Quantification of nitrate leaching from forest soils on a national scale in The Netherlands

Abstract. To evaluate the effects of nitrogen (N) emission policies, reliable information on nitrate concentrations and leaching fluxes from forest ecosystems is necessary. Insight into the regional variability of nitrate concentrations, to support local policy on emission abatement strategies is especially desirable. In this paper, three methods for the calculation of a spatial distribution of soil nitrate concentrations in Dutch forest ecosystems are compared. These are (i) a regression model based on observed nitrate concentrations and additional data on explanatory variables such as soil type, tree species and nitrogen deposition (ii) a semi-empirical dynamic model WANDA, and (iii) a process-oriented dynamic model SMART2. These two dynamic models are frequently used to evaluate the effects of reductions in nitrogen deposition at scales ranging from regional to countrywide. The results of the regression model evaluated the performance of the two dynamic models. Furthermore, the results of the three methods are compared with the steady-state approach currently used for the derivation of nitrogen critical loads. Both dynamic models, in the form of cumulative distribution functions, give similar results on a national scale. Regional variability is predicted differently by both models. Discrepancies are caused mainly by a difference in handling forest filtering and denitrification. All three methods show that, despite the high nitrogen inputs, Dutch forests still accumulate more N than they release. This implies that, in respect of groundwater quality, presently acceptable nitrogen deposition is higher than the (long-term) critical loads. However, in areas with high atmospheric nitrogen input, all three methods indicate that the EU standard for nitrate in groundwater (50 mg NO3 l –1 ) is exceeded. Steady-state with nitrogen deposition seems to have been reached in about 10% of the forested area, with a nitrate concentration greater than 50 mg NO3 –1 . Keywords: soil modelling, up-scaling, model validation, critical load

[1]  P. Gundersen.  Nitrogen deposition and leaching in European forests — Preliminary results from a data compilation , 1995 .

[2]  J. Aber,et al.  Spatial changes in forest floor and foliar chemistry of spruce-fir forests across New England , 1991 .

[3]  Maximilian Posch,et al.  Simulation of the long-term soil response to acid deposition in various buffer ranges , 1989 .

[4]  J. Erisman,et al.  Atmospheric sulphur deposition to forest stands: Throughfall estimates compared to estimates from inference , 1993 .

[5]  Gert Jan Reinds,et al.  Modelling of soil acidity and nitrogen availability in natural ecosystems in response to changes in acid deposition and hydrology , 1995 .

[6]  Edzer Pebesma,et al.  Error assessment in a soil acidification modelling study: efficiency issues and change of support , 2000 .

[7]  J. Alkemade,et al.  Modelling cadmium accumulation at a regional scale in the Netherlands , 1998, Nutrient Cycling in Agroecosystems.

[8]  C. Salm,et al.  Gebiedsspecifieke, kritische depositieniveaus voor stikstof en zuur voor terrestrische ecosystemen , 2000 .

[9]  C. van der Salm,et al.  Modelling the impact of acid deposition and nutrient cycling on forest soils , 1995 .

[10]  P. A. Burrough,et al.  Soil acidification from atmospheric ammonium sulphate in forest canopy throughfall , 1982, Nature.

[11]  Edzer Pebesma,et al.  Mapping groundwater quality in the Netherlands , 1997 .

[12]  Edzer Pebesma,et al.  Spatial aggregation and soil process modelling , 1999 .

[13]  G. Reinds,et al.  Uncertainty assessment in modelling soil acidification at the European scale : A case study , 1999 .

[14]  B. Emmett,et al.  Impact of nitrogen deposition on nitrogen cycling in forests : a synthesis of NITREX data , 1998 .

[15]  G. Reinds,et al.  Assessment of critical loads and their exceedance on European forests using a one-layer steady-state model , 1994 .

[16]  E. Matzner,et al.  Synthesis of Nitrogen Pools and Fluxes from European Forest Ecosystems , 1998 .

[17]  G. Reinds,et al.  Modelling the response of terrestrial ecosystems to acidification and desiccation scenarios , 1995 .

[18]  W. Vries,et al.  Soil response to acid deposition at different regional scales : field and laboratory data, critical loads and model predictions , 1994 .

[19]  H. Kros,et al.  Evaluation of biogeochemical models at local and regional scale , 2002 .

[20]  Jan G. M. Roelofs,et al.  The effects of air‐borne nitrogen pollutants on species diversity in natural and semi‐natural European vegetation , 1998 .

[21]  C. Beier,et al.  A correlative evaluation of nitrogen cycling in the forest ecosystems of the EC projects NITREX and EXMAN , 1995 .

[22]  Albert Tietema,et al.  WANDA, a regional dynamic nitrogen model (With Aggregated Nitrogen DynAmics) for nitrate leaching from forests , 2004 .

[23]  E. Pebesma,et al.  Assessment of the prediction error in a large-scale application of a dynamic soil acidification model , 2002 .

[24]  G. Reinds,et al.  The use of upscaling procedures in the application of soil acidification models at different spatial scales , 1998, Nutrient Cycling in Agroecosystems.

[25]  J. Kros,et al.  Dynamic nitrogen deposition thresholds during forest stand development in a Douglas fir forest analysed with two nitrogen models SMART2 and MERLIN , 2002 .

[26]  W. Vries,et al.  Impacts of acid deposition on concentrations and fluxes of solutes in acid sandy forest soils in the Netherlands , 1995 .