R. Andrés Sánchez, Thomas Meixner, Jennifer McIntosh, and Jon Chorover1
High severity wildfires of conifer forests are thought to be responsible for the majority of long-term landscape erosion. As post-fire erosion occurs, mineral surfaces are exposed to the environment intensifying weathering processes, and consequently altering nutrient cycling. Furthermore, similarly to what occurs in a wildfire, catchments that experience harvesting or deforestation show shifts in net fluxes of elements such as calcium, silicon and aluminum. Additionally, the burned vegetation releases nutrients and other elements that are transported down gradient via overland flow, shallow subsurface flow, and/or groundwater flow.
In 2013, the Thompson Ridge wildfire burned headwater catchments in the Jemez River Basin Critical Zone Observatory (JRB-CZO) within the Valles Caldera National Preserve, New Mexico USA. This study investigates the impact of the wildfire on solute fluxes to the surface water, including how these disturbances evolve with time, and how biogeochemical processes control post-fire solute concentrations in the surface water.
Comparison of pre- and post-fire surface water solute chemistry among the three watersheds shows increases in major cations following fire. Base cation concentrations (e.g., Ca, K and Na), increased immediately within a few weeks after the fire, likely related to leaching from combusted organic matter. These high fluxes persisted for approximately two months, and returned to pre-fire levels only for Na, while Ca and K concentrations stayed high for over two years.
1Department of Soil, Water, and Environmental Sciences, The University of Arizona, Tucson, AZ