Cropland Carbon Uptake Delayed and Reduced by 2019 Midwest Floods

Abstract

While large‐scale floods directly impact human lives and infrastructures, they also profoundly impact agricultural productivity. New satellite observations of vegetation activity and atmospheric CO2 offer the opportunity to quantify the effects of such extreme events on cropland carbon sequestration. Widespread flooding during spring and early summer 2019 induced conditions that delayed crop planting across the U.S. Midwest. As a result, satellite observations of solar‐induced chlorophyll fluorescence from TROPOspheric Monitoring Instrument and Orbiting Carbon Observatory reveal a 16‐day shift in the seasonal cycle of photosynthesis relative to 2018, along with a 15% lower peak value. We estimate a reduction of 0.21 PgC in cropland gross primary productivity in June and July, partially compensated in August and September (+0.14 PgC). The extension of the 2019 growing season into late September is likely to have benefited from increased water availability and late‐season temperature. Ultimately, this change is predicted to reduce the crop productivity in the Midwest Corn/Soy belt by ~15% compared to 2018. Using an atmospheric transport model, we show that a decline of ~0.1 PgC in the net carbon uptake during June and July is consistent with observed CO2 enhancements of up to 10 ppm in the midday boundary layer from Atmospheric Carbon and Transport‐America aircraft and over 3 ppm in column‐averaged dry‐air mole fractions from Orbiting Carbon Observatory. This study quantifies the impact of floods on cropland productivity and demonstrates the potential of combining solar‐induced chlorophyll fluorescence with atmospheric CO2 observations to monitor regional carbon flux anomalies.

Synergistic Satellite Assessment of Global Vegetation Health in Relation to ENSO‐Induced Droughts and Pluvials

“…For the 2015/16 ENSO event, relatively high soil moisture levels provided favorable conditions for vegetation growth in the southern part of the region (Figure , ). In contrast, excessive water associated with possible river flooding may suppress vegetation growth along the Paraná river, similar to recent flood damage reported from croplands within the US Midwest (Yin et al., 2020). The ASWI component information can be used to support the interpretation of the complex responses of vegetation to over‐dry and over‐wet conditions.…”

Midwest US Croplands Determine Model Divergence in North American Carbon Fluxes

“…), many TBMs (or at least their standard, non‐crop‐specific simulations included in model ensembles) are not designed to simulate croplands. Third, cropland management can be heavily affected by extreme weather events (e.g., 2019 Midwest flooding that delayed the growing season; Yin et al., 2020) that are not anticipated by even the most sophisticated models. While other deficiencies, such as the response of photosynthesis to temperature, have been implicated in the phenology bias in boreal ecosystems (e.g., S.‐J.…”

Contrasting Regional Carbon Cycle Responses to Seasonal Climate Anomalies Across the East‐West Divide of Temperate North America

“…Direct phenological mechanisms may also contribute to seasonal compensation effects, as the timing of spring budburst and autumn senescence has been found to be correlated on the scale of individual organisms and the landscape (Fu et al, 2014; Keenan & Richardson, 2015). The impact of seasonal compensation effects on annual GPP anomalies has been studied across northern forests and croplands using upscaled FLUXNET GPP (Buermann et al, 2013), Normalized difference vegetation index (NDVI) (Buermann et al, 2018), and SIF (Butterfield et al, 2020), while seasonal compensation in NEE has been examined for the 2011 Texas‐Mexico drought (Liu, Bowman, Parazoo, et al, 2018), 2012 temperate North America drought (Liu, Bowman, Parazoo, et al, 2018; Wolf et al, 2016), and 2018 MidWest floods (Yin et al, 2020). However, the implications of seasonal compensation effects on variability in the carbon balance across multiple years over temperate North America have not yet been examined.…”