STABLEC - Stable C fraction distribution in soil layers

Inputs:

• SOM3_0 = fraction of total soil organic C which is stable, at surface (fraction)
• PP = depth of topsoil where maximum SOM3 fraction is relatively constant (cm)
• RD = depth at which soil C is relatively stable (~98% stable C) (cm)

Implicit Inputs (i.e., available in the data):

• SLLB = array of depths to bottom of soil layer (cm)
• SLOC = array of total organic C (g[C]/100 g[soil])

Outputs:

• SLSC = array of Stable C (g[C]/100g[soil])

Procedure:

1. Calculate SOM2 fraction at surface

   SOM2_0 = 0.95 * (1 - SOM3_0)
   

2. Call Root_dist function with PP, M=SOM2_0, RD, returns F
3. Calculate array SOM2_frac(j) = MAX (0.02, F(j))
4. Calculate array SOM3_frac(j) = 1 - SOM2_frac(j) / 0.95
5. Calculate array StableC(j) = TOC(j) * SOM3_frac(j)

Example:

FILL, SLSC, STABLEC(), 0.55, 20, 60

Input:

TOC_0 = 5 (g[C]/100 g[soil])
SOM3_0 = 0.55 (fraction of TOC)
PP = 20 (cm)
RD = 60 (cm)

Root distribution function parameters:

M = 0.4275
PP = 20
RD = 60
k = -0.0978

Calculation of stable C:

sllb	TOC	mid	F	SOM2_frac	SOM3_frac	StableC
5	5.00	2.5	0.428	0.428	0.550	2.75
15	5.00	10	0.428	0.428	0.550	2.75
30	4.70	22.5	0.335	0.335	0.648	3.05
60	2.71	45	0.037	0.037	0.961	2.61
90	1.30	75	0.002	0.020	0.979	1.28
110	0.63	100	0.000	0.020	0.979	0.61
150	0.30	130	0.000	0.020	0.979	0.29
180	0.14	165	0.000	0.020	0.979	0.14

More Samples:

The following DOME spreadsheet is using this function. Machakos Overlay DOME

Dome functions page

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