PROTOS

Production and transport of organic solutes: effects of natural climatic variation

Co-ordinator :Dr.ir.Jan Mulder

Dissolved organic matter (DOM), comprising carbon (DOC), nitrogen (DON) and phosphorus (DOP), plays a significant role in terrestrial and aquatic ecosystems. For example,

• Organic acids act as pH buffer, and bind and transport metals
• Dissolved organically-bound forms may contribute significantly to element concentrations
• DON may have a priming effect on soil organic matter decomposition
• Certain DOM fractions are a food resource for aquatic organisms
• DOM plays an important role in soil development.

There is evidence that climatic factors, especially temperature, moisture and water flux, influence concentrations and fluxes of DOM. Therefore this area of research is essential within TERI.

In PROTOS we propose to determine the effects of natural variations in climate and deposition on concentrations and fluxes of DOC, DON and DOP in forest ecosystems, in a North-South transect across Europe. Results will be used to test hypotheses concerning controlling factors. Specifically, we consider

• net production, in soil organic horizons, of organic forms of C, N and P that are potentially transferable to solution
• physical and chemical processes of sorption and dissolved transport,
• mineralisation of DOM.

Of these, the first and third are considered to be influenced most by climatic factors. Proposed field sites are Birkenes (Norway, 58°22'N, 08°13'E), Waldstein (Germany, 50°08'35"N, 11°52'08"E) and Sierra de Gata (Spain,40°18'30"N, 06°43'30"W).

For each site we have extensive long-term data sets on relevant aspects, which will allow the time-period considered to be extended beyond that of the actual project. A core field programme will include measurement of climatic variables, soil physical properties, and composition of water as it moves through the forest ecosystem. We will also characterize DOM by fractionation and isotopic composition.

Hypotheses concerning the processes mentioned above will be formulated in a mathematical model, which has already been partly developed. Laboratory studies will be done to obtain parameters for sorption, formation of DOM as function of soil temperature, moisture and solution composition, and mineralisation of DON. Driving variables will be climatic data and atmospheric input of water and solutes. The model will be tested by comparing predictions with field observations, including "hindcasting" of data obtained previously. A successful application of the model to all three sites, which vary widely in climate, will help assessing and predicting the effect of climatic changes on DOC, DON and DOP in European forest ecosystems.

OBJECTIVES

• Determine concentrations and fluxes of dissolved organic N (DON), dissolved organic C (DOC) and dissolved organic P (DOP) in European forest ecosystems, including the transfer of DON, DOC and DOP to surface water. Field-based monitoring studies will be carried out at a set of forested catchments, representative of different environments in Europe.
• Identify key parameters controlling fluxes of dissolved organic matter (DOM) and quantify the effects of natural climatic variations.
• Determination of key parameter values with respect to production, mineralization, sorption and transport of DOM by means of laboratory studies.
• Further develop and parameterize a mathematical transport model (CHUM) combining the processes, explaining the observed fluxes of natural organic elements in soils (including the transfer to surface water) and quantifying the effect of variations in climatic variables.

contact :

Dr. ir. Jan Mulder
Norwegian Forest Research Institute (NISK)
Hoegskoleveien 12
N-1432 Ås
Norway
Tel: +47-6494 9159/9014
Fax: +47-64942980
jan.mulder@nisk.no

web site :