Contrasting Plant Diversity and Composition in Vegetation Layers Unveil Nature's Blueprint in Highland and Lowland Forests of an East African Park

Abstract

Lowland and highland forests of the Kahuzi-Biega National Park (KBNP) in the eastern Democratic Republic of Congo were studied to understand their ecology. The lowland ranges from 810 to 1230 m asl and the highland from 1935 to 2760 m asl. Ten 1-ha nested plots were established in each area; trees with ≥ 10 cm of dbh were inventoried for the tree layer. In each area, 10 0.1-ha and 10 0.01-ha subplots were established for the shrub and herbaceous layers, respectively. In the tree layer, plant diversity, species richness and species pool size differed at different altitudes; the lowland is more diverse and richer (140 vs. 88 species). In the shrub layer, only the Fisher-alpha index differed, showing high diversity in the lowland (14 ± 7.1 vs. 8.9 ± 2.9). In the herbaceous layer, the highland had a higher number of species (78 vs. 50). Twenty-eight, twenty-nine and five species were common to both highland and lowland in the tree, shrub and herbaceous layers, respectively. Height and dbh classes and basal area did not differ, but the importance value indexes of species and families did. These results show that the lowland and highland forests of KBNP differ in the three layers, suggesting tailored management plans.