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Nitrogen limitation in arid - subhumid ecosystems : a meta - analysis of fertilization studies

Por: Yahdjian, María Laura.
Colaborador(es): Gherardi Arbizu, Laureano | Sala, Osvaldo Esteban.
ISSN: 0140-1963.Tipo de material: Artículos y capítulos. Recurso electrónico.Tema(s): ARID ECOSYSTEMS | META-ANALYSIS | NITROGEN FERTILIZATION | PRIMARY PRODUCTION | RESOURCE LIMITATION | ABOVEGROUND BIOMASS | ARID ENVIRONMENT | FERTILIZER APPLICATION | HUMID ENVIRONMENT | NET PRIMARY PRODUCTION | NITROGEN | NUTRIENT LIMITATION | PASTURE | PRECIPITATION INTENSITY | RESOURCE SCARCITY | TEMPERATURE EFFECT | WATER AVAILABILITY | Recursos en línea: Haga clic para acceso en línea | LINK AL EDITOR En: Journal of Arid Environments vol.75, no.8 (2011) p.675-680Resumen: Evidence supporting water limitation in arid-semiarid ecosystems includes strong correlations between aboveground net primary production [ANPP] and annual precipitation as well as results from experimental water additions. Similarly, there is evidence of N limitation on ANPP in low precipitation ecosystems, but is this a widespread phenomenon? Are all arid-semiarid ecosystems equally limited by nitrogen? Is the response of N fertilization modulated by water availability? We conducted a meta-analysis of ANPP responses to N fertilization across arid to subhumid ecosystems to quantify N limitation, using the effect-size index R which is the ratio of ANPP in fertilized to control plots. Nitrogen addition increased ANPP across all studies by an average of 50 percent, and nitrogen effects increased significantly [P = 0.03] along the 50-650 mm yr-1 precipitation gradient. The response ratio decreased with mean annual temperature in arid and semiarid ecosystems but was insensitive in subhumid systems. Sown pastures showed significant [P = 0.007] higher responses than natural ecosystems. Neither plant-life form nor chemical form of the applied fertilizer showed significant effects on the primary production response to N addition. Our results showed that nitrogen limitation is a widespread phenomenon in low-precipitation ecosystems and that its importance increases with annual precipitation from arid to subhumid regions. Both water and N availability limit primary production, probably at different times during the year; with frequency of N limitation increasing and frequency of water limitation decreasing as annual precipitation increases. Expected increase N deposition, which could be significant even in arid ecosystems, would increase aboveground net primary production in water-limited ecosystems that account for 40 percent of the terrestrial surface.
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Evidence supporting water limitation in arid-semiarid ecosystems includes strong correlations between aboveground net primary production [ANPP] and annual precipitation as well as results from experimental water additions. Similarly, there is evidence of N limitation on ANPP in low precipitation ecosystems, but is this a widespread phenomenon? Are all arid-semiarid ecosystems equally limited by nitrogen? Is the response of N fertilization modulated by water availability? We conducted a meta-analysis of ANPP responses to N fertilization across arid to subhumid ecosystems to quantify N limitation, using the effect-size index R which is the ratio of ANPP in fertilized to control plots. Nitrogen addition increased ANPP across all studies by an average of 50 percent, and nitrogen effects increased significantly [P = 0.03] along the 50-650 mm yr-1 precipitation gradient. The response ratio decreased with mean annual temperature in arid and semiarid ecosystems but was insensitive in subhumid systems. Sown pastures showed significant [P = 0.007] higher responses than natural ecosystems. Neither plant-life form nor chemical form of the applied fertilizer showed significant effects on the primary production response to N addition. Our results showed that nitrogen limitation is a widespread phenomenon in low-precipitation ecosystems and that its importance increases with annual precipitation from arid to subhumid regions. Both water and N availability limit primary production, probably at different times during the year; with frequency of N limitation increasing and frequency of water limitation decreasing as annual precipitation increases. Expected increase N deposition, which could be significant even in arid ecosystems, would increase aboveground net primary production in water-limited ecosystems that account for 40 percent of the terrestrial surface.

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