Floristic Composition and Structure in Relation to Elevation in the Togo Plateau Forest Reserve in Ghana

Abstract

Plateau ecosystems are of special scientific and conservation interests as they harbour rich plant diversity and exhibit considerable spatial variability along elevation gradients. In this study, variations in floristic composition and structure in relation to elevation were studied in six-fringed communities Hohoe (HH), Alavanyo (AL), Santrokofi (SA), Akpafu (AK), Bowuri (BO), and Nkonya (NK) of the Togo Plateau Forest Reserve in Ghana to better provide explicit and effective management of this ecological hotspot. A total of 180 plots (each measuring 25m × 25m) were demarcated across the six communities for sampling of trees (DBH measured at 1.3 m above ground ≥10 cm). Smaller nested plots, measuring 5m × 5m and 1m × 1m were used for sampling saplings (DBH < 10 cm, height > 1.5 m) and seedlings (DBH < 3 cm, height < 1.5 m), respectively. Species identity and abundance and elevation were recorded for each plot. Relationships of elevation gradients with vegetation attributes were analysed using simple linear regression and R software package. A total of 281 plant species (164 trees, 60 saplings and 57 seedlings) belonging to 66 families were recorded in the study. Leguminosae, Apocynaceae and Euphorbiaceae were the most dominant families across and along the elevation gradient. The average basal area of trees was calculated as 44.72 m2/ha and varied across the six communities (ranged from 57.10 m2/ha at BO to 33.10 m2/ha at AL) whereas the Shannon-Weiner Index (H’) averaged as 3.99 and varied across the six communities (ranged from4.14 m2/ha at BO to 3.89m2/ha at AL) and evenness index averaged as 0.96 (ranged from1.00at BO to 0.92 at AL). The saplings and seedlings also follow a similar pattern of composition and structure. The geographical locations of the study communities which somehow correspond with different elevations to the plateau (i.e., BO, NK occur in lower elevations, SA, AL in mid elevations and HH, AL in higher elevations) has been identified as the drivers of the composition and structure across the communities on the landscape. The most important trees listed in the study were C. pentandra, A. zygia, and T. superba. The saplings were A. camerunensis, M. puberula and C. ferruginea. The seedlings were C. odorata, P. hirsuta and C. affer. The most important tree species listed were distributed along a broad range of elevation. Results obtained revealed high biodiversity of the plateau. These findings may lead to a better understanding of the composition and structure of several plateau ecosystems found in Ghana and elsewhere.