TREE STAND STRUCTURE, SPECIES COMPOSITION AND VEGETATION COVER CHANGES IN LONDIANI FOREST KENYA

Abstract

Vegetation is an important variable in land-atmosphere interactions. Sustainable forest management requires monitoring of vegetation cover dynamics to help improve forest health. Many studies have been conducted in many forest ecosystems in Kenya but only a few have analyzed vegetation cover dynamics of the Londiani Forest on tree stand structural heterogeneity. The main aim of this study was to assess tree stand structure, species composition and forest cover change in Londiani Forest in Kericho County over the past 20 years. Specifically, the study aimed to (i) determine tree stand structure and species composition, (ii) determine forest cover change of Londiani Forest, and (iii) evaluate the roles of the forest adjacent community (FAC) influencing vegetation dynamics. Londiani Forest is divided into Kedowa, Chebewor and Londiani. From each of these blocks transect running 100m from the edge of the forest were laid. Quadrats measuring 100x100m were established every 200 meters for the length of the transect. Data on standing/live trees, abundance and tree species were determined and recorded in a data sheet. Diameter at Breast Height (DBH) was measured 1.3m from the ground using a diameter tape. Tree height was also measured using a Suunto clinometer. Nested 25x25m-quadrats for saplings and 1x1m for seedlings were laid where all the saplings and seedlings for each tree species were recorded. Stumps of trees which had been cut previously were counted in addition to identifying tree species which each tree stump was derived from. The use of Normalized Difference Vegetation Indices (NDVI) to detect forest cover changes was employed in the study. Landsat Thematic Mapper TM images were acquired and processed with the Arc Map GIS software version 10. Supervised classification was carried out to delineate the images into three classes (forest, grasslands/ bush lands and bare lands/ water bodies) to analyze the extent of forest cover changes in the selected years (2000, 2003, 2010, 2015 and 2020). Adjacent to each of these forest blocks, 9 villages were selected using the purposive sampling method. Structured questionnaires and interviews were administered; Focus group discussions (FGDs) and interviews were held with the key informants and institutional managers involved in forest management to ascertain the role of the community in vegetation dynamics. Quantifiable data were entered in Ms Excel for data management and calculation of; Total density, species density, diversity, abundance, richness, similarity, evenness and basal area. Predictive Analytics Software (PASW) version 25 was used to analyze various variables between and within the study sites. A total of 1,308 individual trees belonging to 34 different species from 24 families were recorded. Kedowa had an abundance of 457 trees and richness 27, Chebewor 417 trees, richness 19 and Londiani 434 trees, richness 14. Kedowa block had a diversity of H’= 0.864, Chebewor H’= 0.855 and Londiani H’= 0.792. A total of 58 charcoal making spots were recorded. NDVI maps showed that Natural forests increased by 30% between 2000 and 2010, plantation forest increased by 50% between 2000 and 2010. NDVI values for natural forest ranged from 0.4 recorded in the year 2000 to 0.7 in 2010, plantation forest 0.2 in 2000 to 0.5 in 2010. The Londiani Forest Adjacent Communities (FAC) is involved in forest activities confirmed by the high Community Forest Associations (CFA) membership of 81% under different user groups like ecotourism at 10%, bee keeping at 6%, seed and seedling collection at 30% and tree nursery at 53%. The study findings would inform sound decision making on forest management and recommends for adoption of its findings and suggestions by forest management institutions and agencies for a better understanding of forest cover changes which is urgently needed to strengthen operations on forest management.