Are the Tropical Forest Ecosystems Poor in Nitrogen? —Global and Regional Nitrogen Cycles as Revealed by δ¹⁵N—

Abstract

In addition to information and estimation of nitrogen input and release at global and regional levels, accumulated information of natural abundances of ¹⁵N(δ¹⁵N) over 40 years has revealed new findings of ecosystems' nitrogen metabolisms and dynamics. One of such new findings is that tropical rain forests are rich in nitrogen and that the big-size leguminous trees do not fix nitrogen. The further measurements of δ¹⁵N in the various ecosystems in Asia, Africa and South America may improve the knowledge on quantitative nitrogen dynamics.