Topographic variables to determine the diversity of woody species in the exclosure of Northern Ethiopia

Goiteom Woldu; Negasi Solomon; Hadgu Hishe; Hailemariam Gebrewahid; Mewcha Amha Gebremedhin; Emiru Birhane

doi:10.1016/j.heliyon.2019.e03121

Topographic variables to determine the diversity of woody species in the exclosure of Northern Ethiopia

Heliyon. 2019 Dec 31;6(1):e03121. doi: 10.1016/j.heliyon.2019.e03121. eCollection 2020 Jan.

Authors

Goiteom Woldu¹, Negasi Solomon^{2

3}, Hadgu Hishe², Hailemariam Gebrewahid¹, Mewcha Amha Gebremedhin¹, Emiru Birhane^{2

4}

Affiliations

¹ Institute of Geo-Information and Earth Observation Science, Mekelle University, P.O. Box 231, Mekelle, Ethiopia.
² Department of Land Resources Management and Environmental Protection, Mekelle University, P.O. Box 231, Mekelle, Ethiopia.
³ Institute for Environment and Sanitation Studies, University of Ghana, Ghana.
⁴ University of Leuven, Department of Earth and Environmental Sciences, Division Forest, Nature, Landscape, Celestijnenlaan 200E, P.O. Box 2411, Leuven, 3001, Belgium.

Abstract

Exclosures are established with the objective of rehabilitating degraded lands and restoring of woody vegetation. Various studies have been conducted to evaluate the success of exclosure on restoring woody species diversity. However, works focusing on the effect of topographic factors on woody species diversity are scarce. Understanding the factors that determine woody species diversity is important for management purposes. Therefore, this paper analyzes the effect of altitude, slope, and aspect as topographic variables on woody species diversity in Dawsura exclosure in northern Ethiopia. Data on species identity, abundance, slope, elevation and aspect were recorded from 58 sampling plots. Different diversity indices were used to analyze the data and one-way ANOVA and linear regression was conducted. There were a total of 34 woody species represented 15 families, of which 62% and 38% were trees and shrubs respectively. Altitude (r² = 0.63, p = 0.000 and r = 0.794, p < 0.01) and slope (r² = 0.57, p = 0.002 and r = 0.68, p < 0.01) correlated significantly and positively with Shannon diversity, whereas aspect (r² = 0.12, p = 0.378 and r = 0.27, p > 0.05) did not correlate significantly with Shannon diversity. Woody species diversity at moderate (1.44) and high (1.85) altitudes was significantly different from that of low (0.86) altitude areas (p = 0.0013). Furthermore, significantly higher woody species diversity was recorded at steep slope (1.88) and moderately steep slope (1.62) areas as compared to the gentle slope (0.95) areas. No significant variation was observed in woody species diversity among the aspect categories (p > 0.05). The study concludes that woody species diversity is largely regulated by slope and altitude than aspect in the exclosure. We suggest other environmental and anthropogenic variables should be taken into consideration in future studies on woody species diversity.

Keywords: Diversity; Ecology; Environmental assessment; Environmental health; Environmental management; Environmental pollution; Environmental science; Exclosure; Topographic variables; Woody species.