Indigenous woody species diversity in Eucalyptus globulus Labill. ssp. globulus plantations in the Ethiopian highlands

The naturally regenerated native woody species diversity was studied ineucalypt plantations at Menagesha, where there was remnant natural forest, and atChancho, where natural forests were absent. A total of 22 and 20 woody speciesbelonging to 18 and 17 families were found, and of these species, treesaccounted for 68 and 55% at Menagesha and Chancho, respectively. About 83% ofthe woody species found in the adjacent natural forest, including importanttimber species were represented in the eucalypt understory at Menagesha.However, the relative abundance of species in eucalypt plantations and theadjacent natural forest varied considerably. Woody species richness andabundance of sample plots at Menagesha were on average 2.4 times and 5.7times higher, respectively, than the sample plots at Chancho. This resultdemonstrates the crucial role of the remnant small patches of natural forest,as a source of diaspores for the restoration of the woody species diversity indegraded areas of the Ethiopian highlands. There was no significant differencein woody species diversity between the eucalypt stand margin and centre. Theunderstory woody species density in eucalypt plantations was up to 8325stems/ha, indicating that the numerous eucalypt stands have a highpotential for restoring the woody species diversity in the Ethiopian highlands.In order to fully re-establish the diverse and economically valuable naturalforest, complementary measures such as enrichment planting of missing primaryforest species may be required.     

Adventitious bud induction in Eucalyptus globulus Labill

Summary Adventitious buds and shoots of Eucalyptus globulus Labill. (Tasmanian Bluegum) have been regenerated from cotyledons and hypocotyls from mature embryos and seedlings. Adventitious buds, were induced at high frequency with 0.05 μM thidiazuron in combination with 0.2 μM 2,4-dichlorophenoxyacetic acid or 5 μM α-naphthaleneacetic acid. Culture of explants in the dark inhibited bud induction, but up to 86% of cotyledons, longitudinally split just prior to culture, produced adventitious buds, in the light. Development of buds into shoots occurred only at low frequency, after transfer to media containing N⁶-benzylaminopurine.     

蓝桉果实中的脂溶性成分

从蓝桉(Eucalyptus globulusLabill.)果实乙醇提取物的石油醚部位分离鉴定出6个化合物,通过理化和波谱分析结构鉴定为:5-羟基-4′,7-二甲氧基-6-甲基黄酮(1)、blumenol A(2)、蓝桉醇(3)、绿花白千层醇(4)、β-谷甾醇(5)、二十二烷酸(6),其中化合物1~4和化合物6系首次从该植物中分离得到,化合物1和2首次从桉属植物中分离得到.     

CO2 efflux, CO2 concentration and photosynthetic refixation in stems of Eucalyptus globulus (Labill.)

In spite of the importance of respiration in forest carbon budgets,the mechanisms by which physiological factors control stem respirationare unclear. An experiment was set up in a Eucalyptus globulusplantation in central Portugal with monoculture stands of 5-year-oldand 10-year-old trees. CO₂ efflux from stems under shaded andunshaded conditions, as well as the concentration of CO₂ dissolvedin sap [CO₂^*], stem temperature, and sap flow were measuredwith the objective of improving our understanding of the factorscontrolling CO₂ release from stems of E. globulus. CO₂ effluxwas consistently higher in 5-year-old, compared with 10-year-old,stems, averaging 3.4 versus 1.3 µmol m^–2 s^–1,respectively. Temperature and [CO₂^*] both had important, andsimilar, influences on the rate of CO₂ efflux from the stems,but neither explained the difference in the magnitude of CO₂efflux between trees of different age and size. No relationshipwas found between efflux and sap flow, and efflux was independentof tree volume, suggesting the presence of substantial barriersto the diffusion of CO₂ from the xylem to the atmosphere inthis species. The rate of corticular photosynthesis was thesame in trees of both ages and only reduced CO₂ efflux by 7%,probably due to the low irradiance at the stem surface belowthe canopy. The younger trees were growing at a much fasterrate than the older trees. The difference between CO₂ effluxfrom the younger and older stems appears to have resulted froma difference in growth respiration rather than a differencein the rate of diffusion of xylem-transported CO₂. Key words: Eucalyptus globulus, refixation, stem respiration Received 19 May 2008; Revised 14 September 2008 Accepted 8 October 2008     

Productivity, carbon isotope discrimination and leaf traits of trees of Eucalyptus globulus Labill. in relation to water availability

The stand basal area, carbon isotope discrimination (Δ) in tree rings and leaves, leaf area index and leaf traits of trees were measured in 6‐ to 8‐year‐old stands of Eucalyptus globulus Labill. across a gradient of rainfall of 600–1400 mm year^?1 in south‐western Australia to better understand the importance of leaf traits and gas‐exchange as determinants of stand productivity. Δ ranged from 17‰ to 21‰. Δ and basal area were highly, positively correlated with each other and the ratio of mean annual rainfall to potential evaporation (P/PE). Leaf area index, soil water holding capacity and leaf nitrogen content were only weakly correlated with basal area. Δ and P/PE were negatively correlated with leaf nitrogen content. Δ was negatively correlated with leaf density but positively correlated with specific leaf area. This is consistent with the theory that larger leaf nitrogen content and smaller specific leaf area are associated with increased photosynthetic capacity and increased leaf‐scale water‐use‐efficiency, and that Δ is influenced by mesophyll conductance. It is concluded that canopy conductance is a more important determinant of growth in water‐limited conditions than either leaf area index or leaf traits in fertilized stands of E. globulus. Water availability was dictated more by rainfall than soil type.     

(2-O-alpha-D-galactopyranosyl-4-O-methyl-alpha-D-glucurono)-D-xylan from Eucalyptus globulus Labill.

An unusual heteroxylan composed of galactosyl, 4-O-methyl-glucuronosyl and xylosyl residues with molar ratio 1:3:30 was isolated from the wood of Eucalyptus globulus Labill. The results of linkage analysis, supported by data of 1H, 2D 1H-1H COSY and 13C NMR spectroscopy, revealed that the polysaccharide is a (2-O-alpha-D-galactopyranosyl-4-O-methyl-alpha-D- glucurono)-D-xylan with a (1-->4)-linked beta-D-xylopyranosyl backbone branched at O-2 by short side chains composed of terminal 4-O-methyl-alpha-D-glucuronic acid and of 4-O-methyl-alpha-D-glucuronic acid substituted at O-2 with alpha-D-galactose.     

Early ovule development following self- and cross-pollinations in Eucalyptus globulus Labill. ssp. globulus

The study was conducted to identify the self-incompatibility mechanism in Eucalyptus globulus ssp. globulus. Controlled self- and cross-pollinations were conducted on individual flowers from three mature trees that had self-incompatibility levels of 76, 99.6 and 100%. Flowers were harvested at 4, 6 and 8 weeks after pollination. Embryology was investigated by bright field microscopy on material harvested at 4 and 6 weeks after pollination. Fertilization had taken place at 4 weeks after pollination with zygotes and free nuclear endosperm visible. There was a greater proportion of healthy, fertilized ovules in the cross- compared with the self-pollination treatment, and approx. half the ovules examined from both pollen treatments were not fertilized or were degenerating. By 6 weeks after pollination a few zygotes were starting to divide. The number of healthy, fertilized ovules was still greater in the cross-pollination treatment, but the number of healthy fertilized ovules was lower in both treatments compared with 4 weeks after pollination, and many ovules were degenerating. Fertilized ovules were significantly larger than non-fertilized or degenerating ovules and this difference was detectable by eye at 6 and 8 weeks after pollination. The mechanism of self-incompatibility appears to have both late pre- and post-zygotic components.     

The numerical intraspecific taxonomy of Eucalyptus globulus Labill. (Myrtaceae)

The history of the taxonomic perception of Eucalyptus globulus Labill. is described. Morphological-geographical clusters within E. globulus are identified through the use of a polythetic, agglomerative classificatory strategy. The results of the numerical analysis and unpublished data on geographic variation strongly suggest that four subspecies should be recognized. Thus three taxa formerly regarded as species are reduced to subspecies of E. globulus.     

Cold-induced photoinhibition affects establishment of Eucalyptus nitens (Deane and Maiden) Maiden and Eucalyptus globulus Labill

The effects of cold-induced photoinhibition on Eucalyptus globulus and Eucalyptus nitens seedlings were assessed between planting and age 23 weeks. The seedlings were subjected to four treatments before planting: non-hardened (NH) E. globulus and E. nitens, cold-hardened (CH) E. nitens, and nutrient-starved (NS) E. nitens. Seedlings were planted alongside established 1-year-old E. nitens saplings. The experimental site was at 350 m above sea level, which is considered marginal for the establishment of E. globulus plantations due to low mean minimum temperatures. Cold and sunny conditions after frost increased photoinhibition in the order: NH E. globulus > NH and CH E. nitens > NS and established E. nitens. As a result there was 20% mortality of NH E. globulus seedlings. NS E. nitens seedlings were severely photoinhibited and had high anthocyanin levels at planting; levels of photoinhibition decreased after planting, anthocyanin levels remained high and there was no mortality. Carotenoid levels were low in E. globulus compared to E. nitens treatments. It was concluded that cold-induced photoinhibition is a factor determining the range of environments where E. globulus can be successfully planted, and not frost tolerance alone. Anthocyanin was synthesised in response to increased photoinhibition. Anthocyanin levels were correlated to the severity of the photoinhibition. Thus, E. nitens seedlings nutrient starved in the nursery are pre-conditioned to photoinhibitory conditions experienced soon after planting. This treatment is a useful risk-management tool where cold-induced photoinhibition is likely to occur during seedling establishment.     

Control of transpiration in an irrigated Eucalyptus globulus Labill. plantation

Stomatal conductance and transpiration were measured concurrently in an irrigated Eucalyptus globulus Labill. plantation. Canopy stomatal conductance, canopy boundary layer conductance and the dimensionless decoupling coefficient (Ω) were calculated (a) summing the conductance of three canopy layers (g_c) and (b) weighting the contribution of foliage according to the amount of radiation received (g_c′). Canopy transpiration was then calculated from g_c and g_c′ for Ω = 1 (E_eq), Ω = 0 (E_imp) and by weighting E_eq and E_imp using Ω (E_Ω). E_eq, E_imp and E_Ω were compared to transpiration estimated from measurements of heat pulse velocity. The mean value of Ω was 0·63. Transpiration calculated using g_c and assuming perfect coupling (12·5 ± 0·9 mmol m^?2 s^?1) significantly overestimated measured values (8·7 ± 0·8 mmol m^?2 s^?1). Good estimates of canopy transpiration were obtained either (a) calculating E_Ω separately for the individual canopy layers or (b) treating the canopy as a single layer and using g_c′ in a calculation of E_imp (Ω = 0). The latter approach only required measurement of stomatal conductance at a single canopy position but would be unsuitable for use in combined models of canopy transpiration and assimilation. It should however, be suitable for estimating transpiration in forests regardless of the degree of coupling.     

Daily stem growth patterns in irrigated Eucalyptus globulus and E. nitens in relation to climate

Daily increments in stem radius were determined from hourly dendrometer measurements in each of three irrigated Eucalyptus nitens and E. globulus trees. Multiple regressions determined from daily weather variables accounted for 40–50% of the variance in increment. The use of weather variables lagged by 1–2 days increased the variance explained. The diurnal variation in stem radius was resolved into three mathematically defined phases: shrinkage, recovery and increment. The positive daily net increment in stem radius, by definition, occurred in the increment phase. Average weather conditions during this phase (predominantly night-time) did not explain any more variance in increment than the average daily conditions, determined over a 24 h period. Daily increment was resolved into a rate of stem radius increase during the increment phase and the duration (hours) of that phase. Significant species by month interactions were evident with growth in summer characterised by faster rates of stem expansion over shorter time periods within each diurnal cycle. E. nitens tended to have longer increment phases in spring and autumn, and faster phase rates in autumn than E. globulus. Interactions between weather variables and cambial growth were complicated and varied over the year. The correlation between temperature and stem growth varied from positive in spring to zero or negative during summer. The data indicate a need to understand weather-by- climate interactions at the level of whole tree physiology in order to fully understand the effect of weather on cambial activity and therefore stem increment and wood properties. Received: 12 April 1999 / Accepted: 6 July 1999     

Yield models for Eucalyptus globulus fuelwood plantations in Ethiopia

Based on 53 tree analyses and 105 sample plots of Eucalyptus globulus, models for volume and biomass at single tree and stand levels were developed. The possible growing sites were divided into four site classes. In seedling stands, the site class I corresponds to yield class 44 m³ ha⁻¹ year⁻¹, in coppice stands to yield class 46 m³ ha⁻¹ year⁻¹. The site class IV corresponds in seedling stand to yield class 9 m³ ha⁻¹ year⁻¹, in coppice stands to yield class 13 m³ ha⁻¹ year⁻¹. The maximum mean annual increment was reached in seedling stands at the age of 18–19 years, in coppice stands at the age of 14 years.     

Energy evaluation of forest residues originated from Eucalyptus globulus Labill in Galicia

The possibility of retrieving the energy contained in forest residues originating from wood exploitation in Galicia (Spain) is evaluated. This study was made on Eucalyptus globulus Labill occupying a forest surface of 240000 ha. This species plays an important role in the economical development of Galicia, as it is the main forest species for production of pulp. Sampling was made over 1999 in seven different zones, three main stations plus four selected for comparison, situated in Galicia. The residues originating from cutting were sorted into three different groups and their calorific values were measured by static bomb calorimetry. These calorific values, close to 7200 kJ kg(-1), make possible the use of this residual biomass as an energy source. Calorific values were measured by static bomb calorimeter in an oxygen atmosphere. Flammability was determined using a standard epiradiator. Simultaneously, some other parameters, elementary chemical composition, heavy metal contents, moisture, density, ash percentage after combustion in the bomb, and main bioclimatic characteristics, were also determined.     

The apparent feed-forward response to vapour pressure deficit of stomata in droughted, field-grown Eucalyptus globulus Labill

This study tested a multiplicative model of stomatal response to environment for drought‐affected trees of Eucalyptus globulus Labill. growing in southern Australia. The model incorporates a feed‐forward response to vapour pressure deficit of ambient air (δe_a) and performed well if evaluated using reduced major axis regression and log‐transformed data. There was strong evidence from gas‐exchange data, leaf water potentials and sapflow measurements of the feed‐forward response by stomata to leaf‐to‐air vapour pressure deficit (δe_l). The response of stomata to δe_l was irreversible. Stomatal conductance and the rate of net photosynthesis were highly correlated and declined, together with the rate of transpiration, throughout the afternoon as δe_a increased despite increasing leaf water potentials. The concentration of CO₂ inside leaves (c_i) increased as stomatal conductance declined indicating increasing non‐stomatal limitations to photosynthesis. The stomatal response to δe_l of E. globulus in the field is best described as an ‘apparent feed‐forward response’ that probably results from both slowly reversible depression of net photosynthesis and abscisic acid accumulation in guard cells. We suggest that the stomatal response to c_i may strengthen the link between photosynthetic capacity and stomatal conductance during leaf drying as a result of either drought or large δ e_l.     

Factors affecting maintenance, proliferation, and germination of secondary somatic embryos of Eucalyptus globulus Labill

The described protocol for repetitive somatic embryogenesis (SE) in Eucalyptus globulus produced more somatic embryos than the primary SE protocol. Primary somatic embryos (induced on MS_3NAA) were transferred to the same medium, leading to new cycles of somatic embryos, for at least 2 years. The influence of medium (MS and B5), plant growth regulators (auxins and cytokinins), and light on secondary SE was tested. The MS medium without growth regulators (MS_WH) was more efficient for cotyledonary embryo formation and germination than the B5 medium. Reducing auxin (NAA) levels increased the proliferation of globular somatic embryos and allowed SE competence to be maintained on medium free of plant growth regulators. The addition of two cytokinins (BAP and KIN) to the MS medium did not improve proliferation of globular secondary embryos, but was crucial during later stages of the SE process (germination and conversion). Data also show that light may influence the quality of the process, depending on its stage. Darkness should be maintained until the cotyledonary stage is reached, after which exposure to light is recommended.     

Phenology of Eucalyptus weevil, Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae), and chrysomelid beetles in Eucalyptus globulus plantations in south-western Australia

1 In south‐western Australia, Eucalyptus globulus plantations are defoliated by a complex of beetle species, yet only scant information exists on these species under such climatic conditions. To improve management of these defoliating beetles in the region, canopy fogging and shoot clipping were conducted in plantations between 1999 and 2002 to identify and document the phenology of the beetle species present. 2 Eucalyptus weevil, Gonipterus scutellatus, was the most common and destructive defoliating beetle. Gonipterus scutellatus undergoes one principal generation each year with a lesser second generation or cohort in some seasons, which contrasts greatly with reports of two to four annual generations for the species in other regions. This limited reproduction by G. scutellatus may be due to the limited availability from summer onwards of new flushing foliage, which is essential for feeding and oviposition. 3 Several species of chrysomelid beetles were collected in plantations, but these were present in much lower numbers than G. scutellatus and were only a minor concern. However, some species, such as Chrysophtharta variicollis, appear to be capable of developing short‐lived outbreaks. 4 A diverse suite of natural enemies was fogged from plantations but they were significantly less abundant than defoliating beetles and are not likely to provide significant control of beetles. 5 In terms of managing these defoliating beetles, monitoring and control should focus on G. scutellatus, and be conducted during spring when most damage occurs.     

The survival and development of inoculant ectomycorrhizal fungi on roots of outplanted Eucalyptus globulus Labill

The survival and development of two inoculant ectomycorrhizal fungi (Hebeloma westraliense Bough. Tom. and Mal. and Setchelliogaster sp. nov.) on roots of outplanted Eucalyptus globulus Labill. was examined at two expasture field sites in the south-west of Western Australia. Site 1 was a gravelly yellow duplex soil, and Site 2 was a yellow sandy earth. Plants were grown in steamed or unsteamed soil, in root bags designed as field containers for young growing trees. Three, 6 and 12 months after outplanting, plants were removed from these bags and assessed for dry weights of shoots and ectomycorrhizal colonization of roots.The inoculant ectomycorrhizal fungi (identified on the basis of the colour and morphology of their mycorrhizas) survived on roots of E. globulus for at least 12 months after outplanting at both field sites. At Site 1, however, colonization of new fine roots by the inoculant fungi was low (less than 20% of fine root length). Inoculation had no effect on the growth of E. globulus at this site. In contrast, at Site 2 the inoculant ectomycorrhizal fungi colonized up to 30–50% of new fine root length during the first 6 months after outplanting. There was a corresponding growth response to ectomycorrhizal inoculation at this site, with a close relationship (r²=0.82^**) between plant growth at 12 months and root colonization at 3 months. Plant growth at 12 months was related less closely with root colonization at 6 or 12 months. Root colonization by resident ectomycorrhizal fungi increased with time at both field sites. At Site 2, this increase appeared to be at the expense of colonization by the inoculant fungi, which was reduced to less than 10% of fine root length at 12 months. Steaming the soil had little effect on colonization by the inoculant ectomycorrhizal fungi at either field site, but decreased colonization by the resident ectomycorrhizal fungi.     

Stomatal Control of Photosynthesis of Eucalyptus globulus Labill. Trees under Field Conditions in Portugal

Pereira, J. S., Tenhunen, J. D. and Lange, O. L. 1987. Stomatalcontrol of photosynthesis of Eucalyptus globulus Labill. treesunder field conditions in Portugal.—J. exp. Bot. 38: 1678–1688. Stomatal behaviour of adult leaves of Eucalyptus globulus treeswas studied under field conditions in Portugal. In the absenceof severe plant water stress stomata were open when the summedtotal of photosynthetically active photon flux density incidenton both leaf surfaces was above 100 µmol m²s¹ and leafconductance to water vapour reached 245 mmol m ² s¹ on a total(both epidermes) leaf area basis. The stomata of both leaf epidermesresponded similarly to changes in solar radiation and waterstress. Water stress resulted in decreasing daily maxima inleaf conductance as predawn leaf water potential decreased.Maximal leaf conductance decreased to less than 50 mmol m ²s ¹ when predawn leaf water potential decreased below —1·0MPa. At similar values of predawn leaf water potential stomatawere more closed as the leaf to air water vapour partial pressuredifference increased. The effect of increasing air dryness onstomata was greatest at high predawn leaf water potential. Dailymaxima in photosynthetic rates and in leaf conductance werelinearly related to one another in spring and summer. Both decreasedwith increase in leaf water stress. In autumn and winter, increasesin leaf conductance occurring under natural conditions duringthe course of the day were not necessarily accompanied by increasesin net photosynthesis. Stomata were more closed in the afternoonthan in the morning at the same rates of net photosynthesis,temperature or leaf to air water vapour partial pressure difference. Key words: Eucalyptus globulus,, photosynthesis, stomata, water stress.