Description
Compare one species’ abundance shares and return its raw Bray-Curtis numerator contribution.
Ecological sampling summaries distinguish effort, weighted support, taxon counts and relative composition. A denominator-specific fraction or single-species contribution need not describe abundance, completeness or a whole-community index.
Compare one species’ abundance shares and return its raw Bray-Curtis numerator contribution.
When to use this tool
Use Community Composition One Species Turnover when checking a supplied ecological effort, support or count convention.
How to use the tool and how it works
- Enter firstAbundance, secondAbundance, firstTotal, secondTotal. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read firstShare, secondShare, brayCurtisNumeratorTerm, relativeChange. Use the output convention below.
Require positive firstTotal and secondTotal and each abundance between zero and its corresponding total. Return both species shares, brayCurtisNumeratorTerm = abs(firstAbundance-secondAbundance), and relativeChange = secondShare-firstShare.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| firstAbundance | First Abundance | Required. Finite number; minimum 0. |
| secondAbundance | Second Abundance | Required. Finite number; minimum 0. |
| firstTotal | First Total | Required. Finite number; strictly above 0. |
| secondTotal | Second Total | Required. Finite number; strictly above 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| firstShare | First Share | Required. Finite number. |
| secondShare | Second Share | Required. Finite number. |
| brayCurtisNumeratorTerm | One raw-abundance absolute-difference contribution, not a complete index. | Required. Finite number. |
| relativeChange | Second abundance share minus first share, not proportional change. | Required. Finite number. |
{
"input": {
"firstAbundance": 20,
"secondAbundance": 30,
"firstTotal": 100,
"secondTotal": 150
},
"output": {
"firstShare": 0.2,
"secondShare": 0.2,
"brayCurtisNumeratorTerm": 10,
"relativeChange": 0
}
}Limitations and assumptions
- The numerator term uses raw abundances, not relative shares, and is only one species' contribution. relativeChange is a share difference rather than proportional growth; no complete Bray-Curtis index is returned.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use an appropriate sampling, detection and community-analysis method for inference beyond these local summaries.
References
Similar or alternative tools
- Community Rare Count Share
Summarize counts below a supplied rarity cutoff, with exact decimal totals and an approximate numeric share.
- Trait Weight Missing Share
missingWeight sums unobserved weights; share divides it by total weight when positive, otherwise returns zero with defined = false.