Dear CENTURY user,
Thank you for your interest in the CENTURY model. Since the publication the Century manual, there have been some substantial changes to the version 4.0 model, and a research version is available (click to access CENTURY 5). This document describes the changes to the version 4 model, and corrects some errors in the manual. The version of the model available to you is not linked to the Time--Zero output module described in the manual. This is known as the stand-alone version of the model. Now, the PC and UNIX stand-alone versions of the model are identical in function, so the directions for "Executing the UNIX Stand-Alone Version" (section 6.3, page 6-2) should be followed for the version you have. Because this is the stand-alone version of the model, you will need List100 (our binary-to-ASCII translation utility) in addition to the CENTURY, File100, and Event100 executables. It will be necessary to use the model in combination with a spreadsheet, graphics, or statistical package because this version does not include the output module.
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CENTURY and its component programs:
Multiple fix.100 files: The model now uses biome-specific fix.100 files. These files differ primarily in the FWLOSS(x) parameters that adjust the relative impact of a PET equation originally developed for the Tropics (further described on page 3-4, 2nd paragraph under heading 3.3). Select the appropriate fix file for your site from the list below, and copy it to "fix.100" before running your simulation. (When simulating a savanna, use the fix file that corresponds to the grass component of your system).
arcfix.100: arctic tundra
dryffix.100:dr
ffix.100: forest
trpfix.100: tropical
borfix.100: boreal forest
drygfix.100: dry grassland
gfix.100: mesic/subhumid grassland
Page 3-4, 1st paragraph under heading 3.3: The final sentence should read "Snow melt occurs if the average air temperature is greater than TMELT(1) and is a linear function of the average air temperature.
Section 3.7.3, page 3-32: Savanna submodel - many CENTURY users have asked for clarification of the variable SITPOT. It was originally conceived as a measure of the aboveground herbaceous layer production in kg ha-1 yr-1 in the absence of trees (SITPOT = 2400 * monthly N availability [in gN m-2 yr-1]).
Page 3-43, 2nd paragraph, 3rd line from the bottom: "POM (partial organic matter)" should read "POM (particulate organic matter)".
Page 8-1: In the Burke et al. reference, "context" should be "content".
Appendix 2.1:
prdx(1):g biomass/mē/month
bioflg is a continuous measure ranging from 0 to 1
crprtf(x): this nutrient is transferred to a "vegetation
storage pool".
Appendix 2.3:
feramt(x): amount of E to be added (g E / mē) in scheduled
month.
Appendix 2.4:
ffcret is no longer included in the file, so this
parameter will need to be removed from your existing fire.100 files
fret(x) should say: fraction of E in the burned aboveground
material returned to the soil following a fire event.
Appendix 2.5
tmax through tshr
have been changed. The new list is: teff(1), teff(2), teff(3),
tmelt(1), tmelt(2). The tmelt(x) parameters
retain their previous definitions, while the teff(x)
parameters are defined by:
tcalc = teff(1) + teff(2) * exp (teff(3) * stemp)
teff(1) = intercept
teff(2) = slope
teff(3) = exponent (Q10)
tcalc is the temperature component of defac
tmax, topt, tshr are no longer used.
So, be sure to download the new biome-specific fix.100 files from ftp site.
dec1(1) through dec5 = decomposition rate. The fraction of the pool that turns over each year.
Appendix 2.10
decid:
0 = evergreen
1 = temperature-deciduous
2 = drought-deciduous
btolai is a biome-specific parameter. Values we use locally are:
arctic tundra 0.008
boreal forest 0.004
maritime coniferous forest 0.004
temperate coniferous forest 0.004
coniferous/deciduous mix forest 0.007
warm temperate deciduous forest 0.01
tropical evergreen forest 0.01
arid savanna/shrubland 0.007
temperate coniferous savanna 0.004
tropical savanna 0.006
temperate deciduous savanna 0.01
temperate mixed savanna 0.007
grassland 0.008
wooddr(1) controls the proportion of leaves that drop when decid = 1 or 2.
This is especially useful for drought-deciduous systems where only a portion of the leaves drop. Also useful when you are attempting to simulate a deciduous/coniferous mixed system.
Appendix 2.11
remf(x): dead fine branches should be remf(4)
Appendix 2.12
sitlat is used in the pet calculation, so it is not just for reference.
Appendix 2.13
relyld has been removed as an output option
rlvacc should say: "growing season accumulator for C production in forest
leaf compartment"
woodc: sum of C in dead components of forest system (g/mē).
If you are interested in previous applications of the model, check the list of abstracts and journal articles using CENTURY here on our web page. If you have any CENTURY-related questions email us . This is checked regularly, and answers are generally provided within a week. If you do not have access to email or are unable to use ftp, please feel free to contact C Keough by telephone (970.491.2195) or fax ([attn: C. Keough] 970.491.1965). Technical support for the CENTURY model is provided on a time-available basis, and this limited support is available only to users who have thoroughly read the CENTURY version 4.0 manual. (Or see Manual of the Version 5)
Because all CENTURY results (favorable or not) help us to improve the model, we would appreciate a copy of any reports, abstracts, or manuscripts resulting from the use of CENTURY. When possible, the inclusion of "CENTURY model" in the list of key words or phrases improves our ability to track the use of the model. CENTURY is protected by a United States copyright to Colorado State University (1993), all rights reserved. We ask that you do not provide copies of the model, source code, or manual to colleagues unless you contact us directly about doing so. Any such copies should be accompanied by this letter.
On behalf of the entire CENTURY group, thank you again for your interest in the model.
Bill Parton
Dennis Ojima
Dave Schimel
Becky McKeown
Melannie Hartman
Cindy Keough
Becky Techau
