Differences in evapotranspiration from cropland and tallgrass prairie across a gradient of climate in the U.S. Midwest

Authors: Schreiner-Mcgraw, Adam; BAKER, JOHN; WOOD, JEFFREY - UNIVERSITY OF MISSOURI; ABRAHA, MICHAEL - MICHIGAN STATE UNIVERSITY; ROBERTSON, G - MICHIGAN STATE UNIVERSITY; CHEN, JIQUAN - MICHIGAN STATE UNIVERSITY

Submitted to: American Society of Agricultural and Biological Engineers
Publication Type: Abstract Only
Publication Acceptance Date: 8/2/2023
Publication Date: 10/24/2023
Citation: Schreiner-McGraw, A.P., Baker, J.M., Wood, J.D., Abraha, M., Robertson, G.P., Chen, J. 2023. Differences in evapotranspiration from cropland and tallgrass prairie across a gradient of climate in the U.S. Midwest [abstract]. American Society of Agricultural and Biological Engineers. Paper 23033.

Interpretive Summary:

Technical Abstract: Widespread conversion of native prairie to cropland in the Midwest U.S. was one of the largest land use transformations in the history of mankind and has dramatically affected water budgets in the region. There have been mixed results in previous work to quantify how water budgets have been affected, and debate continues about the importance of land use change for altering water budgets in the context of a changing climate. Additionally, the conversion of cropland back to prairie has been proposed to restore soil health and sequester atmospheric carbon dioxide, making it important to understand how this conversion might affect the water budget. In this contribution, we present long-term observations of evapotranspiration (ET) from three locations within the Long-Term Agroecosystem Research (LTAR) network; the Upper Mississippi River Basin (UMRB) in Minnesota, the Kellogg Biological Station (KBS) in Michigan, and the Central Mississippi River Basin (CMRB) in Missouri. At each location, we installed eddy covariance towers to monitor ET and collected a minimum of 5 years of data at both a cropland and a prairie site. With these observations, we show that the difference in ET between cropland and prairie is not consistent. At the UMRB location the cropland site has higher ET than the prairie site (462 mm/yr and 379 mm/yr, respectively; p < 0.001), a difference which is also seen at KBS to a lesser degree (588 mm/yr and 559 mm/yr, respectively; p = 0.02). The cropland has higher ET during the March-May period. We attribute this to increased soil temperatures in the fallow croplands which facilitates ET while the soil in the prairie remains frozen. At the CMRB location, however, the cropland has lower ET than the prairie site (619 mm/yr and 730 mm/yr, respectively; p = 0.03). Unlike the two northern sites, the ground in the CMRB location does not freeze for large portions of the year, making the increased soil temperature at the cropped field less important than the perennial nature of the prairie. At the CMRB location, the peak summer ET is similar between the cropland and prairie sites, but the prairie has an extended growing season that results in higher ET during the spring and fall periods. We will discuss how the conversion between cropland and prairie affects the water budget, highlighting that the conversion will have different effects in different locations.