Composition and diversity of understory plants in the tropical rain forest of Cross River national park (CRNP), Nigeria

Abstract

The study assessed the composition and diversity pattern of understory in Oban division of CRNP with a view to established the contribution of the understory to diversity of the area. The study was conducted in four land use types: primary forest (core), secondary forest (buffer), farm fallow and plantation. Ten transects of 2000m length each were systematically located in each land use type. Four sample plots of 50×50m were located on each transect at an interval of 500m. Each plot was subdivided into nine 10× 10m subplots for shrubs enumeration and a 1×1m mili-acre plot was located at the center of each subplot for herb enumeration. Flora species composition, distribution and diversity were estimated across the land use types using diversity indices. Primary forest (core) was used as baseline for comparison. A total of 608 understory species in 82 Families were recorded in the study area. The highest numbers of understory species (454) were recorded in the core. Species richness (D) for shrubs was higher in the core (D =24.0). Similarity and species diversity (H’) shrubs, was higher in the core (H’= 4.66) and (H’=3.71) respectively. Herb species composition, Species richness and diversity increased were higher in the farm fallow (D26.23) and (H’=4.577). The highest density/ha for all life forms were recorded in the farm fallow. It is imperative that biodiversity assessment in the area should also give attention to understory composition in the area to enhance their conservation.

Key words: Understory, Species, Composition, Diversity, Conservation