Dynamics of Greenhouse Gas Fluxes from Cropped Wetlands Under Corn-Soybean Cultivation
Abstract
Wet meadows and depressional wetlands once comprised a significant portion of the US Corn Belt landscape, and drainage systems have enabled their conversion to croplands. Regardless of the enormous investment to keep wetlands dry, some areas still intermittently flood most years. These "cropped wetlands" under corn-soybean cultivation can be potential hotspots for greenhouse gas (GHG) fluxes due to high fertilization and elevated moisture that stimulate anaerobic microbial processes. We provide preliminary data from five sites in the southern Prairie Pothole Region (Ames, Iowa, USA). Growing-season fluxes of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2) were measured weekly along topographic transects from depressions to uplands. High rainfall events in June flooded all depressions for up to a month, where water depth reached 30 cm. Fluxes of N2O ranged over four orders of magnitude, from -6.02x10-3 to 34.47 mg N2O m-2 h-1. We observed highest fluxes of N2O in the upland parts of the transects under corn cultivation during the initial heavy rain events, while depressions exhibited highest N2O fluxes following drainage. Also, we observed CO2 fluxes ranging over four orders of magnitude, from 0.15 to 1378 mg CO2 m-2 h-1 as well as CH4 fluxes ranging over four orders of magnitude, from -2.05 to 1495 mg CH4 m-2 h-1. The highest CH4 fluxes were observed in flooded depressions under corn cultivation, while the uplands had minimum CH4 production or small net consumption across all five transects. Our data indicate the likely importance of ephemerally flooded cropland soils for closing landscape-scale GHG budgets in the US Corn Belt.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B33G2746T
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0495 Water/energy interactions;
- BIOGEOSCIENCESDE: 1843 Land/atmosphere interactions;
- HYDROLOGY