An assessment of impact of charcoal making on distribution of some tree species in Kibwezi Division
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Date
2002-05
Authors
Kariuki, Peris M.
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Abstract
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
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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.
Description
Department of Environmental Studies and Community Development, 110p, 2002