Comparison of the subspecies of Sclerocarya birreaby sex and environment

Abstract

A comparison of stand parameters between wild and on farm populations of the 3 subspecies of Sclerocarya birrea was done. Using plot-less sampling technique, 100 trees from six populations were measured for diameter at breast height (Dbh), branching height, height and crown diameter. There was significant (p<0.001) difference in Dbh, branching height and tree height between the three subspecies and between the populations. For all subspecies and populations, male trees were taller than female trees although the difference was not significant. While S. birrea subspecies birrea and caffra had trees in the wild taller than those on farm, the opposite was observed among trees of S. birrea subspecies multifoliolata. The mean crown sizes of male and female trees differed significantly (p<0.001) between the three subspecies and within a population. There were positive correlations (p> 50) between altitude and tree diameter, branching height, tree-height and crown diameter. Tree size was not found to increase due to farmers’ selection pressure and farming practices in Tanzania, probably because they are not retained purposely for their fruits as is the case in other countries in southern Africa.

Key words: Sclerocarya birrea, Tanzania, population, habitat, gender