The Effect of Introduced Tree Species On the Soils of Namwasa Central Forest Reserve, Mubende-Uganda

ABSTRACT Humans move tree species beyond their native ranges both deliberately and unknowingly. In areas around Namwasa central forest reserve, most of the trees have been cleared by charcoal burners and cultivators who are residents of the area. The study assessed the diversity and abundance of introduced tree species, assessed the effects of introduced tree species on some selected soil properties and evaluated how significant these trees are economically and ecologically. Floristic information on the tree species was obtained by transects made from five compartments of the forest reserve. Eight small sample plots of dimensions 30m by 15m were made on each transect line separated by a distance of lOOm using tape measures and marked with flagging tapes. Four introduced tree species namely Pinus caribaea, Pinus oocarpa, Eucalyptus grandis and Eucalyptus Urophylla and twenty two native tree species were identified. Random core soil samples (8cm diameter x 15cm height) were collected around the selected tree species in sample plots using a trowel and put in Ziploc bags and later transported to the Uganda government analytical laboratory for analysis. Soil samples were collected from both introduced tree species and the natural forest for comparison. Samples were analyzed for soil parameters such as texture, structure, pH, Mg, Pb, Cl, electrical conductivity, bulk density, No3, Ca, Mn, Cu, So4, P04, Fe, NH3, Na, K, Ni, Zn, and organic matter. Shannon Weiner index (H’) was -1.514, species richness (5) was 24 and species evenness (EH) was 0.477. ANOVA results indicated that introduced tree species significantly affect the selected soil properties. The coefficient results indicate that three introduced tree species have a significant effect on the selected soil properties. Correlation results indicated that ph is negatively correlated all other soil properties (r.