In most climates on Earth, biological processes control soil N. In the Atacama Desert of Chile, aridity severely limits biology, and soils accumulate atmospheric NO3−. We examined this apparent transformation of the soil N cycle using a series of ancient Atacama Desert soils (>2 My) that vary in rainfall (21 to <2 mm yr−1). With decreasing rainfall, soil organic C decreases to 0.3 kg C m−2 and biological activity becomes minimal, while soil NO3− and organic N increase to 4 kg N m−2 and 1.4 kg N m−2, respectively. Atmospheric NO3− (Δ17O = 23.0‰) increases from 39% to 80% of total soil NO3− as rainfall decreases. These soils capture the transition from a steady state, biologically mediated soil N cycle to a dominantly abiotic, transient state of slowly accumulating atmospheric N. This transition suggests that oxidized soil N may be present in an even more arid and abiotic environment: Mars.
|Title||Rainfall limit of the N cycle on Earth|
|Authors||Stephanie A. Ewing, Greg Michalski, Mark Thiemens, R.C. Quinn, J. L. Macalady, S. Kohl, Scott D. Wankel, Carol Kendall, Christopher P McKay, Ronald Amundson|
|Publication Subtype||Journal Article|
|Series Title||Global Biogeochemical Cycles|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Toxic Substances Hydrology Program|