Resumo

CAMPANELLA, MARÍA VICTORIA; ROSTAGNO, CÉSAR MARIO; VIDELA, LINA SONIA  e  BISIGATO, ALEJANDRO JORGE. EFECTO DE LAS PRECIPITACIONES SOBRE EL NITRÓGENO DISPONIBLE EN SUELOS CON DEGRADACIÓN CONTRASTANTE EN EL NE DE CHUBUT. Cienc. suelo [online]. 2015, vol.33, n.2. ISSN 1850-2067.

Annual precipitation exerts a key control on the functioning of arid ecosystems. However, changes in seasonality and/or in the frequency of extreme precipitation events could have great ecological and biogeochemical impacts. Moreover, these impacts would be in relation to the degree of soil conservation. Our objective was to examine the effect of seasonal rainfall events on N availability (nitrate and ammonium) in soils with contrasting degradation in northeastern Chubut. Two steppes with contrasting soil erosion levels were chosen: herbaceous steppe with shrubs (EHA) and degraded shrub steppe (EA). We performed a one-year experiment with 3 factors: rainfall seasonality simulation (winter or spring irrigation), irrigation (with and without), and two plant communities (EHA and EA). Plots were watered in a single event during winter and/or spring, simulating a great rainfall event of 40 mm. Soil samples were taken immediately before watering and 3, 6, and 14 days after watering. Soil samples were separated into superficial (0-5 cm) and sub-superficial (5-15 cm) depths. Total N contents were similar between soils of the two communities. In winter, there was no effect of watering on the contents of ammonium and nitrate, neither in EHA nor EA. In spring, there were higher nitrate contents at the superficial layer on the watered soils in EHA. Our results suggest that nitrates in eroded soils of EA did not respond to watering as a consequence of lower infiltration rates and subsequently lower increases in soil water content in that community in comparison with EHA.

Palavras-chave : Patagonia; desertification; nitrate; infiltration.

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