Long-Term Change in the Nitrogen Cycle of Tropical Forests

• Published in: Science (American Association for the Advancement of Science) 2011-11, Vol.334 (6056), p.664-666
• Main Authors: Hietz, Peter, Turner, Benjamin L., Wanek, Wolfgang, Richter, Andreas, Nock, Charles A., Wright, S. Joseph
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Atmospherics; Availability; Biological and medical sciences; Deposition; Drying; Ecosystem studies; Fertilization; Forest ecosystems; Forestry; Forests; Fundamental and applied biological sciences. Psychology; General forest ecology; Generalities. Production, biomass. Quality of wood and forest products. General forest ecology; Growth rings; Human; Leaves; Legumes; Nitrogen; Nitrogen Cycle; Panama; Plant Leaves; Pollutant emissions; Productivity; Rainforests; Synecology; Terrestrial ecosystems; Thailand; Trees; Tropical Climate; Tropical forests
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1211979

Deposition of reactive nitrogen (N) from human activities has large effects on temperate forests where low natural N availability limits productivity but is not known to affect tropical forests where natural N availability is often much greater. Leaf N and the ratio of N isotopes (δ¹⁵N) increased substantially in a moist forest in Panama between ~1968 and 2007, as did tree-ring δ¹⁵N in a dry forest in Thailand over the past century. A decade of fertilization of a nearby Panamanian forest with N caused similar increases in leaf N and δ¹⁵N. Therefore, our results indicate regional increases in N availability due to anthropogenic N deposition. Atmospheric nitrogen dioxide measurements and increased emissions of anthropogenic reactive N over tropical land areas suggest that these changes are widespread in tropical forests.