Effect of shade on biomass accumulation and partitioning for Eucalyptus camaldulensis sprouts

ABSTRACT

Eucalyptus is widely cultivated in homogeneous monocultures throughout the world alongside plants of the same age. Furthermore, the productivity of forest stands is highly dependent on how solar radiation is intercepted and used. Meanwhile, it is possible to consider cultivating trees of different ages in the same area, and thus under different regimes of available solar radiation, creating a sequence of plantings and harvestings and to develop Eucalyptus-based agroforestry systems. We have examined biomass accumulation of Eucalyptus camaldulensis along a shade gradient. Eucalyptus trees presented power-law responses to increasing irradiance for biomass, indicating it has low plasticity and is unable to maintain growth under lower irradiance levels. Biomass partitioning showed no dependence on available irradiation. Leaf density presented very little increase toward sunnier places meaning that an increment in Eucalyptus biomass would be mostly due to its increase in size and thus higher radiation interception. Careful management of shade will be a key consideration for the integration of Eucalyptus into agroforestry. With knowledge of the growth habits of different species, we will have the potential to propose more perennial ways in which to manage land and reduce anthropogenic disturbances by avoiding clear-cuts of areas that removes all plant structures.     

Temperature effects on wood anatomy, wood density, photosynthesis and biomass partitioning of Eucalyptus grandis seedlings

Wood density, a gross measure of wood mass relative to wood volume, is important in our understanding of stem volume growth, carbon sequestration and leaf water supply. Disproportionate changes in the ratio of wood mass to volume may occur at the level of the whole stem or the individual cell. In general, there is a positive relationship between temperature and wood density of eucalypts, although this relationship has broken down in recent years with wood density decreasing as global temperatures have risen. To determine the anatomical causes of the effects of temperature on wood density, Eucalyptus grandis W. Hill ex Maiden seedlings were grown in controlled-environment cabinets at constant temperatures from 10 to 35 degrees C. The 20% increase in wood density of E. grandis seedlings grown at the higher temperatures was variously related to a 40% reduction in lumen area of xylem vessels, a 10% reduction in the lumen area of fiber cells and a 10% increase in fiber cell wall thickness. The changes in cell wall characteristics could be considered analogous to changes in carbon supply. Lumen area of fiber cells declined because of reduced fiber cell expansion and increased fiber cell wall thickening. Fiber cell wall thickness was positively related to canopy CO2 assimilation rate (Ac), which increased 26-fold because of a 24-fold increase in leaf area and a doubling in leaf CO2 assimilation rate from minima at 10 and 35 degrees C to maxima at 25 and 30 degrees C. Increased Ac increased seedling volume, biomass and wood density; but increased wood density was also related to a shift in partitioning of seedling biomass from roots to stems as temperature increased.     

Five-year vegetation control effects on aboveground biomass and nitrogen content and allocation in Douglas-fir plantations on three contrasting sites

Despite widespread use of intensive vegetation control (VC) in forest management, the effects of VC on allocation of biomass and nutrients between young trees and competing vegetation are not well understood. On three Pacific Northwest sites differing in productivity, soil parent material, and understory vegetation community, we evaluated year-5 effects of presence/absence of 5 years of VC on allocation of aboveground biomass and nitrogen (N) between planted Douglas-fir (Pseudotsuga menziesii var. menziesii) and competing vegetation. Equations for predicting bole, branch, foliar, and total dry weights based on stem diameter at a height of 15 cm and total tree height did not differ significantly among sites or by presence or absence of VC. This contrasts with previous research, using diameter at breast height rather than at 15 cm, which found that separate equations were warranted for trees with and without competing vegetation. Estimated whole-tree biomass among the six site/VC combinations ranged from 0.8 to 7.5 Mg ha⁻¹, and increases in tree biomass associated with VC ranged from 62% to 173% among sites. Among the three sites, there were positive, linear relationships between soil total N content to a depth of 60 cm and both N content of aboveground vegetation (trees plus competing vegetation) and Douglas-fir foliar N concentration. Tree N content increased by 8.4, 8.2, and 40.0 kg N ha⁻¹ with VC at the three sites, whereas competing vegetation N content decreased with VC by 0.9, 18.8, and 32.0 kg N ha⁻¹, respectively, at the same sites. Thus, VC did not lead to a direct compensatory tradeoff between aboveground N content of trees and other vegetation. However, soil N content was linearly related to N accumulation and plant growth across the three sites. In addition to differences in N availability among sites, the effect of VC on the redistribution of resources among trees and competing vegetation also was influenced by vegetation community composition and efficacy of VC treatments.     

Yield-density effects on growth and biomass partitioning in Leucaena leucocephala seedlings

Experiments were conducted to study the effects of density on growth and biomass partitioning of Leucaena leucocephala seedlings.Four plantations with densities of 10,000,20,000,40,000,and 80,000 seedlings ha^-1 were evaluated only from 15 to 25 months after planting.At 15 months,crown height and width decreased with increasing density.Seedling height/dbh ratios increased with increasing density.Biomass increased with greater density according to the yield–density effect equation,which was evident for all densities.With increasing age,biomass division to branches and leaves increased,whereas partitioning to roots decreased in the 10,000 and 20,000 seedlings ha-1 plantings.Partitioning to branches and leaves remained relatively steady,while partitioning to roots increased in the 40,000 and 80,000 seedlings ha^-1 plantings.Biomass division into stem and bark components remained relatively steady in all densities.Yield–density and organ yield–density curves shifted upward with increasing seedling age on a log–log graph throughout the experimental period.     

杂交桉家系在桂北生长及优良性评价

[目的]对广西黄冕林场杂交桉的生长及优良性进行评价,找到更多适合在该区域今后推广种植的优良杂种材料.[方法]对3.5、5.8和8.5 a共3个年度的42个人工杂种家系、9个母本自由授粉家系和1个无性系试验林进行生长调查,开展不同林龄的干形、幼林枝瘿姬小蜂的受害率等的调查,利用方差分析和多性状综合坐标得分法进行分析,获得...     

Seasonal changes in photosynthesis, nitrogen content and nitrogen partitioning in Lindera umbellata leaves grown in high or low irradiance

Seasonal changes in photosynthetic capacity, leaf nitrogen (N) content and N partitioning were studied from before leaf maturation (spring) until death (autumn) in high- and low-light-exposed leaves of a deciduous shrub, Lindera umbellata var. membranacea (Maxim.) Momiyama growing in a natural forest in northeast Japan. In spring, light-saturated photosynthetic rate (Pmax) was low despite high leaf N and Rubisco contents, indicating that the photosynthetic apparatus was not yet functionally developed. Rubisco seemed to be only partially active. In summer and autumn, Pmax per unit leaf N increased and changes in Pmax were correlated with changes in leaf N and two photosynthetic components, Rubisco and chlorophyll. Changes in these components paralleled the changes in leaf N. During leaf senescence, about 70% of leaf N was resorbed. Metabolic proteins that accounted for the majority of leaf N in summer were highly degradable and more than sufficient to explain the high N-resorption efficiency. Structural proteins represented only a small part of leaf N and were relatively resistant to degradation and thus contributed little to N resorption. Leaf N partitioning between metabolic and structural proteins determined the amount of retranslocatable N, but did not strictly determine the N content of a dead leaf or N-resorption efficiency.     

Growth and yield models for Eucalyptus grandis grown in Swaziland

The aim of this study was to develop a stand-level growth and yield model for short-rotation Eucalyptus grandis grown for pulp wood production at Piggs Peak in Swaziland. The data were derived from a Nelder 1a spacing trial established with E. grandis clonal cuttings in 1998 and terminated in 2005. Planting density ranged from almost free-growing trees established at 161 trees ha^?1 to extremely dense stands at 6 809 trees ha^?1. Functions were fitted to describe stand density, dominant height and basal area development over time. The functions performed well when scrutinised for their goodness of fit. They were also found to be consistent with forest growth theory when their logical behaviour was tested over the range of planting densities.     

Defence responses in plantation‐grown Eucalyptus globulus and Eucalyptus nitens after artificial fungal inoculation

The formation of reaction and barrier zones was studied in the xylem of Eucalyptus globulus and Eucalyptus nitens tree stems after wounding and artificial inoculation with two white rot fungi. The study had two objectives: to describe host responses in Eucalyptus spp. by light microscopy and to determine whether they would differ in a fungal treatment (wounding and inoculation by one of two fungal isolates) when compared to a control treatment (wounding only). Eucalyptus globulus and E. nitens developed similar reaction and barrier zones. The E. globulus barrier zone was characterized by kino vein formation. In both hosts, the reaction zone was primarily influenced by content and distribution of living tracheids and parenchyma cells within the sapwood. By contrast, the anatomy of the barrier zone showed similarities to the basic xylem structure of each host, except for some cell types that were newly formed (sclereids, kino veins) or increased in number (parenchyma cells, tracheids). Other cell types were reduced in number or completely absent. Host response in terms of barrier zone width appeared to be greater in the fungal than control treatment. Both wood decay fungi appeared to induce a wider barrier zone in both species than that associated with non‐specific damage caused exclusively by wounding. However, the small number of replicates available for this study was possibly insufficient to provide statistical evidence for different barrier zone width between fungal and control treatments.     

Influence of age and planting density on the energy content of Eucalyptus benthamii,Eucalyptus dunnii and Eucalyptus grandis planted in Uruguay

New Forests - According to some studies, the use of forest biomass for the generation of electric power and/or heat would result in a significant reduction in the emission of greenhouse gases. This...     

连栽对巨尾桉人工林生物量和生产力的影响

对不同连栽代数的巨尾桉人工林的生物量和生产力进行研究。按径级标准木法,测定3年生不同连栽代数的巨尾桉人工林生物量,建立其估算模型,计算出3年生不同连栽代数巨尾桉人工林分的生物量和生产力。结果表明：第1,2,3代巨尾桉人工林年生物量分别为37.81,37.02,26.59 t/ hm2;林分年净生产力分别为12.60,12.34,8.86 t/（hm2·a）;干材年生产力分别为6.12,6.14,4.33 t/（hm2·a）。随着连栽代数的增加,林分的生物量和生产力下降趋势不明显,第2代林干材生产力高于第1,3代林。     

Carbon and biomass partitioning in balsam fir (Abies balsamea)

Balsam fir (Abies balsamea (L.) Mill) was extensively sampled to investigate the effects of forest management practices, site location, within-crown position, tree component (i.e., stem, foliage, branches and roots), and tree social classes on biomass and carbon (C) partitioning at the individual tree level and across ecological regions. The sites were located in three ecologically distinct forest regions of west-central New Brunswick, Canada. There were no significant differences in %C content of trees across ecological regions or across tree social classes. However, at the individual tree level, significant differences were evident in biomass and C allocation between different parts of the tree, between treatment types (i.e., unmanaged and pre-commercially thinned stands) and between within-crown positions, indicating the need for separate estimates of biomass and C content of tree components to obtain more precise estimates of quantities at the stand level. Calculating stand C content based on constant allocation values, as is commonly done, produced errors of up to 15% compared with the values calculated in this study. Three allometric equations of biomass and C that account for partitioning among different parts of the tree were developed and compared: (1) a third-order polynomial, (2) a modified inverse polynomial and (3) a modified Weibull equation. Diameter at breast height (DBH) was used as the only explanatory variable to describe fresh biomass, dry biomass and C content. All regressions derived showed a high correlation with DBH, with most r2 values > 0.95. A comparison of the equation results showed that the modified Weibull equation gave consistent results with the best overall fit and was the simplest of the three equations investigated. The regressions can be used to estimate forest biomass and tree C content at the stand level, given specific information on DBH.     

Stomatal characteristics of Eucalyptus grandis clonal hybrids in response to water stress

This study describes the stomatal response occurring during water stress and subsequent recovery of three Eucalyptus grandis clonal hybrids. The aim was to investigate the degree to which stomatal conductance (g _s) and stomatal density differ between the clonal hybrids across seasons and in response to water stress. Plants from one E. grandis × E. camaldulensis (GC) and two E. grandis × E. urophylla (GU1 and GU2) clones were grown for 18 months in 80 l planting bags. Plants were subjected to three watering treatments: control (100% field capacity), chronic water stress (maintained at 15% of field capacity) and acute water stress (cyclic water stress, where water was withheld until leaf wilting point, and a subsequent period of recovery followed). Stomatal conductance was measured after 6, 12 and 18 months growth. At 12 months of age, the recovery of g _s 1, 2 and 7 d after rewatering (following acute water stress) was further investigated. The GC hybrid showed consistently higher g _s than the GU clones at each measurement period. Stomatal conductance was 24–66% higher during winter (after 12 months growth) than during summer. The recovery of stomatal conductance from acute water stress was more rapid in the GC clone than the GU clones. Chronic water stress was shown to decrease g _s in GU clones by up to 70%, but not in the GC clone. Water stress did not affect stomatal density or size. Remarkably, stomata were absent from the adaxial leaf surface of clone GU1 leaves, but not from the leaves of the other E. urophylla hybrid cross (GU2). Total biomass of the GC clone was significantly greater at 9 months growth, but after 18 months growth the GU1 clone had attained greater biomass accumulation (although not significantly). Measurement of g _s, transpiration, stomatal density and total biomass in the GU1 clone indicated stomatal sensitivity to water stress, a favourable trait during periods of drought. The differing growth strategies of the GU and GC clones could be partially explained by their differences in stomatal sensitivity in response to water stress.     

An evaluation of the conical approximation as a generic model for estimating stem volume, biomass and nutrient content in young Eucalyptus plantations

Accurately and non-destructively quantifying the volume, mass or nutrient content of tree components is fundamental for assessing the impact of site, treatment, and climate on biomass, carbon sequestration, and nutrient uptake of a growing plantation. Typically, this has involved the application of allometric equations utilising diameter and height, but for accurate results, these equations are often specific to species, site, and silvicultural treatment. In this study, we assessed the value of incorporating a third piece of information: the height of diameter measurement. We derived a more general volume equation, based on the conical approximation, using a diameter projected to the base of the tree. Common equations were developed which allowed an accurate estimate of stem volume, dry weight and nutrient content across two key plantation grown eucalypt species, Eucalyptus grandis W. Hill ex Maiden and Eucalyptus globulus (Labill.). The conical model was developed with plantation-grown E. grandis trees ranging from 0.28 to 15.85 m in height (1.05 g to 80.3 kg stem wood dry weight), and E. globulus trees ranging from 0.10 to 34.4 m in height (stem wood dry weight from 0.48 g to 652 kg), grown under a range of contrasting cultural treatments, including spacing (E. grandis), site (E. globulus) and fertilization (nitrogen and phosphorus) for both species. With log transformed data the conical function (V_con) was closely related to stem sectional volume over bark and stem weight (R² = 0.996 and 0.990, respectively) for both E. grandis and E. globulus, and the same regressions can be applied to both species. Back transformed data compared with the original data yielded modelling efficiencies of 0.99 and 0.97, respectively. Relationships between V_con and bark dry weight differed for the two species, reflecting differing bark characteristics. Young trees with juvenile foliage had a different form of relationship to older trees with intermediate or adult foliage, the change of slope corresponding to heights about 1.5 m for E. grandis and age 1 year for E. globulus. The V_con model proved to be robust, and unlike conventional models, does not need additional parameters for estimating biomass under different cultural treatments. More than 99% of the statistical variance of the logarithm of biomass was accounted for in the model. V_con captures most of the change in stem taper associated with cultural treatments and some of the change in stem form that occurs after the crown base has lifted appreciably. Fertilization increased N and P concentrations in stem wood and bark, and regressions to estimate N and P contents (the products of biomass and concentration) were dependent on treatment. For instance, there was a large growth response to N fertilization in E. globulus corresponding with a change (P < 0.05) in the intercept of the regression to estimate N content.     

The effect of wide initial spacing on wood properties in plantation grown Eucalyptus pilularis

Eucalyptus pilularis planted at three initial stocking densities of 833, 1111 and 1,667 stems ha^?1 grown at either square or rectangular spacing was assessed for the effects of stocking and rectangularity on wood properties. Sample trees from each stocking and rectangularity combination were harvested at age 7 years and assessed for the commercially important wood properties of bow, as an indication of growth strain, shrinkage and basic density. Crown length ratio was used as an indicator of stand vigour and clear wood availability. Furthermore comment is made on the financial ramifications of wide inter-row spacing. Stocking and rectangularity significantly influenced bow but not shrinkage or basic density. Reducing within-row spacing to 2 m with a larger between-row-space of 6 m had minimal affect on wood properties. Reducing the number of rows, whilst still retaining a commercial stocking, reduces the establishment costs and increases the ease of mechanical harvesting without adversely affecting log value.     

Genetic parameter estimates for interspecific Eucalyptus hybrids and implications for hybrid breeding strategy

The Forestry Commission of Zimbabwe initiated a hybrid breeding program of Eucalyptus grandis with E. tereticornis (G × T) and E. camaldulensis (G × C) in order to provide suitable genotypes for planting in areas that are marginal for E. grandis in terms of drought and frost. A total of seven hybrid trials were established at four sites, representative of low to medium rainfall. The female parents were from E. grandis preselected for superior volume production. No pure species were included in the trials to act as controls and allow for estimation of hybrid vigour. Survival, growth and stem straightness were assessed at 18 and 43 months from planting. Survival was generally above 80% for all hybrids across sites. G × C hybrids performed better than G × T hybrids, showing a 20% difference in mean height at 43 months. Female and male variances were generally insignificant (P > 0.05) and in some cases, the estimates were 0. This was not unexpected, as the parents for the hybrids were preselected for superior height, diameter at breast height (DBH) and volume production as pure species. Ratio of dominance to phenotypic variance ( $ \hat{d}^{2} $ ) was significant for all traits for all hybrids (P < 0.05). Trait–trait dominance correlations (r _D ) at 43 months between height and DBH were generally large and positive, above 0.6. Type-B dominance correlation (r _BD ) suggested evidence of genotype-by-environment interaction (G × E), but one high elevation site contributed most to the observed G × E. If these results are confirmed in larger mating designs with progeny established on multiple sites, it seems that the most appropriate breeding strategy for E. grandis × E. tereticornis and E. grandis × E. camaldulensis hybrids may be one that exploits both additive and dominance genetic variance, such as the reciprocal recurrent selection (RRS) scheme or RRS with forward selection.     

江苏滨海盐碱地中山杉造林推广试验

报道了落羽杉属杂种－中山杉３０２和４０１两无性 江苏滨海盐碱地上的生态适应性和生长表现。造林试验初步表明，它们在其母本落羽杉和池杉不宜生长的沿海盐碱地上生长良好，是开发利用海涂广阔的土地资源，改善生态环境的优良树种。     

Root distribution of Eucalyptus grandis and Corymbia maculata in degraded saline soils of south-eastern Australia

Planting trees, in farm forestry enterprises, to control rising watertables is an increasing practice for both economic and environmental benefits. One central biophysical issue which determines the effectiveness of trees to control groundwater is the ability of trees to grow roots through degraded soils and take up groundwater. We investigated the effect of soil properties, especially the presence of shallow watertables and site preparation practice, on the vertical and horizontal distributions of Eucalyptus grandis W. Hill ex Maiden and Corymbia maculata (Hook.) K.D. Hill and L.A.S. Johnson roots. In order to improve the reliability of root data, we measured root growth and distribution by three different methods – (i) number of roots intercepting the vertical plane of the soil profile, (ii) root length density in soil cores taken at different depths but in the horizontal plane of the profile, and (iii) root length density in soil cores in the vertical plane at different radial positions from trees and compared the results. Two experimental sites were established in flood-irrigated, farm forestry plantations on contrasting soils in the Murray Riverina region of south-eastern Australia. At one site (Norwood Park), we studied a 58-month-old stand of E. grandis growing in clay loam overlaying medium clay, saline, sodic and alkaline subsoil with a saline (11.5 dS m⁻¹) watertable at 2.8 m depth. Here, there were few roots growing above the watertable. The Karawatha site had adjacent stands of 46-month old E. grandis and C. maculata growing in a sandy, neutral and non-saline soil with a shallow (3.1 m deep) non-saline (2.8 dS m⁻¹) watertable. Here roots proliferated above the watertable in both species but to a much greater extent under C. maculata than under E. grandis. Root distributions in the surface soil were similar at all sites but differences in root growth in the capillary zones paralleled differences in groundwater uptake by trees. We conclude (i) that appropriate matching of species with site characteristics, especially soil and groundwater properties, will enhance tree growth and groundwater uptake and (ii) that extensive planting of C. maculata over non-saline watertables maximises the chances of achieving the multiple objectives of regional groundwater control, fast growth rates and reduced irrigation demand.     

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.     

Interacting effects of irradiance and water stress on dry weight and biomass partitioning in Fagus sylvatica seedlings

Abstract

Actual climate models for central Europe predict prolonged summer droughts. Knowledge on how the interaction between light and water availability affects regeneration will hence be of major importance. In an experiment carried out under controlled conditions, newly emerged beech seedlings were grown in pots with sand during 54 days. Three treatments applying three different light levels (2, 9 and 43% relative light intensity) were combined with two soil water treatments (control and drought). At the end of the experiment, seedlings were separated into leaves, stem and root and the seedlings’ dry mass, leaf area and stem length was determined. Low irradiance (2%) had a strong negative effect on dry weights of seedling components, leaf area and specific leaf mass. Drought clearly affected biomass partitioning for seedlings at high irradiance levels (43%). An interaction between irradiance and drought on biomass partitioning in beech seedlings was observed at medium irradiance level (9%). Within a wide range of light levels in the forests, both light and drought may affect biomass partitioning in young seedlings.     

Growth of Eucalyptus tereticornis and Pinus caribaea at different sites in Northern Nigeria

Trial plantings of exotic tree species commenced in the northern areas of Nigeria over 20 years ago. Based on data from permanent sample plots of Eucalyptus tereticornis and Pinus caribaea, two of the promising exotic tree species tried, growth studies involving development of top height and total volume production (tvp) trends have led to the derivation of growth figures for each of the species.The results showed that, on an average site for E. tereticornis with a top height of 24.8m at a reference age of 15 years, a tvp of about 286 m³/ha at the peak of mai (age 19) could be obtained, while for an average site for P. caribaea, with a top height of 23.4m at age 20, a tvp of about 726 m³/ha at the peak of mai (age 30) could be obtained. The growth figures, which were compared with those obtained in other countries, are discussed in relation to the management of the species.