Abstract: This study was conducted in Western Serengeti with an objective of exploring how plant diversity changes along a gradient of different human influences, starting from a public land (open area), through a game reserve and into a national park. In terms of human influence, there is no legislation governing utilization of public land, whereas game reserve areas enjoy partial protection where prescribed human activities are allowed. For the case of national parks, apart from tourism, human activities are totally prohibited. Three sites were selected for this study namely Mihale, Robanda and Sodeko. The study further aimed to identify plant indicator species associated with different soil characteristics. Species diversity and evenness increased from the public land through the game reserve and maximum diversity was observed in the national park zone, although such results were not statistically significant (p>0.5). Canonical Correspondence Analysis (CCA) results indicated that floristic composition in any study site was dependent on its conservation status as well as its historical background. This was quite obvious for Mihale site but not for Robanda and Sodeko (also known as Tabora B) where much of the game reserve was annexed recently from the public land. Texturally, the soils of Western Serengeti are highly variable, comprising of 11 textural classes, dominated mainly by clay fractions. The chemical and physical characteristics of the soils in Western Serengeti were directly linked to different vegetation typologies occurring in Serengeti with exchangeable bases overriding other factors as determinants of the vegetation. The decline in available phosphorus concentration detected along the soil profiles accumulation of the same in the top soil was an indication that soil phosphorus was chiefly derived from frequent fires that sweep the Serengeti grasslands annually and not from weathering of the parent material. A number of indicator plant species of various ecological conditions conforming to those reported in various literatures were encountered. These included indicators of fallow land; indicators of disturbed and poor soils; indicators of water logged soils and indicators of phosphate and nitrogen rich soils.