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.

Forests are a key terrestrial carbon sink, storing carbon in biomass, the forest floor, and the mineral soil (SOC). Since Pinus radiata D. Don is the most widely planted forest species in Chile, it is important to understand how environmental and soil factors influence these carbon pools. Our objective was to evaluate the effects of climate and site variables on carbon stocks in adult radiata pine plantations across contrasting water and nutrient conditions. Three 1000 m² plots were installed at 20 sites with sandy, granitic, recent ash, and metamorphic soils, which were selected along a productivity gradient. Biomass carbon stocks were estimated using allometric equations, and carbon stocks in the forest floor and mineral soil (up to 1 m deep) were assessed. SOC varied significantly, from 139.9 Mg ha⁻¹ in sandy soils to 382.4 Mg ha⁻¹ in metamorphic soils. Total carbon stocks (TCS) per site ranged from 331.0 Mg ha⁻¹ in sandy soils to 552.9 Mg ha⁻¹ in metamorphic soils. Across all soil types, the forest floor held the lowest carbon stock. Correlation analyses and linear models revealed that variables related to soil water availability, nitrogen content, precipitation, and stand productivity positively increased SOC and TCS stocks. In contrast, temperature, evapotranspiration, and sand content had a negative effect. The developed models will allow more accurate estimation estimates of C stocks at SOC and in the total stand.

Sustaining forest plantation productivity across successive rotations is increasingly challenging under changing environmental conditions. This study evaluated whether repeated establishment silviculture can maintain early second-rotation growth performance of Pinus radiata D. Don in central-south volcanic sandy soils in Chile. An experiment encompassing soil preparation (shovel planting vs. subsoiling + bedding), fertilization (B vs. NPKB), and weed control (pre-planting only vs. 2-year banded application) was conducted over two rotations. Survival, diameter, height, and stand-volume responses were compared between rotations at age 3. The second-rotation establishment period received 33% less annual rainfall than the first. Across all treatment combinations, mean survival decreased from 90.5% during the first rotation to 62.2% during the second rotation, while mean stand volume decreased from 6.58 to 1.16 m³ ha⁻¹. During the second rotation, weed control was the only treatment that significantly increased individual-tree and stand growth: plots receiving pre-planting weed control only averaged 38.7% survival and 0.29 m³ ha⁻¹, whereas those receiving additional 2-year banded vegetation control averaged 85.8% survival and 2.02 m³ ha⁻¹ stand volume. These findings indicate that vegetation control is key to sustaining P. radiata productivity. However, progressively unfavorable environmental conditions will jeopardize forest productivity across rotations.