A Shift From Temperature to Water as the Primary Driver for Interannual Variability of the Tropical Carbon Cycle

Abstract

The relative importance of temperature and water constraints on the tropical carbon cycle is an ongoing debate. Here we combine multiple independent tropical ecosystem carbon exchange simulations with satellite observations and show that the primary control for the tropical carbon cycle has shifted recently from temperature to water. We examined the response of tropical ecosystem processes to climate change and suggest that the emerging role of water as the dominant driver for the tropical carbon cycle is attributable to increased precipitation variability, which is associated with intensified extreme drought and wet conditions. Extreme conditions strengthen water's regulation of ecosystem carbon exchange. The weakening influence of temperature is explained by the previously additive effects of temperature on ecosystem productivity and respiration now becoming opposing effects owing to amplified drought conditions, resulting in a reduction to the net effect of temperature on ecosystem carbon exchange.