Azam khosravi Mashizi

Understanding how plant functional traits shape community structure is essential for predicting vegetation responses to environmental stress. This study quantified plant functional diversity and its environmental drivers across five contrasting climatic zones in the arid and semi-arid ecosystems of Khabr National Park, Iran. Using a trait-based framework and multivariate analyses, we examined patterns of community functional structure, trait-environment relationships, and the effects of grazing and precipitation. Functional diversity varied significantly among habitats, with the highest values observed in temperate and cool mountain zones, indicating greater ecological heterogeneity and adaptive trait differentiation. Random Forest analysis identified elevation, soil phosphorus, and rainfall as the strongest predictors of functional diversity, while multiple regression showed that both precipitation (β = 0.023, p < 0.001) and grazing intensity (β = 1.044, p = 0.015) positively influenced functional richness. Functional diversity was weakly correlated with species richness (r = 0.30), suggesting that trait-based metrics capture distinct dimensions of community organization beyond taxonomic diversity. Overall, our results indicate that moderate grazing and climatic heterogeneity promote functional complementarity and ecosystem resilience in dryland plant communities, highlighting the value of trait-based approaches for sustainable rangeland management under increasing drought and disturbance pressures.