『Summary
Following a wildfire in south-eastern Australia that burnt over
1 million hectares o forested land in early 2003, two former research
catchments (136 and 244 ha), in the East Kiewa valley, Victoria,
were re-instrumented. Discharge, suspended sediment, bedload and
nitrogen (N) and phosphorus (P) were measured for 3 years post-fire.
The nutrient data consisted of 15-min estimation of particulate
P and total Kjeldahl N via a regression with turbidity, and dissolved
forms of P and N estimated from over 1100 water samples. The regression-based
estimation allowed rigorous estimation of errors, seldom reported
in water quality data. The fire appears to have increased the
total P and N exports by around 5-6-fold, peaking at 1.6 kg ha-1
of P and 15.3 kg ha-1 of total combined N. Nutrients
transported as particulate matter dominated the first post-fire
year, with 94% of total combined P and 69% of total combined N.
Although dissolved forms increased in importance, the particulate
load comprised 86% of the total combined P load and 68% of the
total combined N load over the three post-fire years. Concentrations
and loads of P and N exhibited a rapid recovery to unburnt levels
during the second post-fire year. Particulate forms declined sharply
through a reduction in sediment delivery. Nitrate had the slowest
relaxation time, suggesting a persistent subsurface pathway and
the effect of nitrification. Notably, dissolved N fluxes were
predominantly in baseflow even in the first post-fire year. The
errors calculated for this study indicate the uncertainty that
can exist in water quality estimation despite high resolution
experimental design. Loads estimated from intermittent sampling
should be treated with caution. A simple model with time as the
single parameter proved to be a good predictor of mean three monthly
concentrations.
Keywords: Wildfire; Phosphorus; Nitrogen; Eucalypt forests; Water
quality』
Introduction
Site details
Methods
Field
Laboratory
Turbidity
Phosphorus
Nitrogen
Data analysis
Concentrations
Load estimation
Results
N and P relationships with turbidity
Concentrations
Model fitting
Loads
Phosphorus
Nitrogen
Partitioning of particulate and dissolved loads
Temporal distribution of loads
Discussion
Measurement and uncertainty
Concentrations and loads
Comparison with unburnt sites where
Changes attributable to fire
Comparison with other studies
Conclusions
Acknowledgements
References