Greg Michalski Mark Thiemens R.C. Quinn J. L. Macalady S. Kohl Scott D. Wankel Carol Kendall Christopher P McKay Ronald Amundson Stephanie A. Ewing 2007 <p><span>In most climates on Earth, biological processes control soil N. In the Atacama Desert of Chile, aridity severely limits biology, and soils accumulate atmospheric NO</span>₃⁻<span>. We examined this apparent transformation of the soil N cycle using a series of ancient Atacama Desert soils (&gt;2 My) that vary in rainfall (21 to &lt;2 mm yr</span>⁻¹<span>). With decreasing rainfall, soil organic C decreases to 0.3 kg C m</span>⁻²<span>&nbsp;and biological activity becomes minimal, while soil NO</span>₃⁻<span>&nbsp;and organic N increase to 4 kg N m</span>⁻²<span>&nbsp;and 1.4 kg N m</span>⁻²<span>, respectively. Atmospheric NO</span>₃⁻<span>&nbsp;(Δ</span>¹⁷<span>O = 23.0‰) increases from 39% to 80% of total soil NO</span>₃⁻<span>&nbsp;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.</span></p> application/pdf 10.1029/2006GB002838 en American Geophysical Union Rainfall limit of the N cycle on Earth article