Site index functions for Cupressus lusitanica at Munesa Shashemene, Ethiopia

In 25 permanent sample plots in Cupressus lusitanica plantations of the Munesa Shashemene Wood Industry Enterprise, in the Oromia Federal Regional State, Ethiopia, the dominant height growth was observed and site index functions fitted. The plots had been continuously observed from ages 7 (10) to 21 (18) in the Gambo–Shashemene and the Munesa growth districts, respectively. Measurements in each plot were taken 5–8 times, altogether a total of 163 observations were available. Parameterising the general Chapman–Richards function, showed that (i) no point of inflection within the range of the data was found, (ii) the growth rate parameter, k, of the model did not depend on site index, and (iii) the growth rate parameter, k, and thus the shape of the height growth curves differed significantly between the Gambo–Shashemene and Munesa growth districts. Previous site index curves for the same region fitted well for the Gambo–Shashemene district but not so for Munesa. Therefore, it is concluded that when developing and using site index functions, growth districts as a possible reason for different shapes have to be taken into account.