ASSESSMENT OF PLANT SPECIES AND STRUCTURAL VARIATION IN MAJOR URBAN GREEN SPACES OF NAIROBI CITY

Abstract

The  few  remnants  of  urban  green  spaces  are  faced  with  various  threats  due  to  the  changes  in  the  surrounding landscape. The plant composition is being altered by the human encroachment that negatively affects delivery of essential ecosystem services. The status of current urban plant composition in relation to location and disturbance level  of  sites  is  unknown.  This  study  was  therefore  carried  out  to  determine  the  vegetation  composition  of  the major green spaces within Nairobi city namely City park, Karura Forest and Ngong Forest. Transects were laid out along environmental gradients, and plant species within 20 x15 m quadrants were identified, and recorded. The abundance of each species was recorded using a scale of 1 to 5, and the structural composition was determined using the Braun-blanquet method. A higher mean species richness was observed in the plants below 1 m with 130, 81, and 128; and lowest in the 3-8 m with 13, 51 and 44 in City Park, Karura and Ngong’ forests respectively. Teclea simplicifolia, Setaria pricatilis were the most abundant species in 3-8 m and below 1 m layers, respectively. Several species appear only in 1 quadrat out of the sampled in each site, in planning for conservation emphasis should be on such species to avoid their extinction. The neighboring communities should be encouraged to participate in the conservation of these important sites and enhance plant diversity especially indigenous species.

Key words:  Urban parks, remnant green spaces, vegetation structure, species diversity, indigenous species