Abstract
Of the 129 indigenous Acacia species in Africa, 43 species have been confirmed to exist in Kenya. The objective of this study was to investigate Acacia species vegetation in Kenya and to analyze the relationship between the distribution of Acacia species and their growth environments. In this survey, two areas were targeted, representing, as expected, a great variety of plant vegetation. The first area extended from the foot (altitude 2745 m) of Mt. Elgon to the Mombassa coast (1 m), separated by 925 km, and the second extended from the foot (2150 m) of Mt. Kenya to Lake Magadi (620 m), separated by 511 km. Two methods of ecological analysis, regression and ordination analysis, were used to investigate how Acacia species abundance and composition are affected by environmental variables. Of the total 6492 Acacia trees, more than 50 % were Acacia tortilis, Acacia melifera, Acacia nilotica and Acacia seyal var seyal. Regression analysis provides evidence that altitude explains patterns in the abundance of Acacia species. Other environmental variables explained significant amounts of deviance for some, but not all, Acacia species. Ordination analysis and regression analysis suggest that sites with Acacia lahai, Acacia hockii and Acacia abyssinica are generally of higher altitude, contain Croton megalocarpus and Ficus species and are on hillsides. It also suggests that sites with Acacia tortilis and Acacia mellifera occur at lower altitudes; contain Terminalia brownii, Boscia angustifolia, Combretum species and Adansonia digitata; and have salty soil and are in a valley. Each individual Acacia species has a specific ecological characteristic and survival strategy. For example, Acacia tortilis trees have a comparatively high environmental adaptability and competition capability. A. xanthophoria and A. drepanolobium's important survival strategy is their speedy rate of growth.
