Abstract

Solute concentrations and fluxes in rainfall, throughfall and stemflow in two forest types, and stream flow in a 90 ha catchment in southern Chile (39°44?S, 73°10?W) were measured. Bulk precipitation pH was 6.1 and conductivity was low. Cation concentrations in rainfall were low (0.58 mg Ca2+ 1-1, 0.13 mg K+ 1-1, 0.11 mg Mg2+ 1-1 and <0.08 mg NH4-N 1-1), except for sodium (1.10 mg 1-1). Unexpected high levels of nitrate deposition in rainfall (mean concentration 0.38 mg NO3-N 1-1, total flux 6.3 kg NO3-N ha-1) were measured. Concentrations of soluble phosphorous in bulk precipitation and stream flow were below detection limits (<0.90 mg 1-1) for all events. Streamflow pH was 6.3 and conductivity was 28.3 ?s. Stream-water chemistry was also dominated by sodium (2.70 mg 1-1) followed by Ca, Mg and K (1.31, 0.70 and 0.36 mg 1-1). The solute budget indicated a net loss of 3.8 kg Na+ ha-1 year-1, 5.4 kg Mg2+ ha-1 year-1, 1.5 kg Ca2+ ha-1 year-1 and 0.9 kg K+ ha-1 year-1, while 4.9 kg NO3-N ha-1 year-1 was retained by the ecosystem. Stream water is not suitable for domestic use owing to high manganese and, especially, iron concentrations. Throughfall and stemflow chemistry at a pine stand (Pinus radiata D. Don) and a native forest site (Siempreverde type), both located within the catchment, were compared. Nitrate fluxes within both forest sites were similar (1.3 kg NO3-N ha-1 year-1 as throughfall). Cation fluxes in net rainfall (throughfall plus stemflow) at the pine stand generally were higher (34.8 kg Na+ ha-1 year-1, 21.5 kg K+ ha-1 year-1, 5.1 kg Mg2+ ha-1 year-1) compared with the secondary native forest site (24.7 kg Na+ ha-1 year-1, 18.9 kg K+ ha-1 year-1 and 4.4 kg Mg2+ ha-1 year-1). However, calcium deposition beneath the native forest stand was higher (15.9 kg Ca2+ ha-1 year-1) compared with the pine stand (12.6 kg Ca2+ ha-1 year-1). Copyright © 2002 John Wiley & Sons, Ltd.