Abstract

Mortality was modeled for the Acacia melanoxylon, Eucalyptus camaldulensis, and Eucalyptus nitens species at plant densities of 5,000, 7,500, and 10,000 trees ha-1 in a biomass production trial for dendroenergetic purposes. One setup was based on individual tree level and two modeling alternatives were evaluated involving four survival probability equations and eight difference equations. Individual tree survival modeling considered a logistics model, which is a linear combination of variables per tree at current time t and previous time as estimator. These were the main variables of the competition index variation and the basal area growth variation between the current and the previous growth period. The survival probability alternative involved state variables of the stand like age, dominant height, and average square diameter as predictors, while the difference equations were fitted according to age-based changes only. The stand level models showed better results than the individual tree models, and in general, the mortality models based on difference equations presented better precision indicators and parsimony. The relative mortality rate was constant, i.e., (∂N / ∂E)/ N = α, and varied between species, revealing greater mortality, consecutively, in E. nitens, A. melanoxylon, and E. camaldulensis. Although mortality tended to be higher at greater plantation densities, stand density did not significantly affect the fitted models’ parameters.