NIPHYS (Nitrogen Physiology of Forest Plants and Soils) is an investigation of the present effects of soil-borne and deposited nitrogen on forest organisms and soils along a climatic transect through Europe in order to substantiate predictions on effects of changing depositions and global climate on broad-leaved and coniferous trees.


Investigations on forest decline have demonstrated the importance of nitrogen immissions in enhancing various nutritional imbalances in trees and soil acidification. Nevertheless, we are presently unable to quantify several basic questions: (1) What form of nitrogen is used by trees in different environments, (2) what roles are played by soil properties, mycorrhiza, and microorganisms in the transformation of nitrogen in forest soils, (3) which processes regulate the ammonium/nitrate ratio in soil solution. NIPHYS addresses these issues by investigating plant, microbial, and abiotic processes involved in the transformation of ammonium and nitrate in forest soils of different climatic regions. The project combines botanical, microbiological and soil science. Each participant will work at all study sites. NIPHYS will make comparative studies of the objectives.

General objectives are: (1) to compare broad-leaved and coniferous trees, (2) to quantify the ecosystem internal fluxes of ammonium and nitrate, (3) to identify the sources of nitrate in groundwaters, (4) to develop the capacity to predict future development in forest soils with respect to soil acidification and groundwater quality.

Specific objectives are: (1) to identify potential and actual uptake of organic and inorganic nitrogen by broad-leaf trees, conifers, and mycorrhizae at varied availability of ammonium and nitrate in the soil, (2) to determine actual and potential nitrate reduction in different tree compartments, (3) to quantify aerial uptake of nitrogen by trees, (4) to quantify sorption and immobilization of ammonium in soil organic matter and clay particles, (5) to determine actual and potential nitrification and denitrification and their interaction with various soil redox couples, (6) to determine factors regulating the ammonium/nitrate ratio in soil solution.