Nitrogen fluxes from the landscape are controlled by net anthropogenic nitrogen inputs and by climate

Frontiers in Ecology and the Environment - Tập 10 Số 1 - Trang 37-43 - 2012
Robert W. Howarth1, Dennis P. Swaney1, Gilles Billen2, Josette Garnier2, Bongghi Hong1, Christoph Humborg3, Penny J Johnes4, Carl‐Magnus Mörth3, Roxanne Marino1
1Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY
2UMPC Université Paris 6 and CNRS, UMR Sisyphe, Paris, France
3Baltic NEST Institute, Stockholm Resilience Centre, Stockholm, Sweden
4Aquatic Environments Research Centre, School of Human and Environmental Sciences, University of Reading, Whiteknights, Reading, UK

Tóm tắt

The flux of nitrogen (N) to coastal marine ecosystems is strongly correlated with the “net anthropogenic nitrogen inputs” (NANI) to the landscape across 154 watersheds, ranging in size from 16 km2 to 279 000 km2, in the US and Europe. When NANI values are greater than 1070 kg N km−2 yr−1, an average of 25% of the NANI is exported from those watersheds in rivers. Our analysis suggests a possible threshold at lower NANI levels, with a smaller fraction exported when NANI values are below 1070 kg N km−2 yr−1. Synthetic fertilizer is the largest component of NANI in many watersheds, but other inputs also contribute substantially to the N fluxes; in some regions, atmospheric deposition of N is the major component. The flux of N to coastal areas is controlled in part by climate, and a higher percentage of NANI is exported in rivers, from watersheds that have higher freshwater discharge.

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Frontiers in Ecology and the Environment

Tập 10 Số 1

37-43

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