ABSTRACT

The morphometric study of forest species contributes to the understanding of an individual's development based on variables such as diameter at breast height (DBH), height and information on the crown of the tree. The main morphometric characteristics of the trees are the Crown Ratio (CR), Degree of Slenderness (DS), Salience Index (SI), Coverage Index (CI) and Crown Formal (CF). The traditional modeling to obtain these indexes results in a one-off estimate. The objective of this study was to obtain the morphometric indices for black wattle species (Acacia mearnsii de Wild.) throughout its cultivation cycle, using ratio estimates. The data used to carry out this work were obtained in the southern region of the state of Rio Grande do Sul, in three regions, which have a concentration of commercial plantations of the species: Cristal, Encruzilhada do Sul and Piratini. Forty-eight (48) temporary plots were installed in stands between one year and 10.75 years old and 672 trees were sampled to measure the DBH, total height (h), crown length (l) and crown diameter (dc) variables. The modeling of the indexes was performed using ratio estimates. The crowns, on average, occupy 52,10% of the height, this being more prominent in young forests, decreasing throughout the cultivation cycle of the stands. The DS resulting in a value greater than 1, indicating that growth in height exceeds growth in DBH. On average, they have crowns 22 times larger than DBH, with a decreasing trend due to age, growth in height greater than the growth in diameter of the crown, and, in most cases, black watle trees have slender crowns. Precisions are not constant over the ages, and, for the most part, the indices are of medium accuracy. The results presented in this work are useful to understand the dynamic processes occurring in black wattle forests.

Keywords
Morphometry; Black wattle; Index accuracy