Comparisons of Understorey Vegetation in Planted Fallows of Seven Multipurpose Tree Species (MPTS) in South-Western Nigeria

Abstract

Planted fallows of seven multipurpose tree species were analysed in order to reveal their impact on understorey vegetation in South-Western Nigeria. Although having light environment under their canopy comparable with most of the other tree species, Nuclea latifolia and Pterocarpus santalinoides had the lowest density and biomass of understorey vegetation. Only Milletia thoningi had lower understorey biomass than these two tree species although it had higher understorey density. Soil fertility was not a limiting factor for the undergrowth since those three species which had the highest undergrowth density and biomass had either comparable or lower fertility status. This implies that, the suppressive effect of Nuclea latifolia and Pterocarpus santalinoides the understorey growth might have been due to allelopathic effects caused by secondary metabolites leached from the tree canopy during precipitation or from the floor litter during decomposition. Because of the limitations imposed by the lack of randomisation of the tree stands in the site, conventional analysis of variance was not appropriate. Instead, the calculated means for each variable was used to compare the results.