||Galloway et al., Nitrogen Cycles: Past, Present, and Future,
September 2004, Volume 70, Issue 2, pp 153-226 p.160 top paragraph
||Cleveland C.C., Townsend A.R., Schimel D.S., Fisher H., Howarth R.W., Hedin L.O., Perakis S.S., Latty E.F., Von Fischer J.C., Elseroad A. and Wasson M.F. 1999. Global patterns of terrestrial biological nitrogen (N2) fixation in natural ecosystems. Global Biogeochem. Cycles 13: 623–645.
||"In a recent compilation of rates of natural
BNF by Cleveland et al. (primary source), symbiotic BNF rates for several biome types are
based on one-to-few published rates of symbiotic BNF at the plot scale within
each particular biome. For example, based on the few estimates of symbiotic BNF available for tropical rain forests, estimated BNF in these systems represents
24% of total natural terrestrial BNF globally on an annual basis