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Size of precipitation pulses controls nitrogen transformation and losses in an arid Patagonian ecosystem

Por: Yahdjian, María Laura.
Colaborador(es): Sala, Osvaldo Esteban.
ISSN: 1432-9840.Tipo de material: Artículos y capítulos. Recurso electrónico.Tema(s): AMMONIA VOLATILIZATION | ARID ECOSYSTEMS | DENITRIFICATION | NET N MINERALIZATION | NITRATE LEACHING | NITROGEN-WATER INTERACTIONS | PATAGONIAN STEPPE | PRECIPITATION PULSES | SOIL INORGANIC N | AMMONIA | ARID REGION | CLIMATE CHANGE | DENITRIFICATION | GROWING SEASON | GROWTH RATE | IRRIGATION SYSTEM | LEACHING | MINERALIZATION | NITRATE | NUMERICAL MODEL | NUTRIENT AVAILABILITY | NUTRIENT LOSS | PRECIPITATION INTENSITY | RAINFALL | SOIL NITROGEN | STEPPE | VOLATILIZATION | PATAGONIA | Recursos en línea: Haga clic para acceso en línea | LINK AL EDITOR. En: Ecosystems Vol.13, no.4 (2010), p.575-585Resumen: 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 less than 0.05], with small and frequent pulses showing higher responses than large pulses [P less than 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 less than 0.05], but did not stimulate ammonia volatilization. Nitrate leaching also was higher after large than after small precipitation events [P less than 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.
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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 less than 0.05], with small and frequent pulses showing higher responses than large pulses [P less than 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 less than 0.05], but did not stimulate ammonia volatilization. Nitrate leaching also was higher after large than after small precipitation events [P less than 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.

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