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The Eucalyptus genus is extensively planted in Brazil for industrial use, and with the expansion of forest frontiers and climate changes, studies are needed on how these changes affect wood density (WD). The aim of this study was to evaluate the effect of some climate variables on WD of an Eucalyptus urophylla clone for a 4-5 year period. WD from trees collected in 12 sites were evaluated. Five growth rings were identified using a magnifying glass, X-ray densitometry, and forest inventory. WD was correlated with temperature (T), precipitation (P), soil water deficit, ring width, and current annual increment. There was no variation in WD in the first 20 months among sites. From that age on, WD was mainly correlated with T (r > 0.6). The 1 [degrees]C increase in T resulted in a WD reduction of 0.014 g [cm.sup.-1], and increases of 10 [m.sup.-3] [ha.sup.-1] in the final volume were related to an increase of 0.004 g [cm.sup.-1] in WD. Researchers and managers should continue to put efforts into broad experimental networks to assess the effects of climate change on the adaptation and wood quality of Eucalyptus clones. Highlights The influence of climate on E. urophylla wood density was greater after the third year of growth. The mean air temperature was the best correlated climatic variable with E. urophylla wood density. The cross-site climatic gradient was more important in wood density variation of E. urophylla than the variability among the years. Key words: wood quality, climate conditions, annual growth, densitometry, forest expansion, 1. Introduction Plant secondary (radial) growth is a dynamic process and related to external factors such as climate and soil (Pillai et al. 2013; Zhang et al. 2014; Mendivelso et [...]

Environmental conditions can change both the quantity and quality of wood formation. This study aimed to evaluate anatomical and chemical changes in the wood of a Eucalyptus urophylla S.T. Blake clone cultivated in four sites of wide climatic conditions in Brazil. Radial samples were used to evaluate xylem anatomy along the growth cycles. Samples with a quarter of a disk were used to perform chemical analyses of extractives, total lignin (LG), syringyl/guaiacyl (S/G), holocellulose, and elemental analysis of wood. The elements Na, K, Ca, Mg, P, Mn, Fe, Zn, Ni, Cu, Cr, Cd, F, and Cl were also quantified. Correlations using the mean values of the variables per site were higher than those using values per tree growth cycle (years). Mean annual air temperature showed the highest correlations with wood density (r = -0.89) and the anatomical characteristics (vessel area: r = - 0.68; fiber wall thickness: r = -0.70; vessel frequency: r = 0.74; and fiber lumen diameter: r = 0.90). Only LG and S/G showed significant correlations with the meteorological variables, with drier sites presenting a higher S/G. The anatomical characteristics change with regionwide climate features, while wood chemical characteristics showed weaker relations with climatic variations. Key words: wood anatomy, wood chemistry, eucalyptus plantations, climate variables, growth rings. Les conditions environnementales peuvent changer la quantite et la qualite de la formation du bois. Par consequent, la presente etude visait a evaluer les changements anatomiques et chimiques du bois du clone de l'Eucalyptus urophylla S.T. Blake cultive dans quatre sites de conditions climatiques variees au Bresil. Des echantillons radiaux ont ete utilises pour evaluer l'anatomie du xyleme tout au long des cycles de croissance. Des echantillons avec le quart d'un disque ont ete utilises pour effectuer les analyses chimiques : matieres extractibles, lignine (LG) total, syringyl/guaiacyl (S/G), holocellulose et analyse elementaire du bois. Les elements Na, K, Ca, Mg, P, Mn, Fe, Zn, Ni, Cu, Cr, Cd, F et Cl ont egalement ete quantifies. Les correlations utilisant les valeurs moyennes des variables par site etaient plus elevees que celles utilisant les valeurs par cycle de croissance de l'arbre (annees). La temperature annuelle moyenne de l'air a presente les correlations les plus elevees avec la densite du bois (r = -0,89) et les caracteristiques anatomiques (zone du vaisseau : r = -0,68, epaisseur de la paroi vegetale : r = - 0,70, frequence du vaisseau : r = 0,74 et diametre de la lumiere des fibres : r = 0,90). Seuls le LG et les S/G ont presente des correlations importantes avec les variables meteorologiques, les sites plus secs presentant des S/G plus eleves. Les caracteristiques anatomiques changent avec les caracteristiques climatiques regionales alors que les caracteristiques des substances chimiques des arbres ont presente des relations plus faibles avec les variations climatiques. [Traduit par la Redaction] Mots-cles: anatomie du bois, xylochimie, plantations d'eucalyptus, variables climatiques, anneaux de croissance., Introduction Wood formation is a dynamic and continuous process regulated by genetic, environmental, and management factors (Zhang et al. 2014). Wood contains a permanent record of genotype x environment interactions [...]

The extent of the potassium (K) limitation of forest productivity is probably more widespread than previously thought, and K-limitation could influence the response of forests to future global changes. To understand the effects of K-limitation on forest primary production, we have developed the first ecophysiological model simulating the K cycle and its interactions with the carbon (C) and water cycles. We focused on the limitation of the gross primary productivity (GPP) by K availability in tropical eucalypt plantations in Brazil. We used results from large-scale fertilisation experiments as well as C flux measurements in two tropical eucalypt plantations to parameterize the model. The model was parameterized for fertilised conditions and then used to test for the effects of contrasting additions of K fertiliser. Simulations showed that K-deficiency limits GPP by more than 50 % during a 6-year rotation, a value in agreement with the literature. The negative effects of K-deficiency on canopy transpiration and water use efficiency were also reported and discussed. Through a sensitivity analysis, we used the model to identify the most critical processes to consider when studying K-limitation of GPP. The external inputs of K to the stands, such as the atmospheric deposition and weathering fluxes, and the regulation of the internal fluxes of K within the ecosystem were critical for the response of the system to K deficiency. Litter decomposition processes were of lower importance. The new forest K-cycle model developed in the present study includes multiple K processes interacting with the carbon and water cycles, and strong feedbacks on GPP through forest growth were outlined. [ABSTRACT FROM AUTHOR]

Background: Compatible taper and volume equations are key for traditional growth and yield and current process-based or hybrid models. However, most equations do not consider variables such as genotype, water regime and their interaction, limiting the development of general equations for species or regions. Our research investigated taper and individual tree volume equations for eight Eucalyptus genotypes (E. nitens, E. badjensis, E. smithii, E. camaldulensis x globulus and two varieties of low and high productivity of E. globulus and E. nitens x globulus), all materials are growing under summer irrigated vs. no irrigated conditions. Methods: A 7-year old Eucalyptus plantation experiment was sampled considering four representative trees per genotype x water regime combination treatment. Four non-linear taper equations were evaluated: Kozak (2004), Kozak et al. (1969), Ormerod (1973) and Max and Burkhart (1976). In addition, total and merchantable volume was evaluated with the Schumacher and Hall (1933) equation. The effect of genotype, irrigation regime and interaction were evaluated for each equation. Then, the best taper equation was selected from adjusted coefficient of determination, mean square error, and AIC and BIC parameters. Finally, the validation of evaluations was carried out with the Leave-One-Out Jackknife method. Results: Genotype, irrigation regime, or the interaction were not statistically significant for all evaluated taper - volume equations and a generalised model equation was obtained. The best taper equation was Kozak (2004) which showed the best fit and adaptation to irregular boles. Regarding volume equations, all showed a trend to underestimate volume (total and merchantable) in trees with a volume greater than 0.22 m³. Validation of the equations showed reduced bias suggesting that the equations can be used to predict taper and volume regardless of Eucalyptus genotype x irrigation regimen combinations. Conclusions: Our results suggest a negligible or minor effect of irrigation (water resource availability) and genotype (for tested taxas and genotypes) on taper and individual tree volume equations. A generalised taper and volume equation (total and merchantable) may be used for all tested genotypes, regardless of water regime (site water availability). This generalised model would simplify Eucalyptus estimates required for stand management and projection. [ABSTRACT FROM AUTHOR]