Conceptual models of wood formation suggest that trees with large crowns produce low quality wood, but few studies have explicitly examined the relationship between crown size and wood quality. In this study, I examine how crown size influences the strength and stiffness of wood, as measured by Modulus of Elasticity (MOE) and Modulus of Rupture (MOR), using 42- and 72-old year plantation white spruce (Picea glauca) from Ontario, Canada. Mechanical properties were determined from 10x10x140 mm mini-clear samples (n=657), selected from a radial gradient at three heights within the stems. Non-linear mixed-effects models showed that strength and stiffness significantly decreased with crown size, and that MOE and MOR were best predicted by cambial age and crown ratio. The results suggest that the models could be used in conjunction with remotely sensed data to identify high quality timber prior to harvest.

Conceptual models of wood formation suggest that trees with large crowns produce low quality wood, but few studies have explicitly examined the relationship between crown size and wood quality. In this study, I examine how crown size influences the strength and stiffness of wood, as measured by Modulus of Elasticity (MOE) and Modulus of Rupture (MOR), using 42- and 72-old year plantation white spruce (Picea glauca) from Ontario, Canada. Mechanical properties were determined from 10x10x140 mm mini-clear samples (n=657), selected from a radial gradient at three heights within the stems. Non-linear mixed-effects models showed that strength and stiffness significantly decreased with crown size, and that MOE and MOR were best predicted by cambial age and crown ratio. The results suggest that the models could be used in conjunction with remotely sensed data to identify high quality timber prior to harvest.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this research was to determine plant growth and development and fruit yield of the strawberry crop from bare root and plug transplants with different crown diameters. Bare roots transplants were produced by rooting stolons and plug transplants from runner tips collected and rooted in a substrate growing bed. Three classes of crown diameters were compared, in a 2 x 3 factorial and randomized block experimental design, with four replications, 16 plants per plot and a density of 6.6 plants m-2. For bare root transplants, crown diameters were between 3.0 and 5.0 (class 1); 5.1 and 8.0 (class 2) and greater than 8.1 mm (class 3). For plug transplants, runner tips were screened between 2.0 and 3.9 (class 1); 4.0 and 5.5 (class 2) and 5.6 to 7.0 mm (class 3). Transplants of both types were planted at April 16th, 2008, and at this date, crown diameter, shoot and root dry mass and number of leaves were higher in all classes of plug transplants. Ripe fruits were harvested from June 15th to November 7th, 2008, and fresh fruit yield was determined. Plant growth and development were determined at last harvest. Higher growth, development and fruit yield were obtained in plants from plug transplants. For bare root transplants, crown diameters higher than 5.1 mm can be used while for plug transplants the crown diameter of runner tips does not affect plant growth and fruit yield. / O objetivo deste trabalho foi determinar o crescimento e o desenvolvimento da planta e a produtividade de frutas de morangueiro com o emprego de mudas de raízes nuas e de torrão com diferentes diâmetros de coroa. As mudas de raízes nuas foram produzidas pelo enraizamento dos estolões e aquelas de torrão a partir de pontas de estolões coletadas e enraizadas em leito de cultivo preenchido com substrato. Três classes de diâmetro de coroa foram comparadas, em um esquema fatorial 2 x 3, em delineamento blocos ao acaso, com quatro repetições, 16 plantas por parcela e densidade de 6,6 plantas m-2. Nas mudas de raízes nuas os diâmetros de coroa foram entre 3,0 e 5,0 (classe 1), 5,1 e 8,0 (classe 2) e maior do que 8,1 mm (classe 3). Naquelas de torrão, as pontas de estolão foram classificadas entre 2,0 e 3,9 (classe 1), 4,0 e 5,5 (classe 2) e 5,6 a 7,0 mm (classe 3). As mudas de ambos os tipos foram plantadas em 16 de abril de 2008 e nessa data o diâmetro da coroa, a massa seca da parte aérea e das raízes e o número de folhas foram mais elevados nas mudas com torrão. As frutas foram colhidas maduras entre 15 de junho e sete de novembro de 2008 e a produção de frutas foi determinada. Nesta data foi determinado também o crescimento e desenvolvimento das plantas. Maior crescimento, desenvolvimento e produção de frutas foram obtidos com o emprego de mudas com torrão. Com mudas de raízes nuas as classes 2 e 3 devem ser empregadas, enquanto nas mudas com torrão o diâmetro da coroa da pontas de estolão não influencia a produção de frutas.