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Subprogram C2: Nitrogen Induced Ecosystem Changes  
Nitrogen Dose and Nitrogen Form - Ecophysiological Responses  
The goal is to evaluate the importance of qualitative changes in nitrogen availability, caused by nitrogen deposition, for vegetation changes. Nitrogen induced biochemical changes of importance for natural enemies in heather's, blueberry and lingonberry, is characterised. Indicators and criteria for assessment of effects of nitrogen deposition on natural and semi-natural ecosystems are identified in order to define critical loads for nitrogen.

A physiological approach is taken to study nitrogen effects on ground layer species in a coniferous forest. The scientific approach will be to perform experiments with different amounts and different forms of nitrogen in an area with low background deposition of nitrogen (North Sweden).

The project comprises:

· Studies of nitrogen uptake and nitrogen usage in heather's and also biochemical responses of vegetation following a sharp decrease in N input (recovery).

· Identification of critical mechanisms for vegetation changes in systems affected by nitrogen deposition.

· Information collected from these experiments will be used to construct a conceptual model for nitrogen induced vegetation changes. From this, dose-response relationships will be derived.

Torgny Näsholm
SLU, Umeå
torgny.nasholm@genfys.slu.se