Floristic and structural analysis of the woodland vegetation around Dello Menna, southeast Ethiopia

Abstract

Floristic composition and vegetation structure were described for the woodland vegetation around Dello Menna, Bale zone, southeast Ethiopia. A total 50 (20 m × 20 m) quadrats were sampled to identify and describe plant community types, species diversity, richness and evenness and to relate the identified plant community types with some environmental factors and describe the population structure of woody plant species. In each quadrat, data on species identity, abundance, height and Diameter at Breast Height (DBH) of woody plant species, altitude and slope were recorded. Vegetation classification was performed using PC — ORD software package. Sorensen’s similarity coefficient was used to detect dissimilarities among communities. Shannon — Wiener diversity index, species richness and Shannon’s evenness were computed to describe species diversity of the plant community types. Results show that a total of 171 vascular plant species representing 53 families were recorded. Fabaceae is the dominant family represented by 13 genera and 26 species (15%) followed by Asteraceae, Lamiaceae and Anacardiaceae with eight species each (4.6%). Based on the results of vegetation classification, three plant communities (Dalbergia microphylla community, Grewia bicolar- Acacia brevispica community, and Combretum molle-Combretum collinum community) are recognized and described. Species richness, diversity and evenness varied among the plant communities. Species richness and diversity exhibit a bell — shaped pattern along altitude. Species turn over among communities more or less follow altitudinal gradients. Tukey’s pairwise comparison of means among the plant community types shows significant variations in altitude, implying that altitude is one of the most important factors determining the distribution of plant communities. The community Dalbergia microphylla type exhibits the highest species richness and diversity. Analysis of population structure of the dominant species reveals various patterns. Future research directions and recommendations are suggested for the sustainable utilization of the vegetation.