The response of highly productive croplands at northern mid-latitudes to climate change is a primary source of uncertainty in the global carbon cycle, and a concern for future food production. We present a decadal time series (2007 to 2019) of hourly CO2 concentration measured at a very tall tower in the United States Corn Belt. Analyses of this record, with other long-term data in the region, reveal that warming has had a positive impact on net CO2 uptake during the early crop growth stage, but has reduced net CO2 uptake in both croplands and natural ecosystems during the peak growing season. Future increase in summer temperature is projected to reduce annual CO2 sequestration in the Corn Belt by 10–20%. These findings highlight the dynamic control of warming on cropland CO2 exchange and crop yields and challenge the paradigm that warming will continue to favor CO2 sequestration in northern mid-latitude ecosystems.
Bibliographical noteFunding Information:
This research was partially supported by the United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA grant number 2018-67019-27808), the National Science Foundation (grant number 1640337), USDA Agricultural Research Service, and the Minnesota Supercomputing Institute for Advanced Computational Research.
© 2021, The Author(s).