An assessment of impact of charcoal making on distribution of some tree species in Kibwezi Division
Kariuki, Peris M.
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This study was carried out in Kibwezi Division, Makueni District Kenya. The aim was to assess impact of charcoal making, abundance and distribution of some selected tree species. The selected species were: Acacia tortilis (Forrsk.) Hayne, Acacia mellifera (Vahl) Benth, Newtonia hildebrandtii (Vatke) Torre var. hildebrandtii, Haplocoelom foliolosum Hiern Bullock and Terminalia brownii Fresen. Stem sizes of standing trees and stumps were used to investigate the abundance and distribution of selected species and past harvesting patterns in Kibwezi Forest Reserve, DWA Estate Forest and Privately Owned Land, areas subject to different management regimes. Data such as dominant plant species, vegetation cover and kiln sizes were collected by direct field observation from 158 randomly located plots each measuring 20m by 20m. This data was supplemented by interviews and focus group discussions. Data gathered was analysed using descriptive statistics and inferential statistics such as Analysis of variance (ANOVA). Results of data analysis showed significant (P<0.05) differences in distribution of A. tortilis, N. hildebrandtii and H. foliolosum in the three study sites while no significant (P<0.05) variation was observed in the occurrence of A. mellifera and T brownii . Results further indicate differences in the population structure of selected species. The highest percentage of stems for most species among them A. forti/is (29.8%), A. mellifera (44.1%) and T brownii (43.9%) were < 10cm in basal diameter. H. foliolosum had the highest percentage of stems (32.1%) between 20cm and 30cm while N hildebrandtii had most of the stems (34.4%) above 90crn. From this study it was observed that charcoal making was more prevalent in Kibwezi Forest Reserve. Results further showed that at least 32 different tree species are used for charcoal making using the earthmound kiln method. Preferred species such as N hildebrandtii, Balanites aegyptiaca, Berchemia discolor, Acacia senegal and Olea europea ssp africana wer e rarely VI encountered and as a result poor quality species such as Sterculia africana and Commimphora africana are progressively being used to make charcoal in the area. Stumps of over 30 different tree species were found in 55.6% of the plots sampled and there was a significant difference (P<0.05) between the mean of stumps in the three study sites. There were also significant differences in the number of stumps recorded between various stem size classes with the highest (41.1%) ranging from 10cm to 20cm. Over half (60.1%) of stumps were observed to be re-sprouting. A relatively high rate of regeneration was noted among certain species such as Combretum collionum (92.3%) and Euphorbia c,andelabrum (50.6%). Observed impact of charcoal making included loss of vegetation cover, change in population structure of harvested species and change in species composition. The study recommends that a policy on charcoal production and marketing should be formulated. Research on efficient charcoal kilns, alternative fuels and agro-forestry as means of minimizing some negative effects of charcoal making in the study area should be undertaken.