Effect of Environmental Variables on Plant Community Formation and Vegetation Dynamics in Northwest Ethiopia

Abstract

Identifying plant communities has been a central aspect of vegetation science for centuries, with emphasis on the distribution, composition, and classification of plant communities. This study aimed to assess how environmental variables influence plant community formation and vegetation dynamics in northwest Ethiopia. A systematic random sampling technique was employed to gather vegetation data from 50 plots, each measuring 20 × 20 m, arranged at 100-m intervals along seven transects. In each plot, the encountered species and their percentage cover-abundance were recorded, which were subsequently transformed into a modified Braun–Blanquet scale. Additionally, composite soil samples collected from 15 × 15 cm subplots were analyzed for 20 soil parameters. The Shannon–Wiener index was used to measure species diversity. Hierarchical clustering and ordination analyses (DCA and RDA) were conducted on the floristic and environmental data, respectively, using R software. A total of 69 woody plant species from 64 genera and 44 families were recorded at altitudes ranging from 2485 to 2747 m above sea level. The Shannon–Wiener diversity index (H) was 3.74, and the evenness index (J) was 0.90. These high species diversity indices showed ecosystem health, stability, reflecting effective species interactions, and resource utilization. Among 6 terrain variables and 14 edaphic factors, 12 of these environmental factors (altitude, slope, aspect, cutting, silt, pH, sand, organic carbon, organic matter, total nitrogen, phosphorus, and calcium) were found significantly to ($p\le 0.05$) explain the variation in species composition and community formation of four plant communities in the study area. The observed patterns of community formation underscore the need to design different conservation measures tailored to the specific environmental conditions at different elevations.