Exploring the long-term response of undisturbed Mediterranean catchments to changes in atmospheric inputs through time series analysis
Bernal Berenguer, Susana (Centre d'Estudis Avançats de Blanes)
Belillas, Cristina (Centre de Recerca Ecològica i d'Aplicacions Forestals)
Ibáñez Estévez, Juan José (Centre de Recerca Ecològica i d'Aplicacions Forestals)
Àvila i Castells, Anna (Centre de Recerca Ecològica i d'Aplicacions Forestals)

Data:	2013
Resum:	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.
Ajuts:	Ministerio de Ciencia e Innovación CGL2009-13188-C03-01 Ministerio de Economía y Competitividad CGL2011-30590-C02-01 Ministerio de Ciencia e Innovación CSD2008-00040
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió acceptada per publicar
Matèria:	Atmospheric deposition ; Heathlands ; Long-term trend ; Mediterranean catchment ; Stream water chemistry ; Water residence time
Publicat a:	Science of the total environment, Vol. 458-460 (Aug. 2013), p. 535-545, ISSN 1879-1026

DOI: 10.1016/j.scitotenv.2013.04.072

Post-print 42 p, 661.3 KB

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