TITLE:
Hydrological Controls on Nutrient Exportation from Old-Growth Evergreen Rainforests and Eucalyptus nitens Plantation in Headwater Catchments at Southern Chile
AUTHORS:
Carlos E. Oyarzun, Pedro Hervé-Fernández, Dries Huygens, Pascal Boeckx, Niko E. C. Verhoest
KEYWORDS:
Native Rainforests, Exotic Plantations, Nutrient Fluxes, Hydrological Controls, Headwater Catchments
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.5 No.2,
April
9,
2015
ABSTRACT: 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.