| Milicia excelsa (Welw.) C. C. Berg and M. regia (A. Chev.) C. C. Berg (Moraceae), known together as odum, are important timber-producing species which range across Africa from Gambia to Tanzania. The overall goal of this study was to clarify, on both large and small scales, what factors influence the establishment, survival, and growth of this tree. First, the patterns of distribution of Milicia species in Ghana were examined, using data from the 1989 Forest Inventory Project (Ghana Forestry Department-Overseas Development Administration). Milicia species were found to be much more common in the dry forest types than in the wet forests, on average in fifty-two forest reserves.; Two studies were done on factors influencing natural regeneration of Milicia excelsa. In the first, we planted seedlings in artificial gaps of three sizes to evaluate seedling survival, growth and attack by the gall-forming psyllids in the genus Phytolyma. Thirteen months after planting, seedlings were significantly smaller in diameter and height in the small gaps than in the medium and large gaps. Galls were first recorded in a large gap ten months after planting. At eleven months, all five large gaps and one of the four medium gaps had galls. By thirteen months, the percentage of trees with galls was not significantly different by gap size.; In the second regeneration study, a survey of all trees {dollar}>{dollar}30 cm diameter breast height was done on 43 ha. Milicia density in this forest was 0.95 per ha. The population of naturally-occurring seedlings on one hectare was evaluated over thirteen months. It was found that the number of seedlings varied little over this period (mean = 65 seedlings/ha). Seedlings were growing in areas with 2-29% of full solar irradiance. Fruits were found in abundance up to 20 m away from large female trees, while seedlings were found up to 150 m away from parent trees. Phytolyma spp. were not observed on any natural or planted seedlings, although it was present in the crowns of dominant trees. Planted seedlings survived at light levels between 2-37% of full irradiance. Mortality of seedlings was not significantly greater near parent trees.; In the final set of studies, Milicia excelsa was planted in mixed-plantations. The first experiment included mixtures of 11, 25, 50, and 100% Milicia with Terminalia superba, planted in a forest clearing and replicated in an agricultural area. At two months after planting, there were significantly fewer galls on Milicia in the lowest density mixture, at both sites, but there were no differences in gall means at six months. In the second experiment, 50-50 mixtures of Milicia excelsa and Albizzia adianthifolia (Mimosaceae), Tectona grandis (Verbenaceae), Khaya ivorensis (Meliaceae), Ceiba pentandra (Bombacaceae) and a mixture combining all species were planted. We found no significant differences in gall formation among these treatments. |
