Modelling the growth of mean top height and basal area of Eucalyptus grandis in Zimbabwe
Degree GrantorUniversity of Canterbury
Degree NameMaster of Science
Data from Nelder spacing trials for a limited range of ages from 1 to 7, were used to model the growth of basal area and mean top height of Eucalyptus grandis in Zimbabwe. Two projection functions, the log reciprocal and Hossfeld were tested on data arranged as non overlapping (T₁-T₂, T₂-T₃, ...... Tn-₁-Tn) and overlapping (T₁-T₂, T₁-T₃, T₁-Tn, T₂-T₃, T₂-Tn, etc). The log reciprocal performed poorly on both overlapping and non overlapping mean top height (h 100) data. The Hossfeld function fit to overlapping and non overlapping h100 data did not appear to be very different, but overall the fit to overlapping data was slightly superior. The log reciprocal fitted both overlapping and non overlapping basal area (G) data better than it did with h100 data, but the Hossfeld still proved superior with the overlapping data. The functions were first run without the initial stocking variable and although its inclusion caused small improvements in the fitting. The small improvements that were used to eliminate some of the functions were quite important when the h100 and G were converted to volume/ha in the stand volume equation. The Hossfeld function, with the initial stocking included, fitted to overlapping data for both h100 and G, was the preferred choice of projection equation.