Delta13C C3/C4 Diet Mix

Solve a caller two-endmember linear delta13C diet scenario with explicit tissue offset; assumes equal carbon routing and consistent isotope basis, not identified foods or an actual diet diagnosis.

Description

A two-endmember carbon-isotope model assigns a mixture between supplied C3 and C4 dietary endpoints.

A two-endmember carbon-isotope model assigns a mixture between supplied C3 and C4 dietary endpoints. A tissue-to-diet offset must be removed before comparing the measurement with those endpoints.^[1]

Solve a caller two-endmember linear delta13C diet scenario with explicit tissue offset; assumes equal carbon routing and consistent isotope basis, not identified foods or an actual diet diagnosis.

When to use Delta13C C3/C4 Diet Mix

Use this tool to solve a caller two-endmember linear delta13C diet scenario with explicit tissue offset; assumes equal carbon routing and consistent isotope basis, not identified foods or an actual diet diagnosis.

Prepare the artifact, site or survey measurements and any independently established calibration or model choices. Keep paired observations aligned and confirm units and coordinate conventions.

How to use Delta13C C3/C4 Diet Mix and understand its results

Prepare the artifact, site or survey measurements and any independently established calibration or model choices. Keep paired observations aligned and confirm units and coordinate conventions.
Enter measuredDelta13C, tissueDietOffsetPerMil, c3DietEndmemberPerMil, c4DietEndmemberPerMil using the field table and calculation rules, then run the tool.
Read offsetCorrectedDietDelta13C, modelC4Fraction, modelC3Fraction. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
measuredDelta13C	Measured delta13 c	number	Required
tissueDietOffsetPerMil	Tissue diet offset per mil	number	Required
c3DietEndmemberPerMil	C3 diet endmember per mil	number	Required
c4DietEndmemberPerMil	C4 diet endmember per mil	number	Required

Enter finite isotope values and offset in per mil with distinct endpoints. Calculate the corrected diet value and require the resulting C4 fraction to lie in [0,1], rejecting out-of-range mixtures rather than clamping. Return corrected value and complementary C3/C4 fractions.

corrected = measured−tissueOffset; C4 fraction = (corrected−C3 endpoint)/(C4 endpoint−C3 endpoint)

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
offsetCorrectedDietDelta13C	Offset corrected diet delta13 c	number
modelC4Fraction	Model c4 fraction	number
modelC3Fraction	Model c3 fraction	number

json

{
  "input": {
    "measuredDelta13C": -15,
    "tissueDietOffsetPerMil": 5,
    "c3DietEndmemberPerMil": -25,
    "c4DietEndmemberPerMil": -10
  },
  "output": {
    "offsetCorrectedDietDelta13C": -20,
    "modelC4Fraction": 0.3333333333333333,
    "modelC3Fraction": 0.6666666666666667
  }
}

Limitations and assumptions

Linear mixing and equal carbon routing are assumptions. Endpoint and tissue uncertainty are not propagated. Fractions do not uniquely identify foods or establish an actual diet.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Delta15N Trophic Level Scale: Evaluate caller nitrogen-enrichment trophic proxy with independent measurement/baseline uncertainty; signed relative positions remain and baseline/enrichment differences are not dietary diagnosis. For a complementary task, use C:N Ratio Diet Indicator: Convert measured C/N mass percentages to atomic ratio and caller collagen-preservation screen; this ratio is not a diet determination.

References

Delta13C C3/C4 Diet Mix — tool.io

Similar or alternative tools

Delta15N Trophic Level Scale
Evaluate caller nitrogen-enrichment trophic proxy with independent measurement/baseline uncertainty; signed relative positions remain and baseline/enrichment differences are not dietary diagnosis.
C:N Ratio Diet Indicator
Convert measured C/N mass percentages to atomic ratio and caller collagen-preservation screen; this ratio is not a diet determination.