Relationships between herbaceous diversity and biomass in two habitats in arid Mediterranean rangeland

The study investigated plant species diversity patterns along a productivity/cover gradient at two topographical positions (Wadi and hilltop) in a Mediterranean herbaceous plant community in Jordan. Findings revealed that hilltop areas, being less productive, had higher species richness compared to the more productive Wadi areas. In Wadis, species richness showed a unimodal relationship with aboveground biomass, while a positive linear relationship was found on hilltops. Abundant species in Wadis didn't show a significant relationship with productivity, unlike common and rare species which showed a unimodal relationship. On hilltops, all species categories (abundant, common, rare) showed a linear relationship with biomass. β-diversity, indicating species dissimilarity, negatively correlated with biomass on hilltops, but positively in Wadis. The study also found varying relationships between different indices and productivity, suggesting that the significance of abundant, common, and rare species may vary depending on the productivity of the site.