Herbaceous Diversity under Indigenous Tree Canopies in Case of Guduru District, Western Oromia, Ethiopia

Indigenous tree species have an essential value in ecosystems however, most tree planting initiatives have promoted exotic species because of less understanding on their real potential. This study was conducted in grazing land in Guduru district, Western Ethiopia to examine the effect of three indigenous tree species; Acacia abyssinica, Croton Macrostachyus and Ficus sur as well as their canopy cover on herbaceous diversity. Three relatively similar trees per each of the species were selected for the study. A quadrat of 0.5 m × 0.5 m (0.25m2 ) was laid out at different distances from the tree trunk. Shannon diversity index and Margalef’ index was used to estimate the diversity of herbaceous and species richness. Total of twenty seven samples (one hundred and eight subsamples) were laid out to collect data for herbaceous diversity. Two-way analysis of variance (ANOVA) using General Linear Model (GLM) procedure in an arrangement of randomized complete block design was applied with SAS (version 9.1) software to test the differences between the investigated parameters as factor of tree species and canopy cover. When significant differences were detected means were separated using LSD at 5% level of significance. A total of 31 herbaceous species that belonged to twelve families were identified. The highest herbaceous species richness and diversity (1.75, 2.21) were obtained outside the tree canopy. Generally, lower herbaceous richness and diversity were observed under tree canopy which might be because of dense structure of tree canopies and lack of appropriate silvicultural treatments