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THE ROLE OF NITROGEN FROM IMMISSIONS IN SPRUCE ECOSYSTEMS.

Objective

TO GENERATE INFORMATION IN ORDER TO ELUCIDATE THE INTERFERENCE BETWEEN AIR POLLUTION AND KEY PHYSIOLOGICAL PROCESSES IN FOREST TREES.

THE PROPOSED RESEARCH WILL INVESTIGATE THE ROLE OF ATMOSPHERIC NITROGEN INPUT IN CAUSING FOREST DECLINE IN SPRUCE. IT IS HYPOTHESIZED THAT EXCESS NITROGEN UPTAKE STIMULATES GROWTH WHICH UNDER CONDITIONS OF LIMITED CATION SUPPLY WILL LEAD TO A NUTRIENT IMBALANCE WITH THE KNOWN SYMPTOMS OF NEEDLE YELLOWING. THE ROLE OF NITROGEN IS MANIFOLD : (1) IT WILL BE TAKEN UP BY ABOVE-GROUND PARTS AND ACT ON GROWTH, (2) NITRATE WILL CAUSE CATION LEACHING IN THE SOIL PROFILE WITH THE EFFECT OF ACIDIFICATION AND ITS EFFECTS ON ROOTS, (3) AMMONIUM APPEARS TO BE TAKEN UP PREFERENTIALLY BY ROOTS OF SPRUCE, LEAVING NITRATE IN THE SOIL WHICH PROMOTES LEACHING, (4) NITRIFICATION OF AMMONIUM WILL RELEASE PROTONS, THUS ACCELARATING THE ACIDIFICATION PROCESS.
THE PROPOSED STUDY WILL INVESTIGATE THE DIFFERENT FLUXES OF N IN A FOREST ECOSYSTEM USING 15N AS TRACER AND USING FERTILIZATION WITH NITROGEN AND SUGAR IN ORDER TO PERTURB THE NITROGEN BALANCE. THE WORK IS SUPPLEMENTED BY GLASSHOUSE STUDIES ON AERIAL AND ROOT UPTAKE PROCESSES AND BY FERTILIZATION EXPERIMENTS IN THE FIELD. THE NATURAL 15N/14N AND 13C/12C RATIOS WILL BE MEASURED IN DIFFERENT COMPARTMENTS IN ORDER TO GET INSIGHT IN THE NATURAL FATE OF AMMONIUM AND NITRATE. ALL STUDIES WILL BE SUPPLEMENTED BY INVESTIGATIONS OF THE CATION, CARBON AND WATER CYCLING OF THE ECOSYSTEM. IT THEREFORE CONTRIBUTES TO THE ECOSYSTEMS STUDIES ON FOREST DECLINE. IT IS EXPECTED THAT THE PROPOSED STUDY WILL CLARIFY THE IMPACT OF AMMONIUM AND NITRATE IN FOREST ECOSYSTEM AND MAKE RECOMMENDATIONS ABOUT POSSIBLE ACCEPTABLE IMMISSION LOADS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSITAET BAYREUTH
Address
Universitaetsstrasse 30
95447 Bayreuth
Germany