Realistic soil C sink estimate in dry forests of western Argentina based on humic substance content

► In Argentina dry forest soil humic substance proportion respect to total organic matter is low (20%). ► Soil humic substance proportion does not correspond with the precipitation gradient. ► Non-humic substances were lower during rainfall periods indicating soil C losses. ► C sequestration information in Argentina dry forest probably is overestimated. ► C sink estimates could be less realistic according to aridity increase.