Potential of Agroforestry Practices on Woody Species Diversity and Composition: Implication for Conservation of Indigenous Trees in Selected Districts of Tigray, Northern Ethiopia

Abstract

Human activities such as expanding farmland, producing charcoal, and harvesting construction materials and fuel wood are major contributors to forest degradation and biodiversity loss in Northern Ethiopia. This study aimed to assess woody species' diversity, composition, and threat levels in different agroforestry practices to prioritize their conservation. As the result three potential Agroforestry practices were purposively identified and selected for the study. A total of 45 sample plots, 15 plots from each agroforestry practices such as Woodlot agroforestry (WLAF) (10m x 10m), Homegarden Agroforestry (HGAF) (20m x 10m), and Parkland agroforestry (PLAF) (50m x 100m). Data on woody species were analyzed using Past version 2.17c and SPSS version 20. The results identified 36, 26, and 21 woody plant species from 31, 23, and 19 genera, as well aswell as 22, 16, and 15 families in HGAF, PLAF, and WLAF, respectively. Significant differences (p < 0.001) were found among the agroforestry practices in terms of tree density, species richness, species abundance, and Shannon diversity, though species evenness did not vary. The Importance Value Index (IVI) highlighted the top species in HGAF as A. etbaica (75.2), F. albida (33.1), and A. seyal (30.6). Species with low IVI values, such as B. polystachya (1.56), R. vulgaris (1.57), G. ferruginea (1.62), and C. aurantiifolia (0.90), require significant conservation efforts. In PLAF, the key species were F. albida (131.03), A. seyal (59.33), and C. africana (26.21). In WLAF, E. globulus (61.8), A. seyal (8.83), and C. edulis (31.4) were the most abundant, frequent, and dominant. Trees and shrubs in HGAF and WLAF had smaller stem diameters compared to those in PLAF. However, WLAF had greater tree height and basal area (BA, m²) than both HGAF and PLAF, with HGAF also showing a higher BA than PLAF (p ≤ 0.05). The study concluded that HGAF and PLAF are vital for sustaining local livelihoods, providing food, and conserving biodiversity. These agroforestry systems enhance natural forests and help prevent the extinction of woody species. Therefore, developing and enhancing HGAF, and PLAF in densely populated landscapes should be integral to biodiversity conservation strategies.