Table 1.

Compilation N outputs estimates from biocrusts to subsurface soil from various location worldwide and the respective percentage of Archean land crust cover needed to reach the modern N land-to-ocean export flux

	Location	Net N outputs from crusts to subsurface soil (m−2 yr−1)	Percentage of Archean land coverage needed to reach the modern N export flux
Johnson et al.43	Colorado Plateau	2.080–8.820a	1.13–0.27%
Thiet et al.46	Lake Michigan	0.020–0.800a	117.8–2.94%
Rychert & Skujins49; West & Skujins50	Cold desert	0.19–1.9	12.4–1.24%
Rychert et al.51	Australia	0.025	94.2%
Evans & Johansen52	Sonoran Desert	0.133–0.342	17.71–6.88%
Evans & Lange53; Belnap54, 55; Russow et al.56; Stewart et al.57–59; Caputa et al.60	Global	0.0133–1.9	177–1.24%
Elbert et al.42	Global	0.144b	16.35%

The modern export flux is set to 0.15 Tmol yr⁻¹ based on N/C data from shales and continental organics¹⁵. Detailed calculations are described in the methods section and available in Supplementary Table 1

^aDirect estimate of N export fluxes from modern biocrusts, all other values of N outputs from crusts to subsurface soil are extrapolated from the nitrogen import fluxes

^bGeometric mean value given by Elbert et al.⁴²