EEB428H1 Study Guide - Final Guide: Global Warming Potential, Soil Acidification, Nitrogen Fixation
20 Apr 2016
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Lecture 5: perturbations to the n-cycle & consequences of global eutrophication. Atmospheric n2 needs to be transformed into another form (fixed) to be useable biologically. Without humans: small flux (little in and out), big pool. Oligotrophic: low low productive potential (low in soil) Nitrogen in the pre-industrial world: unreactive nitrogen in the atmosphere 90-130 tg n/y [biological nitrogen fixation denitrification] reactive nitrogen in terrestrial ecosystems. We have double the natural rate of fixation: fertilizers (50% of new) Initial fate of nitrogen fertilizers: 100 produced -> applied -> 47 in crop -. Terrestrial eutrophication elsewhere by leaching, aquatic eutrophication and marine from further leaching. Some of these wetland habitats is where this nitrogen can be denitrificated to n2: fossil fuel combustion, production of legume crops. Hydrocarbons combusted with air = nitrogen oxides. Loss of species richness in enriched soils; replacement of prairie flora by fast-growing. European weed grasses which increases the nitrogen amount in soils.
