Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States

Abstract

This report synthesizes current research relating atmospheric nitrogen (N) deposition to effects on terrestrial and aquatic ecosystems in the United States and to identify empirical critical loads for atmospheric N deposition. The report evaluates the following receptors: freshwater diatoms, mycorrhizal fungi and other soil microbes, lichens, herbaceous plants, shrubs, and trees. The main responses reported fell into two categories: (1) biogeochemical; and (2) individual species, population, and community responses. The range of critical loads for nutrient N reported for U.S. ecoregions, inland surface waters, and freshwater wetlands is 1 to 39 kg N ha^-1 y^-1. This range spans the range of N deposition observed over most of the country. The empirical critical loads for N tend to increase in the following sequence for different life forms: diatoms, lichens and bryophytes, mycorrhizal fungi, herbaceous plants and shrubs, trees.

Titles contained within Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States

• Introduction, Chapter 1
• Ecosystem classification, Chapter 2
• Deposition, Chapter 3
• Methods, Chapter 4
• Tundra, Chapter 5
• Taiga, Chapter 6
• Northern forests, Chapter 7
• Northwestern forested mountains, Chapter 8
• Marine west coast forests, Chapter 9
• Eastern temperate forests, Chapter 10
• Great plains, Chapter 11
• North American deserts, Chapter 12
• Mediterranean California, Chapter 13
• Southern semi-arid highlands, Chapter 14
• Temperate sierras, Chapter 15
• Tropical and subtropical humid forests
• Wetlands, Chapter 17
• Inland surface waters, Chapter 18
• Synthesis, Chapter 19
• Appendices

Citation

Pardo, L.H.; Robin-Abbott, M.J.; Driscoll, C.T., eds. 2011. Assessment of Nitrogen deposition effects and empirical critical loads of Nitrogen for ecoregions of the United States. Gen. Tech. Rep. NRS-80. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station. 291 p.