Geocheminar spring-2012

Atmospheric nitrogen deposition is increasing in tropical regions, with potential to alter carbon storage and loss in these ecosystems. The driving question of this study was: 1) Does increased nitrogen have the potential to alter carbon storage and loss in tropical forests, despite high background nitrogen availability to plants? This study utilized a long-term nitrogen fertilization experiment in a lower elevation rainforest and an upper elevation cloud forest in Puerto Rico. Nitrogen fertilization increased bulk soil carbon storage for both of these tropical forests, with decreased losses of carbon via respiration from soils. A laboratory soil incubation experiment showed that soil respiration had higher temperature sensitivity in nitrogen fertilized soils. This study clearly indicates that carbon biogeochemical cycles can be highly sensitive to increased nitrogen availability in nitrogen-rich tropical forests. Atmospheric nitrogen deposition in tropical forests has the potential to increase soil carbon cycling, with implications for global carbon cycling and climate change.