Biomass equations for quillay ( Quillaja saponaria mol) in the semiarid region of Central Chile

Abstract

Quillaja is one of the most important species growing in the semiarid region of Chile because of the high content of saponin in its bark. The wood is normally used as charcoal. Biomass equations to estimate the weight of total stem bark, commercial bark, stem wood, branches and total tree were developed. Data were obtained in three areas located in the north, centre and south of the Chilean semiarid region. Thirty trees were completely weighed. Individual tree components and total tree weights were regressed against DBH, basal diameter, total height and number of main branches, and a combination of them, using the allometric equation of the form Y = a X b and a multiple linear model, both weighted and unweighted. The best results were obtained with the second kind of model, giving better estimates for total tree and stem bark weights. The poorest estimates were obtained for commercial bark.