Not all tropical rainforests 'leak' large amounts of nitrogen

What is it about?

It is often thought that plant growth is limited by phosphorus in tropical rainforests, while these forests have plenty of nitrogen (partly because they sometimes have many legume trees than can add more nitrogen to the ecosystem). Because of its abundance, these forests are often observed to 'leak' excess nitrogen as gases or in streamwater. However, rainforests are extremely diverse in their soil types, topography, species composition, temperature and rainfall. Here, we demonstrate that steep, high rainfall rainforests in Costa Rica actually leak very little usable nitrogen- most is lost in the form of larger particles that organisms can't access directly.

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Why is it important?

Treating all rainforests as one system that behaves similarly (for example, in global climate models) might lead to errors, for example in estimating plant growth responses to climate change, or in modeling production of greenhouses by forest soils. This work is important because it demonstrates that not all rainforests behave the way that we would expect. Thus, we need to design more experiments that compare forests, and figure out why some seem to be nitrogen-leaky, while others aren't.