ABSTRACT In the Brazilian planted forest sector, most of the species used are from the genus Eucalyptus. Even though Southern Brazil has a suitable climate for species of the genus Pinus, the planting of frost-resistant Eucalyptus species has been increasing annually. The objective of this study was to evaluate the basic density, fiber dimensions, and chemical composition of Eucalyptus benthamii, Eucalyptus dunnii, Eucalyptus saligna, and Eucalyptus cloeziana woods. The trees used were from a six-year-old experimental plantation located in Canoinhas, state of Santa Catarina. For each species, three trees were selected, and discs were removed from each tree at 0%, 25%, 50%, 75%, and 100% of the commercial stem height. To evaluate the quality of the wood, the basic wood density, fiber dimensions, and chemical composition of the wood were determined by comparing the values between species and between the heights in the stem. The highest basic density was that of the wood of E. cloeziana; this species also had the greatest length and width of fibers. E. dunnii had the lowest levels of lignin and the highest levels of holocellulose. The highest lignin content was found in the wood of E. benthamii, E. saligna, and E. cloeziana. The relationship between wood properties and stem height was not relevant. The results highlight the tendency for higher extractives to be found at taller heights (100%), and holocellulose and lignin content are similar at all heights.

RESUMO No setor de florestas plantadas brasileiro, a maioria das espécies utilizadas são do gênero Eucalyptus. Embora o Sul do Brasil tenha clima propicio para espécies do gênero Pinus, o plantio de espécies de Eucalyptus resistentes à geada vem aumentando anualmente. O objetivo deste estudo foi avaliar a densidade básica, as dimensões das fibras e a composição química da madeira de Eucalyptus benthamii, Eucalyptus dunnii, Eucalyptus saligna e Eucalyptus cloeziana. As árvores utilizadas foram provenientes de um plantio experimental de seis anos localizado em Canoinhas, estado de Santa Catarina. Para cada espécie, três árvores foram selecionadas e os discos foram removidos de cada árvore a 0%, 25%, 50%, 75% e 100% da altura do caule comercial. Para avaliar a qualidade da madeira, a densidade básica, as dimensões das fibras e a composição química foram determinadas comparando-se os valores entre as espécies e entre as alturas no fuste. A maior densidade básica foi a da madeira de E. cloeziana; esta espécie também apresentou o maior comprimento e largura das fibras. E. dunnii apresentou os menores teores de lignina e os maiores teores de holocelulose. O maior teor de lignina foi encontrado na madeira de E. benthamii, E. saligna e E. cloeziana. A relação entre as propriedades da madeira e a altura do fuste não foi relevante. Os resultados destacam a tendência de maiores extrativos serem encontrados nas partes mais altas (100%), e os teores de holocelulose e lignina são similares em todas as alturas.

ABSTRACT Accurate forest biomass estimates require the selection of appropriate models of individual trees. Thus, two properties are required in tree biomass modeling: (1) additivity of biomass components and (2) estimator efficiency. This study aimed to develop a system of equations to estimate young eucalyptus aboveground biomass and guarantee additivity and estimator efficiency. Aboveground eucalyptus biomass models were calibrated using four methods: generalized least squares (GLS), weighted least squares (WLS), seemingly unrelated regression (SUR), and weighted seemingly unrelated regression (WSUR). The approaches were compared with regard to performance, additivity, and estimator efficiency. The methods did not differ with regard to the mean biomass estimation; therefore, their performance was similar. The GLS and WLS approaches did not satisfy the additivity principle, as the sum of the biomass components was not equal to total biomass. However, this was not observed with the SUR and WSUR approaches. With regard to estimator efficiency, the WSUR approach resulted in narrow confidence intervals and an efficiency gain of over 20%. The WSUR approach should be used in forest biomass modeling as it resulted in effective estimators while ensuring equation additivity, thus providing an easy and accurate alternative to estimate the initial biomass of eucalyptus stands in ecophysiological models.

Resumo: O objetivo deste trabalho foi avaliar a interação genótipo x ambiente (GxA) em progênies de polinização aberta de Eucalyptus saligna, para seleção simultânea para maior estabilidade e adaptabilidade para volume de madeira, bem como comparar as estratégias de seleção por análises conjunta e individuais em três ambientes. Foram instalados três experimentos, em delineamento de blocos ao acaso, com quatro repetições e parcelas de seis plantas, com 102 a 122 progênies. Três anos após o plantio, foram avaliados a taxa de sobrevivência e o volume de madeira. Os parâmetros genéticos foram estimados pelos métodos da máxima verossimilhança restrita e melhor predição linear não viciada (REML/Blup), e a análise de estabilidade e adaptabilidade foi realizada pela média harmônica do desempenho relativo dos valores genéticos (MHPRVG). A maior taxa de sobrevivência (82%) foi observada em Sabinópolis e o maior volume (120 m³ ha-1) em Lençóis Paulista. As herdabilidades médias das progênies para as duas variáveis avaliadas foram consideradas altas, e as correlações genéticas entre taxa de sobrevivência e volume foram baixas para todos os locais. A interação GxA foi significativa e do tipo complexa, com correlação genotípica entre ambientes de 47%, o que indica que o ordenamento das melhores progênies foi diferente para cada local estudado. A análise de estabilidade e adaptabilidade indicou a possibilidade de selecionar progênies com comportamento plástico nos três ambientes; contudo, para melhoria da qualidade das características avaliadas, é necessária a seleção de progênies específicas para cada ambiente.

Abstract: The objective of this work was to evaluate the genotype x environment (GxE) interaction in open-pollinated Eucalyptus saligna progenies for simultaneous selection for greater stability and adaptability for wood volume, as well as to compare the selection strategies through combined and individual analyses in three environments. Three experiments were conducted in a randomized complete block design, with four replicates and six plants per plot, with 102 to 122 progenies. Three years after planting, survival rate and wood volume were evaluated. The genetic parameters were estimated by the maximum restricted likelihood and best linear unbiased prediction (REML/Blup) methods, and the stability and adaptability analysis was conducted using the harmonic mean of the relative performance of genetic values (HMRPGV). The highest survival rate (82%) was observed in Sabinópolis and the highest volume (120 m³ ha-1) in Lençóis Paulista. The mean heritability of progenies for the two analyzed variables was considered high, and the genetic correlations between survival rate and volume were weak for all sites. The G×E interaction was significant and of the complex type, with genotype correlation between sites of 47%, indicating that the ranking of the best progenies differed in each studied environment. The analysis of stability and adaptability indicated the possibility of selecting progenies with good performance in the three environments; however, to improve the quality of the evaluated characteristics, it is necessary to select specific progenies for each environment.