The Effect of Prairie Burning on Soil Organic Matter Dynamics and Physical Structure - Implications for Critical Zone Functions.

Fire is a driver of carbon dynamics in prairie ecosystems, and exerts an influence on both the quantity and speciation of soil organic matter. Consequently, the physical structure and hydrology of the unsaturated zone may be affected by the frequency and intensity of burning. Thus, prairie burning has implications for the functioning of the critical zone, with the soil as an interface between the atmospheric and lithospheric components. This study investigates both short- and long-term effects of burning at Konza prairie on soil organic matter, dissolved carbon, pore gas and soil structure, and will examine the further implications for hydrology via numerical modelling. Konza prairie in north-eastern Kansas is a mesic tallgrass prairie, overlying complex shale and limestone lithology, in which long-term manipulation of burn frequencies has been conducted. Soil monitoring arrays, including moisture, temperature and matric potential probes, and pore gas and water samplers were installed in two watersheds. These sites will be burned and monitored in Fall 2016 and Spring 2017. Water and gas samples obtained during burning will be analysed for dissolved organic carbon species, nitrate, nitrite, carbon dioxide and ammonia, in order to comment on the immediate changes during the event. Quantification of the long-term changes is underway; in which the bulk density, soil water characteristic curves, hydraulic conductivity, and carbon content and types is assessed for unburned watersheds and watersheds having 1-yr, 2-yr, 4-yr and 20-yr burn frequencies. Hydrological modelling will be conducted using input data derived from the physical analyses, in order to determine the effects of burn frequency on groundwater recharge, nutrient transport and potential soil moisture fluctuations over various timescales.