Comparison of Century4 and Century 5.4

Comparison of Century4 and Century 5.4 - C3 Grass

Thomas E. Hilinski, Natural Resource Ecology Laboratory, Colorado State University. November 2004.

Summary

A comparison between Century4 and Century 5.4.5 for a C3 grassland simulation shows very close agreement in soil water, NPP, respiration, N fixation, and N uptake. Century4 has higher amounts of soil C and soil N, which can be accounted for by the higher decomposition rate in Century5. The DEFAC for Century5 is approximately 27% higher, while litter and surface soil C and N pools are approximately 30% and 20% lower, respectively, than Century4.

The surface mineralized N pools are similar in average magnitude, though the annual oscillation in pool size is much greater in Century4. This is due to the difference in algorithms managing the mineralized pools. The annual maximum monthly gross mineralization is approximately 26% lower in Century5, while the annual minimum values are nearly identical.

Simulation Configuration

The simulations used a version of Century4 with fixes for the output timing (dated April 2000). The version of Century5 used is 5.4.5.4.

Site and management files used are c3grs.100 and c3grs.sch. The schedule for output was modified so the simulation wrote output each month for the last 12 years. The statistics herein are taken from that output.

Statistics

Mean values are the mean monthly value for the output time. Totals are the sum of the monthly values over the output time. Minimum and maximum values are monthly minimum and maximum values.

Water Output Variables

The water driving variable, RAIN, is identical between versions. Post-2001 offset of Century4 is due to the time bookkeeping issues in Century4.

	Change from Century4 to Century5 (%)
AVH2O(1) mean	-18.9
EVAP total	10.2
TRAN total	-3.6
DEFAC maximum	26.6

View the graphs (PDF file).

N Output Variables

	Change from Century4 to Century5 (%)
EUPACC(1)	-5.2
GROMIN(1) total	-26.5
VOLGMA total	80.8
SOM1E(1,1) mean	-32.6
SOM1E(2,1) mean	-30.0
SOM2E(1) mean	-24.9
SOM3E(1) mean	-4.5

View the graphs (PDF file).

C Output Variables

	Change from Century4 to Century5 (%)
SOM1C(1) mean	-16.2
SOM1C(2) mean	-20.4
SOM2C mean	-20.7
SOM3C mean	-6.1
CPRODA total	-0.25
RESP(1) total	0.9

View the graphs (PDF file).