The supplementary information provides details on the methods used to find the basal area-BNF rate regression, the specific literature that was used to derive both these regressions and the %Ndfa for different genera. The text describes further methods used to compare previous global estimates of BNF to the conterminous US scale and to examine the relevance of P. contorta as an additional source of N.

This dataset is associated with the following publication: Staccone, A., W. Liao, S. Perakis, J. Compton, C. Clark, and D. Menge. A spatially explicit, empirical estimate of tree-based biological nitrogen fixation in forests of the United States. Global Biogeochemical Cycles. American Geophysical Union, Washington, DC, USA, 42(2): e2019GB006241, (2020).