Title : Plant diversity, structure, and functional use of three homegarden agroforestry system
Abstract:
Traditional homegarden agroforestry systems (HGAFS), with their multi-strata arrangement, serve as a refuge for a wide range of plants, providing significant ecological value and household utility. The distribution of plant species diversity and their functional roles in home gardens varied across horizontal zones, vertical strata, and along altitudinal gradients. Traditional homegarden agroforestry systems (HGAFS) support high plant diversity and multiple functional roles through both their multistrata (vertical) structure and horizontal spatial organization. Developing productive and resilient HGAFS tailored to specific contexts requires insight into how spatial structure influences plant diversity and functional use. This study investigates the composition, diversity, vegetation structure, and functional uses of three agroforestry systems, based on data from 39 home gardens and 112 main plots. Field data on species presence, abundance, and diversity, along with structural characteristics, were collected across vertical and horizontal gradients. The analysis focused on key biodiversity indicators, including species richness, total abundance, Shannon diversity index (H'), Simpson diversity index (D), Margalef index, and species evenness (J). Additionally, a composite biodiversity index was developed to summarize and rank the overall biodiversity performance of the three agroforestry systems. Statistical analyses, including descriptive statistics, ANOVA, and heatmap analysis, were employed. Taxonomic assessment revealed a total of 160 plant species across 111 genera and 74 families, with native species comprising 75–83% of the total. This highlights the significant role of traditional agroforestry systems as vital reservoirs for native flora. Plant species richness and diversity indices (Shannon, Simpson, Margalef, Jaccard, and the composite index) were influenced by both the agroforestry system and vertical and horizontal stratification. Coffee-fruit home gardens exhibited the highest species richness (92), followed by Enset-coffee systems (83) and Enset-based systems (63). Similarly, coffee-fruit home gardens had the highest diversity indices, followed by Enset-coffee and Enset-based agroforestry systems. The Composite Biodiversity Index (0–1) showed a decreasing trend: coffee-fruit system (0.816) > coffee-Enset system (0.575) > Enset system (0.000), emphasizing the higher biodiversity conservation potential of coffee-fruit home gardens. Significantly higher values were observed within 10 meters of the house and at mid-altitudes (1600–2000 masl).The functional uses of species, including root and tuber crops, vegetables, spices, stimulants, and medicinal plants, were highest in the inner zone (0–10m) and decreased with distance from the house. Furthermore, plant species richness showed an increasing trend with greater functional use in the studied agroforestry systems, suggesting that multifunctional agroforestry practices can enhance plant biodiversity. The vertical structure of the studied home gardens comprised four distinct strata, each associated with specific functional groups. This study demonstrates that HGAFS in Ethiopia are multifunctional refuges for native flora, where farmers enhance primary consumption, ecological services, and plant diversity through intensive horizontal and vertical garden management. However, their sustainability is threatened by socio-economic change, shift in land management, and pest and disease outbreak, underscoring the need for targeted interventions.
Keywords: homegarden, functional use, plant diversity, spatial factors, structural arrangement, Wenago
