Extended Abstract
Background and Objectives: Long-term monitoring of forest soil variables is essential for assessing ecosystem dynamics, forest health, and the impacts of environmental and anthropogenic factors on soil. Key soil parameters including microbial respiration, soil moisture, organic carbon stocks, available phosphorus, and nitrogen are of strategic importance in forest ecosystems, particularly under current climate change and global warming conditions. This study pursues to measure the physical and chemical properties of the soil in the studied forest stands (in the selected fixed and permanent sample plots), and also to enable long-term monitoring of the trend of changes in the soil of these forest sites.
Materials and Methods: This study aimed to monitor soil changes and analyze correlations between soil factors in two sample plots (Parikdan= south slope and Sarabtaveh= north slope) in Boyer-Ahmad County, Kohgiluyeh and Boyer-Ahmad Province. Two randomly selected one-hectare plots (100×100 m) were inventoried, with five systematic soil samples collected from 0-30 cm depth in each plot to measure carbon, nitrogen, phosphorus, moisture, microbial respiration, bulk density, and gravel percentage. Soil data collection was repeated annually over the three-years (2018-2020) project period.
Results: The results revealed that in the Sarabtaveh site, soil organic carbon (2.94%), total nitrogen (0.26%), available phosphorus (16.21%), soil moisture (15.25%), and microbial respiration (640.88 mg CO₂/kg soil/day) were recorded, while the Parikdan site showed values of 2.85%, 0.22%, 17.57%, 15.44%, and 707.74 mg CO₂/kg soil/day, respectively. The mean soil carbon stock was estimated at 81.91 ton/ha in Sarabtaveh and 86.37 ton/ha in Parikdan.
Conclusion: Monitoring soil parameter dynamics and their interrelationships in forest ecosystems is critically important, as soil serves as the fundamental substrate that governs nutrient cycling, carbon sequestration, and biodiversity maintenance. Three-year monitoring revealed significant differences in soil carbon stock dynamics (p<0.05). In both sites, soil organic carbon demonstrated the strongest correlation (r>0.85, p<0.01) with total carbon stock, indicating its pivotal role in carbon sequestration potential. The soil moisture content, microbial respiration, and available phosphorus were significantly higher in the Parikadan sample plot compared to the Sarabtaveh plot. This difference can be attributed to the greater species diversity, higher vegetation density, and larger canopy cover in the Parikadon plot. The current study's results revealed a significant positive correlation between soil organic carbon content and total nitrogen. The increase in nitrogen mediated through changes in litter quantity and quality as well as alterations in the microbial decomposer community directly influences soil organic carbon levels.
