Nitrogen circulation in a Mediterranean holm oak forest, La Castanya, Montseny, northeastern Spain

Abstract

Bulk deposition, wet-only deposition, throughfall and dry deposition inferred from washing foliage and surrogate surfaces were used to describe inorganic N inputs to a forested catchment in the Montseny Mountains (La Castanya, Catalonia, Spain). Bulk inputs of inorganic N were moderate, with a mean of 5.7 kg N ha -1 yr -1 , ranging between 4 and 10 kg N ha -1 yr -1 for the period 1983 to 2000. Dry deposition fluxes estimated from washing branches added about 9 kg N ha -1 yr -1 to wet inputs and the total atmospheric deposition was estimated in 15 kg N ha -1 yr -1 . Despite this substantial input flux, nearly all the inorganic nitrogen was retained within the forest ecosystem: NH 4 + and NO 3 -concentrations decreased dramatically as water crossed the canopy and the soil profile. In the stream, at baseflow conditions, NH 4 + and NO 3 -concentrations were always below the analytical detection limit (< 2 µeq L -1 ). Only briefly during peak flows did NO 3 -concentrations increase up to 100 µeq L -1 . Averaged over 10 years (1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994), the export of N at the catchment outlet was 0.05 kg N ha -1 yr -1 . This indicates a very tight N cycling allowing for an increase of N availability in these undisturbed forest ecosystems.

Nitrogen concentrations in a small Mediterranean stream: 1. Nitrate 2. Ammonium

“…A direct relationship should be expected between ∆t and ∆NO 3 -N/∆Q since long ∆t and therefore, antecedent dry conditions, favour solute accumulation in catchments and the successive solute flushing in stream water (Walling and Foster, 1975;Walling and Webb, 1986). Indeed, nitrate flushing can occur during the transition from dry to wet conditions in small catchments (Ávila, 2002;Ávila et al, 1992;Biron et al, 1999). Nevertheless, establishing a more general empirical model relating the solute's responses with the antecedent hydrological condition is difficult because data from a wide spectrum of antecedent hydro-climatic conditions are required.…”

INCA : summary and conclusions

“…The influence of climate on hydrology and stream biogeochemistry is evident, and the papers highlight the importance of the transition period from dry to humid conditions on runoff generation , Gallart et al, 2002 and nitrogen dynamics (Avila, 2002;. Detailed studies of this transition period are essential for achieving a comprehensive understanding of how Mediterranean catchments function.…”

“…The contributions to this volume from Spain relate to field investigations of the hydrology and inorganic nitrogen fluxes for Holm oak and pine forested catchments in the northeast of the country under dry and sub-humid (Avila, 2002;Gallart et al, 2002) Mediterranean climate conditions. The influence of climate on hydrology and stream biogeochemistry is evident, and the papers highlight the importance of the transition period from dry to humid conditions on runoff generation , Gallart et al, 2002 and nitrogen dynamics (Avila, 2002;.…”

“…This study was for the Fuiosos catchment near to Barcelona (catchment area 10.5 km 2 with granite bedrock and rainfall averaging 613 mm yr -1 ). The nitrogen fluxes are followed through the catchment compartments, with special emphasis to the inorganic atmospheric N fluxes via wet and dry deposition in a study by Avila (2002). This work related to a small catchment in the Montseny Mountains of Catalonia, La Castanya (5.9 ha in area with bedrock comprising metamorphic rocks, mainly phyllite and gneiss, rainfall 901 mm yr and that the highest concentrations occurred during storm events: high flow events accounted for about a half of the nitrate flux.…”

Assessing nitrogen dynamics in European ecosystems, integrating measurement and modelling: conclusions

“…The case studies for rivers are for the: l Scandinavia and the Baltic states (Kaste and Skjelkvåle, 2002;Rankinen et al, 2002;Vagstad et al, 2004); l The Netherlands Raat et al, 2002). l Germany (Langusch and Matzner, 2002a, b); l United Kingdom (Fisher and Acreman, 2004;Hill, 2000;Jarvie et al, 2002;Kennedy and Murphy, 2004;Limbrick, 2002;Machefert et al, 2002;Machefert and Dise, 2004;Neal, 2002a, b;Neal et al, 2004a, b;Snook and Whitehead, 2004;Whitehead et al 2002a, b); l France (Ruiz et al, 2002a, b); l Spain (Avila et al, 2002;Gallart et al, 2002).…”