Eng Saeid Tahmasebian, Dr Ghasemali Dianati Tilaki, Dr Yahya Kooch, Dr Ivan Vasinev,
Volume 4, Issue 2 (9-2025)
Background and objectives: Managing forest-rangeland ecosystem management and afforestation are crucial for shaping species composition, establishment, and ecosystem resilience, extending beyond mere wood or biomass production. In arid and semi-arid regions, the combined effects of grazing, water scarcity, and restoration interventions create synergistic impacts. This study investigated how these factors influence understory cover, floristic composition, life forms, and diversity indices in afforestation stands and forest habitats under various management regimes in Bashgol, Qazvin.
Materials and methods: The study was conducted in the forest-rangeland habitats of Bashgol, Qazvin Province (Central Alborz). To minimize environmental heterogeneity, sites were selected at elevations between 1480–1550 m a.s.l. and with slopes less than 10%. Five management regimes were evaluated: afforestation, exclosure, pit-seeding, light grazing, and heavy grazing. For each regime, three 100-meter transects were established, with a total of 75 plots surveyed (15 plots per regime). Along each transect, ten 1.5 m² quadrats were demarcated, and five were randomly selected for detailed measurement. Within each selected plot, cover percentage, floristic composition, and life forms were recorded. Shannon–Wiener, Simpson, Margalef, Menhinick, evenness, and alpha and beta diversity indices were calculated. These indices were then compared using analysis of variance (ANOVA) and Duncan's test.
Results: Floristic analysis revealed that perennial species constituted the dominant component of the community, accounting for 77.63% of the total cover, while annual plants accounted for 22.37%. Among the evaluated regimes, complete exclosure exhibited the highest canopy cover (73%). Despite having lower overall vegetation cover, afforestation resulted in superior diversity metrics, achieving the highest Shannon–Wiener (1.31) and Simpson (0.38) indices. Conversely, heavy grazing recorded the lowest values for both indices (0.29 and 0.14, respectively), with these treatment differences being statistically significant. Margalef richness was also significantly influenced by management, with exclosure, afforestation, and light grazing maintaining higher richness, while heavy grazing showed the lowest. In contrast, Menhinick richness peaked under light grazing. The highest alpha (α)-diversity was observed under light grazing (2.56), whereas the lowest occurred under pit-seeding (0.63). Beta diversity reached its maximum in afforestation (0.69) and its minimum in exclosure (0.35). ANOVA confirmed that the management regime had a significant effect on both alpha and beta diversity.
Conclusion: The dominance of perennial species suggests ecological stability, while the presence of annual plants indicates responsiveness to environmental stress. Exclosure, by eliminating grazing and trampling, resulted in the highest vegetation cover. Afforestation, through the creation of microclimatic heterogeneity, fostered the highest beta diversity. The superior richness and alpha diversity observed under light grazing, coupled with their severe decline under heavy grazing, supports the Intermediate Disturbance Hypothesis. No single management regime optimized all indices simultaneously; therefore, the specific objectives of each site should guide the management approach. Heavy grazing leads to undesirable consequences, and a combination of rotational exclosures, controlled light grazing, and low-impact afforestation is recommended.
