Fig 1. Substrate-derived CO₂ (μg C-CO₂ g dw soil^-1) in soils from three ecosystems as induced by three different amounts of ¹³C-glucose (15%, 50%, and 200% of the microbial biomass carbon).

A-F: Cumulative accumulation of substrate-derived CO₂ over 30 days of incubation. G-H: Total substrate-derived CO₂ after 30 days of incubation. N: NH₄NO₃. Statistically significant differences (P < 0.05) are marked with different letters. NS: no significant differences. Error bars represent standard errors (n = 4). Two-way ANOVA results are reported in S1 Table.