Defense chemistry of cyanogenic Eucalyptus cladocalyx seedlings is affected by water supply

Cyanogenesis is a widespread and effective defense mechanism in plants. Published evidence suggests that cyanogenic capacity (i.e., cyanogenic glycoside concentration) is enhanced in response to water stress, although potentially confounding variables preclude a definite conclusion. We used highly cyanogenic Eucalyptus cladocalyx var. nana F. Muell. seedlings grown with varying amounts of water and nitrogen (N) to determine the relationship between cyanogenic capacity and water stress. We also examined whether variation in cyanogenic capacity affects phenolic biosynthesis because both pathways use phenylalanine as a substrate. Cyanogenic capacity in fully expanded leaves increased 70% in response to moderate water stress when N availability was high but only 30% when growth was N-limited. Absolute cyanogenic capacity also increased with increasing N supply. Total phenolics and condensed tannins decreased with increasing N supply, but these compounds were unaffected by water stress. We conclude that, under the influence of water stress, the enhanced demand for phenylalanine for cyanogenic glycoside biosynthesis can be sustained by enhanced shikimate pathway flux without affecting phenolic metabolism.     

Temporal variation of microfibril angle in Eucalyptus nitens grown in different irrigation regimes

In 1990, a 2-ha plantation of Eucalyptus nitens (Deane and Maiden) Maiden was established in southeastern Tasmania and subjected to different irrigation regimes. Point dendrometers were installed in March 1995 to monitor radial stem movement every 15 min over several growing seasons. In this study, data from two growing seasons (1996-1998) were considered. From these measurements, daily increments of stem radius were determined. At the end of the second growing season, we extracted 12-mm cores and measured microfibril angles (MFA) of the wood at high resolution. Microfibril angles were rescaled on a time axis and mapped to daily and distance-based elements. Among treatments, irrigated trees in particular formed higher MFA early in the growing season (September-November) and lower MFA later in the growing season. Trees subjected to cyclic droughts showed clear relationships between MFA and soil water deficits, with MFA increasing in response to water stress release. Increases in MFA were preceded by accelerations in daily increment of stem radius. Among treatments, trees subjected to severe drought had the smallest MFA and generally low fluctuations in MFA. Irrigated trees were susceptible to changes in climate, whereas growth of the trees in the other treatments was limited by water availability. Use of path-analysis showed that temperature had an effect on stem radius increment but not on MFA; wind speed was the only factor that influenced MFA directly. Microfibril angle was correlated with stem shrinking and expansion phases; growth period length and growth rates were positively related to MFA.     

Identification of ISSR markers linked to flowering traits in a representative sample of Eucalyptus cladocalyx

Early flowering and flower abundance have long been considered desirable traits in eucalypt breeding programs. In particular, flowers of Eucalyptus cladocalyx provide a nectar source for the production of honey in arid ecosystems. To identify inter-simple sequence repeat(ISSR) markers that are associated with early flowering and flower abundance in the southern Atacama Desert, we used a sample of 47 trees, representing five Australian provenances of E. cladocalyx. A unified mixed linear model(which considered the effect of genetic structure and the kinship relationship among trees) revealed that three loci were significantly associated with early flowering, which accounted for 10–16 % of the phenotypic variation, while two loci accounted for 11–13 % in flowering intensity.Locus ISO1–500 bpwas associated with both flowering traits. This result is consistent with our previous findings indicating that marker-assisted selection on early flowering should have significant and positive impact on flowering intensity. The application of marker-assisted selection to identify trees that flower early and intensively may increase honey production, a resource that generates additional income for the local farmers of the southern Atacama Desert.     

Temporal and spatial variation of pollen yield in natural populations of Pinus roxburghii

Male components of the reproduction process in Pinus roxburghii were investigated for their variation in time and space as well as pollination,viz.flowering phenology,pollen production variability and pollen dispersal,for five successive years at two different locations (at the lower and higher elevations).The study reveals that elevation and the hour of the day are the main determinants of anthesis and microsporangium dehiscence,because both are related to temperature and humidity.The receptivity of ovulate cone strobili or female strobili occurred earlier at the lower elevation than at the higher elevation,with a longer receptivity period in the latter case.The phenology of male and female cones varied significantly between years and elevations.The determinations of pollen yield considered various sources of variability,i.e.,the number of pollen strobili per branch,strobili per tree,microsporangia per tree and pollen grains per tree.Each of these parameters revealed significant year-to-year and elevation effects.Year-to-year variation in the production of pollen cone and pollen grains with mass production after a three-year period revealed a three-year cycle of masting in pollen production in P.roxburghii.The pollen dispersal decreased quickly with distance from the pollen source.As a consequence,a distance of 600 m was proposed as a minimum to prevent contamination by pollen in the management of seed orchards.The results ultimately suggest that the ample production of pollen grains per tree along with flowering synchrony and long dispersal of pollen grains results in homogeneity in large populations.     

湘西土家族苗族自治州不同海拔梯度 景观格局时空变化特征

探究区域尺度不同海拔梯度下的景观格局变化特征,对维护区域可持续发展具有重要意义 。本研究以湘西土家 族苗族自治州(以下简称湘西州)为研究区,基于 30m分辨率的 CLCD土地覆盖数据集,利用 ArcGIS和 Fragstats 软件进 行统计处理,对比分析 2000~2020年不同海拔梯度景观格局的动态变化特征,结果表明:①研究区土地利用类型的变化特 征主要是农业用地和森林的相互转换,其中森林为研究区内的优势景观,海拔越高优势度越大,且面积保持逐年增长,主要 得益于植树造林、封山育林等林业工程取得良好成效,其次是农业用地,其面积逐年减少,是建筑用地的主要来源;②对比 研究区各景观指数近20年来的变化趋势,研究区内景观破碎程度降低,由小斑块向大斑块聚集,反映出湘西州城镇空间结 构不断优化,土地利用与开发逐渐规模化;高海拔山地地区也能因地制宜,在不破坏生态环境的前提下发展药材种植经济 ; ③在湘西州划分的 4个海拔梯度中, T1~T3梯度的土地利用与景观格局时空变化特征较为接近, T4梯度才出现了明显差 异 。说明在以山地地形为主体的湘西州,海拔 1500m左右是生态环境发生变化的重要分界线 。通过剖析湘西州的景观空 间结构及其影响因子,可为湘西州的景观规划发展以及生态资源的保护、管理和合理开发提供科学支持和规划建议。     

Temporal variation and high-resolution spatial heterogeneity in soil CO2 efflux in a short-rotation tree plantation

Soil CO2 efflux (SR) is the second largest carbon flux on earth. We investigated the driving factors of the seasonal change and short-distance spatial variation in SR in a short-rotation plantation of willow (Salix viminalis Orm). Total annual SR ranged from 723 to 1149 g Cm(-2) year(-1). Both an exponential and a logistic model were fitted to the data, with soil temperature at a depth of 5 cm as the independent variable. The R2 values for individual sampling points ranged from 0.83 to 0.95 and from 0.85 to 0.93 for the exponential and logistic models, respectively, indicating that soil temperature largely determined the seasonal variation in SR. Modeled soil SR at 10 degrees C ranged from 1.22 to 1.95 micromol m(-2) s(-1), whereas modeled annual Q(10) values were between 3.31 and 6.13. These high Q(10) values were attributed to the absence of drought during the study in 2005. When the coefficients of the general SR models were replaced by linear dependencies on soil and vegetation-related characteristics, the resulting spatially explicit exponential and logistic SR models explained 85 and 86%, respectively, of the variability within the dataset. The analysis indicated that soil carbon concentration, leaf area index, soil pH and root biomass caused differences in SR at the short distances considered in this study. However, incorporating information on variables considered to account for spatial variability in the model did not result in a higher R2 compared with a simple temperature function. When the general SR models were applied to independent datasets from the same plantation, the logistic model provided a better fit than the exponential model when drought occurred. Drought greatly reduced the annual Q(10) values of SR.     

Temporal and spatial variation of flowering among Pinus nigra Arn. clones under changing climatic conditions

Until recently, the most important factors affecting the economics and genetics of the seed crop from seed orchards were considered to be the timing and duration of flowering, variation in fertility and the total number of clones used to establish the seed orchards. Change in climatic conditions however is an emerging factor that could prove crucial regarding the timing of flowering and synchronization among clones and thus, the quality and quantity of seed production. The temporal and spatial variation in flowering phenology and the duration of flowering were studied in consecutive years in a Pinus nigra Arn. seed orchard. Sixty plus trees representing the distribution of the species in Northern Greece were used to establish the seed orchard, and nineteen ramets per clone were planted in a honeycomb experimental design in order to avoid kinship. Temporal variation among clones, as well as spatial variation among ramets within clones growing at different sites of the orchard were recorded, for initiation and duration of male and female flowering. The majority of clones were synchronized in dates of flowering during the year with weather conditions close to the long-term climatic conditions, except for a limited number of clones that were precocious or late flowering. The pronounced variability in climatic conditions over the 2 years strongly affected the flowering and synchronization among clones, resulting in almost complete asynchrony during the xerothermic year, which was characterized by a prolonged mean monthly temperature increase of 2.3 °C and a water deficit of 53% in a 7-month-period (November to May). These results suggest that one of the effects of a warmer and drier climate may be the lack of flowering synchronization, as pollen shedding might be completed before female conelets reach the phase of receptivity. The restriction of male parentage to a limited number of clones severely violates the panmixia assumption and could result in fertilization failure. The projected climate change for the Mediterranean region could potentially prove detrimental for fertility and flowering synchronization of forest trees, having consequences on the quantity and genetic diversity of the seed crop in seed orchards, and the natural regeneration of forest trees in forest ecosystems due to the reduced percentage of sound seed.     

Assessing genetic variation to improve stem straightness in Eucalyptus globulus

Context

Stem straightness is an important trait for growers and processors of Eucalyptus globulus logs for solid-wood products.

Aims

The aims of the study were to determine the extent of genetic variation in stem deviation from straightness in E. globulus and assess the utility of a six-point subjective scoring method as a selection criterion for stem straightness.

Methods

Two E. globulus progeny trials, grown under solid-wood product regimes, were studied. At age 9 years (post-thinning), stem straightness was measured using both image analysis and a six-point subjective scale. Diameter at breast height (DBH; 1.3 m) was measured at both age 5 (pre-thinning) and age 9 years.

Results

Significant additive genetic variation was observed. Strong, positive and significant additive genetic correlations were observed between the stem straightness assessment methods and between DBH at ages 5 and 9 years. Significant positive genetic correlations were shown between subjectively scored stem straightness and DBH at both ages 5 and 9 years.

Conclusion

The six-point subjective scoring method is a cost-effective selection criterion for stem straightness in E. globulus. The image measurement technique may be applied where objective estimates of stem straightness are required, for training purposes and to verify subjective scores.     

Wood anatomy and biometric parameters variation of Eucalyptus globulus clones

Variation in wood anatomy and biometric variables was studied in 14 7-year-old Eucalyptus globulus clones grown in a clonal trial in Arauco, Bio-Bio Region, Chile. Biometric characteristics were measured for each tree and the anatomical variables were measured at three radial positions by image analysis on transverse microsections cut from radial increment cores sampled at breast height. Results showed, that among clones wide ranges of variation were found for vessel frequency, vessel area and vessel coverage. However, narrow ranges of variation were found for fiber wall thickness, fiber diameter and lumen diameter. From pith to bark, mean vessel area and vessel coverage increased gradually, whereas the vessel frequency decreased. The fiber wall thickness did not differ significantly from pith to bark. Mean fiber and lumen diameters showed the same radial pattern, increasing from pith to the midpoint of the radius to reach a plateau close to the bark. Furthermore, important commercial volume gains that can exceed 100% were found. Considering the commercial importance of tree volume, vessel and fiber anatomy in the pulping and papermaking process, it is suggested that the information given in this study may be used as an additional criteria for the selection of E. globulus.     

Daily patterns of stem size variation in irrigated and unirrigated Eucalyptus globulus

High resolution measurements of stem diameter variation provide a means to study short-term dynamics of tree growth and water status. In this 14-month study, daily changes in stem radius of Eucalyptus globulus Labill. seedlings were measured with electronic point dendrometers in a plantation in southern Tasmania, Australia. The daily patterns of stem expansion and shrinkage were classified into three phases: shrinkage; recovery; and increase in diameter from one maximum to the next, or increment. This study showed that rapid onset of even mild drought in irrigated trees caused distinct changes in daily patterns of stem diameter variation, particularly the duration of daily stem increment. The duration of the daily increment phase was directly related to increment magnitude. The dynamics of daily increment were significantly affected by mean minimum temperature, indicating a temperature limitation on metabolic processes underlying diameter growth in these trees. Most likely due to differences in conductance, the duration but not rate of the incremental daily expansion was greater in fast- than in slow-growing trees.     

High resolution temporal variation in wood properties in irrigated and nonirrigated Eucalyptus globulus

? Environmental determinants of wood properties variation were examined in Eucalyptus globulus, a globally important hardwood plantation species, in southern Tasmania, Australia.

? Radial variation in wood properties, measured with the SilviScan system, were re-scaled from distance to time abscissa using stem radial growth data measured with dendrometers. With this re-scaled data it was possible to evaluate how water availability and temperature affected wood density, microfibril angle (MFA) and fibre and vessel transverse dimensions in irrigated and non-irrigated trees.

? Wood density, fibre radial diameter and MFA were sensitive to water availability. Wood density increased and fibre radial diameter decreased in response to reduced water availability. When high water availability was maintained, wood density was negatively correlated with temperature. Together, temperature and soil matric potential explained about 60% of temporal variation in wood density variation. In contrast MFA was not related to temperature but decreased with increasing water stress. Slower growing trees also had lower MFA than faster growing trees. Slower growing trees had a larger number of vessels per unit area of wood than faster growing trees within this even aged stand. However, vessel radius to the 4th power was significantly higher in faster growing trees than in slower growing trees.

? Overall, E. globulus wood properties were sensitive to temporal changes in environmental conditions (particularly water availability) and associated growth rates. The data provided support for the hypothesis that growth rates are hydraulically mediated.

     

Pathogenic variation in Cylindrocladium quinqueseptatum causing leaf blight of Eucalyptus1

A wide range of pathogenic variation was observed among the five isolates of Cylindrocladium quinqueseptatum leaf blight (CLB) which could be distinguished as different physiologic strains on 11 differential provenances of Eucalyptus. Susceptibility ranking of different provenances to five isolates also differed significantly indicating differential interaction between isolates and provenances. Analysis of variance showed that CLB severity of a provenance is mainly governed by the genetically different isolates and also that the provenances have closer genetical relationship. The results provide the first evidence for the existence of physiologic strains in C. quinqueseptatum.     

Temporal variation in nutrient concentrations of Pinus sylvestris needles

Temporal variation in nutrient concentrations of Scots pine (Pinus sylvestris L.) needles was studied during a three‐year period in three stands of differing stages of development. Concentrations of N, P and K varied significantly between years; this variation was related to differences in needle dry weight. Concentrations of all measured nutrients (N, P, K, Ca, Mg, Mn, Cu, Zn, Fe, B) and Al varied between seasons; this variation was related to nutrient mobility and the annual physiological cycle. Concentrations of the mobile nutrients N, P and K decreased in spring and early summer during shoot and needle elongation and increased in late summer and autumn during needle senescence and litterfall. Concentrations of Mg, Cu, Zn and B followed somewhat similar patterns. The poorly mobile nutrients Ca, Mn and Fe accumulated gradually in needles during each growing season. Needle nutrient concentrations were stable during the nonactive period.     

Temporal and spatial dynamics of an old-growth beech forest in western Japan

Dendrochronological approaches enable us to understand forest stand dynamics by estimation of disturbance history and age structure. The present study was conducted in an old-growth beech forest in a forest reserve in western Japan. Increment cores were taken for tree ring analysis from all canopy trees in a 50 m × 130 m study plot. Radial growth release criteria were developed to identify significant growth releases in each tree ring series and to characterize the disturbance history of the study site. The age structure of the forest was indicative of continuous establishment by Fagus crenata and simultaneous establishment by Magnolia obovata. A variety of low-intensity disturbances were identified in each decade, especially after the 1900s, but the occurrence of high-intensity catastrophic disturbance was rare, and likely played an important role in maintaining species diversity in the existing forest canopy. The results also suggest that F. crenata regenerates gradually before and after both large- and small-scale disturbances, whereas M. obovata and Betula grossa regenerate only after large-scale catastrophic disturbances.     

Temporal variation in nutrient status of a floodplain forest soil

Seasonal variation in nutrient status of a floodplain soil was studied in a silver maple (Acer saccharinum L.) forest in central Illinois. Statistically significant temporal differences were measured in the concentration of NH₄-N, NO₃-N, and extractable P. Patterns of variation in NH₄-N and NO₃-N were related to organic C content and mineralization processes in the soil. Variation in extractable P was affected by flood-induced anaerobic conditions and soil pH. Temporal variation in soil nutrient status was one of the most dynamic features of nutrient cycling in the floodplain forest ecosystem. The potential for seasonal variation in the availability of nutrients should be considered when chemical data are used to characterize forest soil fertility and site productivity. Samples should be collected at several points in time if possible.     

Patterns of longitudinal within-tree variation in pulpwood and solidwood traits differ among Eucalyptus globulus genotypes

Wood discs were sampled from 6 heights up the stem of 248 trees representing 10 subraces and 116 families grown in an E. globulus base-population progeny trial. The lower stem had the least favourable wood properties for kraft pulpwood and most solidwood applications: bark was thickest, basic density was lowest and kino, decay and shrinkage traits were greatest at or below 12% of tree height. Significant genetic differences at the subrace level were revealed in diameter, bark thickness, basic density, decay and gross shrinkage and at the family within subrace level in diameter, basic density and decay. However, subrace-by-height-category interactions in bark thickness, basic density, decay and gross shrinkage indicated that differences among subraces were dependent on height in these traits. Examination of longitudinal trends revealed some evidence that the zone of thick basal bark extended further up the stem in thicker-barked subraces and that the Southern Tasmania subrace might be less effective than other subraces in restricting the longitudinal spread of decay after infection.     

尾叶桉家系木材性状的变异研究

对75个月生32个尾叶桉家系的6个与木材相关的性状进行了研究.6个木材性状在家系间存在显著或极显著差异,说明通过家系选择可以获得性状优良的家系/无性系;木材基本密度、木材含水量、纤维宽、纤维长宽比与生长、形质性状间的相关关系不显著,表明该4个研究性状能各自遗传,可以分别独立选择;纤维长与树高、胸径及单株材积相关关系达到显著或极显著水平,说明纤维长度随树龄增长而增加,材性逐渐得到改善;所有木材性状间的遗传力均在0.5左右,说明各性状受到中等水平的遗传控制;水分含量、基本密度、树皮厚度、纤维长宽比性状的遗传变异系数较高,表明尾叶桉家系在4个性状上具有较丰富的遗传变异,进行性状遗传改良可获得较高遗传增益,按25%入选率,预期遗传增益可达5.68%～17.66%.     

Within tree variation in anatomical properties of some clones of Eucalyptus tereticornis Sm.

 Within tree variation in anatomical properties of four and half year old grown Eucalyptus tereticornis Sm. clones have been investigated and correlated with specific gravity. Vessel frequency, vessel diameter and fiber length were found to vary significantly from bottom to top with no definite trend. Significant variation exists in all the clones of different parameters. Fiber length was positively correlated with fiber diameter and double wall thickness. Tissue proportions did not show any significant variation from bottom to top. However, highly significant differences have been found between clones among four cell types except fibers. Specific gravity is positively correlated with ray percentage, fiber percentage – vessel percentage ratio and negatively correlated with vessel percentage, while all other anatomical parameters including height and girth have no effect. Received 25 August 1998     

Aggressiveness,cultural characteristics and genetic variation of Ceratocystis fimbriata on Eucalyptus spp.

Ceratocystis wilt caused by Ceratocystis fimbriata is currently one of the most important diseases affecting Eucalyptus in Brazil. This disease is controlled by planting resistant clones; however, possible variability in the pathogen population may compromise the selection of resistant genotypes. Therefore, this study aimed to evaluate the aggressiveness of C. fimbriata isolates obtained from Eucalyptus spp, as well as their cultural characteristics and genetic variation of their ITS rDNA gene region. We found a significant isolate × clone interaction, with the isolate RM35 being the most aggressive and presenting a broader spectrum of aggressiveness, causing greater xylem discoloration on a larger number of clones. This isolate is the most suitable for artificial inoculations focusing on the selection of resistant materials. Clones CLR‐236 and CLR‐212 were identified as the most resistant and clones CLR‐223 and CLR‐240 as the most susceptible and those that are recommended as reliable comparators in artificial inoculations. All isolates were morphologically similar and differed from C. fimbriata from sweet potato by the formation of a wide mouth endoconidiophore that produces doliform endoconidia. According to the culture media and temperature applied, the most favourable conditions for mycelial growth were observed using malt extract agar (MEA) and temperatures ranging from 24 to 26°C. There was no correlation between sporulation and aggressiveness. Great variation in ITS sequences was observed, and a total of five ITS genotypes were identified among the ten isolates tested.