Aims: This study aimed to compare soil physico-chemical properties and evaluate below-ground carbon storage (soil and fine roots) in three plantations of Quercus castaneifolia C.A.M., Alnus subcordata C.A.M., and Acer velutinum Bioss., adjacent to a natural forest stand in the Hyrcanian region. There is limited site-specific data on carbon storage and its economic value in pure native plantation stands of Hyrcanian forests.
Materials & Methods: Across each stand (three plantations and one natural forest), five 400 m² (20 × 20 m) sample plots were established (20 plots in total). Composite soil samples were collected from two depths (0-5 and 5-15 cm) at five points per plot, yielding 10 composite samples per stand. The Laboratory analyses comprised soil texture, pH, organic carbon (OC), total nitrogen (TN), moisture content, and fine root biomass. The carbon storage in soil and fine roots was converted to CO₂ equivalents, followed by economic assessment based on a rate of USD 75 per ton. Finally, the soil parameters and the economic value of carbon storage were compared among the stands using one-way ANOVA followed by LSD test and different depths using independent T-test methods.
Findings: Soil moisture in our study site (29.37–46.80%) was significantly lower (P ≤ 0.01) in Q. castaneifolia stands. Both organic carbon (2.23–5.62%) and pH (5.94–6.36) varied significantly (P ≤ 0.01) among stands at both depths, while total nitrogen (0.12–0.25%) was highest in A. subcordata and lowest in Q. castaneifolia. Furthermore, the natural forest stand showed the highest root biomass values at both depths. Soil carbon storage correlated positively with bulk density (R² = 0.32) and moisture (R² = 0.38). Total below-ground carbon storage (0–15 cm) differed significantly (P ≤ 0.05), ranking as natural forest (99.40 t.ha⁻¹) and A. velutinum (95.18 t.ha⁻¹) > A. subcordata (81.72 t.ha⁻¹) > Q. castaneifolia (70.68 t.ha⁻¹). The economic values of CO₂ storage per hectare were USD 27,345 (natural forest), USD 26,197 (A. velutinum), USD 23,044 (A. subcordata), and USD 19,453 (Q. castaneifolia).
Conclusion: Acer velutinum demonstrated below-ground carbon storage levels comparable to those of natural forests, suggesting that this species should be prioritized in future reforestation projects aimed at maximizing carbon storage. The key drivers of soil bulk density and moisture content play a critical role in carbon storage in soil. However, further research is necessary to fully assess carbon stocks, including aboveground biomass (e.g., tree trunks and litter), to obtain a comprehensive understanding of the storage potential of these ecosystems.
Article Type:
Original Research |
Subject:
Forest Ecology and Management Received: 2025/04/24 | Revised: 2025/07/14 | Accepted: 2025/07/5 | Published: 2025/06/9