The Vegetation of Some Hillsides in Uganda: Illustrations of Human Influence in Tropical Ecology. II

Abstract

The catena system is used to describe the belts of vegetation on a hillside on the Sese Islands in Lake Victoria and 5 between Lake Victoria and Lake Kyoga, in Uganda. The hills are in the equatorial belt, with rainfall varying from over 20 cm. in the south to less than 10 cm. in the north. In general the 2 most southerly catenas show belts of short grassland on the hillsides, with closed evergreen forest on the tops and at the bases; the 2 northern catenas have woodlands on the tops and sides and more or less open grassland in the valleys. All hillsides show much evidence of human influence and some are now carrying a dense human population. Houses and cultivations are on the sides and tops of hills, rather than in the valleys. There is a great diversity of soils on each hillside, differing in color, reaction and phosphate, lime and potash content. The soils of inhabited areas are usually redder in color and richer in nutrients. The secondary nature of the vegetation is discussed and the ways in which man has altered it, by cutting forests, by burning, by conscious and unconscious encouragement of some indigenous spp. and by the introduction of exotics.