Homegardens plant species richness and their use types have positive associations across agricultural landscapes of Northwest Ethiopia

Homegardens are important refugia for plant biodiversity mainly in degrading landscapes. However, the factors mediating these roles were little understood, particularly in an agrarian country such as Ethiopia. With the present study, we examined the effects of elevation gradient, and distance from houses on the compositions of the plant species and use types. Moreover, we explored how distance from the houses and the plant use types were related to species richness. For this, multistage and stratified random sampling systems were used to select the study district and 12 kebeles (the smallest administrative units in the Ethiopian administrative system) based on traditional agroclimatic zones. The floristic data were collected from 357 homegardens through plant inventory. Moreover, a semi-structured questionnaire was used to gather the use of the plants. The effect of elevational gradient on floristic species and use composition were tested by employing adonis2 function within the vegan package. The effects of plant use types and distance from the houses on species richness were tested using the Generalized Linear Mixed Effects Model where the 12 kebeles were entered in the model as random factors. One-way ANOVA was used to test the effects of elevation, distance from the house, and species richness on the corresponding plant use types. The results showed that a total of 238 plant species that belong to 81 families were recorded from 357 homegardens. The plant species and use type composition in home -gardens were significantly affected by elevation and there is significant dissimilarity among the study sites (P = 0.001). The plant species richness decreased with increasing distance from the house but increased with increasing use types (P < 0.001). Similarly, the plant use types significantly decreased with increasing distance from the house and elevational gradient (P < 0.004) but increased on the continuum of the species richness (P < 0.001). The overall results highlight that conservation schemes need to take into account the determinants of floristic composition and the multidimensional relationship between species richness, farmers' plant use types, and management practices to make better use of the homegardens as refugia during this continuing biodiversity degradation.