Size of Precipitation Pulses Controls Nitrogen Transformation and Losses in an Arid Patagonian Ecosystem

• Published in: Ecosystems (New York) Vol. 13; no. 4; pp. 575 - 585
• Main Authors: Yahdjian, Laura, Sala, Osvaldo E
• Format: Journal Article
• Language: English
• Published: New York New York : Springer-Verlag 01.06.2010; Springer Science+Business Media; Springer-Verlag; Springer; Springer Nature B.V
• Subjects: Ammonia; ammonia volatilization; Ammonium; Animal and plant ecology; Animal, plant and microbial ecology; Argentina; arid ecosystems; Arid soils; Arid zones; Biological and medical sciences; Biomedical and Life Sciences; Climate change; Climatic changes; Denitrification; Desert soils; Ecology; Ecosystems; Environmental Management; Extreme weather; Fundamental and applied biological sciences. Psychology; General aspects; Geoecology/Natural Processes; Growing season; Hydrology/Water Resources; irrigation; Irrigation effects; Leaching; Life Sciences; Mineralization; net N mineralization; nitrate leaching; Nitrates; Nitrogen; nitrogen-water interactions; Patagonian steppe; Plant growth; Plant Sciences; Precipitation; precipitation pulses; Rain; Rain and rainfall; Rainfall; seasonal variation; Soil ecology; soil inorganic N; Soil water; Steppe soils; Steppes; Synecology; Terrestrial ecosystems; volatilization; Water content; Zoology; Argentina; soil inorganic N; arid ecosystems; nitrogen–water interactions; nitrate leaching; ammonia volatilization; precipitation pulses; Patagonian steppe; denitrification; net N mineralization; nitrogen-water interactions; Arid environment; Interaction; Nitrates; Nitrogen; Leaching; Ammonia; Soils; Precipitation; Mineralization; Steppe; Ecosystem; Volatilization; Denitrification
• DOI: 10.1007/s10021-010-9341-6
• ISSN: 1432-9840

Arid ecosystems receive precipitation pulses of different sizes that may differentially affect nitrogen (N) losses and N turnover during the growing season. We designed a rainfall manipulation experiment in the Patagonian steppe, southern Argentina, where we simulated different precipitation patterns by adding the same amount of water in evenly spaced three-small rainfall events or in one-single large rainfall event, three times during a growing season. We measured the effect of the size of rainfall pulses on N mineralization and N losses by denitrification, ammonia volatilization, and nitrate and ammonia leaching. Irrigation pulses stimulated N mineralization (P < 0.05), with small and frequent pulses showing higher responses than large pulses (P < 0.10). Irrigation effects were transient and did not result in changes in seasonal net N mineralization suggesting a long-term substrate limitation. Water pulses stimulated gaseous N losses by denitrification, with large pulses showing higher responses than small pulses (P < 0.05), but did not stimulate ammonia volatilization. Nitrate leaching also was higher after large than after small precipitation events (P < 0.05). Small events produced higher N transformations and lower N losses by denitrification and nitrate leaching than large events, which would produce higher N availability for plant growth. Climate change is expected to increase the frequency of extreme precipitation events and the proportion of large to small rainfall events. Our results suggest that these changes would result in reduced N availability and a competitive advantage for deep-rooted species that prefer nitrate over ammonia. Similarly, the ammonium:nitrate ratio might decrease because large events foster nitrate losses but not ammonium losses.