Hi Amor,
Every day it is first calculated how much carbon potentially could flow out of each pool (SOM1 / SOM2 / SOM3 and the litter pools). This depends on the available water and the temperature. Combining the water factor (WFSOM) and the temperature factor (TFSOM), a decomposition factor (DEFAC) is calculated: DEFAC = TFSOM * WFSOM. This DEFAC is one of the defining factors for the decomposition, the others being whether the decomposition is stimulated by a cultivation event and ?for SOM1? a texture factor (high for sandy soils and low for clayey soils).
For the soil, the volumetric water content is converted to water-filled pore fraction and, depending in the texture, the soil type is classified as coarse / medium / fine. With this the water factor is calculated. For the surface layer, which has no texture, common relationships of LL, DUL and SAT don't work, so the water factor is made dependent on the ratio of rain+irrigation (corrected for runoff) and the potential evapotranspiration (PET).
Then it is calculated how much CO2 would be lost in the daily decomposition fraction of each pool and this is deducted from the carbon flow out of the pool. The remaining is what goes to another pool. For instance, it can go from SOM1 to SOM2 or SOM3 and which of these two flows gets more depends on the texture: for a clayey soil more goes to SOM3 than for a sandy soil.
Arjan Gijsman
Univ. Florida / Centro Internacional de Agricultura Tropical (CIAT)
-----Original Message-----
From: DSSAT - Crop Models and Applications [mailto:[log in to unmask]]On Behalf Of Ines, Amor
Sent: Friday, November 10, 2006 1:53 AM
To: [log in to unmask]
Subject: role of soil moisture and soil temp in C cycling in CENTURY
Dear list,
Could somebody who worked with/developed DSSAT-CENTURY share me a litte about the role of soil mositure and soil temp in OM decomposition (C-cycling in general), what are the flow of processes between C-pools (i.e., non-labile - "intermediate" - labile pools???). I am interested particularly on the mechanics involved.
Thanks in advance for your kind help.
Regards,
Amor
-----
Dr. Amor VM Ines
Dept. of Biological and Agricultural Engineering
Texas A&M University
2117 TAMU 301B Scoates Hall
College Station, TX 77843
Tel: 979-458-4651
Fax: 979-862-3442
Email: [log in to unmask]
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