Biometric assessment of early stem growth at a commercial stand of African mahogany (Khaya grandifoliola)

African mahogany species (Khaya spp.) have proven to be promising in the Brazilian forestry scenario, replacing native mahogany owing to their medium-fast growth and relevant timber value. This study aimed to carry out forest inventory and assessments of a Khaya grandifoliola plantation in the first years after planting, test hypsometric models to describe tree growth, and identify the maximum commercial stem yield (i.e., greater than 6 m in height). The stand was located in the municipality of Piracanjuba (GO), where seedlings of seed origin were used. Twenty random plots with a 15 m radius were allocated, and the total height (HT), stem height (HS), diameter at breast height (DBH), crown area, and forest canopy were measured. Four hypsometric models were employed in this study. The best equation was selected based on determination coefficients and standard errors. Further, the models were cross-validated to evaluate predictability and bias. At four years of planting, the largest class of HS was found to range from 3.1 to 4.1 m, and most trees had a DBH ranging from 0.084 to 0.126 m. The percentage of trees with stems > 6 m was 8.35%. The linear model ensured more consistent results for estimating HT, while the quadratic and Weibull models led to more consistent results for HS. By using models, stem measurements can be measured based on DBH, ultimately aiding the selection of stem management strategies for the growth of forests with greater commercial value.

Brief history of Eucalyptus breeding in Brazil under perspective of biometric advances / Breve histórico do melhoramento genético do eucalipto no Brasil sob a ótica dos avanços biométricos

ABSTRACT: Forest breeding is a science that has been developing in Brazil since 1941 being the Eucalyptus a highlighted genus in this scenario. In a global scene, Brazil is displayed prominently in productivity of Eucalyptus planting, due to favorable environmental conditions to cultivation development, and the incentive in research for improvement of traits of interest t observed in it species and hybrids. This research included a historical review of Eucalyptus breeding over the years under genetic biometric perspective in Brazil, from reports describing the pioneer planting up to the current genome wide selection (GWS) that came as a complement of forest breeding success. This review showed some of the tracks performed by researchers aiming to improve the productive and quality of phenotypic traits from Eucalyptus genus.

RESUMO: O melhoramento florestal é uma ciência que tem tido desenvolvimento no Brasil desde o ano de 1941 e um gênero que obteve grande repercussão neste cenário foi o Eucalyptus . O Brasil apresenta-se em destaque no panorama mundial quanto à produtividade dos plantios de eucalipto, em virtude das condições ambientais favoráveis ao desenvolvimento da cultura e ao incentivo em pesquisas destinadas às melhorias dos caracteres de interesse, presentes em suas espécies e híbridos. Este trabalho inclui uma revisão histórica do melhoramento do eucalipto ao longo dos anos no Brasil, sob a ótica da genética biométrica, desde o relato que descreve o plantio pioneiro de suas espécies no país, até a atual aplicação de seleção genômica ampla (SGA), que surgiu como um complemento de sucesso no melhoramento florestal. A pesquisa ilustra ainda alguns dos caminhos percorridos por pesquisadores a fim de aumentar a produtividade e a qualidade dos caracteres fenotípicos do gênero Eucalyptus.