Relationship Between Carbon Stock and Stand Cumulative Production at Harvesting Age of Pinus radiata Plantations: A Comparison Between Granitic and Metamorphic Soils

The relationship between stand cumulative production at harvesting age and carbon stock for different soil types in forest plantations is critical for sustainable forest management and climate change mitigation. This study evaluated carbon stocks in Pinus radiata D. Don on granitic and metamorphic soils in central Chile. We selected 10 plantations and established three 1000 m2 stands per plantation to quantify the carbon stock of total biomass using allometric equations and in situ carbon assessments of the forest floor and mineral soil (up to 1 m deep). A strong positive correlation was observed between stand cumulative production at harvesting age and total carbon stock (r2 = 0.767), regardless of the soil type. Metamorphic and granitic soils demonstrated a high carbon stock capacity, particularly in deeper soil layers (40–100 cm), with soil contributing over 40% of the total soil carbon stock. Soil bulk density and carbon concentration were strongly correlated (r2 = 0.74), emphasizing the role of soil physical properties in carbon storage at deep soil horizons. These findings highlight the critical role of subsoils as carbon reservoirs. Predictive linear models developed from this study offer a useful and simple approach for estimating carbon stocks, contributing to national carbon neutrality goals and sustainable forest management.