The influence of plantation age and environment on the relationship between leaf mass and leaf area of black wattle (Acacia mearnsii De Wild.)

Abstract

The larger the exposed leaf area, the higher are the amount of photosynthates and dry matter. Since leaf area is an indicative of production, it can be used to model the forest canopy even considering the difficulty of modeling such variable. We aimed to analyze the relationship between leaf dry mass and leaf area in black-wattle plantations throughout its cultivation cycle at different locations. For that, the area and dry mass of leaves were measured in 1-, 3-, 5-, and 7-year-old commercial plantations of black-wattle in Cristal and Piratini municipalities, Rio Grande do Sul state, Southern Brazil. Three 9 x 14 m plots were established on each plantation. Plants were measured for their circumference at breast height (1.3 m aboveground) and two trees having the two mean values at each plot were selected for determination of leaf biomass and area. In order to measure leaf area, three 50-g samples were taken along the entire crown of each tree. Fitting statistics and the evaluation of the models we used indicated that the relationship between leaf area and leaf dry mass is not influenced by the planting site, but rather by plantation age. Moreover, the analyses also showed that leaf dry mass can be used to estimate leaf area, since the correlation between these variables is very strong.