How Do Croplands Reduce CO2 During the Growing Season?

By Susan Trumbore

Regional variations in the seasonal drawdown of atmospheric CO2 can be used as a benchmark for evaluating models and satellite-derived estimates of land carbon uptake.

The major patterns of CO2 uptake by photosynthesis (GPP, gross primary production) during the growing season (June-July-August, in arbitrary units), resulting from satellite data products based on solar induced fluorescence (SIF) and models that (a, left panel) best reproduced observed atmospheric CO2 variations during 2007-2010, and (b, right panel) show less correspondence with atmospheric CO2 records. Models with higher explanatory power (left) indicate higher seasonal uptake in croplands and forests compared to those with less explanatory power (right). Credit: Sun et al. [2021], Figure 3a and b

The land-atmosphere carbon balance has long been one of the most uncertain components in the global carbon cycle. However, increases in carbon dioxide (CO2) observation networks and global satellite observations provide increasing constraints, especially for the seasonal uptake of CO2 in the temperate growing season. Sun et al. [2021] evaluate seasonal land carbon uptake from a range of prognostic and diagnostic land models by comparing the atmospheric CO2 pattern derived from coupling modeled fluxes to atmospheric transport models to actual patterns observed with a network of tall tower stations in continental North America. Models that best reproduced the observed spatial and temporal variability in atmospheric CO2 were those that had strongest growing season uptake in croplands, which runs counter to the general vies of that this uptake is dominated by forests.

Citation: Sun, W., Fang, Y., Luo, R. et al. [2021]. Midwest U.S. croplands determine model divergence in North American carbon fluxes. AGU Advances, 2, e2020AV000310. https://doi.org/10.1029/2020AV000310

—Susan Trumbore, Editor-in-Chief, AGU Advances

This article appeared on the EOS website at https://eos.org/editor-highlights/how-do-croplands-reduce-co2-during-the-growing-season


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