A YIELD TABLE MODEL FOR THE GROWTH OF <em>PINUS</em> <em>PATULA</em> IN ETHIOPIA

Abstract

Top height development of 8 permanent Pinus patula plots was used to show that the site index system for Uganda did suit well for Ethiopian stands. It also did not deviate much from the top height development found for South Africa. From 140 felled trees of Pinus patula, well distributed not only over the range of breast height diameters and heights but also over the agroclimatic zones of Ethiopia, a new stem form factor equation was calculated. From further 54 temporary plots in Pinus patula plantations in 10 plantation areas of Ethiopia the other necessary equations for a growth and yield model for unthinned Pinus patula stands were derived. Site index (top height at age 20) turned out to vary between 18 and 33 m, depending on elevation, soil type and initial spacing. Stem number development of these unthinned stands exhibited a much higher mortality at lower heights compared with the South African stands and much smaller mortality subsequently. Thus basal area per hectare developed more slowly over top height than in South African stands, exhibiting no maximum before a top height of 30 m, at this height reaching about the same level as the South African stands. Mean annual increment according to this growth model compares well with the best site class reported for northern Tanzania but is far below the mean annual increment of naturally regenerated stands of Pinus patula in Mexico at the same site index.