Increasing genomic prediction accuracy for unphenotyped full-sib families by modeling additive and dominance effects with large datasets in white spruce.

Introduction: Genomic selection is becoming a standard technique in plant breeding and is now being introduced into forest tree breeding. Despite promising results to predict the genetic merit of superior material based on their additive breeding values, many studies and operational programs still neglect non-additive effects and their potential for enhancing genetic gains. Methods: Using two large comprehensive datasets totaling 4,066 trees from 146 full-sib families of white spruce (Picea glauca (Moench) Voss), we evaluated the effect of the inclusion of dominance on the precision of genetic parameter estimates and on the accuracy of conventional pedigree-based (ABLUP-AD) and genomic-based (GBLUP-AD) models. Results: While wood quality traits were mostly additively inherited, considerable non-additive effects and lower heritabilities were detected for growth traits. For growth, GBLUP-AD better partitioned the additive and dominance effects into roughly equal variances, while ABLUP-AD strongly overestimated dominance. The predictive abilities of breeding and total genetic value estimates were similar between ABLUP-AD and GBLUP-AD when predicting individuals from the same families as those included in the training dataset. However, GBLUP-AD outperformed ABLUP-AD when predicting for new unphenotyped families that were not represented in the training dataset, with, on average, 22% and 53% higher predictive ability of breeding and genetic values, respectively. Resampling simulations showed that GBLUP-AD required smaller sample sizes than ABLUP-AD to produce precise estimates of genetic variances and accurate predictions of genetic values. Still, regardless of the method used, large training datasets were needed to estimate additive and non-additive genetic variances precisely. Discussion: This study highlights the different quantitative genetic architectures between growth and wood traits. Furthermore, the usefulness of genomic additive-dominance models for predicting new families should allow practicing mating allocation to maximize the total genetic values for the propagation of elite material.

Divergent selection predating the Last Glacial Maximum mainly acted on macro-phenotypes in Norway spruce.

The current distribution and population structure of many species were, to a large extent, shaped by cycles of isolation in glacial refugia and subsequent population expansions. Isolation in and postglacial expansion through heterogeneous environments led to either neutral or adaptive divergence. Norway spruce is no exception, and its current distribution is the consequence of a constant interplay between evolutionary and demographic processes. We investigated population differentiation and adaptation of Norway spruce for juvenile growth, diameter of the stem, wood density, and tracheid traits at breast height. Data from 4461 phenotyped and genotyped Norway spruce from 396 half-sib families in two progeny tests were used to test for divergent selection in the framework of Q ST vs. F ST. We show that the macroscopic resultant trait (stem diameter), unlike its microscopic components (tracheid dimensions) and juvenile growth, was under divergent selection that predated the Last Glacial Maximum. Altogether, the current variation in these phenotypic traits in Norway spruce is better explained by local adaptation to ancestral environments than to current ones, where populations were partly preadapted, mainly through growth-related traits.

Extraction of branch factors and model construction for Larix plantation using terrestrial laser scanning (TLS).

Forest parameters could be estimated without damage using terrestrial laser scanning (TLS). In this study, 1266 sets of branch parameters, including branch height, branch chord length, branch length, branch angle, branch diameter and the branch arc height, of 26 Larix trees were extracted based on TLS using point cloud processing software in the way of human-computer interaction. The average of extracted maximum relative height of the branches was 0.83. The accuracy of the extracted branch attributes followed the order of branch height > branch chord length > branch length > branchdiameter (with the branch diameter >20 mm) > branch arc height. After dividing the crown into four parts, it proved that the density of the branches increased while the extraction ratio and precision of branches decreased with the increase of crown height. Due to the low accuracy of branch diameter extraction, we developed a base diameter prediction model using the branch chord length, the height of branch, diameter at breast height and tree height as independent variables. The measured, extracted and model predicted values of different base diameter were compared, and discovered that accuracy of model prediction was greater than that of extraction by TLS. For timber production, the most worthy wood was the middle and lower section of the tree. The method could accurately extract tree height, diameter at breast height (DBH) and the branch attributes with the relative branch height of less than 0.8, providing the parameters that are necessary to develop a wood quality model.

Leveraging breeding programs and genomic data in Norway spruce (Picea abies L. Karst) for GWAS analysis.

BACKGROUND: Genome-wide association studies (GWAS) identify loci underlying the variation of complex traits. One of the main limitations of GWAS is the availability of reliable phenotypic data, particularly for long-lived tree species. Although an extensive amount of phenotypic data already exists in breeding programs, accounting for its high heterogeneity is a great challenge. We combine spatial and factor-analytics analyses to standardize the heterogeneous data from 120 field experiments of 483,424 progenies of Norway spruce to implement the largest reported GWAS for trees using 134 605 SNPs from exome sequencing of 5056 parental trees. RESULTS: We identify 55 novel quantitative trait loci (QTLs) that are associated with phenotypic variation. The largest number of QTLs is associated with the budburst stage, followed by diameter at breast height, wood quality, and frost damage. Two QTLs with the largest effect have a pleiotropic effect for budburst stage, frost damage, and diameter and are associated with MAP3K genes. Genotype data called from exome capture, recently developed SNP array and gene expression data indirectly support this discovery. CONCLUSION: Several important QTLs associated with growth and frost damage have been verified in several southern and northern progeny plantations, indicating that these loci can be used in QTL-assisted genomic selection. Our study also demonstrates that existing heterogeneous phenotypic data from breeding programs, collected over several decades, is an important source for GWAS and that such integration into GWAS should be a major area of inquiry in the future.

A large-scale image dataset of wood surface defects for automated vision-based quality control processes.

The wood industry is facing many challenges. The high variability of raw material and the complexity of manufacturing processes results in a wide range of visible structure defects, which have to be controlled by trained specialists. These manual processes are not only tedious and biased, but also less effective. To overcome the drawbacks of the manual quality control processes, several automated vision-based systems have been proposed. Even though some conducted studies achieved a higher recognition rate than trained experts, researchers have to deal with a lack of large-scale databases and authentic data in this field. To address this issue, we performed a data acquisition experiment set in the industrial environment, where we were able to acquire an extensive set of authentic data from a production line. For this purpose, we designed and implemented a complex technical solution suitable for high-speed acquisition during harsh manufacturing conditions. In this data note, we present a large-scale dataset of high-resolution sawn timber surface images containing more than 43 000 labelled surface defects and covering 10 types of the most common wood defects. Moreover, with each image record, we provide two types of labels allowing researchers to perform semantic segmentation, as well as defect classification, and localization.

EgPHI-1, a PHOSPHATE-INDUCED-1 gene from Eucalyptus globulus, is involved in shoot growth, xylem fiber length and secondary cell wall properties.

MAIN CONCLUSION: EgPHI-1 is a member of PHI-1/EXO/EXL protein family. Its overexpression in tobacco resulted in changes in biomass partitioning, xylem fiber length, secondary cell wall thickening and composition, and lignification. Here, we report the functional characterization of a PHOSPHATE-INDUCED PROTEIN 1 homologue showing differential expression in xylem cells from Eucalyptus species of contrasting phenotypes for wood quality and growth traits. Our results indicated that this gene is a member of the PHI-1/EXO/EXL family. Analysis of the promoter cis-acting regulatory elements and expression responses to different treatments revealed that the Eucalyptus globulus PHI-1 (EgPHI-1) is transcriptionally regulated by auxin, cytokinin, wounding and drought. EgPHI-1 overexpression in transgenic tobacco changed the partitioning of biomass, favoring its allocation to shoots in detriment of roots. The stem of the transgenic plants showed longer xylem fibers and reduced cellulose content, while the leaf xylem had enhanced secondary cell wall thickness. UV microspectrophotometry of individual cell wall layers of fibers and vessels has shown that the transgenic plants exhibit differences in the lignification of S2 layer in both cell types. Taken together, the results suggest that EgPHI-1 mediates the elongation of secondary xylem fibers, secondary cell wall thickening and composition, and lignification, making it an attractive target for biotechnological applications in forestry and biofuel crops.

Brazilian cerrado species: wood characteristics / Espécies do cerrado brasileiro: características da madeira

The characterization of wood anatomy and proprieties can provide subsidies for rational use of tree species. Enables, oftentimes, the definition of technological potential of wood - and wood products - through the assessment of quality information and also allows it ́s correct identification, contributing to the timber production chain. The objective of this study was to contribute to the knowledge about wood properties of the Cerrado biome (Brazilian savanna) species trough the anatomical characterization and determination of density profile. Twenty trees species belonging to thirteen families occurring in Pirenópolis, Goiás and Brasília, Federal District, Brazil, was selected and radial samples were removed from the tree trunks at the DBH (1.30 m) in a non-destructive way using an incremental probe and a motorized extractor. The qualitative and quantitative anatomical parameters of vessels and fibers and the wood density were determined in the collected samples. Species presented fibers with mean values between 900.5 and 2052.9 µm for the length; 18.1 and 27.7 µm for the diameter; and 4.4 to 9.4 µm for the wall thickness. The species presented a variation in the vessel dimensions from 29.2 to 155.6 µm for the diameter; 17.7 to 32.5% for occupied area; and 2.6 to 165 to vessels.mm-2. The apparent density presented mean values between 0.36 and 1.21 g cm-3. The specie that presented the highest variation of wood density was A. fraxinifolium. According to the radial profiles two patterns of increasing and stable variation in the apparent density of the pith to bark were defined as a function of the wood anatomical characteristics.

A caracterização anatômica e das propriedades da madeira pode auxiliar na tomada de decisão quanto ao uso racional de espécies. Possibilita, muitas vezes, a definição do potencial tecnológico da madeira - e produtos - fornecendo acesso a informações sobre a sua qualidade, além de sua correta identificação, contribuído com a cadeia produtiva madeireira. O objetivo deste estudo foi investigar e caracterizar as propriedades da madeira de espécies arbóreas do Cerrado, através da descrição anatômica e determinação do perfil de densidade. Foram selecionadas 20 espécies pertencentes a treze famílias, na cidade de Pirenópolis, Goiás e Brasília, Distrito Federal, Brasil, e amostras radiais foram retiradas dos troncos das árvores no DAP (1,30 m) de forma não destrutiva, utilizando-se uma sonda de incremento e um extrator motorizado. Nas amostras coletadas, foram determinados os parâmetros anatômicos qualitativos e quantitativos dos vasos e das fibras e a densidade aparente da madeira. As espécies apresentaram fibras com valores médios entre 900,5 a 2052,9 µm para o comprimento; 18,1 a 27,7 µm para o diâmetro e 4,4 a 9,4 µm para a espessura da parede; e variação nas dimensões dos vasos de 29,2 a 155,6 µm para o diâmetro; 17,7 a 32,5% para área ocupada; e 2,6 a 165 vasos.mm-2 para a frequencia dos vasos. A densidade aparente apresentou valores médios entre 0,36 e 1,21 g cm-3. A espécie que apresentou a maior variação de densidade de madeira foi A. fraxinifolium. De acordo com os perfis radiais, dois padrões de variação crescente e estável na densidade aparente, da medula para casca, foram definidos como uma função das características anatômicas.

Genetic Improvement of Sawn-Board Stiffness and Strength in Scots Pine (Pinus sylvestris L.).

Given an overall aim of improving Scots pine structural wood quality by selective tree breeding, we investigated the potential of non-destructive acoustic sensing tools to accurately predict wood stiffness (modulus of elasticity, MOE) and strength (modulus of rupture, MOR) of sawn boards. Non-destructive measurements of wood density (DEN), acoustic velocity (VEL) and MOE were carried out at different stages of wood processing chain (standing trees, felled logs and sawn boards), whilst destructively measured stiffness and strength served as benchmark traits. All acoustic based MOE and VEL estimates proved to be good proxies (rA > 0.65) for sawn-board stiffness while MOETREE, VELHIT and resistograph wood density (DENRES) measured on standing trees and MOELOG and VELFAK measured on felled logs well reflected board strength. Individual-tree narrow-sense heritability ( h i 2 ) for VEL, MOE and MOR were weak (0.05-0.26) but were substantially stronger for wood density (0.34-0.40). Moreover, additive genetic coefficients of variation for MOE and MOR were in the range from 5.4% to 9.1%, offering potential targets for exploitation by selective breeding. Consequently, selective breeding based on MOETREE, DENRES or stem straightness (STR) could improve several structural wood traits simultaneously.

Multi-trait genomic selection for weevil resistance, growth, and wood quality in Norway spruce.

Plantation-grown trees have to cope with an increasing pressure of pest and disease in the context of climate change, and breeding approaches using genomics may offer efficient and flexible tools to face this pressure. In the present study, we targeted genetic improvement of resistance of an introduced conifer species in Canada, Norway spruce (Picea abies (L.) Karst.), to the native white pine weevil (Pissodes strobi Peck). We developed single- and multi-trait genomic selection (GS) models and selection indices considering the relationships between weevil resistance, intrinsic wood quality, and growth traits. Weevil resistance, acoustic velocity as a proxy for mechanical wood stiffness, and average wood density showed moderate-to-high heritability and low genotype-by-environment interactions. Weevil resistance was genetically positively correlated with tree height, height-to-diameter at breast height (DBH) ratio, and acoustic velocity. The accuracy of the different GS models tested (GBLUP, threshold GBLUP, Bayesian ridge regression, BayesCπ) was high and did not differ among each other. Multi-trait models performed similarly as single-trait models when all trees were phenotyped. However, when weevil attack data were not available for all trees, weevil resistance was more accurately predicted by integrating genetically correlated growth traits into multi-trait GS models. A GS index that corresponded to the breeders' priorities achieved near maximum gains for weevil resistance, acoustic velocity, and height growth, but a small decrease for DBH. The results of this study indicate that it is possible to breed for high-quality, weevil-resistant Norway spruce reforestation stock with high accuracy achieved from single-trait or multi-trait GS.

Tannic extract potential as natural wood preservative of Acacia mearnsii

ABSTRACT High toxicity of the preservatives most frequently used in wood treatment and the resulting risks of handling pose a threat to small producers and to the environment. In an attempt to mitigate these problems, the present study was conducted with the objective of evaluating the preservative effect of tannic extract on biodeterioration of Acacia mearnsii wood. For this purpose, untreated and preserved specimens, some with tannin extract and some with a preservative mixture based on CCB (Chromated Copper Borate), were submitted to accelerated rotting trials with the fungus that causes white rot (Pycnoporus sanguineus) for 16 weeks. The evaluations were made with a basis on weight loss and chemical components analysis, and they showed that the natural resistance of Acacia wood is moderate when exposed to the white rot fungus. The tannin concentrations showed similar effects to those of the CBB mixture in all evaluations, i.e., they significantly increased the biological resistance of the material, which started to be classified as very resistant to the fungus. Overall, the results suggest that tannin can be considered as a potential natural preservative product.

Assemblage composition of fungal wood-decay species has a major influence on how climate and wood quality modify decomposition.

The interactions among saprotrophic fungal species, as well as their interactions with environmental factors, may have a major influence on wood decay and carbon release in ecosystems. We studied the effect that decomposer diversity (species richness and assemblage composition) has on wood decomposition when the climatic variables and substrate quality vary simultaneously. We used two temperatures (16 and 21°C) and two humidity levels (70% and 90%) with two wood qualities (wood from managed and old-growth forests) of Pinus sylvestris. In a 9-month experiment, the effects of fungal diversity were tested using four wood-decaying fungi (Antrodia xantha, Dichomitus squalens, Fomitopsis pinicola and Gloeophyllum protractum) at assemblage levels of one, two and four species. Wood quality and assemblage composition affected the influence of climatic factors on decomposition rates. Fungal assemblage composition was found to be more important than fungal species richness, indicating that species-specific fungal traits are of paramount importance in driving decomposition. We conclude that models containing fungal wood-decay species (and wood-based carbon) need to take into account species-specific and assemblage composition-specific properties to improve predictive capacity in regard to decomposition-related carbon dynamics.

Axial variation of basic density of Araucaria angustifolia wood in different diameter classes / Variação axial da massa específica básica da madeira de Araucaria angustifolia em diferentes classes diamétricas

ABSTRACT: The study of the wood characteristics is of fundamental importance for the correct use of this raw material and, among its properties, the basic density is a major, being reference in the quality of this material. This study aimed to evaluate the axial variation of basic density of the wood of Araucaria angustifolia (Bertoloni) O. Kuntze in different diameter classes. For this, three trees were selected in six diameter classes, called class 1 (20-30cm), class 2 (30.1-40cm), class 3 (40.1-50cm), class 4 (50.1-60cm), class 5 (60.1-70cm) and class 6 (70.1-80cm). From each individual sampled was withdrawn a disc at 0.1m (base), 25, 50, 75 and 100% of the height of the first live branch and in the diameter at 1.30m from the ground (DBH), which were used for determining basic density. The weighted average basic density was equal to 0.422g cm-3 and, regardless of the diameter class analyzed, this property decreased in the axial direction. Diameter induced variation of basic density, but has not been verified a positive or negative systematic tendency in relation to the sampled interval.

RESUMO: O estudo das características da madeira é de fundamental importância para o correto uso dessa matéria-prima e, dentre as suas propriedades, a massa específica é uma das principais, por ser referência na qualidade desse material. Este estudo teve por objetivo avaliar a variação axial da massa específica básica da madeira de Araucaria angustifolia (Bertoloni) O. Kuntze, em diferentes classes de diâmetros. Para isso, três árvores foram selecionadas em seis classes diamétricas, denominadas de classe 1(20-30cm), classe 2 (30,1-40cm), classe 3 (40,1-50cm), classe 4 (50,1-60cm), classe 5 (60,1-70cm) e classe 6 (70,1-80cm). De cada indivíduo amostrado, foi retirado um disco a 0,1m (base), 25, 50, 75 e 100% da altura do primeiro galho vivo e no diâmetro a 1,30m do solo (DAP), que foram utilizados para a determinação da massa específica básica. O valor médio ponderado da massa específica básica foi igual a 0,422g cm-3 e, independentemente da classe diamétrica analisada, essa propriedade decresceu no sentido axial. O diâmetro induziu a variação da massa específica básica, porém não foi verificada uma tendência sistemática positiva ou negativa em relação ao intervalo amostrado.

Quantitative trait loci influencing forking defects in an outbred pedigree of loblolly pine.

BACKGROUND: The use of wood as an industrial raw material has led to development of plantation forestry, in which trees are planted, managed, and harvested as crops. The productivity of such plantations often exceeds that of less-intensively-managed forests, and land managers have the option of choosing specific planting stock to produce specific types of wood for industrial use. Stem forking, or division of the stem into two or more stems of roughly equal size, is a character trait important in determining the quality of the stem for production of solid wood products. This trait typically has very low individual-tree heritability, but can be more accurately assessed in clonally-replicated plantings where each genotype is represented by several individual trees. We report results from a quantitative trait mapping experiment in a clonally-replicated full-sibling family of loblolly pine (Pinus taeda L.). RESULTS: Quantitative trait loci influencing forking defects were identified in an outbred full-sibling family of loblolly pine, using single-nucleotide polymorphism markers. Genetic markers in this family segregated either in 1:2:1 (F2 intercross-like segregation) or 1:1 ratio (backcross-like segregation). An integrated linkage map combining markers with different segregation ratios was assembled for this full-sib family, and a total of 409 SNP markers were mapped on 12 linkage groups, covering 1622 cM. Two and three trait loci were identified for forking and ramicorn branch traits, respectively, using the interval mapping method. Three trait loci were detected for both traits using multiple-trait analysis. CONCLUSIONS: The detection of three loci for forking and ramicorn branching in a multiple-trait analysis could mean that there are genes with pleiotropic effects on both traits, or that separate genes affecting different traits are clustered together. The detection of genetic loci associated with variation in stem quality traits in this study supports the hypothesis that marker-assisted selection can be used to decrease the rate of stem defects in breeding populations of loblolly pine.

Functional multi-locus QTL mapping of temporal trends in Scots pine wood traits.

Quantitative trait loci (QTL) mapping of wood properties in conifer species has focused on single time point measurements or on trait means based on heterogeneous wood samples (e.g., increment cores), thus ignoring systematic within-tree trends. In this study, functional QTL mapping was performed for a set of important wood properties in increment cores from a 17-yr-old Scots pine (Pinus sylvestris L.) full-sib family with the aim of detecting wood trait QTL for general intercepts (means) and for linear slopes by increasing cambial age. Two multi-locus functional QTL analysis approaches were proposed and their performances were compared on trait datasets comprising 2 to 9 time points, 91 to 455 individual tree measurements and genotype datasets of amplified length polymorphisms (AFLP), and single nucleotide polymorphism (SNP) markers. The first method was a multilevel LASSO analysis whereby trend parameter estimation and QTL mapping were conducted consecutively; the second method was our Bayesian linear mixed model whereby trends and underlying genetic effects were estimated simultaneously. We also compared several different hypothesis testing methods under either the LASSO or the Bayesian framework to perform QTL inference. In total, five and four significant QTL were observed for the intercepts and slopes, respectively, across wood traits such as earlywood percentage, wood density, radial fiberwidth, and spiral grain angle. Four of these QTL were represented by candidate gene SNPs, thus providing promising targets for future research in QTL mapping and molecular function. Bayesian and LASSO methods both detected similar sets of QTL given datasets that comprised large numbers of individuals.

Idade de segregação do lenho juvenil e adulto para Pinus elliottii Engel / Age of segregation of juvenile and mature Pinus elliottii Engel wood

A madeira juvenil em maior proporção no fuste e suas características físicas, mecânicas, químicas e anatômicas diminuem a qualidade do material. Esse estudo teve como objetivo estimar a idade de segregação do lenho juvenil e adulto pelo comprimento dos traqueoides em Pinus elliottii Engel, aos 30 anos de idade. Para tanto, seis árvores foram selecionadas, com base no diâmetro dominante, em um povoamento localizado no Colégio Agrícola de Frederico Westphalen/UFSM. Após o abate, no disco correspondente a 0,15 metros de altura, foram marcadas e seccionadas baguetas centrais de onde se retirou o lenho inicial dos trinta anéis de crescimento, no sentido medula-casca, para maceração. A segregação dos dois tipos de lenhos foi determinada pela variação radial da característica anatômica em estudo através de duas regressões lineares simples. Os resultados indicaram que o comprimento dos traqueoides apresentou padrão de variação crescente no sentido medula-casca, indicando assim que os menores valores foram observados próximos à medula e correspondem aos primeiros anéis de crescimento. A idade de segregação do lenho de Pinus elliottii definida por meio do comprimento de traqueoides foi de, aproximadamente, dez anos.

The juvenile wood in greater proportion in the stem and its physical, mechanical, chemical and anatomical characteristics decrease the quality of the material. This study was undertaken to estimate the segregation age of juvenile and mature wood by tracheid length of Pinus elliottii Engel, at 30 years of age. Six trees were selected, on the basis of the dominant diameter, in a stand located in Agricultural College of Frederico Westphalen/UFSM. After cutting down, in the disk corresponding to the 0.15 meters, were marked and sectioned centrals baguettes from where was removed the initial wood of the thirty growth rings, in pith-to-bark direction, for maceration. The segregation of the two types of wood was defined by radial variation of the anatomical characteristic in study through two simple linear regressions. The results indicated that the tracheid length showed a pattern of increasing from pith to bark, indicating that the lowest values were observed near the pith and correspond to the first growth rings. The age of segregation of the Pinus elliottii wood defined by tracheid length was, approximately, ten years-old.

Dureza Rockwell da madeira de três espécies amazônicas submetidas a ensaios de apodrecimento acelerado / Rockwell hardness of the wood of three Amazon species submitted to decay accelerated tests

Objetivou-se avaliar o emprego de ensaios de dureza Rockwell na caracterização da biodeterioração das madeiras de Simarouba amara (marupá), Cariniana micrantha (jequitibá) e Dipteryx odorata (cumaru), submetidas ao ataque dos fungos apodrecedores Trametes versicolor (podridão branca) e Gloeophyllum trabeum (podridão parda). Para tanto, corpos de prova de cada espécie amazônica foram submetidos a ensaios de apodrecimento acelerado, de acordo com a ASTM D2017 (2005), durante 20 semanas. A caracterização da dureza Rockwell foi realizada semanalmente até a 4ª semana e, posteriormente, a cada duas semanas, até a 20ª semana. Adicionalmente, foram determinadas as perdas de massa, conforme critérios estabelecidos pela ASTM D2017 (2005). Quanto aos resultados, destaca-se que a dureza Rockwell pode ser empregada como ferramenta principal na caracterização da biodeterioração da madeira, sendo sensível na predição dos estágios iniciais. Dentre as madeiras amazônicas, o cumaru apresentou a maior resistência natural aos fungos apodrecedores. Com relação aos fungos, a podridão parda atacou mais intensamente as três madeiras amazônicas.

This study aimed to evaluate the use of Rockwell hardness in the characterization of the biodeterioration of Simarouba amara (marupá), Cariniana micrantha (jequitibá) e Dipteryx odorata (cumaru) woods, which were submitted to decay fungi Trametes versicolor (white rot) and Gloeophyllum trabeum (brown rot). For this purpose, specimens of each Amazon species were submitted to decay fungi, according to ASTM D2017 (2005). The characterization of the Rockwell hardness was performed weekly until the fourth week, and then every two weeks until the twentieth week. Additionally, it was determined the mass loss, according to criteria established by ASTM D2017 (2005). The results indicated that the Rockwell hardness can be used as a primary tool in the characterization of the biodeterioration of wood, being sensitive in predicting the early stages. Among the Amazon woods, cumaru wood showed a greater natural resistance to decay fungi. With respect to decay fungi, brown rot more intensely attacked the three Amazon woods.

Resistência ao impacto da madeira de nogueira-pecã em diferentes condições de umidade / Impact strength of nogueira-pecã wood on different moisture conditions

Os estudos de resistência da madeira ao impacto referem-se à eficiência com que este material absorve energia de um impacto e dissipa-a sem danos a sua estrutura. Dessa forma, o objetivo deste estudo foi avaliar a influência do teor de umidade na resistência ao impacto da madeira de nogueira-pecã (Carya illinoinensis). Para tanto, foram utilizadas árvores procedentes de duas regiões fisiográficas do estado do Rio Grande do Sul. Os corpos de prova, em condições de equilíbrio a 12% de umidade e saturados, foram submetidos ao impacto utilizando-se pêndulo de CHARPY, e avaliados quanto à resistência oferecida com a aplicação da carga nos planos tangencial e radial e posições de retirada (medula - casca) nas toras, para as duas regiões fisiográficas em cada condição de umidade. Para auxiliar na interpretação dos dados, determinou-se a massa específica aparente a 12% e saturada, trabalho absorvido, coeficiente de resiliência e a cota dinâmica. Pôde-se verificar, por meio dos resultados, que a madeira de nogueira-pecã é mais resistente ao impacto na condição saturada.

The studies of wood impact strength refers to the efficiency of this material in absorb impact energy and dissipate it without structural damages. The present study aimed to evaluate the influence of moisture content on the impact strength of nogueira-pecã (Carya illinoinensis) wood. For this, trees from two physiographic regions of state of Rio Grande do Sul were used. The samples, stabilized at 12% of moisture content and in green conditions (saturated), were submitted to impact tests through a CHARPY pendulum, and were evaluated for the resistance to the application of loads in the tangential and radial sections, and in the positions of the log (pith-bark) for the two physiographic regions at each moisture condition. Moreover, the apparent specific gravity at 12% and in green conditions (saturated), the absorbed work, the resilience coefficient and the dynamic quote were determined. The main results showed that the nogueira-pecã wood is more resistant to the impact when it is in green conditions.

Idade de segregação do lenho juvenil e adulto pela variação da massa específica de açoita-cavalo / Estimating the age of demarcation of young and mature wood in açoita-cavalo

O presente trabalho teve como objetivo estimar a idade de segregação do lenho de Luehea divaricata Mart. (açoita-cavalo) por meio da variação radial da massa específica. Para o desenvolvimento do estudo, foram coletadas dez árvores de duas regiões do Estado do Rio Grande do Sul. Foi retirado um disco por árvore, com aproximadamente 2cm de espessura a 0,10m de altura do tronco. De cada disco, retirou-se, com auxílio de uma serra-fita, uma bagueta central de 2,0cm de largura, bem orientada no sentido radial, incluindo a medula no centro, dividiu-se então a bagueta em duas amostras "A" e "B". A massa específica foi obtida da relação entre peso seco e volume úmido. O volume úmido foi determinado de acordo com a norma ASTM D 2395 - 93, 1995. A segregação dos lenhos foi encontrada por regressão linear simples dos dados de variação da massa específica no sentido medula-casca. Foi feita uma regressão linear na faixa crescente dos dados e outra na faixa decrescente. A intersecção das retas extrapoladas foi adotada como idade de segregação. Os resultados obtidos mostraram que o lenho de açoita-cavalo segrega em aproximadamente 26 anos para a região da Depressão Central e 23 anos para a região da Encosta Superior do Nordeste. Nos dados de variação de massa específica, foi feita uma análise de variância multifatorial. Constatou-se que há diferença significativa entre lenhos e entre regiões. Por outro lado, as amostras A e B de cada árvore não foram estatisticamente diferentes entre si.

This study aims to estimate the age of segregation of young and mature wood of Luehea divaricata Mart., using the radial variation of specific gravity. To the development of this study were collected ten trees from two regions of the state of Rio Grande do Sul. Discs with thickness of 2cm at 0.1m of height from the base of the trunk were used. From each disk, with the aid of a band saw, a central ribbon 2.0cm wide, and oriented in the radial direction was taken, including the pith, then splitted into two samples "A" and "B". The specific gravity was calculated as ratio between dry weight and wet volume. The wet volume was determined according to ASTM D 2395 - 93, 1997. The age of segregation was found by simple linear regression of the data of variation of specific gravity from pith to bark. The intersection of extrapolated lines was adopted as the age of segregation. The results showed that the wood segregates in 26 year for the region of Central Depression and in 23 years for the Northeast Upper Hillside. Was made a multifactorial analysis of variance in the specific gravity data, showing that there are statistical difference between regions and woods. However, there are no statistical difference between samples.

Variação axial e efeito do desbaste na massa específica das árvores centrais de Eucalyptus grandis / Axial variation and effect of thinning on basic density of central trees of Eucalyptus grandis

Este estudo teve como objetivo avaliar a variação axial e o efeito do desbaste na massa específica das árvores centrais de Eucalyptus grandis aos 18 anos de idade. Para tanto, foi analisado um experimento situado próximo ao litoral do Rio Grande do Sul, instalado em delineamento blocos ao acaso com quatro repetições. Os tratamentos foram definidos devido ao número de desbastes aplicados e variaram de zero até seis intervenções. As árvores foram selecionadas, em cada tratamento, com base no diâmetro central e, após o abate, foram medidas e cubadas pelo método de Smalian. Em seguida, foram retirados discos nas posições 0, 25, 50, 75 e 100 por cento da altura comercial e na altura do peito (DAP), destinados à determinação da massa específica. Os resultados indicaram que a massa específica básica apresentou um decréscimo até a região do DAP, seguido de acréscimo, sem tendência de estabilização com a altura em todos os tratamentos analisados. O desbaste induziu a variação da massa específica básica em árvores centrais, porém não foi verificada uma tendência sistemática positiva ou negativa em relação ao espaço vital proporcionado pelo desbaste.

This study was undertaken to evaluate the axial variation and the effect of thinning on the basic density of Eucalyptus grandis central diameter trees with 18 years of age. A thinning experiment, located in the northern coast of Rio Grande do Sul, installed in random blocks with four repetitions was evaluated. The treatments were defined according to the number of interventions applied that ranged from zero to six. The trees were selected, in each treatment, on the basis of the central diameter. After cutting down, the trees were measured and the volume determined by Smalian method. Afterwards, disks were taken at the base, 25, 50, 75 and 100 percent of the commercial height, and at the breast height (DBH), for basic density determination. The results indicated that basic density showed a decrease up to DBH, followed by an increase, without a clear tendency to stabilize with the height in all treatments analyzed. The thinning caused variation in basic density of the central trees; however, there was no positive or negative precise trend related to the beneficial space provided by thinning.