Table 1 Summary of repeated-measures analysis of variance of year, CO2, N, species richness (SR), and C3 versus C4 functional group (FuncGroup) effects on total biomass and soil net N mineralization.

Three-way or higher interactions involving treatments and two-way interactions or higher involving covariates shown only if significant. Five-way interactions were not tested. N mineralization data were missing for 2008 and 2017. Biomass was log-transformed prior to analysis. Year was a continuous term; Year and Year × Year terms were included in the model to assess linear and nonlinear changes over time involving CO2 and functional groups. Significant terms (P < 0.05) in bold font.

EffectTotal biomass
(g m−2)
Net N mineralization
(mg kg−1 day−1)
Whole modelR2 = 0.609, P < 0.0001,
n = 1760
R2 = 0.086, P < 0.0001,
n = 1582
FP > FFP > F
Year158.95<0.00010.310.5787
CO22.920.15210.750.4020
N13.140.000512.190.0008
SR10.110.00220.010.9187
FuncGroup42.32<0.00015.520.0195
Year × CO21.960.16140.390.5327
Year × N2.260.13262.080.1493
Year × SR23.64<0.00010.000.96865
Year × FuncGroup296.56<0.00011.460.2269
CO2 × N0.010.93420.670.4170
CO2 × SR0.010.92650.360.5505
CO2 × FuncGroup0.020.89650.490.4853
N × SR1.420.23790.730.3953
N × FuncGroup0.480.48855.480.0221
SR × FuncGroup0.400.53140.560.4574
Year × CO2 × FuncGroup7.240.00723.990.0461
Year × CO2 × FuncGroup × SR3.890.04861.160.2827
Year × Year104.34<0.000120.87<0.0001
Year × Year × CO20.230.63250.420.5189
Year × Year × CO2 × FuncGroup0.080.77090.270.6034