Assessment of crown woody biomass in <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> and <Emphasis Type="Italic">E. globulus</Emphasis> plantations

Young trees were harvested to explore non-destructive methodologies to estimate live branch dry weights in young fast-growing Eucalyptus species under different spacing and fertilizer treatments. Branch growth can vary with silvicultural management such as spacing, fertilizing and thinning, and over relatively short periods in response to environmental conditions. Many published regressions based on standard measurements of height and diameter are site, age and treatment specific. The aim of this study was to improve our capacity to predict woody crown dry weight, based on stem measurements, and to minimize (or eliminate) treatment effects on the resulting model. In young trees, branches are temporary support structures for foliage and are often discarded as the base of the green crown rises. As temporary structures they represent an investment of biomass and nutrient elements, and are subject to selection pressures to maximize the return on investment by the tree. Trees were harvested from existing plantation experiments located in south-eastern Queensland for E. grandis W. Hill ex Maiden (ranging from 0.28 to 15.85 m in height, to 5 years old) and south-western Australia for E. globulus Labill. (0.10–34.4 m in height, to 10.2 years) in order to examine the impact of spacing, nitrogen and phosphorus fertilization on early growth. Relationships to estimate crown woody biomass from non-destructive measurements were developed, and these relationships tended to have different slopes and intercepts for trees with predominantly juvenile foliage and those with intermediate or adult foliage. Dry weight of whole-crown live branch wood (W_branch) was related to heights and/or diameter at breast height (D_BH), but the regressions parameters were different, depending on treatment. The relationships became more generic (i.e. less dependent on treatment effects) between W_branch and stem sectional area at the height of the base of the green crown (SA_CB), consistent with the pipe model theory (R² > 0.91 for the two species for trees with intermediate/adult leaves). However, W_branch was more closely related again to the stem volume above the base of the green crown and treatment effects were not significant (V_Con,gc, R² > 0.93). Branches exit the stem below the green crown, and for E. grandis the best relationship was on stem volume above the lowest live branch (V_Con,llb, R² 0.94). Limited sampling from four other species with similar or contrasting crown characteristics indicated that the relationship could be applied quite generally. Individual E. grandis branch woody dry weight was closely related to the conical volume of the main (first order) branch (V_con,br, R² 0.98₎. The whole crown equivalent, branch woody dry weight plus stem dry weight above the lowest live branch, was also closely related to the stem volume within the woody crown (V_Con,llb, R² 0.97–0.99). While the slope of this relationship was still significantly different between trees with juvenile and intermediate/adult foliage, it had a similar form, suggesting that trees with juvenile foliage allocated a different proportion of their woody biomass within the crown to branches than older trees.     

Chloride content and biomass partitioning in Eucalyptus hybrids grown on saline sites

Eucalyptus camaldulensis × globulus and E. camaldulensis × grandis hybrids have been developed to combine the salt–waterlogging tolerance and high-quality wood fibre of their respective parents. The aim is to develop trees that will grow in relatively dry and/or saline environments and provide commercial wood products. Previous studies indicate that the hybrids exhibit faster growth than either of their pure species parents, and that there are significant differences in growth rates between them. We undertook a comparative study of the partitioning of above-ground biomass (AGB) to examine biomass and chloride (Cl) allocation of trees growing on two saline-irrigated sites in south-eastern Australia. Eucalyptus camaldulensis × globulus had a higher proportion of AGB in leaves (20–29% cf. 15–16%), and lower proportion in live branches (3–10% cf. 6–14%) than E. camaldulensis × grandis. The concentration of Cl was highest in the stembark (4.2–9.6 g kg⁻¹) and lowest in the stemwood (0.6–2.0 g kg⁻¹), suggesting that trees can export Cl through bark shedding. Total Cl content was strongly related to volume under bark (R² = 0.99), and differences in partitioning of Cl into tree components differed between the hybrids in the same way as AGB. Preferential partitioning of Cl to live branches rather than foliage in E. camaldulensis × grandis suggests that this hybrid may be compartmentalising Cl to reduce the risk of Cl toxicity in the leaves.     

Aboveground nutrient components of Eucalyptus camaldulensis and E. grandis in semiarid Brazil under the nature and the mycorrhizal inoculation conditions

A study was conducted to evaluate the aboveground biomass, nutrient content and the percentages of mycorrhizal colonization in Eucalyptus camaldulensis and Eucalyptus grandis plantations in the semiarid region (15° 09′ S 43° 49′ W) in the north of the State of Minas Gerais in Brazil. Results show that the total above-ground biomass (dry matter) was 33.6 Mg·ha⁻¹ for E. camaldulensis and 53.1 Mg·ha⁻¹ for E. grandis. The biomass of the stem wood, leaves, branches, and stem bark for E. camaldulensis accounted for 64.4%, 19.6%, 15.4%, and 0.6% of the total biomass, respectively (Table 2); meanwhile a similar partition of the total above-ground biomass was also found for E. grandis. The dry matter of leaves and branches of E. camaldulensis accounted for 35% of total biomass, and the contents of N, P, K, Ca, Mg, and S in leaves and branches accounted for 15.5%, 0.7%, 12.3%, 22.6%, 1.9%, and 1.4% of those in total above-ground biomass, respectively. In the trunk (bark and wood), nutrient accumulation in general was lower. Nutrient content of E. grandis presented little variation compared with that of E. camaldulensis. Wood localized in superior parts of trunk presented a higher concentration of P and bark contained significant amounts of nutrients, especially in E. grandis. This indicated that leaving vegetal waste is of importance on the site in reducing the loss of tree productivity in this semi-arid region. The two species showed mycotrophy.     

Biomass equations for selected drought-tolerant eucalypts in South Africa

In the water-scarce environment of South Africa, drought-tolerant eucalypt species have the potential to contribute to the timber and biomass resource. Biomass functions are a necessary prerequisite to predict yield and carbon sequestration. In this study preliminary biomass models for Eucalyptus cladocalyx, E. gomphocephala and E. grandis · E. camaldulensis from the dry West Coast of South Africa were developed. The study was based on 33 trees, which were destructively sampled for biomass components (branchwood, stems, bark and foliage). Simultaneous regression equations based on seemingly unrelated regression were fitted to estimate biomass while ensuring additivity. Models were of the classical allometric form, ln(Y) = a+x₁ln(dbh)+x₂ln(h), of which the best models explained between 70% and 98% of the variation of the predicted biomass quantities. A general model for the pooled data of all species showed a good fit as well as robust model behaviour. The average biomass proportions of the stemwood, bark, branches and foliage were 60%, 6%, 29% and 5%, respectively.     

Genetic control of wood density and bark thickness,and their correlations with diameter,in pure and hybrid populations of Eucalyptus grandis and E. urophylla in South Africa

Tree diameter under and over bark at breast height (dbh), wood density and bark thickness were assessed on samples from control-pollinated families of Eucalyptus grandis, E. urophylla, E. grandis × E. urophylla and E. urophylla × E. grandis. The material was planted in field trials in the coastal Zululand region of South Africa. At 75 months, between three and seven of the best trees per family were felled and wood samples collected. Genetic parameters for wood density, bark thickness and bark percentage (ratio of double bark thickness to overbark diameter) and the inter-trait correlations for the different species and hybrids were calculated. Genetic parameter estimates for wood density, bark thickness and bark percentage in the E. urophylla × E. grandis hybrids showed these traits to be under total additive genetic control. This was confirmed by the intermediate hybrid means for these traits relative to those of the parental species. There was a very low correlation between dbh and wood density for the E. urophylla × E. grandis hybrids (r_G = –0.07 and r_P = 0.064). Amongst the E. urophylla families there was a moderate positive and significant phenotypic correlation between wood density and bark thickness (r_P = 0.391), and between wood density and bark percentage (r_P = 0.442).     

Functions for Biomass Estimation of Young Pinus sylvestris,Picea abies and Betula spp. from Stands in Northern Sweden with High Stand Densities

New silvicultural regimes with high within-stand competition require new functions for estimation of standing stock and growth of biomass components, since the allometry of trees is changed by light competition. This paper presents functions for estimation of the aboveground biomass dry weights for stem wood, stem bark, branches and leaves of young (diameter at breast height <10 cm) Scots pine (Pinus sylvestris L.), Norway spruce [Picea abies (L.) Karst.] and birch (Betula pendula Roth. and Betula pubescens Ehrh.) trees growing in dense mixed stands. The functions were derived from a sample consisting of 84 Scots pine, 43 Norway spruce and 66 birch trees from six stands in northern Sweden with high stand densities (>10000 st ha^-1). The logarithmically transformed power function displayed a good ability to stabilize the variance of dry weights and showed a good fit to the material (0.37< R ² <0.99). A comparison with the most commonly used biomass functions in Sweden today showed that they overestimated the weight of stem wood and branches, while the weight of foliage was underestimated. The nature of these discrepancies suggested that the precision of biomass estimations might also be improved for young trees at wider spacing.     

Calibration and Uncertainty Analysis of a Carbon Accounting Model to Stem Wood Density and Partitioning of Biomass for Eucalyptus globulus and Pinus Radiata

There is a need to calibrate models for carbon accounting in forest systems if they are to be applied for carbon trading and off-set schemes. One such model, Full Carbon Accounting Model (FullCAM), calculates stem mass by taking annual inputs of tree growth in stem volume and multiplying these by basic stem wood density. Stem mass is then multiplied by user-entered coefficients to determine the mass of other tree components. Using datasets of Pinus radiata and Eucalyptus globulus that comprised of between 73 and 187 observations, we determined empirical relationships that can be used in FullCAM to relate basic stem wood density to stand age, and masses of bark, foliage or branches to mass of stem wood for these two species. All fitted relationships were highly significant (p < 0.001), explaining between 35 and 89% of the variance. These calibrations were then tested using three case studies where data on volume yield curves and repeated measures of biomass of stand components were available: one of P. radiata and two of E. globulus. Although accumulation of biomass in foliage and branches were not well predicted by the model, sensitivity analysis showed that this was relatively unimportant to total carbon storage because of the dominance of the stem, particularly once the stand is older than 5 years. Indeed, FullCAM accounted for 99% of the variance in measured above-ground biomass at all three sites because calibrations for the mass of stem was reasonably well constrained. Uncertainty analysis showed that despite the standard errors of parameters used in relationships for basic density and biomass partitioning, and for estimates of carbon contents of tree components, we can be 95% confident that sequestration of carbon in trees and debris of Pinus radiata and Eucalyptus globulus plantations are, on average, within 13% of that predicted by FullCAM. Ensis is a joint venture between CSIRO FFP P/L and Scion Australasia P/L     

The long‐term survival of Phytophthora cinnamomi in mature Banksia grandis killed by the pathogen

The ability of Phytophthora cinnamomi to survive long dry periods is the key to its persistence in the south‐west of Western Australia. It has been proposed that dead Banksia grandis are a significant long‐term reservoir for P. cinnamomi inoculum. To test this, 36 healthy B. grandis trees were inoculated in April 1999, and the presence of viable propagules in planta was determined between 2 and 34 months after tree death. By 10 months after inoculation, 75% of the trees had died, with the remaining seven trees dying by 22 months. The pathogen was more commonly recovered from bark than from wood, except from those trees that died at 22 months, and more commonly from above‐ground trunks than below‐ground trunks and roots until 8 months after plant death. In trees that died 12 months after inoculation, P. cinnamomi was recovered from 60% of trunk and root core samples at 3 months, declining to 33% at 10 months, 5.5% at 12 months and 0.1% at 34 months after tree death. In trees that died at 22 months, P. cinnamomi was recovered from 87% of trunk and root samples 2 months after tree death, decreasing to 0.5% by 33 months. This study suggests that the pathogen does not have a saprotrophic phase within dead B. grandis tissue, and B. grandis is unlikely to be a long‐term reservoir for P. cinnamomi. However, the manipulation of the density of B. grandis and the use of fire to facilitate the breakdown of dead Banksia trunks in the Eucalyptus marginata (jarrah) forest may reduce the spread and impact of P. cinnamomi.     

Performance of eight tree species in the highland Vertisols of central Ethiopia: growth, foliage nutrient concentration and effect on soil chemical properties

The coverage of trees in the highland Vertisol areas of Ethiopia is very scarce. A tree screening trial was conducted from 1997 to 2002 in Ginchi (central Ethiopia) to select fast growing and high biomass producing tree species; evaluate foliage macronutrient concentration of different tree species; and assess effects of trees on soil chemical properties beneath their canopies. Acacia decurrens Willd, A. mearnsii De Wild and Eucalyptus globulus Labill attained the highest height growth at 64 months as compared to other indigenous and exotic species. E. globulus provided better height increment from 24 to 36 and 36 to 64 months than other tree and shrub species. Acacia mearnssi and A. saligna Labill Wendl produced high biomass at 40 and 64 months. Differences between the highest and lowest dry biomass at 12, 40 and 64 months were 1.13, 29.19 and 38.89 kg tree⁻¹, respectively. None of the tree species resulted in a foliage to stem biomass ratio of >0.98 at 40 and 64 months. Sesbania sesban (L.) Merr had high N and P concentrations in its foliages and stems at 12 and 40 months. Total N under Acacia abyssinica Hochst. Ex Benth, A.␣saligna and S. sesban was slightly greater at 40 months than 12 months.     

Mixed-species plantations of Acacia mangium and Eucalyptus grandis in Brazil: 2: Nitrogen accumulation in the stands and biological N2 fixation

The sustainability of plantation forests is closely dependent on soil nitrogen availability in short-rotation forests established on low-fertility soils. Planting an understorey of nitrogen-fixing trees might be an attractive option for maintaining the N fertility of soils. The development of mono-specific stands of Acacia mangium (100A:0E) and Eucalyptus grandis (0A:100E) was compared with mixed-species plantations, where A. mangium was planted in a mixture at a density of 50% of that of E. grandis (50A:100E). N₂ fixation by A. mangium was quantified in 100A:0E and 50A:100E at age 18 and 30 months by the ¹⁵N natural abundance method and in 50A:100E at age 30 months by the ¹⁵N dilution method. The consistency of results obtained by isotopic methods was checked against observations of nodulation, Specific Acetylene Reduction Activity (SARA), as well as the dynamics of N accumulation within both species. The different tree components (leaves, branches, stems, stumps, coarse roots, medium-sized roots and fine roots) were sampled on 5–10 trees per species for each age. Litter fall was assessed up to 30 months after planting and used to estimate fine root mortality. Higher N concentrations in A. mangium tree components than in E. grandis might be a result of N₂ fixation. However, no evidence of N transfer from A. mangium to E. grandis was found. SARA values were not significantly different in 100A:0E and 50A:100E but the biomass of nodules was 20–30 times higher in 100A:0E than in 50A:100E. At age 18 months, higher δ¹⁵N values found in A. mangium tree components than in E. grandis components prevented reliable estimations of the percentage of N derived from atmospheric fixation (%Ndfa). At age 30 months, %Ndfa estimated by natural abundance and by ¹⁵N dilution amounted to 10–20 and 60%, respectively. The amount of N derived from N₂ fixation in the standing biomass was estimated at 62 kg N ha⁻¹ in 100A:0E and 3 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 16 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The total amount of atmospheric N₂ fixed since planting (including fine root mortality and litter fall) was estimated at 66 kg N ha⁻¹ in 100A:0E and 7 kg N ha⁻¹ in 50A:100E by the ¹⁵N natural abundance method, and 31 kg N ha⁻¹ in 50A:100E by the ¹⁵N dilution method. The most reliable estimation of N₂ fixation was likely to be achieved using the ¹⁵N dilution method and sampling the whole plant.     

First report of Teratosphaeria gauchensis causing stem canker of Eucalyptus in Kenya

Teratosphaeria stem canker is an important disease of Eucalyptus species in many parts of the world where these trees are intensively propagated in plantations. Symptoms similar to those of Teratosphaeria stem canker were observed on Eucalyptus grandis and a E. grandis × E. camaldulensis hybrid clone in the Central Highlands of Kenya. Symptomatic bark samples were collected from two sites and the associated fungus isolated and identified using DNA sequence analyses of multiple gene regions. The pathogen was identified as Teratosphaeria gauchensis. This represents the first report of the disease and the pathogen in Kenya.     

Assessment of leaf mass and leaf area of tree crowns in young Eucalyptus grandis and E. globulus plantations from measurements made on the stems

Leaf area is a key driver of growth models and leaf weight is important for studying carbon and nutrient cycling in forestry. Both can change over relatively short intervals in young plantations in response to silvicultural treatments and climatic conditions. Relationships to estimate leaf dry weight and leaf area of young Eucalyptus grandis W. Hill ex Maiden and Eucalyptus globulus (Labill.) were developed from harvested trees ranging from 0.28 to 15.85 m and 0.12 to 34.4 m in height respectively. Trees were harvested from existing experiments in south-eastern Queensland and south-west Western Australia in order to assess the effects of spacing and application of nitrogen and phosphorus fertilizer on early plantation growth. A range of tree measurements were taken to determine the most efficient way to monitor the performance of young plantation eucalyptus. Leaf weight (W_leaf, kg) and leaf area (m²) were related to stem cross sectional area at the height of the base of the green crown (SA_CB), but the slope and intercept of the relationship differed for trees with predominantly juvenile foliage and those with predominantly intermediate or adult foliage. Specific leaf area (m² kg^?2) changed as the trees aged and leaf area was more closely related to the size of the support structure, represented by the stem volume within the green crown, approximated by the volume of a cone above the base of the green crown (V_C,gc). Significantly, the relationships also applied to individual branches, that is, leaf weight was related to sectional area near the base of the branch (SA_b) and leaf area to the volume of the main (first order) branch (V_C,br). Most of the published work has been directed at trees of commercial size or to small trees in pot experiments, much less to small trees in the establishment phase of growth of interest to experimenters and managers looking at early intervention. This study provides a mechanism to directly assess canopies of intermediate size trees which are of interest for assessing treatment effects or early intervention for managers.     

Susceptibility of Eucalyptus grandis and Acacia mearnsii seedlings to five Phytophthora species common in South African plantations

Eucalyptus grandis and its hybrids, as well as Acacia mearnsii, are important non‐native trees commonly propagated for forestry purposes in South Africa. In this study, we conducted pathogenicity trials to assess the relative importance of five commonly isolated Phytophthora spp. (Phytophthora alticola, P. cinnamomi, P. frigida, P. multivora and P. nicotianae) from the plantation environment on E. grandis and A. mearnsii seedlings. Overall E. grandis was more susceptible to the tested Phytophthora spp. than A. mearnsii. Phytophthora cinnamomi was the only pathogen that had a significant negative effect on both the host tree species, leading to a reduction in root and shoot weight as well as to death in the case of E. grandis. Phytophthora alticola and P. nicotianae exclusively affected E. grandis and A. mearnsii, respectively. This study updated the current knowledge on the pathogenicity of Phytophthora spp. on two important non‐native commercially propagated tree species from South Africa.     

Weeds in <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> subsp. <Emphasis Type="Italic">maidenii</Emphasis> (F. Muell) establishment: effects of competition on sapling growth and survivorship

The effect of herbaceous vegetation on growth and survival was assessed in planted eucalyptus saplings grown under four levels of weed cover. Seedlings of Eucalyptus globulus subsp. maidenii were planted with 0 (W0), 25 (W25), 50 (W50) and 100% (W100) weed cover. Weed species composition and aboveground biomass was determined. Soil water content was evaluated by the gravimetric method. Seedling leaf area, diameter and height were evaluated at planting and during the 3 months following establishment. Tree height, diameter and stem volume was estimated at 12, 24 and 36 months. First year tree survival was recorded. The ratio of cumulative stem growth under W100: cumulative stem growth under W0 was used to measure competitive performance. Regression analysis was used to determine competition thresholds. Weeds seriously threaten the growth of E. globulus subsp. maidenii. Early negative effects of competition on growth were evident as from the second month after establishment, and both seedlings and 1-year-old saplings were more affected than 2- and 3-year-old ones. A “minimum-response threshold” was determined near 500 kg/ha (corresponding to W25 cover). No clear effect was found between sapling survival and weed biomass.     

Integrated individual tree biomass simultaneous equations for two larch species in northeastern and northern China

Forest biomass estimation at large scale has become an important topic in the background of facing global climate change, and it is fundamental to develop individual tree biomass equations suitable for large-scale estimation. Based on the measured data of biomass components and stem volume from 100 sample trees of two larch species (Larix gmelinii and L. principis-rupprechtii) in northeastern and northern China, an integrated equation system including individual tree biomass equations, stem volume equation and height–diameter regression model were constructed using the dummy variable model and error-in-variable simultaneous equations. In the system, all the parameters of equations were estimated simultaneously, so that the aboveground biomass equation was compatible to stem volume equation and biomass conversion factor (B_CF) function; the belowground biomass equation was compatible to root-to-shoot ratio (R_SR) function; and stem wood, stem bark, branch and foliage biomass equations were additive to aboveground biomass equation. In addition, the system also ensured the compatibility between one- and two-variable models. The results showed that: (1) whether aboveground biomass equations or belowground biomass equations and stem volume equations, the estimates for larch in northeastern China were greater than those in northern China; (2) B_CF of a larch tree decreased with the growing diameter while R_SR increased with the growing diameter; (3) the proportion of stem wood biomass to aboveground biomass increased with the growing diameter while those of stem bark, branch, and foliage biomass decreased.     

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties; II. Fibre length and coarseness

Within-tree variation in fibre length and coarseness was studied in fifty trees of E. globulus and E. nitens to develop a non-destructive sampling strategy. Trees, aged 5 to 9 years, were sampled across a range of sites in southern Australia. Simulated core samples were removed at six fixed heights easily accessible from the ground (0.5, 0.7, ... 1.5 m) and at eight percentage heights (0, 10, 20, ... 70%). Whole-tree values, calculated from percentage height data, were correlated with the core data to determine the optimal sampling height. Core samples were found to be reliable predictors of whole-tree fibre length, but results were variable for fibre coarseness. Simulated cores taken from the recommended sampling heights explained 87% and 71% of variation in whole-tree fibre length for E. globulus and E. nitens respectively and 54% and 45% of the variation in whole-tree fibre coarseness. Fibre length at all fixed heights showed good correlations with whole-tree values at all sites for E. globulus. For E. nitens the correlations were slightly lower and variable across sites. Results for fibre coarseness varied across sampling heights and sites for both species. The recommended sampling height for fibre length is 1.5 m for both species, whilst for fibre coarseness, the recommended sampling heights are 0.9 and 1.1 m for E. globulus, and 0.9 and 1.3 m for E. nitens. Radial orientation of cores was not important and neither fibre length nor coarseness were related to tree size or basic density. To estimate stand mean fibre length to an accuracy of ±5% would require sampling 9 whole trees or taking cores from 13 trees for E. globulus and 4 whole trees or cores from 8 trees for E. nitens. For estimating stand mean fibre coarseness, 10 whole trees of E. globulus and 7 whole trees are needed for E. nitens. Core sampling for stand mean coarseness would require more trees: 13 to 21 for E. globulus and 11 to 16 trees for E. nitens. Received 17 September 1998     

First report of Teratosphaeria zuluensis causing stem canker of Eucalyptus grandis in Uganda

Teratosphaeria stem canker is one of the most important diseases to have emerged on non‐native plantation‐grown Eucalyptus trees globally. In 2012, Eucalyptus grandis trees with typical Teratosphaeria stem canker symptoms were observed in Uganda. Multigene sequence analyses of isolates from these cankers led to the identification of T. gauchensis, previously recorded in Uganda, and T. zuluensis. This study represents the first report of T. zuluensis in Uganda. Furthermore, this is the first report of the co‐occurrence of T. zuluensis and T. gauchensis in a single area.     

Biomass production and potential water stress increase with planting density in four highly productive clonal Eucalyptus genotypes§

The choice of planting density and tree genotype are basic decisions when establishing a forest stand. Understanding the interaction between planting density and genotype, and their relationship with biomass production and potential water stress, is crucial as forest managers are faced with a changing climate. However, few studies have investigated this relationship, especially in areas with highly productive forests. This study aimed to determine the interaction between biomass production and leaf water potential, as a surrogate of potential water stress, in different clonal Eucalyptus genotypes across a range of planting densities. Four clones (two clones of E. urophylla × E. grandis, one clone of E. urophylla, and one clone of E. grandis × E. camaldulensis) and four planting densities (ranging from 591 to 2 949 trees ha^?1) were evaluated in an experimental stand in south-eastern Brazil. Biomass production was estimated 2.5 years after planting and predawn (ψ_pd) and midday (ψ_md) leaf water potential were measured 2 and 2.5 years after planting, in February (wet season) and August (dry season) in 2014. For all clones, total stand stemwood biomass production increased and leaf water potential decreased with planting density, and their interaction was significant. Thus, wood biomass at tighter spacings was higher but exhibited lower leaf water potentials, resulting in a trade-off between productivity and potential water stress. These are preliminary findings and still need to be supported by more experimental evidence and repetitions. However, in light of the increased frequency of extreme climate events, silvicultural practices that are tailored to the potential productivity of each region and that result in low potential water stress should be considered.     

新疆杨元素含量与生物量研究

新疆杨(Populus bolleana Lauche)在我国新疆栽培最早,尤以和田、喀什地区生长最好。青海、甘肃、宁夏亦早有栽培,近十余年在陕西、内蒙、山西、辽宁、吉林诸省和北京市也有引种,是我国干旱、半干旱地区农田防护林及人工丰产林的优良树种。为进一步利用新疆杨资源,研究其生物量将具有实际应用价值。     

Combining empirical models and the process-based model 3-PG to predict Eucalyptus nitens plantations growth in Spain

Empirical, statistically based models were used to describe the growth and development of Eucalyptus nitens plantations for a range of site productivities and the standard biomass and pulp silvicultural regime currently applied in Northern Spain. The results obtained, along with data gathered from a network of 68 plots, 48 trees felled for biomass estimations and 73 trees sampled for foliar area estimation were used to parameterize the 3-PG model for this species in Northern Spain. Most parameters associated with allometric relationships and partitioning (i.e. bark and branch fraction, basic density, age modifier and mortality) were derived from local data, and the remaining parameters were obtained from published studies on E. nitens or default values previously used for E. globulus. The parameterized model was validated with data from three trials measured from age 3 years until age 8-14 years, and performed better than the empirical model in terms of total stand under bark volume, mean diameter at breast height, basal area and foliar biomass. The process-based model was then used to forecast changes in plantations subjected to a clearwood regime, initializing the model at age 3 years, considering 3 prunings, 2 thinnings and lengthening the rotation to 18 years. This integrated regime was able to provide biomass for bioenergy, pulp or fibreboard wood and also solid wood, with thinning operations assisting the financial viability, and was a potentially good alternative for productive sites.