Nitrate Leaching under changed climate conditions and forest management

Nitrate concentrations in groundwater resources have increased since the 1960ties and constrain - among some other factors – its usage as drinking water in parts of the Jura and the Central Plateau of Switzerland. While leaching from agricultural land probably is the main cause, nitrate leaching from forests are, in comparison, generally small but may increase due increased nitrogen deposition and warm and dry periods. However, current exceedance maps calculated as described in Rihm et al. (1996) do not include the saturation state of soils and probable changes of forest use. Timeframe of future changes can therefore not be derived from these maps.

Objectives

The objective of this project is to explore the possibility and limitations of the available datasets and methods to better estimate the risk of future nitrate leaching in Switzerland.

Research Approach

Nitrate leaching measurements on the LWF (i.e. the Swiss ICP-Forests level II plots) and the similarly equipped IAP-plots will be up-scaled using measurements of soil chemistry analyses and ground vegetation surveys on the Swiss ICP-Forests level I plots and similarly investigated plots and mapped data.

Expected scientific results

The project is expected to produce new refined results on the estimation of nitrate leaching from forests and the estimating C/N ratios and other saturation indicators with mapped data or survey data.

Practical Relevance

The project will provide a tool that allows to estimate the nitrate leaching risk for forests. This will allow the national, cantonal or communal authorities as well as private companies to focus their ground water quality protection efforts (e.g. adjustment of forest management plans and practices) in forests to sensible areas. The results will indicate the general trends of nitrate leaching in Switzerland which is of relevance fort he necessary measures e.g. in agriculture and prevention of air pollution.

Reports

Waldner, P.; Braun, S.; Rihm, B.; 2019. Schlussbericht des Projekts ‚Nitrate leaching risks mapping‘ (NitLeach II). Birmensdorf, Eidg. Forschungsanstalt WSL; Witterswil, Institut für Angewandte Pflanzenbiologie; Bern, Meteotest, 46 S. PDF