Journal of Tropical Ecology

Research Article

Reduced abundance of late-successional trees but not of seedlings in heavily compared with lightly logged sites of three East African tropical forests

Jasper Mbae Kirikaa1a2, Katrin Böhning-Gaesea3a4, Bonny Dumboa5 and Nina Farwiga1a2 c1

a1 Department of Ornithology, National Museums of Kenya, Nairobi, Kenya

a2 Institut für Zoologie, Abt. V. – Ökologie, Johannes-Gutenberg Universität Mainz, Becherweg 13, 55128 Mainz, Germany

a3 Johann Wolfgang Goethe Universität, Department of Biological Sciences, Siesmayerstr. 70, D-60323 Frankfurt (Main), Germany

a4 Biodiversity and Climate Research Centre (BiK-F), Senckenberganlage 25, D-60325 Frankfurt (Main), Germany

a5 P.O. Box 143, Kakamega, Kenya

Abstract:

Logged forests form an increasingly large proportion of tropical landscapes but disproportionately few studies have studied the impact of forest disturbance, e.g. lightly vs. heavily logged, on tree and seedling communities simultaneously. We sampled all trees (on 1 ha) and all recently germinated seedlings (on 90 m2) in three lightly and three heavily logged sites in each of the following three East African tropical forests: Budongo Forest and Mabira Forest in Uganda and Kakamega Forest in Kenya. We analysed species richness, diversity, abundance and community composition of late- and early-successional trees and seedlings. We recorded no difference in species richness or diversity of late-successional or early-successional trees between lightly and heavily logged sites. However, the abundance of late-successional species was lower in heavily than lightly logged sites. Moreover, there was no difference in species richness or diversity of trees among the three forests. Yet, abundances of late-successional trees were higher in Budongo Forest than in Mabira Forest and Kakamega Forest. Species richness, diversity and abundance of seedlings did not differ between lightly and heavily logged sites. Only the abundance of seedlings of late-successional species differed among the forests with more individuals in Budongo Forest than in Mabira Forest. This was corroborated by non-metric multidimensional scaling (NMDS) showing clear differences in composition of tree and seedling communities among the three forests. Thus, both, the tree and seedling communities differed significantly among the three forests but not between lightly and heavily logged sites.

(Accepted May 07 2010)

Correspondence:

c1 Corresponding author. Email: farwig@staff.uni-marburg.de Present address: Dept. Ecology – Conservation Ecology, Faculty of Biology, Philipps-Universität Marburg, Karl-von-Frisch-Str. 8, 35032 Marburg, Germany.