The effects on non-commercial of forest resources on the species composition and nutrients at Uplands, Kenya

Abstract

Research to investigate the effects of the continued use of the forest resources by the forest neighbouring communities was carried out at Uplands forest, in Kenya, between October 199~ and March 2000. The investigations were carried out with two objectives i.e. to find out whether the continued use of forest resources, have any effect on either the species composition or the nutritional status of the forest The natural or indigenous forests in Kenya are protected and managed towards conservation of biodiversity but more for the conservation of soil and water resources. Extraction of resources from these forests have been under a presidential ban since mid. 1980' s. The legalized activities in forests which includes fuelwood( as dead wood collection), grazing of livestock and farming under the famous shamba system are restricted to areas under plantations. In Uplands forest, the research findings on the non-commercial use of the forest resources revelled two activities as the most destructive to both the species and nutrients i.e. charcoal and timber. The other activities e.g. fuelwood collection, tool handles, bee-keeping etc. had only peripheral effects as compared to these two. A total of 57 species of trees, shrubs and lianas were found in area of the forest covered by the research and a few others might occur beyond the area sampled. 40 species of trees and shrubs were found in the test site and 36 species in the reference site plots. The frequency of three pioneer species i.e. Neoboutonia macrocalyx, Macaranga kilimandscharica and Tabernamontana stapfiana was found to be higher in the test than reference site which could be as a result of the canopy gaps. Allophylus abyssinicus, Neoboutonia macrocalyx and Psychotria fractinervata, the most dominant species in both sites, were chosen for the study of p..utrients in the forest ecosystem. For the organic or non-metallic nutrients i.e. carbon, nitrogen, sulphur and phosphorous, Allophylus abyssinicus had the lowest content in both sites. Neoboutonia macrocalyx had the highest content of nitrogen and phosphorous, while Psychotria fractinervata had the highest content of carbon and sulphur. Allophylus abyssinicus had the highest C:N ratio while Neobautonia macrocalyx had the highest S:N.ratio The content of sulphur and nitrogen showed a type of correlation due to their correlated functioning in proteinsysnthesis. Nitrogen is the limiting resource in primary productivity and so the sulphur in excess of the available nitrogen, is stored in form of sulphate sulphur. Potassium (K+>,Calcium (Ca2+), Magnesium (Mg21and Sodium (Na1are the metallic macronutrients or alkali and alkaline earth metals. Neoboutonia macrocalyx had the highest content ofK+ in both sites. All the three species had higher content ofCa 2+in the reference site. Allophylus abyssinicus and Neoboutonia macrocalyx had higher content ofMg 2+inthe reference while Pschotriafractinervata had the highest in the test site. Neoboutonia macrocalyx and Psychotriafractinervata had the highest content ofNa+ in the reference while Allophylus abyssinicus had the highest in the test site. Manganese (Mn2+), Aluminum (Al31and Iron (Fe+), which are trace elements and required by plants in very low quantities, had higher concentration in the soil and especially in the test site and thus the acidic nature ofthe soil (pH range 3.5-4.0).while that of the reference was less acidic (pH range 5.0-6.0). All the three species had higher content ofMn2+ in the test site while they had higher content of Fe+ in the reference site. Allophylus abyssinicus had the highest content of Fe+ in the reference compared to the other two species. Psychotria fractinervata and Neoboutonia macrocalyx had slightly higher content of Al3+in the test site.