| Measurements
of nitrate deposition and streamwater chemistry in the Tillingbourne Catchment,
in Southern England, made in 1979-1982 and 1999-2001 show a 216% increase in
Nitrogen leaching despite a reduction in N inputs. Both the historical and
current data sets have been modelled using the Integrated Nitrogen Model in
Catchments (INCA). The process-based model is shown to reproduce the historical
patterns of N release from the catchment. However, modelling the increased
leaching of N during recent years required an increase of the mineralisation
control parameter in the model, suggesting enhanced mineralisation rates.
Comparing historic and current soils data for C/N ratios shows that there has
been a reduction in C/N from 38 to 26%
in the humus layer and a reduction from
33 to 26%
in the mineral soil horizon. This significant fall in C/N is
consistent with the increase in N saturation in the H and Ah horizons of the
major catchment soil.
Keywords: acid deposition, recovery, nitrogen, Carbon-Nitrogen ratios,
Tillingbourne, Thames, catchment studies, nutrient leaching, modelling |