Silvia Monteoliva

Dry weight partitioning and hydraulic traits in young Pinus taeda trees fertilized with nitrogen and phosphorus in a subtropical area

Plants of Pinus taeda L. from each of four families were fertilized with nitrogen (N), phosphorus (P) or N + P at planting. The H family had the highest growth in dry mass while the L family had the lowest growth. Measurements of plant hydraulic architecture traits were performed during the first year after planting. Stomatal conductance (gs), water potential at predawn (Ψpredawn) and at midday (Ψmidday), branch hydraulic conductivity (ks and kl) and shoot hydraulic conductance (K) were measured. One year after planting, dry weight partitioning of all aboveground organs was performed. Phosphorus fertilization increased growth in all four families, while N fertilization had a negative effect on growth. L family plants were more negatively affected than H family plants. This negative effect was not due to limitations in N or P uptake because plants from all the families and treatments had the same N and P concentration in the needles. Phosphorus fertilization changed some hydraulic parameters, but those changes did not affect growth. However, the negative effect of N can be explained by changes in hydraulic traits. L family plants had a high leaf dry weight per branch, which was increased by N fertilization. This change occurred together with a decrease in shoot conductance. Therefore, the reduction in gs was not enough to avoid the drop in Ψmidday. Consequently, stomatal closure and the deficient water status of the needles resulted in a reduction in growth. In H family plants, the increase in the number of needles per branch due to N fertilization was counteracted by a reduction in gs and also by a reduction in tracheid lumen size and length. Because of these two changes, Ψmidday did not drop and water availability in the needles was adequate for sustained growth. In conclusion, fertilization affects the hydraulic architecture of plants, and different families develop different strategies. Some of the hydraulic changes can explain the negative effect of N fertilization on growth.

Variation of wood Density and fibre length in six Willow Clones (Salix SPP.)

The variability of wood basic density and fibre length was determined in six 13-year-old willow clones growing under two different site conditions in Argentina. Values of basic density and wood fibre length were obtained and variance analyses were performed considering site and clone as sources of variation. Components of genetic and phenotypic variations were determined to calculate heritability in the broad sense. Site influence was significant for basic density, which ranged from 0.364 kg/dm3 and 0.455 kg/dm3. Clones “americano” and hybrid cv “A 13-44” showed the highest density values in both sites. For fibre length, values of the continental site were significantly higher. For each clone, mean values vary between 837.1 μm and 1142.1 μm. Heritability values show that the genetic control is stronger for density (h2 = 0.65) than for fibre length (h2 = 0.32). The clones “americano” and “13-44” stand out because of their high density and long fibres.

BASIC DENSITY AND FIBRE LENGTH AT BREAST HEIGHT OF EUCALYPTUS GLOBULUS SSP. GLOBULUS FOR PARAMETER PREDICTION OF THE WHOLE TREE

The aim of the present work was to analyze the associations between basic density and fibre length at breast height (BH) and of the whole tree. This study focused on the need to find a sampling point representative for the whole tree, using 35-year-old Eucalyptus globulus ssp. globulus plantations established under two different growing conditions in the province of Buenos Aires, Argentina.The relationship between whole-tree and BH values was quantified using linear regression analysis. Relationships were obtained for each growing site and wood features.

Estudio de algunas propiedades físicas de la madera de "Acacia melanoxylon" en Argentina

El objetivo del trabajo fue caracterizar la madera de Acacia melanoxylon R.Br en terminos de densidad normal, contraccion e hinchamiento maximos, anisotropia dimensional y contenido de humedad en el punto de saturacion de las fibras. En el marco de una investigacion mas amplia, se seleccionaron 10 arboles en dos sitios la Provincia de Buenos Aires, Argentina. Para la determinacion de las propiedades fisicas se emplearon las normas argentinas IRAM 9532(1963), 9543(1966) y 9544(1973), y para el analisis de la varianza, modelos lineales mixtos. Los valores medios de los coeficientes de contraccion lineal para el conjunto de los arboles fueron de 0,16 y 0,30 en sus orientaciones radial y tangencial respectivamente. El punto de saturacion de las fibras correspondio a un contenido humedad del 24,7%. Los coeficientes de anisotropia dimensional tomaron un valor de 2, por lo que se espera un comportamiento normal en el secado. El sitio no influyo significativamente en la expresion de las propiedades fisicas analizadas. En cambio, la varianza entre arboles para todas las propiedades contribuyo a la varianza aleatoria total con el 29,8-46,5%. La densidad normal promedio fue de 604 Kg/m3, aumentando significativamente desde la medula hacia la corteza. No hubo correlaciones significativas entre densidad y cambios dimensionales.

Densidad básica, longitud de fibras y crecimiento en dos procedencias de Eucalyptus globulus en Argentina

Los objetivos del presente trabajo fueron evaluar la variacion de la densidad basica y la longitud de fibras de la madera de dos procedencias de Eucalyptus globulus implantadas en la provincia de Buenos Aires, Argentina. Se analizo ademas la relacion entre estas propiedades de la madera con los crecimientos de los arboles. Se estudiaron arboles de siete anos de edad, 10 de procedencia local y 10 de Valdivia-Chile. Se determinaron la densidad basica y la longitud de fibras a diferentes alturas en el fuste y en tres posiciones radiales para la longitud de fibras. Se encontraron diferencias significativas para la densidad (local 546,9 ± 36 kg m-3; Valdivia-Chile 490,8 ± 38 kg m-3), pero no para la longitud de fibras (local 863,6 ± 38,8 µm; Valdivia-Chile 830,2 ± 67,4 µm). Asimismo, se encontraron diferencias significativas con la altura de muestreo para la densidad y para la longitud de fibras, y con la posicion radial para longitud de fibras. A lo largo del fuste las procedencias manifestaron patrones diferentes de variacion para la densidad: la local, aumento en sentido base-apice y Valdivia-Chile mostro ausencia de variacion; y tendencias de descenso leve base-apice para la longitud de fibras. La varianza debida a arboles fue de 62 % para la densidad y 59 % para la longitud de fibras. Las procedencias se diferenciaron solo por su incremento medio anual en altura (Valdivia-Chile 2,6 m ano-1 ± 0,3 m ano-1, local 2,1 m ano-1 ± 0,2 m ano-1), no encontrandose correlaciones entre crecimientos medios y las propiedades de la madera.

Contenido de duramen y de albura en Eucalyptus globulus y Acacia melanoxylon implantadas en Argentina

e aims of the work were to determine heartwood and sapwood content in Eucalyptus globulus and Acacia melanoxylon trees, to study their variation and to establish relationships between heart- wood and log volume and diameter. Ten trees of 9-years old E. globulus and ten trees of A. melano- xylon between 19 and 32 years old were sampled in Buenos Aires, Argentina. Heartwood area, vo- lumes and percentage, and sapwood width were measured and calculated at four discs by tree (base, 1.3 m, 30% and 50% of total height). E. globulus heartwood percentage decreased signicantly from the base upwards (46% at the base and 30% at the last sample height); in A. melanoxylon axial die- rences were not signicant (48% to 31%). Sapwood width was relatively constant with sample height and its means were 26 mm for both species. Average heartwood volume represented 37 % of the log volume for E. globulus and 43 % for A. melanoxylon. For both species, linear regression models show positives relationships between heartwood volume and two variables of commercial and inventorial importance: log volume and diameter at breast height.Fil: Monteoliva, Silvia Estela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ingenieria Agricola y Forestal. Catedra de Xilotecnologia; Argentina

Wood color of Acacia melanoxylon: CIE color system application.

SUMMARY The aims of this study were to describe wood color of Acacia melanoxylon with CIE color system and to analyze color variation between sapwood and heartwood among sites. Twenty trees were selected at four sites in Buenos Aires Province (Argentine). Destructive sampling was done, and one disc was taken at the base. Each disc was cut in radial boards (2 cm thick) and four zones were demarcated: sapwood, two transitions zones (or external heartwood) and central heartwood. The parameters x, y, Luminance, dominant wavelength (DWL) and purity excitation (EP) were measured. The x, y and DW values differed among sites; although for luminance and EP no difference was found. Differences between sapwood and heartwood values were remarkable for all the variables. Sapwood and heartwood chromospheres were optically different. Sapwood color was light and varied between greenyellow zone and yellow saturated zone. Heartwood color predominates from yellow to saturated yellow orange. DWL ranges were 564-574 nm and low saturated (23-28%). Dispersion variables inside heartwood showed no relationship between external and central heartwood sectoring; therefore, three zones with similar optical properties would be considered as heartwood.

Functional relationships between wood structure and vulnerability to xylem cavitation in races of Eucalyptus globulus differing in wood density

Wood density can be considered as a measure of the internal wood structure, and it is usually used as a proxy measure of other mechanical and functional traits. Eucalyptus is one of the most important commercial forestry genera worldwide, but the relationship between wood density and vulnerability to cavitation in this genus has been little studied. The analysis is hampered by, among other things, its anatomical complexity, so it becomes necessary to address more complex techniques and analyses to elucidate the way in which the different anatomical elements are functionally integrated. In this study, vulnerability to cavitation in two races of Eucalyptus globulus Labill. with different wood density was evaluated through Path analysis, a multivariate method that allows evaluation of descriptive models of causal relationship between variables. A model relating anatomical variables with wood properties and functional parameters was proposed and tested. We found significant differences in wood basic density and vulnerability to cavitation between races. The main exogenous variables predicting vulnerability to cavitation were vessel hydraulic diameter and fibre wall fraction. Fibre wall fraction showed a direct impact on wood basic density and the slope of vulnerability curve, and an indirect and negative effect over the pressure imposing 50% of conductivity loss (P50) through them. Hydraulic diameter showed a direct negative effect on P50, but an indirect and positive influence over this variable through wood density on one hand, and through maximum hydraulic conductivity (ks max) and slope on the other. Our results highlight the complexity of the relationship between xylem efficiency and safety in species with solitary vessels such as Eucalyptus spp., with no evident compromise at the intraspecific level.

Densidad y propiedades mecánicas de la madera de Acacia melanoxylon implantada en Argentina

The aim of this paper was to determine the density (at 12 % m. c.) and the mechanical properties of sawn wood of Argentinean Acacia melanoxylon, and to study the relationship between these properties. Test samples were randomly selected from the material obtained by sawing 20 trees harvested in four different plantations grown in the southeast of Buenos Aires province. Density was determined according to IRAM 9544 and mechanical tests were carried out by following the procedures of ASTM D 143. The mean value obtained for density reached 564 kg.m -3 . Strength exhibited the following mean values:

Tensiones de crecimiento en Eucalytpus dunnii Maiden.: parámetros dendrométricos y anatomía de la madera

El objetivo del trabajo fue determinar el efecto de los parametros dendrometricos de los arboles y la anatomia de la madera sobre las tensiones de crecimiento en tres procedencias de Eucalytpus dunnii Maiden. Se muestrearon 15 arboles de E. dunnii de 19 anos en Corrientes, Argentina (28o 26’ 23,7’’ S 58o 59’ 47,7’’ O a una altitud de 65 m). Se determinaron tensiones de crecimiento a traves de dos metodos: indicador de tensiones de crecimiento (GSI, CIRAD-Foret) e indice de rajado en rollizo (IR). Se midio la altura total del arbol, el diametro (DAP), la relacion altura/diametro, un indice de competencia individual y algunas propiedades anatomicas (espesor de pared fibras, area de pared ocupada, diametro y frecuencia de vasos). Las procedencias no fueron una fuente significativa de variacion para ninguna de las variables. El GSI e IR mostraron magnitudes mas bajas que la citadas para la especie (GSI: 0,039-0,137 mm e IR: 0,241-1,866 %). Los valores del espesor de pared de las fibras (3,39 µm ±0,35) son un poco elevados con respecto a los valores esperados lo que podria indicar presencia de leno de tension. La altura del arbol y la competencia individual no presentaron una asociacion significativa con las tensiones de crecimiento. El DAP y la relacion AT/DAP tuvieron una relacion significativa con el IR solamente (R2=0,42 para AT/DAP y 0,27 para DAP). Las relaciones entre tensiones y las variables anatomicas cuantitativas no fueron significativas en ningun caso.