桉树人工林木材干燥皱缩特性的研究

本文研究了尾巨桉、尾圆桉和大花序桉等3种人工林桉树木材的干燥皱缩特性和干燥基准,分别测试了3种人工林桉树木材的表面开裂、端部开裂和内部开裂、干燥速度、干燥时间和皱缩等干燥皱缩特性指标,分析了木材细胞皱缩的形成机理和发生条件,木材构造对木材细胞皱缩的重要作用;比较了3种人工林桉树木材的干燥皱缩特性和干燥基准的差异,并对其进行了评价.结果显示,尾圆桉和大花序桉的干燥特性基本接近.     

Phosphorus enrichment from point to catchment scale following fire in eucalypt forests

Erosion studies at multiple scales have shown selectivity in particle transport and delivery can be inferred from nutrient enrichment. Most studies reveal the enrichment ratio (ER) of phosphorus on sediment is high, demonstrating the deposition of coarser particles over the transport pathway. Experimental work on burnt landscapes often takes place at the hillslope plot scale (1–10 m²) by necessity, with inferences made on system sediment and nutrient responses from small areas. Scale effects on generation and delivery need to be considered in such cases. In a study in wet eucalypt forests burnt by wildfire, phosphorus concentration on mineral sediment and organic material at the point (0.01 m²), plot (1–10 m²) and catchment (10⁶ m²) was used to estimate ERs over two scales. The data revealed ERs of 1.5 from point to plot and 2 from plot to catchment. These ratios are relatively low compared with other studies. We suggest the principal reason is short transport pathways which act to decrease deposition, due to the spatial heterogeneity of post-burn soil hydraulic properties. The association of total phosphorus with mineral material was slightly higher than with organic matter. The study suggests that using plot scale hillslope experiments to infer sediment and nutrient loss after wildfire would have overestimated losses by around 100%.     

Harnessing forest ecological sciences in the service of stewardship and sustainability: A perspective from ‘down-under’

Australia's native forests are predominantly Crown land, managed by the States. Regional Forest Agreements between four of the States and the Federal Government (1997–2001) resulted in a 36% increase in the area of conservation reserves and a 15% decrease in area of multiple-use (including timber harvesting) forests. The limited acceptance of timber harvesting in native forests, together with the rapid expansion of hardwood plantations, has diverted research focus away from native forests. Recent events including a prolonged drought and two forest fires totaling more than 3 million ha should have stimulated research in native forests on the effects of fire on ecosystem processes, on the management of fire and on management of water catchments; fires, far more than logging, are shaping our native forests in recent times. In particular, the use of prescribed fire to reduce fuels has decreased. We argue that Australian research effort in native eucalypt forests is lacking in two key areas – the effects of fire on carbon storage in forests and soils, and on the management of water yield from forested catchments. The results of forest research are variously published in the scientific journals, and increasingly in consultancy reports to governments or a to a range of organizations and industries. The question of who does the harnessing of knowledge coming from the science of forest ecology is compounded by constant changes in both political and management arrangements. If forest science is to assume a greater role in politics and forest management in Australia, scientists must enter the foray, using the fighting words of politics rather than maintaining the protective mantle of neutrality. With research in native forests being continually downgraded at both State and Federal levels, we take a somewhat less than optimistic view about how well ecological sciences will be harnessed in the service of forest stewardship and sustainability in Australia.     

The impact of timing and duration of grass control on growth of a young Eucalyptus globulus Labill. plantation

Interference by an introduced grass, Holcus lanatus L. (Yorkshire fog grass) in a young E. globulus (Tasmanian blue gum) plantation was investigated. The objectives were to determine (1) the critical period of competition, and (2) how the timing and duration of competition was related to the interaction between tree growth and resource availability. This was investigated during the first two years of establishment. Weed interference was severe with height and diameter growth of weedy trees being 52% and 40% of weed-free trees, respectively, at age two years. Most growth losses occurred during the first year. The critical period of weed interference was from planting to age 18 m and effective weed control was required for this period to maximise tree growth potential. The application of nitrogen to weedy trees promoted a significant growth response suggesting that competition for nitrogen was occurring. There was no significant response to level of irrigation. The use of critical period analysis is discussed.     

离子注入对桉树苗期光合特性的影响

对经注入处理后播种育苗14个月的桉家系苗期净光合速率、蒸腾速率、气孔导度、胞间CO2浓度、光能及水分利用效率进行测定分析,结果表明:各性状在家系间差异显著,且性状在季节间的差异也达显著水平。注入家系与对照家系在光合特性上出现分化,注入家系的水分利用效率显著高于对照家系,但光合利用效率两者差异不显著,反映出家系间的差异,注入有助于提高光合特性;利用光能和水分利用效率对家系进行选择,6号家系在这两种性状上均表现较佳,是高光效、低水耗家系,在今后选择优良无性系时加以重视。     

好食脉孢霉拮抗细菌的分离与鉴定

从桉树枯叶中分离到4株（ED018、ED013、ED015、ED014）对好食脉孢霉（Neurospora sitophila）具有拮抗作用的细菌。它们在Martin平板上对崎生长36h后,抑菌圈分别平均为26.2mm、24.1mm、23.8mm和19.0mm,与多菌灵有极显著性的差异。细菌菌株表现明显的抑制好食脉孢霉孢子的萌发作用,在棉籽壳自然基质培养基上,也表现明显的拮抗作用,对多种常见食用菌菌丝生长无抑制作用,对曲霉有抑制作用,对常见多种污染霉菌无抑制作用。4株细菌菌株均表现为革兰氏阳性,杆状,具芽孢,运动,结合其生理生化反应特征,鉴定4株菌株均属于芽孢杆菌属（Bacillus spp.）。     

Fine root production and turnover in Brazilian Eucalyptus plantations under contrasting nitrogen fertilization regimes

Nitrogen fertilization increased largely over the last decade in tropical eucalypt plantations but the behaviour of belowground tree components has received little attention. Sequential soil coring and ingrowth core methods were used in a randomized block experiment, from 18 to 32 months after planting Eucalyptus grandis, in Brazil, in order to estimate annual fine root production and turnover under contrasting N fertilization regimes (120 kg N ha⁻¹ vs. 0 kg N ha⁻¹). The response of growth in tree height and basal area to N fertilizer application decreased with stand age and was no longer significant at 36 months of age. The ingrowth core method provided only qualitative information about the seasonal course of fine root production and turnover. Mean fine root biomasses (diameter <2 mm) in the 0–30 cm layer measured by monthly coring amounted to 0.91 and 0.84 t ha⁻¹ in the 0 N and the 120 N treatments, respectively. Fine root production was significantly higher in the 0 N treatment (1.66 t ha⁻¹ year⁻¹) than in the 120 N treatment (1.12 t ha⁻¹ year⁻¹), probably as a result of the greater tree growth in the control treatment throughout the sampling period. Fine root turnover was 1.8 and 1.3 year⁻¹ in the 0 N and the 120 N treatments, respectively. However, large fine root biomass (diameter <1 mm) was found down to a depth of 3 m one year after planting: 1.67 and 1.61 t ha⁻¹ in the 0 N and the 120 N treatments, respectively. Fine root turnover might not be insubstantial in deep soil layers where large changes in soil water content were observed.     

Eucalypt plantations as habitat for birds on previously cleared farmland in south-eastern Australia

In parts of Australia, extensive areas of cleared land are now being planted with commercial plantations of native eucalypts. Questions arise about the extent to which such plantations can rectify previous loss of habitat and contribute to biodiversity conservation. This study assessed abundance of bird species (as one aspect of biodiversity) on 105 sites (25 cleared land, 58 plantations and 22 native forest) in two regions of rural Victoria, south-eastern Australia. Generalised linear modelling was used to assess some of the landscape and habitat variables that contributed to the value of plantation sites for particular groups of bird species. These models demonstrated the importance of on-site habitat variables in explaining the abundance of groups of bird species, with landscape context making small additional contributions.Mean abundance of forest and woodland birds was higher in eucalypt plantations than cleared farmland, and marginally lower than in native forest. Patterns differed between bird guilds. For example, insectivores that forage in the canopy and tall shrub layers were at least as common in plantations as in native forest, with birds in the latter group using young eucalypts as if they were tall shrubs. Birds that forage from open ground among trees were more common in plantations than native forest, and may benefit substantially from the new habitat fortuitously provided for them. This group includes several species that have declined in natural woodland habitats. Nectarivores, carnivores and birds that forage among low shrubs were less common in plantations than in native forest. Insectivores that forage from eucalypt bark made little use of plantations. Different approaches to plantation design and management would be needed to cater for groups such as these. Specific measures include planting of rough-barked eucalypts in addition to smooth-barked species, and provision of artificial hollows. Retention of existing remnants of native forest (e.g. old trees and forest patches) is a priority, to supply habitat elements that would otherwise be missing for long periods.     

邓恩桉茎段组织培养试验初探

采集邓恩桉茎段进行组织培养。试验结果表明:半木质化或刚木质化的茎段用浓度为0.1%Hgcl2消毒6min,用无菌水冲洗3～4次,再用Hgcl2消毒2 min效果最好,杀伤率低,获得率高达67.5%;芽分化及增殖培养基用改良MS+3%糖+3%的琼脂+VC0.01 mg∕L+VB20.015 mg∕L+BA0.5 mg/L+NAA0.25 mg/L,增殖系数达4倍,芽生长正常,不产生"玻璃化"苗;在IBA0.5 mg/L+ABT0.25 mg/L及IBA0.5 mg/L+NAA0.5 mg/L两种激素组合对邓恩桉不定根诱导有一点作用,但效果不理想,生根率只有20%,愈伤头大,上杯不容易成活。     

A PHENOTYPIC ASSESSMENT OF PINUS TAEDA PROGENIES IN THE EASTERN TRANSVAAL / 'N FENOTIPIESE BEPALING VAN PINUS TAEDA-NAGESLAG IN OOS-TRANSVAAL

Two P. taeda progeny trials, one polycross and one containing specific crosses, were assessed at Tweefontein State Forest. Most of the families were represented in both trials, which were laid out as completely random designs. Stem form and volume production were taken into account. Although definite shortcomings exist in the lay-out of the trials, certain conclusions can be drawn about the suitability of the clones for further breeding.

Expressed as “selection index-values” families are ranked in order of performance and previous findings are confirmed to a certain extent. As the demand for softwood in the Republic is expected to triple by the year 2000, volume production of timber of acceptable quality should receive high priority when assessing families in the tree breeding programme.