Determinant Factor of Plant Species Diversity in the Organic Agriculture-Dominated System of Gedeo Zone, Southern Ethiopia

Agricultural intensification is a major challenge for biodiversity conservation in many parts of the world. Organic agriculture is perceived as a possible solution for biodiversity conservation in agriculture dominant systems. This study aimed at investigating the current status of plant species diversity and its determinants in organic agriculture-dominated areas of Gedeo zone, Southern Ethiopia. Multistage sampling procedures were used to obtain 108 households from three agroecological zones of the study area, and plant species data were collected from the quadrants laid in farms of sampled farmers. Besides, diversity management practice data were collected using focus group discussion. A total of 234 plant species belonging to 82 plant families were identified. Most (69.2%) of species in the system were native. The mean value of richness and Shannon index evenness for the whole system was 10.36, 2.06, and 0.89 for highland midland and lowland agroecological zones, respectively, which is relatively high compared with other agriculture-dominated systems in the tropics. The diversity of overall plant species were significantly affected by both agroecological zones and the wealth status of farmers. Midland and lowland agroecological zones had the highest richness values for total plant species than highland. Similarly, highest richness was recorded among farmers of rich and medium wealth classes than poor. The diversity of tree species was significantly affected by both agroecological zone and wealth status of farmer households. The lowland agroecological zone had a significantly higher number of tree species than midland and lowland agroecological zones, while the rich farmer had higher tree diversity compared to medium and poor farmers. The study also identified that diversity of shrubs were significantly influenced by agroecological zone. The midland agroecological had a significantly higher number of shrubs diversity compared to lowland and highland agroecological zones. In this study, herbaceous species diversity was not influenced by both agroecological zone and farmer wealth class. The function of plant species and indigenous plant species maintenance practice had its own effect on plant species diversity in the study area, since the area is dominated with organic agriculture. Therefore, to maintain the current status of the system and to improve the farmer’s livelihood, development planners may need to design agroecological-based plant species conservation strategies that give due consideration for indigenous plant species conservation practices and function of plant species.