U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Main content area

Water controls on nitrogen transformations and stocks in an arid ecosystem

Lara G. Reichmann, Osvaldo E. Sala, Bebra P. C. Peters
Ecosphere 2013 v.4 no.1 pp. 1-17
ammonium nitrate, ammonium nitrogen, arid zones, biogeochemical cycles, deserts, drought, ecosystems, fertilizer rates, field experimentation, grasslands, leaching, leaves, microbial activity, mineralization, nitrate nitrogen, nitrogen, nitrogen fertilizers, nutrient uptake, primary productivity, rain, rainfall simulation, soil, soil fertility, soil microorganisms, Chihuahuan Desert
Following water, nitrogen (N) is the most frequent limiting factor to aboveground net primary production in arid ecosystems. Increased water availability can stimulate both plant nitrogen uptake and microbial nitrogen mineralization, but may also stimulate losses from the ecosystem. Here, we assess the effect of water availability on nitrogen stocks and transformations in an arid ecosystem. We conducted a field experiment with five levels of precipitation input (−80%, −50%, ambient, +50%, +80%) and two levels of N fertilization (ambient or 10 g·m−2·yr−1 NH4NO3) in a desert grassland of the Chihuahuan Desert. 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.