Land Cover, Woody Plant Diversity and Anthropogenic Disturbance on Tulimani Hill Ecosystem in Makueni County, Kenya.
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Date
2025-02
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Kenyatta University
Abstract
Despite its designation as a forest reserve by the Kenya National government in 2018, very limited information existed on the composition, diversity and patterns in the plant and animal life of Tulimani Hill. This research aimed at addressing the gaps by documenting the land use and land cover changes on Tulimani Hill, assessing woody plant diversity and abundance and identifying indicators of anthropogenic disturbance. Global Information Systems (GIS) techniques were used for land cover mapping using satellite images. Data collection involved 24 plots, each 20m x 20m, systematically placed along six line transects of 600m laid from the forest edge to hilltop. The first plot on every transect was set up 100m from the forest boundary followed by additional plots at intervals of 150m. The distance between the transects was 200m. In all plots, the woody plants were identified, counted and recorded. For species with difficulties in identification, the voucher specimens were collected for further analysis and determination at the National Museum of Kenya. Diameter at breast height (DBH) for trees above 10cm in diameter was measured and recorded. Percentage cover of species was estimated visually. Indicators of human impact were noted in each plot to gauge the extent of human influence. Arc Map version 10.8 software was used to process Landsat satellite images. Analysis of vegetation data were done using PAST 4.17 software, where data from the plots were organized into four categories based on the distance from the forest boundary (100m, 250m, 400m and 550m). Kruskal Wallis Test was used to determine variations in the species mean diversity indices, species mean densities, mean basal area of trees and mean cover with distance from the forest boundary to the hilltop. Dunn’s Post hoc test was done to separate the means. Shannon –Wiener Diversity index was used to compute species diversity. Spearman’s rank correlation was used to test the relationship between the indicators of human disturbance with distance from forest boundary. Land cover types on Tulimani Hill have undergone changes since 2012. Agricultural land increased by 113 hectares, built-up areas increased by 3.08 hectares and barren land increased by 27.84 hectares. Woody vegetation decreased between 2012 and 2022 by 102.42 hectares. Shrubland and grassland increased between 2012 and 2017 by 4.15 hectares but decreased between 2017 and 2022 by 45.64 hectares. The study recorded 50 species from 23 families with Fabaceae, Euphorbiaceae and Lamiaceae being the dominant families. Tree basal area, plant frequency, density, and cover were found to be variable among species. The correlation between the number of cut stems with distance up the hill was significant (r=-0.400, P =0.025). There was a significant correlation between the number of footpaths, charcoal kilns, and beehives with distance up the hill (r=-0.800; P=0.022), (r = 0.800; P=0.026) and (r=0.900, P=0.029) respectively. There was a significant reduction in evidence of cattle grazing and spread of invasive species with distance from the forest boundary (r=-0.100; P=0.023), (r=-0.900; P=0.040). The hill hosts a diverse array of woody plant species and indicators of human-related disturbances were more pronounced closer to the forest edge. The people in the local community are urged to plant more trees to alleviate degradation of Tulimani Hill forest. Public awareness, education and alternative livelihood projects can mitigate human impact, while a management plan is essential to combat illegal activities on the hill.
Description
A Thesis Submitted in Partial Fulfillment for the Award of Degree of Master of Science (Plant Ecology) in the School of Pure and Applied Sciences of Kenyatta University, February 2025.
Supervisor
1. Emily Wabuyele
2. Paul K Muoria