Distribution and population structure of Prunus Africana in mount Kenya forest

Abstract

Prunus africana has been declining over much of its geographical range due to unsustainable harvesting of the bark for its medicinal properties. In Kenya, bark harvesting for trade began in the 1970s from unknown forests, and the effects of this harvesting on the species' distribution and population structure are not well known. One of the locations where this species occur in Kenya is Mt. Kenya forest where this study was conducted. The goal of the study was to establish the distribution and population structure of P. africana in Mt. Kenya forest to provide information useful for knowledge about population status, management, conservation and monitoring of the species. Thirty eight (38) belt transects (50m x 500m) subdivided in to 25m x 25m plots were established at varying altitudes on four broad vegetation types (moist montane, moist intermediate, dry intermediate and dry montane) of Mt. Kenya forest and used for sampling. Farms were estimated in acres and sampled too. The data collected on P. africana included abundance, Diameter at breast height (DBH), and phenology. Tree species identification and measurements were done for the three tree species nearest to P. africana in the study plots. One-way-ANOV A was used to test for differences in abundance and size of the species (P. africana) among vegetation types, canopy cover classes and different altitudes. The altitudinal distribution of P. africana ranged between 1600m to 2500m above sea level. Four hundred and thirty six (436) individuals of P. africana were observed in 207 out of 1500 plots sampled in forest while 116 individuals were observed in 31 out of 48 farms sampled. The mean density of P. africana in the study forest was 4.8 tree/ha while in the farms it was 5.2 trees/ha. Density in the forest varied significantly among vegetation types (F3,34= 10.32, P< 0.05) and canopy cover classes (F2,30=21.53, P<0.05). There was significant difference in number of individuals in different developmental stages in forest (F2,24=11.49, P<0.05) while there was no significant difference in number of individuals in farms (F2,12= 0.21, P> 0.05). A total of 44 tree species belonging to 23 families were found to comprise the three nearest neighbours of P. africana in different vegetation types. This study provided crucial information in establishing the status of P. africana in Mt. Kenya forest. It was concluded that vegetation type, general canopy cover and altitude are some of the factors that influence the distribution and population structure of P. africana. The study confirmed earlier reports that the species prefers open to closed canopy forests'