An inventory and assessment of exotic and native plant species diversity in the Kenyan rangelands: Case study of Narok North Sub-County

Abstract

A botanical inventory and diversity of exotic and native species was assessed in the rangeland of Narok North sub-County, Kenya. A total of 72 species were recorded, composed of 64 species of trees and shrubs and eight species of herbs. They belonged to 34 families and 52 genera. Fabaceae was the richest family with 16 species, followed by Euphorbiaceae (five), Moraceae and Myrtaceae (four each). In total, 48 species were native and 24 exotics with a diversity index H of 1.082 and 0.604, respectively. Hypericum revolutum, a native shrub, was the most dominant with an importance value of 3.81, followed by three exotic species; Datura suaveolens (an invasive species), Dovyalis caffra and Hibiscus rosa- sinesis with importance values of 3.40, 3.35 and 3.23, respectively. The native species were abundant in undisturbed areas while the exotics were most common in areas with vegetation cover less than 60%. Four invasive alien species were encountered namely; D. suaveolens, Lantana camara, L. trifolia and Opuntia ficusindica. They all had a high density that indicated greater establishment success. This inventory affirms that the rangelands of Narok North are undergoing serious changes in vegetation structure and composition due to human activities and requires urgent attention to conserve biodiversity and genetic resources.