Long-Term Effects of Forest Management Interventions on Carbon Stocks and Soil Microbial Activity in Degraded Semi-Arid Oak Forests of Iran

The semi-arid oak forests of Iran have undergone severe degradation due to unsustainable management and overgrazing. This study evaluates the long-term impacts of forest management practices, specifically livestock exclusion and enrichment planting combined with protection, on carbon stocks and soil microbial respiration in the degraded Zagros oak forests. The treatments were initiated in 1989 at the Baloot Boland site and extended in 2003 to two additional sites, Ghaleche and Kalchonak. All tree species and their diameter at breast height (DBH) were recorded, and soil physical and chemical indicators were determined and analyzed. Treatments involving livestock exclusion and enrichment with protection led to greater tree density, carbon storage, and microbial respiration compared to untreated controls. Carbon biomass for control, livestock exclusion, and enrichment with protection were 3, 7.48, and 10.20 Mg ha–1, respectively. The highest tree density (122.71 trees ha–1) and soil microbial respiration rate (0.67 µmol m–2 s–1) were recorded under the enrichment with protection treatment. Soil carbon stock in control site was 2.15 Mg ha–1, while for livestock exclusion and enrichment with protection were 4.95 and 5.66 Mg ha–1, respectively. Results of the correlation analysis showed that key factors influencing soil carbon storage were tree density, soil microbial respiration, soil bulk density, and soil organic carbon. Moreover, soil moisture content was significantly correlated with soil organic carbon. These findings suggest that integrating livestock exclusion with active enrichment and protection is an effective strategy for restoring ecosystem functions and enhancing soil biological activity in degraded oak forests. Furthermore, the management practices led to higher soil carbon stock and biomass carbon in the studied oak forests.