Biofuels, cropland expansion, and the extensive margin

Table 1 Carbon and nitrogen pools and fluxes used for a C4 crop parameterization

Variable	Values^a for C4	Source and comments
C_v	649	Evrendilek [28]
N_v	9.9	Evrendilek [28]
C_s	3071.5	Evrendilek [28]
N_s	307.1	Evrendilek [28]
N_av	2.64	Based on 0.86%, the mean N_av/N_s ratio
GPP	649	Evrendilek [28]
NPP	296.6	Evrendilek [28]
NPPSAT	296.6	Evrendilek [28]
NUPTAKE	3.98	Calculated from NPP_n, 75% NPP_n = NUPTAKE

^aUnits for annual gross primary production (GPP), net primary production (NPP), and NPPSAT are in grams of carbon per square meter per year (g C m⁻² year⁻¹). Units for vegetation C (C_v) and soil C (C_s) are in grams of carbon per square meter (g C m⁻²). Units for vegetation N (N_v), soil N (N_s), and inorganic N (N_av) are grams of nitrogen per square meter (g N m⁻²) Units for annual N uptake by vegetation (NUPTAKE) are in grams of nitrogen per square meter per year (g N m⁻² year⁻¹).

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