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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.

Forestal Mininco S.A., Los Angeles, Chile. E-mail: frodriguez@formin.clSUMMARYGrowth response of a two-year-old Pinus taeda L. (loblolly pine) plantation is evaluated for differing soil preparationand phosphorus fertilization regimes. The study was of first and second rotation sites on the Diaz de Vivar soilseries, Kandihumults subgroup of the ultisols order, Corrientes Province, Argentina. A divided plot design was usedin each trial, using a factorial experiment of 3 x 2 with three replicates. Treatment was: plowing; 50 and 80 cmripping plus plowing, combined with 0 and 120 g/plant of triple super phosphate (0 - 46 - 0). On first rotation sites,higher responses resulted from 50 and 80 cm ripping showing a large difference compared with plowed-only areas.At second rotation sites, no significant distinction was seen between soil preparation methods. For both site types,the application of phosphorus had a significant positive effect on growth.Key words: Pinus taeda L., ripping, fertilization, Argentina.RESUMENSe evalua la respuesta del crecimiento de una plantacion de Pinus taeda L. de dos anos, bajo diferentes modalidadesde roturacion de suelos y fertilizacion con fosforo en terrenos de primera y segunda rotacion de la serie Diaz deVivar, pertenecientes al subgrupo de los Kandihumultes tipicos del orden Ultisoles, del Noreste de la provincia deCorrientes, Argentina. El diseno utilizado en cada ensayo corresponde a parcelas divididas en un experimentofactorial de 3 x 2 con tres repeticiones. Los tratamientos corresponden a la aplicacion de rastra, subsolado a 50 y80 cm de profundidad mas rastra, combinados con 0 y 120 g pl

RESUMEN: Enterolobium cyclocarpum es un árbol tropical multipropósito, cuyo crecimiento y supervivencia de procedencias distintas en sitios específicos se desconoce. El objetivo fue evaluar las diferencias en crecimiento y supervivencia de 10 procedencias entre y dentro de las localidades y la interacción genotipo x ambiente en dos localidades en la costa de Oaxaca, México. Las plantas se cultivaron en vivero durante seis meses antes de la plantación. Los incrementos periódicos anuales de diámetro basal, altura y diámetro de copa, además del número de bifurcaciones y supervivencia se determinaron dos años después de la plantación. Las diferencias en precipitación y las propiedades del suelo (químicas y físicas) de las localidades ocasionaron diferencias en incremento. Todas las variables tuvieron mayores valores en la localidad Pinotepa de Don Luis que en Valdeflores, excepto el incremento periódico anual de altura y supervivencia. En Pinotepa de Don Luis la procedencia local tuvo mejores incrementos de diámetro basal, altura y diámetro de copa. En Valdeflores, la procedencia la más cercana (Colotepec) presentó mayores incrementos de diámetro basal y diámetro de copa. Los valores bajos de la correlación genética tipo B indicaron interacción genotipo x ambiente alto, y las procedencias fueron más inestables en el crecimiento en altura y número de bifurcaciones. La interacción genotipo x ambiente limita seleccionar una procedencia para establecerse en ambos ambientes; por tanto, la procedencia a plantar dependerá del ambiente y del objetivo. Los resultados permiten recomendar el uso de procedencias locales o más cercanas al sitio de plantación.