Current and potential carbon storage in soils of Chilean Patagonia

Introduction Climate change mitigation increasingly relies on enhancing soil organic carbon (SOC) storage, particularly in soils with strong mineral stabilization mechanisms. This study aimed to quantify the current and potential SOC storage capacity of volcanic soils. Methods A national soil database covering the Chilean latitudinal gradient (n = 1,660) was used to develop quantile regression models relating SOC to Al a in order to estimate upper and lower SOC storage thresholds. These models were then applied to soils from the Aysén Region under different land uses (n = 173) to evaluate current SOC stocks relative to their storage potential. Results Results indicated that approaches based on soil texture were inadequate for estimating SOC storage in volcanic soils, highlighting the importance of mineral reactivity indicators such as Al a . SOC storage potential increased with soil reactivity, with the highest potential values observed in soils with Al a > 600 mg kg −1 . Soils in the Aysén Region showed a high SOC storage potential, averaging 358 t C ha −1 , yet current stocks were on average 33.5% below this capacity. Agricultural crops and grasslands exhibited the largest gaps between current and potential SOC stocks, whereas wetlands and peatlands were close to or exceeded their estimated storage capacity due to hydromorphic conditions. Discussion These findings demonstrate the high carbon sequestration potential of volcanic soils in southern Chile and highlight the importance of mineralogical controls, particularly reactive aluminum, in regulating SOC stabilization and informing land management strategies aimed at increasing soil carbon storage.