Tropentag, October 5 - 7, 2004 in Berlin "Rural Poverty Reduction through Research for Development and Transformation"

Species Diversity in Remnant Natural Forests of Timber Plantations in Ghana

¹University of Hamburg, International Center for Graduate Studies, Germany
²Federal Research Centre for Forestry and Forest Products, Institute for World Forestry, Germany
³University of Hamburg, Biocenter Grindel, Germany

Abstract

Tropical forests are biologically the richest ecosystems in the world but the conversion of tropical forests into plantations of mostly exotic tree species is widely practised and threatens the continual existence of native tropical trees. As a perspective, it is envisaged that remnant natural forests will be conserved to act as important reservoirs of native flora and fauna within extended plantations.

The Institute for World Forestry of the Federal Research Centre for Forestry and Forest Products in collaboration with the International Center for Graduate Studies of the University of Hamburg and DuPaul Wood Treatment Ltd., Ghana is undertaking field research in forest plantations of the Ashanti region in Ghana. The objective of this study is to assess the ecological status of natural forest fragments and the regeneration potential for the sustenance of native tree species and possible enrichment of exotic tree plantations. A full sampling method was used for the assessment of trees with a DBH ≥ 10 cm, while a systematic sampling method was used to assess the tree regeneration. In this regard mammal and bird surveys were carried out to determine their potential as seed dispersers.

The full sampling of two distinct natural forest patches revealed a total of 224 living trees belonging to 26 species and 13 families. The regeneration study recorded a total of 47 tree species representing 20 families of trees. Birds and mammals amongst other seed dispersal vectors account for the increased number of tree species in the regeneration stages. A bird survey with the point count method was used to compare the diversities of birds in the different vegetation strata on the plantation: Remnant natural forest, afforested sites and a neighbouring agroforestry area. The agroforestry area recorded the highest bird diversity (Shannon index) of 2.074 while the remnant natural forest and the afforested sites showed approximately the same diversity level (1.693, 1.682 resp.). A survey of important seed dispersing mammals (including 3 bat species) showed that 14 species exist in and around the plantation indicating also that, mammals play an important role in seed dispersal of the native flora.

Keywords: Diversity, plantation, regeneration, remnant natural forest

Contact Address: Jobst-Michael Schroeder, Federal Research Centre for Forestry and Forest Products, Institute for World Forestry, Leuschnerstraße 91, 21031 Hamburg, Germany, e-mail: j.m.schroederholz.uni-hamburg.de