Efectos del fuego sobre el quimismo de los arroyos en cuencas de landa

Effects of fire on stream water chemistry in heathland watersheds. Conductivity, PH. and concentrations of Nat. K + , Ca2+ and Mg2+ were monitored for up to two years in baseflow water of four streams draining burned and unburned watersheds in Calluna-dominated dry heathlands in Montseny (Barcelona, N E Spain). No significant changes attributable to fire were observed in any of the six measured variables. Lack of sensitivity of baseflow chemistry to burning probably derives from retentior, in soil exchange sites of cations presumably leached from the ash layer. Absorption of nutrients by rapidly regrowing Pteridium aquilinum might have also contributed to cation immobilization.Se midieron la conductividad. el p H y las concentraciones de N a f , K + , Ca2+ y Mg'+ durante dos años en el caudal de base de cuatro arroyos que drenan landas de Calluna quemadas y no quemadas en La Calma (Montseny, Barcelona). No se encontraron efectos significativos del fuego sobrc ninguna de las seis variables estudiadas. La insensibilidad del quimismo del caudal dc base frente al fuego se debe probablemente a la retencion, por el complejo de intercambio del suelo. de 10s cationes presumiblemente lixiviados de la capa de cenizas. La absorción de nutrientes por parte de Pteridium aquilinum, cuyos frondes rebrotan rápidamente tras el incendio, podria tambien contribuir a la inmovilizacibn de 10s cationes

Exploring the long-term response of undisturbed Mediterranean catchments to changes in atmospheric inputs through time series analysis

The aim of this study was to gain insights on the potential hydrological and biogeochemical mechanisms controlling the response of two nested Mediterranean catchments to long-term changes in atmospheric inorganic nitrogen and sulphate deposition. One catchment was steep and fully forested (TM9, 5.9 ha) and the other one had gentler slopes and heathlands in the upper part while side slopes were steep and forested (TM0, 205 ha). Both catchments were highly responsive to the 45% decline in sulphate concentration measured in atmospheric deposition during the 1980s and 1990s, with stream concentrations decreasing by 1.4 to 3.4 μeq L− 1 y− 1. Long-term changes in inorganic nitrogen in both, atmospheric deposition and stream water were small compared to sulphate. The quick response to changes in atmospheric inputs could be explained by the small residence time of water (4-5 months) in these catchments (inferred from chloride time series variance analysis), which was attributed to steep slopes and the role of macropore flow bypassing the soil matrix during wet periods. The estimated residence time for sulphate (1.5-3 months) was substantially lower than for chloride suggesting unaccounted sources of sulphate (i.e., dry deposition, or depletion of soil adsorbed sulphate). In both catchments, inorganic nitrogen concentration in stream water was strongly damped compared to precipitation and its residence time was of the order of decades, indicating that this essential nutrient was strongly retained in these catchments. Inorganic nitrogen concentration tended to be higher at TM0 than at TM9 which was attributed to the presence of nitrogen fixing species in the heathlands. Our results indicate that these Mediterranean catchments react rapidly to environmental changes, which make them especially vulnerable to changes in atmospheric deposition

Densitat urbana Complexe esportiu

En una ciutat com Barcelona on l'escassetat de sòl és un problema, es prova la vialitat dels camps de futbol a través d'un exercici de densificació. Mantenint l'ús actual del solar, i rendibilitzant el sòl a través de nous usos compatibles amb el camp de futbol, es proposa un espai viu durant les 24 hores el dia

Densitat urbana Complexe esportiu

En una ciutat com Barcelona on l'escassetat de sòl és un problema, es prova la vialitat dels camps de futbol a través d'un exercici de densificació. Mantenint l'ús actual del solar, i rendibilitzant el sòl a través de nous usos compatibles amb el camp de futbol, es proposa un espai viu durant les 24 hores el dia

Densitat urbana Complexe esportiu

En una ciutat com Barcelona on l'escassetat de sòl és un problema, es prova la vialitat dels camps de futbol a través d'un exercici de densificació. Mantenint l'ús actual del solar, i rendibilitzant el sòl a través de nous usos compatibles amb el camp de futbol, es proposa un espai viu durant les 24 hores el dia

Efectos del fuego sobre el quimismo de los arroyos en cuencas de landa

Effects of fire on stream water chemistry in heathland watersheds. Conductivity, PH. and concentrations of Nat. K + , Ca2+ and Mg2+ were monitored for up to two years in baseflow water of four streams draining burned and unburned watersheds in Calluna-dominated dry heathlands in Montseny (Barcelona, N E Spain). No significant changes attributable to fire were observed in any of the six measured variables. Lack of sensitivity of baseflow chemistry to burning probably derives from retentior, in soil exchange sites of cations presumably leached from the ash layer. Absorption of nutrients by rapidly regrowing Pteridium aquilinum might have also contributed to cation immobilization.Se midieron la conductividad. el p H y las concentraciones de N a f , K + , Ca2+ y Mg'+ durante dos años en el caudal de base de cuatro arroyos que drenan landas de Calluna quemadas y no quemadas en La Calma (Montseny, Barcelona). No se encontraron efectos significativos del fuego sobrc ninguna de las seis variables estudiadas. La insensibilidad del quimismo del caudal dc base frente al fuego se debe probablemente a la retencion, por el complejo de intercambio del suelo. de 10s cationes presumiblemente lixiviados de la capa de cenizas. La absorción de nutrientes por parte de Pteridium aquilinum, cuyos frondes rebrotan rápidamente tras el incendio, podria tambien contribuir a la inmovilizacibn de 10s cationes