Effects of green pruning on growth and stem shape of Eucalyptus nitens (Deane and Maiden) Maiden

An experiment was established in two high quality Eucalyptus nitens Deane and Maiden (Maiden) plantations in Tasmania. At the start of the experiment the trees were three years old and the plantations were on the point of canopy closure. Selected trees were pruned to remove 0, 50% or 70% of the lower green crown length, and each was surrounded by eight unpruned trees. The 50% treatment had no impact on height or diameter increment in the two years following treatment, but removal of 70% of the lower crown length resulted in significant decreases in both height and diameter increment. There were no changes in the height of 50%-pruned trees relative to the height of surrounding unpruned trees (relative height), and it was concluded that dominance would not be affected by this treatment. The relative height of 70%-pruned trees was less at one site, and this treatment may result in loss of dominance. Stem taper was generally unaffected by either pruning treatment. Changes in stem form were restricted to trees in the 70% pruning treatment and were only transient. It was concluded that removal of 50% of the lower green crown length is an appropriate level of pruning for the species provided that growth rates are rapid and pruning is timed to coincide with canopy closure. Since dominance was unaffected by this level of pruning, thinning at the time of pruning is unnecessary. It may be possible to minimise the impact on growth of higher levels of pruning by thinning at the time of pruning.     

Root exposure effects on water relations of Eucalyptus nitens nursery stock

Bare-root seedlings of Eucalyptus nitens frequently exhibit water stress after planting resulting in leaf lamina damage and reduced leaf area. Two trials examined effects of root exposure and desiccation between lifting and transplanting on post-planting water relations, leaf retention and root growth. Plants with roots exposed on a glasshouse bench initially lost water rapidly. In one trial ₁ declined to around –2.0 MPa within 2.5 h, after which there was no further change with exposure up to 7.5 h. In the second trial, the initial decline in ₁ was more rapid, reaching below –2.0 MPa in the first hour, before remaining stable with continuing exposure up to 4.5 h. A further decline then continued to –4.0 MPa after 7.5 h.Two days after transplanting into potting mix, day – time leaf water potentials in all desiccation treatments had declined to near –2.0 MPa. Hydraulic resistivity, measured as leaf specific resistivity two days after transplanting, increased following exposure for greater than 2.5 h, but there was no further increase between 4.5 and 7.5 h. The increase in resistivity corresponded with leaf water potential declining below –2.0 MPa during exposure.In the second trial, increasing root exposure time resulted in decreased leaf area due to lamina necrosis. Root growth, measured three weeks after planting, was also reduced. and there was also a positive curvilinear relationship between leaf area remaining at three weeks and new root growth. The results are discussed in terms of hardiness and the management of E. nitens seedlings from nursery to plantation.     

Changes in water relations of Eucalyptus nitens nursery stock during and after lifting and transplanting

Field symptoms of transplanting shock in Eucalyptus nitens open rooted (1/2 + 1/2) transplants suggest water stress. To identify stages in the development of symptoms, changes in water relations were monitored from undisturbed seedlings growing in a commercial nursery through lifting, transplanting into pots and re-establishment of normal water relations. Hydraulic resistance measured as leaf specific resistivity increased with each step in the transplanting process. Resistivity after lifting was double that measured on undisturbed plants in the nursery and subsequently doubled with each of the two successive stages, root trimming and planting out. Resistivity fell after the initial rise, returning to the values recorded in the nursery in two stages. An initial rapid decrease, which was not accompanied by any measurable root growth, was followed by a seven day period without a change in resistivity before a further gradual decrease as root volume increased with new root growth.All water relations measurements were taken on trees which had not suffered any permanent leaf damage as a result of transplanting. For a small group of trees which did suffer damage there was a significant relationship between root volume at planting and the retained healthy leaf area. Before shoot growth had recommenced the final ratio of turgid leaf area to initial root volume was comparable with plants immediately after lifting and before trimming. The results are discussed in terms of the changes in predawn leaf water potential, leaf water potential and the leaf damage or defoliation symptoms occuring in plantations.     

Herbicides are more cost-effective than alternative weed control methods for increasing early growth of Eucalyptus dunnii and Eucalyptus saligna

Effective weed control is an essential management task in establishing commercial tree plantations. Much of the current weed control strategies employed in Australian forestry relies on the use of available herbicides. However, given community concern regarding the use of herbicides, investigation of alternative weed control methods is warranted. We tested the ability and cost-effectiveness of mechanical (hand weeding and inter-row slashing), mulching (sawdust over newsprint, woodchips and jute), cover crops and herbicide applications for weed control in establishing eucalypt plantations. Jute matting and herbicide treatments reduced weed competition and increased seedling growth to age 2 years in plantations of Eucalyptus dunnii and Eucalyptus saligna in northern NSW, Australia. Growth increased by 269 % (Experiment 1) and 196 % (Experiment 2) in the Jute and by 216 % (Experiment 2) in the Herbicide treatments when compared to the control (no weed control) at 2 years age. As the Jute material deteriorated, after nearly 2 years, weed cover increased and there were significantly more weeds present in the Jute treatment compared to the Herbicide treatment. Jute matting costs approximately 15 times more than the herbicide regime used and, therefore, could not presently be considered a viable option for weed control in commercial eucalypt plantations. Other weed control treatments, including hand weeding, sawdust and woodchip mulches, slashing and sowing cover crops did not effectively control weeds and did not improve survival or increase seedling growth to age 2 relative to the control. We conclude that herbicides remain the most cost-effective weed control option available to commercial growers of eucalypt plantations.     

Phosphorus fertiliser source and weed control effects on growth of three-year-old second-rotation Pinus radiata on Orthic Pumice soil in New Zealand

Little information is available on the interactive effects of soluble and less-soluble phosphorus (P) fertilisers and weed control on growth and P nutrition of second-rotation Pinus radiata plantations. A study was initiated on three-year-old second-rotation P. radiata and to determine the relationship between needle P concentrations and soil P forms in an Orthic Pumice soil two years after application. Four rates of P (0, 50, 100, and 200 kg P ha^?1) were applied as two forms of P fertiliser sources (triple superphosphate [TSP] and Ben-Guerir phosphate rock [BGPR]) in combination with weed control (weedy and weed-free). The results showed that the applied TSP and BGPR can increase tree needle P concentrations even when the needle P concentrations before fertiliser application were marginally higher than the critical P concentrations. The application of P fertilisers had no effect on tree growth during the two-year period of the trial, though it increased P. radiata needle P concentrations. However, the weed removal increased tree height, diameter at breast height, and basal area. In this plantation site the higher needle P concentrations than the critical P concentration suggests that the growth increase due to weed removal treatment was probably due to an increase in the availability of soil water and nutrients other than P. The needle P concentrations of P. radiata can be predicted by soil tests, Bray-2 P, Olsen P, resin-P_i, and NaOH-P_i tests. Of these soil tests, Bray-2 P seems to be the best test in predicting soil P availability to P. radiata. The P concentrations in the needles had a relationship with the NaOH-P_i fraction but had no relationship with the H₂SO₄-P_i fraction. These results suggest that P. radiata was probably taking up P mainly from the pool of P-adsorbed to allophane and Fe+Al oxides (NaOH-P_i) in this high P-fixing acidic soil.     

Weed control and autumn-olive affect early growth and survival of black walnut in a hardwood clearcut

Eight years after planting in a hardwood clearcut, black walnut trees in plots with weed control had significantly better survival and were taller and larger in diameter than those in plots without weed control. Planting autumn-olive with walnut also significantly increased height and diameter of the walnuts but did not affect their survival.     

外生菌根菌对巨桉人工林土壤理化性质的影响

该文调查了四川乐山沙湾、眉山丹棱巨桉人工林下外生菌根菌土,测定了土壤养分情况。结果表明：两地所采集的菌根土的理化指标与对照相比有明显变化,样地Ⅰ菌根土pH值显著高于对照土,有机质含量与对照相比并不显著,样地ⅡpH值显著低于对照,而有机质含量明显高于对照;两样地菌根土的全N、水解N、全P和有效P含量均显著高于对照;大孢硬皮马勃的菌根土全K含量与对照相比并不显著,彩色豆马勃和马勃状硬皮马勃的菌根土全K含量均显著低于对照（P〈0.05）;样地Ⅰ菌根土速效K含量与对照差异不显著,样地Ⅱ菌根土速效K含量显著低于对照。由此可见,巨桉外生菌根真菌对提高巨桉人工林的土壤肥力,维护人工林地力具有一定作用。     

次生林和桉树人工林林下植物多样性对比分析

通过对华南地区阔叶次生林和桉树人工林的林下植物多样性进行调查对比分析,发现次生林林下植物123种,分属52科;桉树人工林林下植物102种,分属49科,两者数量上相差不大,相同的有64种。2个生境物种构成不同,次生林的丰富度指数、均匀度指数、多样性指数均略高于桉树人工林,方差分析显示两者各样方林下植物分布差异显著。2种生境中重要值前10的物种只有3个相同,两者林下植物重要值都集中在前10个物种中,均约占一半。总体上桉树人工林林下植物多样性与次生林的相近。     

Effect of mechanical site preparation and fertilisation on early growth and survival of a black pine plantation in northern Greece

Pine plantations on selected sites in the extensive zone of degraded oak coppice of northern Greece are deemed necessary for increasing wood production in the area and suitable site preparation may accelerate early tree growth. Seven site preparation treatments including raking (R), with sub-soiling (RS), disc harrowing (RD), tine ploughing (RT) and their combinations (RSD), (RDT) and (RSDT) were compared for the establishment of black pine (Pinus nigra Arn) in an oak coppice site, of conglomerate parent material at Anthrakia, northern Greece. The randomised blocks trial of three replications and 110 trees per treatment, half of which were fertilised with 150 g NPK per plant, was assessed at the age of 15 years for diameter, dominant tree height and survival. There was no significant difference between the treatments in any of the traits examined, nor did the fertilisation had any effect. Only the fertiliser × treatment interaction was found significant at p<0.001 for dominant height, accounting for 37% of the observed variation in this trait. The lack of response to site preparation treatments may be attributed to the hard Bt3 clay horizon, extending beyond cultivation depth (50 cm), that prevents the roots penetration into deeper moist soil layers. The F × T interaction, where the combination of (RSDT) treatment and fertiliser was found to accelerate tree height growth in relation to the same treatment without fertiliser, indicates that thorough soil cultivation is needed for fertilisation to be effective in such sites.     

Effect of site preparation intensity on the early growth of loblolly pine (Pinus taeda L.) and the incidence of pine tip moth (Rhyacionia spp.)

Twelve, 16-ha study sites were established in recently harvested (1980) stands of natural pine-mixed hardwoods located in the Piedmonts of South Carolina and Georgia. Treatments applied were check (no site preparation), herbicide-burn (3.4 kg ae Glyphosate/ha), chop-burn, shear-disc, shear-V blade-disc, shear-pile, and shear-pile-disc. Measurements collected after two growing seasons included pine height, diameter, and occurrence of pine tip moth (Rhyacionia spp.) infestation on the terminal shoot. After the second growing season, tree volume was 58% greater on mechanically-treated areas compared to the check and herbicide-burn areas. Average pine tip moth incidence was 15% for the check treatment and ranged from 24 to 36% for the other six treatments. Although the disced treatments had higher tip moth infestation (32 to 36%) compared to the check plots (15%), pine growth was significantly greater for treatments involving discing.     

我国巨桉引种及经营技术研究进展

随着国民经济的发展和天然林保护工程的实施,我国木材的供需矛盾日益突出。虽然发展工业人工林是缓解这一矛盾的有效措施之一,但目前的工人林生产中尚存在许多问题,比如土壤酸化严重、地力衰退加剧、水土保持效益低下等。如何解决这些问题已成为当前人工林研究中的热点和重点。巨桉因其具有“速生、优质、丰产”的特性而被我国南方许多地方作为营造短周期工业用材林(特别是纸浆林)的重要树种。本文就我国近十多年对巨桉的研究作了简要评述,内容主要包括种源引种试验、遗传改良、引种生态适宜区区划和经营管理等方面,并提出了今后巨桉研究的方向和重点。     

Effect of residue management and fertiliser application on the productivity of a Eucalyptus hybrid and Acacia mangium planted on sloping terrain in northern Vietnam

Forest plantation growers in Vietnam commonly burn residues after harvesting and often apply suboptimal amounts of nutrients during plantation establishment. We examined whether the retention of forest residue, and application of phosphorus fertiliser at higher rates, can increase rates of growth. A factorial combination of residue management (burning vs retention) and phosphorus fertiliser application at planting (15 vs 100 kg ha^?1) treatments were applied at a steeply sloping site in northern Vietnam. Two adjacent experiments were established, one with Acacia mangium and the other with a Eucalyptus hybrid (Eucalyptus urophylla × Eucalyptus pellita). Standing volume and leaf area index in A. mangium were greater following burning; this was mostly attributable to the significantly higher survival rate of seedlings. Burning of residues was associated with increases in the number of large branches per tree, and a higher crown damage index (CDI). In the Eucalyptus hybrid, diameter and height responses to the higher rate of fertiliser were observed at age 6 and 12 months, but not beyond. High phosphorus application also led to higher CDI. Standard fertiliser treatment, applied in amounts equivalent to 17, 15 and 8 kg ha^?1 of nitrogen, phosphorus and potassium, respectively, was adequate to meet the early growth requirement of eucalypt and acacia plantations at this site. The relatively low amounts of harvest residue and high fertility levels at the site may have masked more significant responses of trees to the silvicultural treatments applied in this study. On steep slopes, especially if soil is poorly fertile, harvest residue retention with adequate weed and termite control may be preferential to burning as it is closely correlated with reducing factors that negatively impact productivity, i.e. water run-off and soil erosion.     

Effect of ectomycorrhizal fungi on bacterial wilt of Eucalyptus

Bacterial wilt caused by Pseudomonas solanacearum, is a very serious disease of Eucalyptus in southern China, mainly in Guangdong, Hainan and Guangxi provinces. It causes the death of seedlings and young trees and the mortality may exceed 90 percent in some sites. Susceptible species include E. grandis, E. urophylla, hybrids between the two and E. citriodora. In nursery and field trials with E. urophylla and field trial with E. grandis x E. urophylla inoculation of ectomycorrhizal fungi was found to reduce the incidence of the disease. Some fungal isolates were more effective than others.     

Identification,pathogenicity and control of powdery mildew caused by Erysiphe elevata on Eucalyptus pellita in Sumatra,Indonesia

Powdery mildews are biotrophic ascomycetes that do not typically kill their hosts, but instead interfere with normal plant growth. In Indonesia, white powdery spots were observed forming on the upper part of fully developed leaves of Eucalyptus pellita planted in sand beds of a clonal nursery. Thus, this study aimed to identify the causal agent of eucalypt powdery mildew in Indonesia as well as to develop control strategies to better manage the disease. Pathogen identification was based on morphology, molecular characterization of DNA sequencing the ITS region and pathogenicity test. In addition, considering that some powdery mildews are inhibited by free moisture on leaves, efficacy of foliar watering was tested for disease control. Phylogenetic analyses showed that isolates collected from infected eucalypt plants grouped together with other sequences of the Erysiphe elevata clade with bootstrap support of 99%; a similar result was also confirmed by morphological observations. Pathogenicity of powdery mildew on eucalypt plants was confirmed through artificial inoculation, thus fulfilling the Koch's postulates. For disease control, foliar watering reduced the incidence of powdery mildew on mother plants. The reduction of the disease incidence began to be more evident at 2 weeks after trial establishment, and in the fourth week, the incidence was below 10% in all three treatments, while the control was above 20%. Therefore, we concluded that E. elevata is the causal agent of powdery mildew in Indonesia and that one application of foliar watering per week was enough to minimize the disease impact in the nursery.     

Impact of seedling type on early growth of poplar plantations on forest and agricultural land

Today, most poplar plantations in the temperate region are established on abandoned marginal agricultural land, but there is great potential for planting poplars on forest land as the available area is large and does not compete with food production. The objective of this study was to examine how different planting types (un-rooted cuttings, bare-rooted and containerized plants) affect the establishment and early growth of poplar plants on forest and agricultural sites. Our results suggest that on the agricultural site, survival and growth during the first two years are not influenced by plant type. However, at the forest sites, survival of rooted plants was superior compared to un-rooted cuttings. The height and biomass (stem and root) increment of bare-rooted plants was low; greater height and biomass growth was found for containerized plants. Container sizes had no effect on height growth, but leaf and stem biomasses were higher if the largest containers were used. When using the largest containers, concentrations of macronutrients (N, P) were increased compared to bare-rooted plants. Thus, these results suggest that practices for establishing poplar plantations of agricultural land include planting of un-rooted cutting, but on forest land, a plant grown in a container of 470?ml should be used. Together, this can reduce the cost of establishment, increase the available area for poplar plantations and have an impact on poplar plantation economics in Sweden.     

桉树近熟林追肥效果初探

传统的桉树经营措施一般只追肥到2-3a,本文对桉树4年生左右的近熟林追肥的效果进行了研究,追肥8个月后的结果表明追肥林比对照平均提高产量1.42m3/667m2,可实现纯利润278.02元/667m2;近熟期的追肥对不同的品种的增产效果不同,其中LH1增产1.78m3/667m2,U6增产1.50m3/667m2,W5增产0.96m3/667m2。追肥的增产效果说明,对近熟林追施肥是挖掘桉树速生潜力的有效技术措施。     

Effect of NaCl and high pH on seedling growth of 15 Eucalyptus camaldulensis Dehnh. provenances

Eucalyptus camaldulensis Dehnh. is a moderately salt-tolerant Australian tree species widely used in farm forestry, often in salt-affected landscapes. In a glasshouse experiment, E. camaldulensis seedlings from 15 wide-ranging Australian seed sources (provenances), were cultured in sand-filled pots and treated for 57 days with control (no added NaCl in tap water, neutral pH), saline (150 mol m^–3 NaCl, stepped high pH (pH 7.6 to 9.5) and combined NaCl and high pH solutions. Significant differences were found among provenances in height and shoot dry weight. Differences in provenance response to treatment were found for dry weight but not for height. Reductions in shoot dry weight due to NaCl and high pH ranged from 42.9% to 82.0% and 4.3% to 51.7% respectively. Provenances from Lake Hindmarsh-SE (Victoria) and Lake Albacutya-N (Victoria) had relatively high tolerance to both stresses whereas those from Lake Albacutya-S (Victoria), Lowan Valley (Victoria), Silverton (New South Wales) and Katherine (Northern Territory) had low tolerance to both stresses. Provenances from De Grey River and Fitzroy River (Western Australia) were most tolerant of high pH. The performance of these provenances in this experiment generally accorded well with that in saline field environments.     

Effect of post-planting inoculation with Bradyrhizobium sp and mycorrhizal fungi on the growth of Brazilian rosewood,Dalbergia nigra Allem. ex Benth., in two tropical soils

Six months after planting, seedlings of the leguminous treeDalbergia nigra, known as Brazilian rosewood, wereinoculated with a selected Bradyrhizobium strainBHICB-DN 15,either alone or in combination with mycorrhizal fungi to determine their effecton the growth of D. nigra in Atlantic forest andeucalyptussoils. Height growth of D. nigra was similar in both soilsand six months after inoculation Bradyrhizobium did notaffect the D. nigra height growth, but it did improve drymass and especially in the nitrogen content of plants grown in eucalyptus soil.The success of the delayed inoculation with BHICB-DN 15 confirms its competitiveability vis-à-vis indigenous soil rhizobia. Co-inoculationof BHICB-DN 15 and mycorrhizal fungi did not increase plant dry weight,nitrogenand phosphorus content or mycorrhizal colonization. These results suggest thatthe BHICB-DN 15 strain had no synergistic relationship with the mycorrhizalfungi or that there was incompatibility between symbionts, in both soils.     

Woody and herbaceous competition effects on the growth of naturally regenerated loblolly and shortleaf pines through 11 years

Four levels of vegetative competition were used to quantify the growth of loblolly and shortleaf pines (Pinus taeda L. and P. echinata Mill.) in naturally regenerated, even-aged stands on the Upper Coastal Plain of southeastern Arkansas, USA. Treatments included: (1) no competition control, (2) woody competition control, (3) herbaceous competition control, and (4) total control of nonpine vegetation. After pines became established from natural seeding, herbicides were used to control herbaceous plants for 4 consecutive years and woody plants for 5 consecutive years. Even though 89% of crop pines on untreated check plots were free-to-grow 11 years after establishment, crop pines on vegetation control plots were larger (P<0.001) in mean dbh, total height, and volume per tree. From age 5 through 11 years, crop pine diameter growth increased on woody control plots and decreased on herbaceous control plots because of hardwood competition in the latter treatment. At age 11, crop pine volume production averaged 207 m³/ha on total control plots, 158 m³/ha on herbaceous control plots, 130 m³/ha on woody control plots, and 102 m³/ha on untreated check plots.