Soil Trace Gas Emission Across Landscape Transition from Agricultural Field to Riparian Buffer.

In 2015, a new riparian buffer initiative aimed at enhancing protection of Minnesota’s water quality was signed into law. The new regulations clarified that all bodies of water listed on a buffer protection map were to have an average 15 m of perennial vegetation buffer, impacting nearly 45,000 hectares of land throughout the state. While improving water quality via mitigation of runoff and erosion is a likely outcome of the legislation, the impact of transitioning from agricultural fields to riparian buffer on Minnesota’s soil trace gas emissions is not fully understood. This study aimed to examine the fluxes of carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), and ammonia (NH3) from soils along a landscape transition from agricultural field to a small, currently existing riparian buffer zone near Collegeville, MN. A microcosm study was designed to quantify fluxes of trace gas emissions from soils collected along a transect gradient from an actively cropped field into a riparian buffer. Emissions of CO2, N2O, CH4, and NH3 were measured for 17 d with a mobile-FTIR gas analyzer integrated with a modified microcosm gas-sampling lid. Preliminary results from the microcosm study suggest that CO2 fluxes from the riparian soils were significantly higher than the field soils, correlating with higher TOC concentrations in the riparian soil. Emissions of N2O were highest in the transitional zones between field and riparian buffer. Fluxes of N2O were measured shortly after initial wet-up of soils to 50% water-holding capacity and again on day 6 when soils were re-wetted to the initial moisture content, but seldom during relatively dry conditions. Results from this study may offer additional information to understand soil biogeochemical processes, as well as provide greater understanding of potential impacts that new Minnesota legislation may have on soil/landscape greenhouse gas budgets.