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The Status of Prunus africana ( Syn. Pegium africanum Hook. F.) in Kakamega and South Nandi Forests, Kenya
Abstract
This study was done to examine the structure and assess the natural regeneration potential of Prunus africana in South Nandi forest and selected sites of Kakamega forest, Western Kenya. Forest survey was carried out to investigate the structure of P. africana, the forest was stratified into three different forest types that is pure, mixed and natural forest in Kakamega forest. South Nandi forest was taken as one stand since the whole forest is natural and it was not possible to stratify it like Kakamega forest. Transect belts measuring 0.04 km wide nnd 1.5 km long were laid in both forests along an access line. A total of 140 and 134 plots measuring 0.02 ha each were established along these transects in Kakamega and South Nandi forests respectively. At the centre of each plot was a P. africana tree whose diameter at breast height (dbh), height and crown length were assessed. Samplings of the species of (>1.5 m in height and <5 cm diameter) were counted on each plot, and seedlings (<1.5 m in height) were also counted in smaller plots of 5 in radius from the central P. africana. Sampled trees of P. africana showed a discontinuous size distribution of height and dbh where the young regeneration was not replacing the mature trees coming to the end of their reproductive life in both forests. There is a shift in dbh classes from seedlings and saplings to large diameter classes and this was more pronounced in South Nandi and the natural stand in Kakamega forest. Thus the results do deviate from the hypothesized inverted 'J' shape of dbh distribution in both forests. The natural regeneration levels were found to be high in both forests since there were many seedlings counted in the forest floor, but they hardly reach the size of 1m hence there were few saplings in both forests. As a result, this reduces the rate of regeneration of P. africana in both forests. Stand density, crown size and density of P. africana were found to have little effect on the density of seedlings and saplings counted in both forests suggesting light may not be a significant factor at germination, but could influence subsequent growth. This is evident by the absence of saplings in both forests. This study has given important information on the stand structure of P. africana and the potential for its natural regeneration in Kakamega and South Nandi forests, which can be used as a tool for future management of the species.
... Export peaked at 500 tons in 1998 and about 300 tons were shipped in 2000. Only one exporter (Jonathan Leakey) has been involved in the Prunus africana trade in Kenya (Nzilani, 2001) and he ships dried or chipped bark to Prosynthese (a subsidiary of Groupe Fournier of France). ...
... Mature trees are also exploited for their timber. Following harvest of mature trees for local and export timber products (Nzilani, 2001) examined the Kakamega and South Nandi forests in western Kenya. She found few saplings and young trees, suggesting poor recruitment resulting from the removal of mature trees. ...
... It is distributed mostly along the eastern side of Africa from Ethiopia to South Africa, though there are populations in several West African countries and in the Comoros and Madagascar ( Fig. 1; Hall et al., 2000). Seeds of P. africana germinate well under shady conditions but require light gaps to survive beyond the sapling stage (Kiama and Kiyiapi, 2001;Nzilani, 2002;Tsingalia, 1989). These traits have led most authors to refer to P. africana as a secondary forest species (Cunningham and Mbenkum, 1993;Geldenhuys, 1981;Sheldon et al., 1997;Stewart, 2003). ...
... As for the poor seedling survival described by others and the lack of recruitment into the smaller stem size classes reported in this study, natural forest succession processes may be to blame. Though their seeds germinate successfully in shaded conditions, the seedlings of P. africana appear to require large light gaps in the canopy to survive to the pole stage (Kiama and Kiyiapi, 2001;Nzilani, 2002;Tsingalia, 1989). At central Isecheno, in particular, anthropogenic disturbance has been limited in recent decades (Fashing et al., 2004) and probably has not been of sufficient severity to create the large light gaps required for the successful regeneration of P. africana. ...
Prunus africana (Hook.f.) Kalkm. is a secondary forest canopy tree species that has been declining over much of its geographical range in sub-Saharan Africa during recent decades due to unsustainable harvesting of its bark for the international medicinal plant trade. One of the locations where the species is experiencing rapid mortality is Isecheno study site in the Kakamega Forest, Kenya where this study was conducted. Between 1997 and 2003, 21% of the P. africana (⩾10 cm DBH) at Isecheno died and an additional 9% experienced ⩾50% canopy dieback. However, scars from bark harvesting on P. africana were relatively small and scarred trees were not more likely to be dead or dying than unscarred trees, suggesting that bark exploitation is not causing P. africana mortality at Isecheno. Other possible causes that require further evaluation include disease, insect attack, nutrient deficiency, and/or climatic fluctuation. The poor regeneration of P. africana at Isecheno can likely be explained by the relative lack of recent disturbance coupled with the thick undergrowth layer at this site. P. africana mortality is of concern not only because the species is listed as Vulnerable by IUCN, but also because black and white colobus monkeys [Colobus guereza (Rüppell, 1835)] at Isecheno exploit it as their top food species and are particularly reliant on its leaves during times of `preferred' Moraceae fruit scarcity. The anticipated continued decline of P. africana may have adverse effects on C. guereza feeding habits, intergroup relations, and population density at Isecheno. Conservation of P. africana offers a formidable challenge since the species appears to require disturbance for regeneration, yet at sites where disturbance is occurring, P. africana is often a target of bark harvesters engaging in unsustainable levels of exploitation.
... It is distributed mostly along the eastern side of Africa from Ethiopia to South Africa, though there are populations in several West African countries and in the Comoros and Madagascar (Hall et al. 2000). Seeds of P. africana germinate well under shady conditions but require light gaps to survive beyond the sapling stage (Tsingalia 1989;Kiama and Kiyiapi 2001;Nzilani 2002). The tree is valued for its medicinal extract from its bark for the treatment of benign prostatic hyperplasia, a common condition in elderly men. ...
Prunus africana (Hook.f.) Kalkml., the African cherry, is an evergreen climax vegetation tree species typically reaching 25-30 m in height and occurs primarily in montane and submontane forests. In this study, the genetic structure of P. africana was analyzed using a coding chloroplast DNA region; Megakaryocyte-Associated Tyrosine Kinase Gene (MATK) and nuclear ribosomal internal transcribed spacer (nrITS) with 63 individuals in East Africa. This study detected low levels of genetic diversity as revealed by nucleotide diversity in nrDNA (ʌ = 0.00529) and cpDNA (0.00448). As revealed by the results of AMOVA analysis, genetic differentiation for cpDNA (F ST = 0.0275) was obviously lower than for nrDNA data (F ST = 0.237) in P. africana. Gene flow among populations based on nrDNA data (Nm = 2.641) was significantly higher than that based on cpDNA (Nm = 0.82). Mantel test revealed a significant correlation between genetic and geographic distances for cpDNA (r 2 = 3.0 × 10-5) and nrDNA (r 2 = 7.0 × 10-5). Demographic history analyses based on pair-wise nucleotide sequence mismatch distributions revealed that only the Kakamega population was in mutation-drift disequilibrium. Tajima's D neutrality test, however, revealed significant signatures of recent population expansion in only the Kakamega population (D =-1.85646; P < 0.05). This study therefore proposes immediate ex situ and in situ conservation of P. africana populations in Mabira and Elgon forests coupled with in situ conservation of Budongo, Kakamega and Monduli forests. _____________________________________________________________________________________________________________
... It is a tree species with maximum action priority in Africa [16] since it has been declining over much of its geographical range in Sub-Saharan Africa [17]. The seeds of P. africana germinate well under shady conditions but require light gaps to survive beyond sapling stage [18,19]. The population of mature P. africana in Sub-Sahara Africa has declined due to exploitation for large scale bark harvest [20]. ...
Prunus africana has been severely exploited for its valuable products rendering it unstable and at risk of extinction. Studies were therefore carried out on its regeneration density and population structure across different human disturbance gradients in South West Mau Forest (SWMF) Kenya. Four study sites with {undisturbed, low, moderate and high} human disturbances were identified in SWMF. In each study site three line transects, 100 m apart and running up to 1 km inside the forest were established. Four sample plots 20 m x 50 m were laid at 250 m intervals along each line transect then divided further into 10 subplots each 10 m x 10 m and nested 5m x 5 m sub-subplots. At the centre of each sub-subplot, a 1 m x 1 m quadrant was laid. In each sub plot Diameter at Breast Height (DBH) of all adult trees and poles were measured while the number of saplings in each sub-subplot and seedlings in each quadrant were counted. Light screening efficiency was evaluated in all study sites as an indicator of canopy openings. One way Analysis of Variance (ANOVA) was used to test for significant differences of the studied variables, Tukey Post Hoc test was used in pairwise mean comparison and parametric Pearson correlation analysis was used to test for relationship between variables. Bar graphs and line graphs were used to depict trends in population structure and diameter-size distribution respectively. Animal trails, old charcoal production sites, tree harvesting and debarking of P. africana were found as significant human forest disturbances (p < 0.05) that negatively influenced its relative abundance (r =-0.077). Canopy openings as consequence of disturbance negatively influenced its regeneration density (r =-0.089). The relatively undisturbed site of the forest had a stable population structure for P. africana that followed reverse-J curve irrespective of the high debarking rate (90%) that decreased across the disturbance gradient. These findings suggest a need for designing sustainable management strategies that will lead to rehabilitation, restoration and monitoring of P. africana population dynamics in SWMF.
... It is distributed mostly along the eastern side of Africa from Ethiopia to South Africa, though there are populations in several West African countries and in the Comoros and Madagascar (Hall et al. 2000). Seeds of P. africana germinate well under shady conditions but require light gaps to survive beyond the sapling stage (Tsingalia 1989;Kiama and Kiyiapi 2001;Nzilani 2002). The tree is valued for its medicinal extract from its bark for the treatment of benign prostatic hyperplasia, a common condition in elderly men. ...
Prunus africana (Hook.f.) Kalkml., the African cherry, is an evergreen climax vegetation tree species typically reaching 25–30 m in height and occurs primarily in montane and submontane forests. In this study, the genetic structure of P. africana was analyzed using a coding chloroplast DNA region; Megakaryocyte-Associated Tyrosine Kinase Gene (MATK) and nuclear ribosomal internal transcribed spacer (nrITS) with 63 individuals in East Africa. This study detected low levels of genetic diversity as revealed by nucleotide diversity in nrDNA ( = 0.00529) and cpDNA (0.00448). As revealed by the results of AMOVA analysis, genetic differentiation for cpDNA (FST = 0.0275) was obviously lower than for nrDNA data (FST = 0.237) in P. africana. Gene flow among populations based on nrDNA data (Nm = 2.641) was significantly higher than that based on cpDNA (Nm = 0.82). Mantel test revealed a significant correlation between genetic and geographic distances for cpDNA (r2 = 3.0 × 10-5) and nrDNA (r2 = 7.0 × 10-5). Demographic history analyses based on pair-wise nucleotide sequence mismatch distributions revealed that only the Kakamega population was in mutation-drift disequilibrium. Tajima’s D neutrality test, however, revealed significant signatures of recent population expansion in only the Kakamega population (D = –1.85646; P < 0.05). This study therefore proposes immediate ex situ and in situ conservation of P. africana populations in Mabira and Elgon forests coupled with in situ conservation of Budongo, Kakamega and Monduli forests.
An annotated checklist of the Kakamega Forest in Kakamega District is presented. The checklist includes the plants found mainly in Buyangu National Reserve, and the Nature Reserves of Isecheno and Yala. It also includes the adjacent forest fragments of Malava, Kisere and Kaimosi. Nine hundred and eighty six (986) plant taxa (including 36 introduced or cultivated, 12 probably misidentified, 111 photo recorded taxa, and 83 undocumented plant taxa) in 129 families and 527 genera are recorded. This represents about 15.2% of the total number of 6506 Kenyan vascular plant species. For each taxon documented, a short description of its habit and distribution is given. Also 181 synonyms are listed.
For the last 35 years, the African cherry (Prunus africana (Hook. f.) Kalm.) has been used in the treatment of benign prostatic hyperplasia and other disorders. The bark, from which the treatment is derived, is entirely wild-collected. The major exporters of bark include Cameroon, Madagascar, Equatorial Guinea, and Kenya. Groupe Fournier of France and Indena of Italy produce 86% of the world's bark extract, both for their own products and for the free market. Worldwide exports of dried bark in 2000 have been estimated at 1350-1525 metric tons per year, down from its peak of 3225 tons in 1997. Bark extracts (6370-7225 kg per year) are worth an estimated $4.36 million US dollars per year. In 2000, Plantecam, the largest bark exporter in Africa, closed its extraction factory in Cameroon, due to complex ecological, social, and economic factors. Wild-collection is no longer sustainable (and probably never was) where harvest seriously affects morbidity and mortality rates of harvested populations. Since 1995, it has been included in CITES Appendix II as an endangered species. In this paper, alternatives to wild-collection to meet future market demand are investigated, including conservation practices, enrichment plantings, small- and large-scale production, and protection of genetic resources. The species is at the beginning of a transition from an exclusively wild-collected species to that of a cultivated medicinal tree.
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