New Publication Soil Rewetting Drives Seasonal CO₂ Release in South America's Temperate Region
A new study published in Geophysical Research Letters sheds light on a key driver of the seasonal carbon cycle in the South American Temperate (SAT) region: the rewetting of dry soils following the dry season. The research, conducted by Sanam N. Vardag, Eva-Marie Metz, Lukas Artelt, and André Butz (all from Institute of Environmental Physics), together with Sourish Basu (NASA Goddard Space Flight Center), combines satellite-based CO₂ observations with dynamic vegetation models to better understand carbon dynamics in this data-scarce region.
The team discovered that the onset of rainfall triggers a rapid increase in heterotrophic (soil-based) respiration—releasing CO₂ into the atmosphere—while plant carbon uptake lags behind. This leads to a net CO₂ release during the early rainy season, particularly between September and October. The effect is especially pronounced in the semi-arid areas of the SAT region, but it significantly shapes the carbon balance of the entire region.
These findings emphasize the pivotal role of soil rewetting in seasonal carbon fluxes and highlight the importance of accurately representing these processes in global carbon cycle models. The study complements similar insights from southern Africa (Metz et al., 2025; Metz et al., 2023), pointing to a broader relevance of soil moisture dynamics across semi-arid ecosystems worldwide.