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Rainfall limit of the N cycle on Earth
Division of Ecosystem Sciences, Department of Environmental Science Policy and Management, University of California, Berkeley, California, USA
Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, Indiana, USA
Division of Physical Sciences, University of California, San Diego, La Jolla, California, USA
SETI Institute, NASA Ames Research Center, Moffett Field, California, USA
Penn State Astrobiology Research Center, Department of Geosciences, Pennsylvania State University, University Park, Pennsylvania, USA
Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada, USA
U.S. Geological Survey, Menlo Park, California, USA
U.S. Geological Survey, Menlo Park, California, USA
NASA-Ames Research Center, Moffett Field, California, USA
Division of Ecosystem Sciences, Department of Environmental Science Policy and Management, University of California, Berkeley, California, USA
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.
Received 9 September 2006; accepted 23 May 2007; published 8 August 2007.
Citation: (2007), Rainfall limit of the N cycle on Earth, Global Biogeochem. Cycles, 21, GB3009, doi:10.1029/2006GB002838.
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