How does soil hydrology fit into the organic matter-nitrogen relationship?

Nitrogen is perhaps the most limiting nutrient in the biosphere, and human acceleration of the nitrogen cycle causes havoc in ecological systems, where organisms are adapted to low-nitrogen conditions. Accelerated nitrogen cycling also adversely impacts air and water quality – it functions as a greenhouse gas, generates smog, depletes ozone, and causes algae blooms and fish kills. Much biogeochemical research has thus focused on the role of soil organic matter (the massive reservoir of decomposing remains of once-living biomass) in retaining nitrogen, dramatically slowing its cycling through the environment. Historically, however, nitrogen retention theories have focused on the role of soil organic matter in the absence of soil hydrology. In a new paper led by our colleague Michael Castellano at Iowa State, we contrast coarse vs. fine textured soil along a hillslope in Maryland to test hypotheses that nitrogen retention in soil organic matter is regulated by soil texture and the ease with which water transports organic matter and nitrogen through different types soil. This research was conducted out of Jason Kaye’s lab at Penn State. See the paper here.