University of Arkansas, Fayetteville Division of Agriculture
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Abstract

Atmospheric carbon dioxide (CO2) levels are rapidly increasing, surpassing 400 ppm in 2013 from a pre-industrial revolution level of around 280 ppm. Researchers have been looking at methods to reduce CO2 levels in the atmosphere, including promoting carbon sequestration in soils. Carbon sequestration is the process where CO2 is naturally or artificially transferred out of the atmosphere and stored in the ocean, plant biomass, soils, and geologic formations. Seemingly contradictory to the notion of carbon sequestration is the use of fire as a management treatment for the restoration of native prairie grass ecosystems. Fire combusts plant biomass and produces CO2 as one of its products, potentially leading to increased atmospheric CO2 concentrations. The first objective of this research was to determine particulate (easily broken down) and total (easily broken down plus stable) soil organic matter content and CO2 respiration (output) in Woolsey Wet Prairie Sanctuary (WWPS) soil that has been restored and managed with annual burning for 10 years compared to soil from non-restored adjacent fields growing tall fescue. The first objective was accomplished by taking soil samples and CO2 respiration measurements before the 2017 annual prescribed burn. The second objective was to determine short-term impacts of the prescribed burn on soil carbon release and storage. The second objective was accomplished by comparing CO2 respiration before the fire management in the spring, then comparing to CO2 respiration 2, 7, 16, and 29 days post-treatment, and collecting soil samples. Soil samples were taken before the prescribed burn, two weeks after the burn, and two months after the burn to compare short-term changes in particulate organic matter (easily broken down; POM) and stable organic matter (OM). Results indicated high productivity in the wetland low-lying areas with statistically greater levels of POM and OM compared to the other sample sites. Additionally, there was no statistically significant change measured in POM following the annual prescribed burn at any sample site, nor a statistically significant increase in CO2 respiration. The results indicate that the managed wetland area is functioning as a highly-productive carbon sink.

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