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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGEMENT TECHNOLOGIES FOR CONSERVATION OF WESTERN RANGELANDS

Location: Range Management Research

Title: Water controls on nitrogen transformations and stocks in an arid ecosystem

Authors
item Reichmann, Lara -
item Sala, Osvaldo -
item Peters, Debra

Submitted to: Ecosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2012
Publication Date: January 15, 2013
Repository URL: http://handle.nal.usda.gov/10113/57140
Citation: Reichmann, L., Sala, O.S., Peters, D.C. 2013. Water controls on nitrogen transformations and stocks in an arid ecosystem. Ecosphere. 4(1):Article 11.

Interpretive Summary: We used a manipulation experiment to examine the effects of changes in rainfall and nitrogen fertilization on different stocks of nitrogen in the Chihuahuan Desert. We measured in situ net N mineralization, plant N uptake, foliar N, N leaching under the grass-rooting zone, and soil N availability for two years of manipulations. Our results showed that increased water availability did not affect net N mineralization, but there was higher plant N uptake than with drought. The accumulation of inorganic N during drought was the result of a decoupling between microbial and plant activity, and suggests that the cycling of N is more open in dry years than in wet years.

Technical Abstract: Our objective was to assess nitrogen responses to long-term changes in precipitation and nitrogen availability in the Northern Chihuahuan Desert (NM, USA), using rainfall manipulations (80% reduced PPT, ambient, 80% increased) and fertilization additions (with and without ammonium nitrate). We measured in situ net N mineralization, plant N uptake, foliar N, N leaching under grass-rooting zone, and soil N availability during two years. Our results showed that increased water availability did not affect net N mineralization, but there was higher plant N uptake than with drought. Soil inorganic N pools were 2–4 times lower with increased water availability compared to drought conditions. N leaching below grass-rooting zone was higher in dry than wet conditions because of higher available N. Increased water availability differentially affected N species significantly reducing the NO3:NH4 ratio. The accumulation of inorganic N during drought was the result of a decoupling between microbial and plant activity, and suggests that the cycling of N is more open in dry years than in wet years.

Last Modified: 7/28/2014
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