Author(s)

Carlos E. Oyarzun^1*, Pedro Hervé-Fernández^2,3, Dries Huygens^3,4,5, Pascal Boeckx³, Niko E. C. Verhoest²

¹Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
²Laboratory of Hydrology and Water Management, Faculty Bioscience Engineering, Ghent University, Ghent, Belgium.
³Isotope Bioscience Laboratory (ISOFYS), Ghent University, Ghent, Belgium.
⁴Institute of Agricultural Engineering and Soil Science, Faculty of Agricultural Sciences, Universidad Austral de Chile, Valdivia, Chile.
⁵Instituto Multidisciplinario de Biología Vegetal (IMBIV), Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina.

Soil cover disturbances have a direct effect on biogeochemistry, potentially enhancing nutrient loss, land degradation and associated changes in ecosystem services and livelihood support. The objective of this study was to assess how canopy affected throughfall chemistry and how hydrology affected stream nutrient load responses in two watersheds dominated by native old-growth evergreen rainforest (NF) and exotic plantation of Eucalyptus nitens (EP), located at the Coastal mountain range of southern Chile (40°;S). We measured nitrogen (NO₃-N, NH₄-N, Organic-N, Total-N) and total phosphorus (Total-P) at catchment discharge, and δ¹⁸O in throughfall precipitation and stream discharge in both catchments, in order to separate throughfall (or new water) contributions during storm events. It was hypothesized that all nutrients showed an increase in concentration as discharge increased (or enhanced hydrological access), in EP; but not in NF. Our results indicated that Organic-N, Total-N and Total-P concentrations were positively related to discharge. However, NO₃^--N showed a negative correlation with catchment discharge. Organic-N and Total-P showed a flush during storm events; the opposite was observed for NO₃^--N. However, this behavior suggested that NO₃^--N was being retained by charged particles or soil micro biota, whether Organic-N was flushed as it was more concentrated in big pore water that was not tightly attached, compared with NO₃^--N.

Native Rainforests, Exotic Plantations, Nutrient Fluxes, Hydrological Controls, Headwater Catchments

Oyarzun, C. , Hervé-Fernández, P. , Huygens, D. , Boeckx, P. and Verhoest, N. (2015) Hydrological Controls on Nutrient Exportation from Old-Growth Evergreen Rainforests and Eucalyptus nitens Plantation in Headwater Catchments at Southern Chile. Open Journal of Modern Hydrology, 5, 19-31. doi: 10.4236/ojmh.2015.52003.