Collaborative Research: Controls Over Nitrogen Loss from Very Wet Tropical Forests

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Humans have changed the global nitrogen cycle to an extraordinary degree. Such changes have brought clear benefits to society, but increasingly, the excess of nitrogen now present in many ecosystems is causing a litany of environmental and public health concerns. Thus, it has become critical to understand how ecosystems gain, store and lose nitrogen, and to do so in an increasingly varied range of ecosystems as changes in the nitrogen cycle become truly global in scope. This project seeks to understand the nitrogen balance of a tropical rainforest, in part because current and predicted future changes to the nitrogen cycle are most pronounced in the tropical portions of the world. The project explores why the wettest of tropical forests, as typified by a field site in southern Costa Rica, seem to exhibit a much different nitrogen cycle than do the drier portions of the tropical biome. A variety of techniques will be used ? ranging from watershed nitrogen balance, to isotopic measurements, to experimental fertilizer plots to explore how nitrogen is cycled within this ecosystem, and what forms of nitrogen dominate losses to the surrounding environment. Key aspects of the carbon and phosphorus cycles will be measured in tandem with a focus on nitrogen, because prior work in this site suggests that both elements may play important roles in determining the size and forms of nitrogen loss.The wettest of tropical forests remain one of the more poorly studied ecosystems of the world, and yet they appear to be hotspots for carbon storage and for nutrient export to coastal oceans, as well as key regions for tropical forest conservation. This project will shed light on how such forests work on an ecosystem scale, thereby aiding the ability to predict how they may respond not only to a changing nitrogen cycle, but also to changes in climate and land use. The project will also provide support for numerous junior scientists, including an early stage assistant professor and several undergraduate and graduate students. Finally, the project will support a new collaboration between the P.I. and a professional journalist that is aimed at communicating the importance of tropical forests to a broader audience.