) influence on E, which exhibited a 3-fold range from 1.6 to 5.3 GPa, across 30 sites. When compared to the weed-free controls, weed competition had a significant (P < 0.0001) and substantial effect on E, increasing values by on average 16% (2.76 GPa vs. 2.38 GPa).The positive linear relationship between stem slenderness (determined as tree height/ground-line tree diameter) and E was by far the strongest relationship (R² = 0.71; P < 0.001) among the 20 variables that were significantly related to E. A multiple regression model that included stem slenderness, mean minimum air temperature in mid-autumn, T_min, as positive linear relationships and net nitrogen (N) mineralisation in a negative linear form accounted for 86% of the variance in E. A cross-validation indicated that this model was stable and unbiased, with the validation accounting for 82% of the variance in E. The final path analysis model included T_min, net N mineralisation, below canopy solar radiation and stem slenderness as significant (P < 0.05) direct influences on E. Below canopy radiation, maximum air temperature during mid-summer, soil total phosphorus and carbon:nitrogen ratio were indirectly associated with E through their significant (P < 0.05) direct relationship with stem slenderness.These results provide considerable insight into how environment regulates E of juvenile P. radiata. Low fertility sites that have warm air temperatures and either a high canopy leaf area index, or high levels of woody weed competition, are most likely to produce trees with high stem slenderness and high E. Conversely, sites that are cool over summer and autumn and high in fertility, with low levels of intra- or inter-specific competition for light are likely to produce trees with low stem slenderness and low E.     

Tree Regeneration and Sapling Damage of Pedunculate Oak Quercus robur in a Grazed Forest in Galicia, NW Spain: A Comparison of Continuous and Rotational Grazing Systems

Forest grazing has been recognised as being a useful tool in fire-risk reduction, in addition to having the potential to preserve or enhance forest biodiversity if managed correctly. Concern for natural regeneration of forest trees in Europe has also prompted interest in the effects of large herbivores on seedling and sapling growth and mortality. An investigation was carried out into sapling damage and density of natural regeneration of oak (Quercus robur) in a mature, pony-grazed, Pinus radiata forest in Galicia, NW Spain under two different grazing regimes (continuous and rotational). In all treatments significantly more oak seedlings and saplings were recorded in areas of grass sward than areas dominated by taller ground flora species. Damage to oak saplings was assessed from the form (height and canopy) relative to stem diameter. The height and average canopy diameter of similar-aged saplings were found to be significantly greater in ungrazed (control) than both continuous and rotationally grazed treatments. Height and canopy diameters of similar-aged oak were not significantly different between the two grazing treatments. Significant differences were observed in tree form, with unbrowsed saplings having the greatest height to canopy width ratio and those in the continuously browsed plots having the smallest. An obvious decrease in the goodness of fit (R²) of regression analyses were found in continuously grazed areas compared to rotational and control plots for both height and canopy data. The differences in damage observed were not significantly different enough to suggest one method of grazing over the other as being better for minimising sapling damage. Management requirements are more likely to dictate grazing regime. Overall, stock density is likely to have a more significant effect on damage than stocking system.     

Species and site selection for timber production on farm boundaries in the humid Atlantic Lowlands of Costa Rica and Panama

In 1987–89 the CATIE-GTZ Agroforestry Project set up experiments with five timber tree species planted in single lines on twelve farm boundaries in cooperation with local farmers. When the trees were five years old, their height, diameter and total stem volume were: Acacia mangium 17 m, 19 cm and 67 m³ km^–1, Cordia alliodora 14 m, 20 cm and 46 m³ km^–1, Eucalyptus deglupta 22 m, 24 cm and 85 m³ km^–1, Tectona grandis 17 m, 20 m and 64 m³ km^–1, Terminalia ivorensis 18 m, 23 cm and 104 m³ km^–1. Considering these excellent growth rates, planting of Cordia alliodora, Eucalyptus deglupta and Tectona grandis in lines on farm boundaries should be promoted. T. ivorensis and A. mangium are not recommendable for sites with impeded drainage because of mortality caused by root rot, mostly due to Rosellinia sp.     

Natural abundance of <Superscript>15</Superscript>N in two cacao plantations with legume and non-legume shade trees

Natural abundance of ¹⁵N was sampled in young and mature leaves, branches, stem, and coarse roots of trees in a cacao (Theobroma cacao) plantation shaded by legume tree Inga edulis and scattered non-legumes, in a cacao plantation with mixed-species shade (legume Gliricidia sepium and several non-legumes), and in a tree hedgerow bordering the plantations in Guácimo, in the humid Caribbean lowlands of Costa Rica. The deviation of the sample ¹⁵N proportion from that of atmosphere (δ¹⁵N) was similar in non-legumes Cordia alliodora, Posoqueria latifolia, Rollinia pittieri, and T. cacao. Deep-rooted Hieronyma alchorneoides had lower δ¹⁵N than other non-N₂-fixers, which probably reflected uptake from a partially different soil N pool. Gliricidia sepium had low δ¹⁵N. Inga edulis had high δ¹⁵N in leaves and branches but low in stem and coarse roots. The percentage of N fixed from atmosphere out of total tree N (%N_f) in G. sepium varied 56–74%; N₂ fixation was more active in July (the rainiest season) than in March (the relatively dry season). The variation of δ¹⁵N between organs in I. edulis was probably associated to ¹⁵N fractionation in leaves. Stem and coarse root δ¹⁵N was assumed to reflect the actual ratio of N₂ fixation to soil N uptake; stem-based estimates of %N_f in I. edulis were 48–63%. Theobroma cacao below I. edulis had lower δ¹⁵N than T. cacao below mixed-species shade, which may indicate direct N transfer from I. edulis to T. cacao but results so far were inconclusive. Further research should address the ¹⁵N fractionation in the studied species for improving the accuracy of the N transfer estimates. The δ¹⁵N appeared to vary according to ecophysiological characteristics of the trees.     

Efficiency of neem and groundnut oils in protecting leguminous tree seeds against seed beetles in the Sahel

The objective of our study was to test the comparative efficiency of neem (Azadirachta indica) kernel oil, groundnut oil and a synthetic insecticide, K-Othrine®, in protecting stocks of leguminous tree seeds against seed beetles under Sahelian conditions. The following insect/seed combinations were used as models: Caryedon acaciae/Acacia nilotica, C. longispinosus/A. raddiana and C. serratus/Tamarindus indica. Neem oil, when used at concentrations of 5 to 20 ml per kg of seeds, had pronounced adulticidal and ovicidal effects which were maintained for five months. No significant fall in seed viability was observed except in the case of C. acaciae/A. nilotica. Groundnut oil, when used at concentrations of 5 to 20 ml per kg of seeds, had pronounced adulticidal and ovicidal effects which were relatively short-lived. A significant fall in seed viability was observed over five months. K-Othrine®, when used at concentrations ranging from 25 to 100 mg per kg, had high adulticidal effects which were maintained for five months. However, K-Othrine® was found to have no ovicide properties. No significant fall in seed viability was observed. This study concluded that it is possible to use neem oil, a product that can be obtained locally at low cost, to efficiently protect tree seed stocks in the Sahel.This revised version was published online in November 2005 with corrections to the Cover Date.     

Direct impacts of sheep upon Douglas-fir trees in two agrosilvopastoral systems

Livestock may provide important service and production functions in agroforestry systems. However, use of livestock in conifer/improved pasture agrosilvopastoral systems is currently limited by concerns about potential damage to trees by livestock. Effects of sheep grazing on Douglas-fir (Pseudotsuga menziesii) trees in two patterns of sheep/pasture/conifer agroforest (cluster and grid plantations) were studied from 4 years after planting (1983) until the first precommercial thinning at age 10 years (1988). Trees averaged over 1 m in height when grazing began in summer 1983. Some browsing of tree lateral branches by sheep occurred regardless of grazing season in 1983–1985. However, the 2 to 10% of current year's lateral branch growth removed by grazing sheep was too low to impact tree growth. Sheep removed the terminal leaders from only 3 to 9% of trees each year during 1983–1985. Most browsing of terminals occurred in the summer when other forages had become mature and were relatively unpalatable to sheep. Less than 13% of agroforest trees were debarked by sheep each year during 1983–1987. By the end of grazing in 1987, less than 8% of agroforest trees had sustained a level of debarking likely to impact future growth (>50% of tree circumference debarked). Grazing had no discernible effect upon tree diameter or height in any year (P > 0.05). Total tree mortality attributable to sheep grazing during 1983–1987 was only 0.9%, including three trees girdled by sheep and two debarked trees which were subsequently attacked by insects. Overall, grazing had no detrimental impact on timber stand growth or mortality.Submitted as Oregon Agricultural Experiment Station Technical Paper No. 9628.     

Tree-root systems and herbaceous species-characteristics under tree species introduced into grazing lands in subhumid Cameroon

The effect of tree species on the characteristics of the herbaceous stratum, during the first five years of a fallow, was evaluated in the North of Cameroon (average annual temperature 28.2 °C, total annual rainfall 1050 mm). Treatments included a natural grazed herbaceous fallow, a natural ungrazed herbaceous fallow and three planted tree fallows (Acacia polyacantha Willd. ssp. campylacantha (Hochst. ex A. Rich.), Senna siamea Lam. and Eucalyptus camaldulensis Dehnh.), which were protected against grazing. Because tree species influenced light interception in different ways, as well as having different root patterns, they had different effects on the herbaceous stratum in terms of species composition and biomass. The grazed herbaceous fallow maintained the greatest species richness. Protection against grazing or the introduction of tree species associated with the absence of grazing induced both a progressive evolution to a particular species composition. The ungrazed herbaceous fallow consisted mainly of Andropogon gayanus Kunth, which provided the greatest biomass (8 t dry matter ha^–1 at the end of the fallow period). E. camaldulensis provided little shade and the lowest fine root mass in the top layer allowing the growth of A. gayanus and thus a greater herbaceous biomass (3.5 t DM ha^–1) than that found under the other tree species. Under the heavy shade of A. polyacantha, the herbaceous stratum consisted mainly of annual Pennisetum spp. (2.2 t DM ha^–1) and showed the greatest N concentration (1.3%), probably due to N₂ fixation by the tree species. After the fourth year, despite the relatively open tree canopy, S. siamea, which showed the highest fine root mass, had a strong depressive effect on the herbaceous stratum. This revised version was published online in June 2006 with corrections to the Cover Date.     

Tamarack and Black Spruce Growth on a Boreal Fen in Central Alberta 9 Years after Drainage

Tree growth was measured before, and 9 years after draining a boreal fen that supported a 50- to 60-year-old stand of tamarack (Larix laricina (Du Roi) K. Koch) and black spruce (Picea mariana (Mill.) B.S.P.). Treatments consisted of a series of ditches spaced 30, 40 or 50 m apart, and an undrained control. Nine years after drainage, the diameter, height, basal area, and volume growth of tamarack had increased by 2–5 times that on the control site. Black spruce growth on the drained site was 1.6–5 times that on the control. Tamarack average volume growth (1.20 m³ ha⁻¹ year⁻¹) on the drained site was superior to that of black spruce (0.21 m³ ha⁻¹ year⁻¹). In general for both species, there were no significant differences in growth between trees on the different ditch spacings. This result was attributed to the water table being low enough that adequate aeration zones existed across the strips between ditches on all spacings. Regeneration after treatment was greater on the drained than on the control plots, particularly in the disturbed areas near the ditches where new tamarack seedlings reached densities between 9400 and 12,000 stems ha⁻¹. There was no relationship between increased tree growth and tree distance from the ditches for both species, probably because the water table had been lowered sufficiently so that inadequate substrate aeration was no longer a limiting factor.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Variation in wood properties of six natural acacia hybrid clones in northern Vietnam

Wood properties of six 8-year-old natural acacia hybrid clones between Acacia mangium and Acacia auriculiformis, planted in Bavi, Vietnam, were studied. The hybrid clones possessed obvious heterosis in growth and in some wood properties. The characteristics of growth, air-dry specific gravity, lengths of fibers and vessel elements, S₂ microfibril angle, green moisture content, and shrinkage were examined to clarify the variation among clones. From the results, the differences among the clones in growth and in some wood properties were significant. The pattern of distribution of specific gravity showed that there were low and high specific gravity zones in the stem. Specific gravity at stump height or at 3.0 m was useful for prediction of specific gravity in the whole tree stem. Moreover, clones with high specific gravity can be predicted at a young age. There was no significant correlation between diameter growth and specific gravity. Of the six clones studied, clone BV5 was selected as the best based on its growth ability and specific gravity. Part of this report was presented at the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, August 2007     

Realized genetic gains observed in second generation seedling seed orchards of Eucalyptus pellita in Indonesia

The first generation genetic gains in four second-generation seedling seed orchards of Eucalyptus pellita established at two locations in Indonesia (Kalimantan and Sumatra) were examined by analyzing data on the height, diameter and stem form of the trees during years 1 to 3. The seed orchards each consisted of 60 open-pollinated families: 48–49 families from first-generation plus trees (improved population) and 11–12 families from natural forest (unimproved population). The realized gains for height and diameter were ca. 16 and 19%, respectively. These gains were highly significant and consistent, irrespective of age and location. However, the gains in stem form were much lower (4%) in Kalimantan than in Sumatra (21%) and only significant in the latter, possibly because of the more intensive silvicultural management regimes at the Sumatran sites. The results confirmed that the first-generation tree improvement program for E. pellita has been effective in Indonesia, and that it should provide improved seeds for operational plantation, thus raising their productivity.     

松材线虫(Bursaphelenchus xylophilus)耐久型幼虫(LIV)携带的香茅醇假单胞杆菌(Pseudomonas citronellolis)分离与鉴定

[目的]目前有关松材线虫与伴生细菌的关系及伴生细菌的病原作用是松树枯萎病研究的重点。为了揭示松材线虫与伴生细菌之间存在的密切关系,作者对松材线虫L_IV幼虫携带的细菌进行了分离鉴定。[方法]根据培养性状和16S rDNA序列同源性以及系统发育学等方面进行分析鉴定。[结果]确定L_IV幼虫携带的是香茅醇假单胞杆菌（Pseudomonas citronellolis）,携带率为100%;每条L_IV幼虫携带量在1.4×10⁵~4.5×10⁵。L_IV幼虫生活在松褐天牛体内,是引起松材线虫病侵染流行的唯一虫态;新发现的香茅醇假单胞杆菌能分解纤维素及降解或合成萜烯和酚类化合物。[结论]L_IV幼虫携带香茅醇假单胞杆菌的发现,揭示了松树、松褐天牛、松材线虫、细菌同为一体的紧密关系,并为揭示松树枯萎病机制提供了一种新病原和重要的研究思路。