Montane forest root growth and soil organic layer depth as potential factors stabilizing Cenozoic global change

Abstract

Tree roots and their symbiotic fungal partners are believed to play a major role in regulating long-term global climate, but feedbacks between global temperature and biotic weathering have not yet been explored in detail. In situ field data from a 3000 m altitudinal transect in Peru show fine root growth decreases and organic layer depth increases with the cooler temperatures that prevail at increased altitude. We hypothesize that this observation suggests a negative feedback: as global temperatures rise, the soil organic layer will shrink, and more roots will grow in the mineral layer, thereby accelerating weathering and reducing atmospheric CO2. We examine this mechanism with a process-based biological weathering model and demonstrate that this negative feedback could have contributed to moderating long-term global Cenozoic climate during major Cenozoic CO2 changes linked to volcanic degassing and tectonic uplift events. Key Points Weathering rates decrease at elevation partially due to a thick soil organic layer If global climate is perturbed, montane ecosystems may buffer perturbations We show two tectonic events when this may have occurred ©2014. American Geophysical Union. All Rights Reserved.