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The chemical structure of dioxane lignins isolated from two groups of Eucalyptus globulus genotypes with contrasting pulpwood characteristics were evaluated. Six genotypes were selected and separated in two groups (G1 and G2) based on differences in wood density, pulp yield and chemical characteristics. Lignin was isolated from both milled wood and kraft pulps produced at kappa number 16, and were characterized by different techniques such as FTIR, elemental analysis, molar mass distribution and 31P NMR spectroscopy. From the different characteristics evaluated, some were determined as more relevant, such as syringyl (S) and guaiacyl (G) amounts, S/G ratio and condensed biphenyl units, were correlated with the pulp yield. High correlations were found between pulp yield and syringyl units (R² = 0,69), and pulp yield and syringyl/guaicyl ratio (R² = 0,88). The condensed 5-5 biphenyl units presented a negative correlation with pulp yield (R² = 0,76). The information obtained explained part of the difference in pulpability of the contrasting genotypes and can be used for the selection and improvement of the species for the pulp and paper industry.

Forest structure and function are subject to risks of growth declines from intensified drought and frequent extreme events related to climate warming. Knowledge of tree growth declines will help anticipate future responses of forests to climate change. In this study, we investigated tree growth declines over the last four centuries in a juniper forest on the eastern Tibetan Plateau. By analyzing the radial growth trajectories of individual trees, we identified two events of intense growth decline, one in 1817–1830 and the other in 1969–1999 over the past four centuries. The intensity of the recent decline was unprecedented in the period under study. Ring-width chronology showed a positive correlation with self-calibrating Palmer Drought Severity Indices and a negative correlation with mean monthly temperatures in May and June. The recent intensified growth decline may have been due to temperature-induced frequent droughts in the study area. Our findings suggest that trees in this juniper forest may face a higher risk of growth decline and even mortality under continued climate warming.

The aim of study was to determine the effects of grain direction on the lateral nail strength and thermal conductivity of structural plywood panels. Experiment were made with plywood manufactured from Scots pine, maritime pine and black pine. A rotary peeler with a maximum horizontal holding capacity of 80 cm was used for veneer manufacturing. The highest values of max load (2,17 kN), stiffness (2,52 kN/ mm) and displacement at ultimate load (36,8 mm) were obtained from C1PR group panels manufactured from black pine. Also, it was determined the mechanical properties in perpendicular to grain were higher than those in parallel to grain. The black pine panels gave highest average thermal conductivity value (0,168 W/mK), while that of Scots pine was lowest (0,145 W/mK). Thermal conductivity of panels in perpendicular to the grain of main axis of plywood was always found to be higher than the values obtained from measurements parallel to the grain.

Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regeneration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 individual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater (359%) in forest gaps than on the closed-canopy forest floor. The regeneration density in gaps of plantation forests was significantly greater (P < 0.05) than that of natural forest because the regeneration in gaps of plantation forests was improved by both gap effects and experimental measures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a significantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and precipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management.

The present paper reports the results of an investigation regarding the determination of bending strength and stiffness in specimens of laminated veneer lumber (LVL) manufactured from Argentinean Eucalyptus grandis and tested edgewise according to European standards. For this purpose an empirical research project with one sample containing 44 specimens with nominal sizes of 24.3 mm in width, 100 mm in depth and 2.44m in length was carried out. The characteristic strength value was 74 % and 118 % higher, respectively, than those adopted by Argentinean standards for the best strength class of sawn and glued laminated timber of the same species. It was similar to that reported for LVL of Norway spruce and lower than that published for LVL made from Uruguayan Eucalyptus grandis even though in the latter case the reported value was not obtained according to European standards. The modulus of elasticity mean value was 22 % and 14 % higher, respectively, than those adopted by Argentinean standards for the best strength class of sawn and glued laminated timber of the same species. Modulus of elasticity also exhibited a mean value 22 % and 53 % higher, respectively, than those published for LVL manufactured from Norway spruce and Uruguayan Eucalyptus grandis. A relatively low variation of results was found for both strength (COV = 9 %) and modulus of elasticity (COV = 10 %) and the particularly high stiffness/density relation previously published for sawn timber of this Argentinean deciduous species was confirmed by the results of this study. The coefficient of determination (R2) between density and modulus of elasticity was equal to 0.67 whereas R2 reached 0.37 between modulus of elasticity and strength and 0.19 between density and strength. Fil: Saviana, Julien. Universidad Tecnológica Nacional. Facultad Regional Concepción del Uruguay. Departamento Ingeniería Civil. Grupo de Estudio de Maderas; Argentina. Fil: Sosa Zitto, María Alexandra. Universidad Tecnológica Nacional. Facultad Regional Concepción del Uruguay. Departamento Ingeniería Civil. Grupo de Estudio de Maderas; Argentina. Fil: Piter, Juan Carlos Jesús. Universidad Tecnológica Nacional. Facultad Regional Concepción del Uruguay. Departamento Ingeniería Civil. Grupo de Estudio de Maderas; Argentina. Peer Reviewed

Cellulose is one of many important polymers in plants. Cellulose is made of repeat units of the monomer glucose. Cellulose is a major industrial biopolymer in the forest products, textile, and chemical industries. It also forms a large portion of the biomass useful in the generation of energy. Moreover, cellulose-based biomass is a renewable energy source that can be used for the generation of ethanol as a fuel. Cellulose is synthesized by a variety of living organisms such as plants and algae. It is the major component of plant cell walls with secondary cell walls having a much higher content of cellulose. The relationship between cellulose and lignin biosynthesis is complicated, but it is confirmed that inhibition of lignin biosynthesis in transgenic trees will increase cellulose biosynthesis and plant growth. Cellulose accumulation may be increased by down-regulating 4-coumarate:coenzyme A ligase (4CL, EC 6.2.1.12) as shown in transgenic aspen. There is no similar reports on down-regulating 4CL in transgenic conifers. Based on our establishedAgrobacterium tumefaciens-mediated transformation system in loblolly pine, we are able to produce antisense 4-CL transgenic loblolly pine which is predicted to have increasing cellulose accumulation. The overall objective of this project is to genetically engineer forest tree species such as loblolly pine with reduced amount of lignin and increased cellulose content. The research strategy includes: (1) isolate the 4-coumarate:coenzyme A ligase gene from loblolly pine seedlings by reverse transcription-polymerase chain reaction (RT-PCR) and Rapid Amplification of cDNA Ends-Polymerase Chain Reaction (RACE-PCR) techniques from the cDNA library; (2) construct binary expression vectors with antisense 4CL coding sequences and introduce antisense constructs of the 4-coumarate:coenzyme A ligase gene cloned from loblolly pine into the loblolly pine to down regulate the 4-coumarate:coenzyme A ligase gene expression; (3) study the effect of the antisense transgene expression on lignin content, cellulose accumulation, and loblolly pine biomass; and (4) select fast growth and high cellulose accumulation transgenic loblolly pine lines for future commercial application.

Khaya anthotheca is a hardwood species from Africa and recently introduced to Brazil. This species yields high-quality wood for diverse applications, but little has been done toward an effective propagation method for large-scale production in nurseries. We evaluated the effects of different concentrations of macro and micronutrients (i.e., 100, 50 and 25% of the concentration of a referenced solution) combined with indole-3-butyric acid (IBA) at 0 and 2 g L−1 on the survival rate of mini-stumps and the survival and adventitious rooting of K. anthotheca mini-cuttings. The mini-stumps were grown from a source of seeds imported from Ghana, West Africa. The mini-stumps survived at a high rate (97%). Consistently high shoot yields were obtained from the mini-stumps (average of 1.8 per mini-stump). High survival percentage of mini-cuttings and adventitious rooting were observed when solutions with 100 and 50% of the nutrients concentration were combined with 2 g L−1 IBA. Histological sections analyzed through optical microscopy indicated the tissues from mini-cutting stems were juvenile, which might have stimulated adventitious rooting. These results have important implications for further work aimed at establishing propagation strategies for K. anthotheca, which are of prime importance for assisting breeding programs of this species.

Studying intra-annual growth dynamics through a modelling approach has proved useful for characterizing differences in wood phenology between species and deviations from the expected tree growth due to climate change. The aim of this paper was to determine the climatic factors and the inter- and intra-specific competition traits that drive intra-annual secondary growth dynamics in three Mediterranean tree species that naturally co-exist in the Spanish Northern Plateau (Pinus pinea L., Juniperus thurifera L., and Quercus ilex subsp. ballota (Desf.) Samp.). For this purpose, we obtained girth increment data from band dendrometers installed on 58 trees from May 2012 to April 2015. Half of them were located in a high-density plot and half were in a low-density plot. These data were analysed through a nonlinear multifactorial model considering daily and cumulative climatic effects together with inter- and intra-specific competition indices. Our results provide evidence of a spatiotemporal niche separation between species. Compared with other species, Q. ilex subsp. ballota showed a wider thermal amplitude, a higher mean optimum temperature for growth, and a milder effect of drought on its secondary growth. Under current climate change projections, simulations based on our model predict a secondary growth reduction for P. pinea and a growth enhancement for Q. ilex subsp. ballota in these Mediterranean mixtures.