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 ¼ 0.63, p ¼ 0.000 and r ¼ 0.794, p < 0.01) and
slope (r2 ¼ 0.57, p ¼ 0.002 and r ¼ 0.68, p < 0.01) correlated significantly and positively with Shannon diversity,
whereas aspect (r2 ¼ 0.12, p ¼ 0.378 and r ¼ 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 ¼ 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
