Dynamic growth and yield model including environmental factors for Eucalyptus nitens (Deane & Maiden) Maiden short rotation woody crops in Northwest Spain

Abstract

A dynamic model consisting of two projection functions, dominant height and basal area, was developed for the prediction of stand growth in Eucalyptus nitens bioenergy plantations aged 2–6 years and with stockings of 2,300 and 5,600 trees ha−1. The data came from 40 permanent sample plots, representing site quality variability across the distribution area of E. nitens crops. Three inventories were carried out to collect tree data and determine stand variables. Additionally, edaphic, physiographic and climatic information were obtained and included in the model. For both functions, an ADA growth model was selected, which achieved high accuracy. The corresponding growth curves developed in this study had values of 5, 8, 11 and 14 m for dominant height and 4, 14, 24 and 34 m2 ha−1 for basal area at the base age of 4 years. The inclusion of environmental factors (i.e. soil and climatic variables) as parameters in the model resulted in good estimations and increased the model’s flexibility to adapt to small variations in site conditions. The model developed here is thus shown to be useful for simulating the growth of E. nitens crops when environmental information is available. A prediction function was fitted for use in stands without diameter inventories or not previously occupied by E. nitens, and including environmental variables improved its accuracy. Biomass mean annual increment varied from 3.25 to 18.45 Mg ha−1 year−1 at the end of the rotation, projected as between 6 and 12 years depending on site quality.