Analysis of Plant Diversity and Importance Value Index in Central Ethiopian Agroforestry Systems

Despite offering multiple benefits, agroforestry practices have declined due to uncertain landownership, population growth, and limited awareness and scientific data. This study aimed to investigate the composition, diversity, and importance value index (IVI) of woody plant species in home gardens (HGs) and parklands in three districts of the North Shewa Zone. The study used surveys and sampling techniques to collect data from 80 HGs to 33 parklands. Species richness, Shannon diversity, and evenness were analyzed using R software with Version 4.2.2. Their mean values were compared between the two agroforestry systems and among districts using Tukey's pairwise comparison in SPSS (Version 20) statistics at a p value < 0.05. Additionally, the IVI was used for the structural analysis of woody species. The findings showed that 136 plant species from 58 families were identified. The Fabaceae family dominated in both HG and parkland practices. Trees were the most common growth form. HGs showed higher diversity (114 species) compared to parklands (79 species). Species richness also varied by districts, with Tarmaber having the most (86) and Ensaro the least (42) for HGs, and Tarmaber (37) had more than Mojana-Werena (21) for parklands. Tarmaber also scored the highest Shannon diversity for HGs (1.94) and parklands (1.74), followed by Mojana-Wedera. Overall, HGs displayed significantly higher richness and diversity than parklands across the study area at a p < 0.05. Interestingly, parkland data showed no significant differences in diversity metrics. The study also revealed 61.03% native (indigenous and endemic) and 38.24% exotic species. This growing interest in including exotic species necessitates addressing potential ecological disruptions while promoting overall plant diversity. The first five most frequent species in the sampled HGs were Rhamnus prinoides, Croton macrostachyus, Eucalyptus globulus, Schinus molle, and Ziziphus spina-christi, which occurred in 20.18%, 7.89%, 5.26%, 5.26%, and 4.39% of all HGs, respectively. Similarly, the most frequent species in parklands were C. macrostachyus, E. globulus, Olea europaea, Erythrina brucei, and Juniperus procera, with occurrence rates of 27.85%, 12.66%, 11.39%, 10.13%, and 10.13% of all sampled parkland, respectively. Based on the IVI, R. prinoides (265.11%) emerged as the dominant in HGs, followed by E. globulus (85.53%), Cupressus lusitanica (17.27%), C. macrostachyus (13.45%), and Z. spina-christi (9.53%). In parklands, E. globulus (142.32%) had the highest IVI, followed by C. macrostachyus (33.53%), A. abyssinica (18.13%), Z. spina-christi (17.46%), and O. europaea (14.28%). These findings highlight the ecological significance of these species in their respective habitats. Finally, the identification of plant species in both HGs and parklands provides valuable information for conservation efforts and the development of effective land management practices.