Methodology & verification
This database exists to be trusted and cited. Here is exactly how a record is built, what its verification level means, and what we will and will not claim.
Thresholds
A plant is classed as a hyperaccumulator of an element when its living above-ground tissue exceeds a defined, element-specific dry-weight threshold, following van der Ent et al. (2013):
| Element | Threshold (µg g⁻¹) | Tier |
|---|---|---|
| Nickel (Ni) | 1,000 | Primary |
| Zinc (Zn) | 3,000 | Primary |
| Cadmium (Cd) | 100 | Primary |
| Cobalt (Co) | 300 | Primary |
| Manganese (Mn) | 10,000 | Primary |
| Rare Earth Elements (REE) | 1,000 | Primary |
| Copper (Cu) | 300 | Tracked |
| Arsenic (As) | 1,000 | Tracked |
| Selenium (Se) | 100 | Tracked |
| Thallium (Tl) | 100 | Tracked |
| Lead (Pb) | 1,000 | Tracked |
Verification levels
Every concentration in the database carries one of three provenance flags, shown on each species and in the exported data:
- primary-measured — the value is cited from the primary study that measured it.
- review-cited — the value is compiled from an authoritative review (e.g. the global hyperaccumulator database or a peer-reviewed synthesis). This is the honest default for well-established figures we have not yet re-read at source.
- hypothesized — reported in the literature but not yet independently confirmed; treated with explicit caution.
The daily research pipeline promotes review-cited records to primary-measured as the primary sources are re-read, and adds new species with citations. Coverage grows continuously; the launch dataset is the verified core, nickel-weighted because nickel is the largest and best-documented group.
Sourcing rules
- Every
maxconcentration references at least one entry in our bibliography. Records without a citation are not published — the build fails. - Concentrations are foliar or shoot dry-weight maxima in µg g⁻¹ unless a note says otherwise. Exceptional specialised-tissue values (latex, phloem sap) are described in the notes, never substituted for the comparable shoot value.
- Accepted names follow current taxonomy; widely used older names are recorded as synonyms so searches still resolve.
- No number, citation, or finding is invented. Where a value cannot be established, it is marked hypothesized and bounded, or omitted.
- Some historical records — especially for copper, cobalt, and lead — are known to be inflated by soil-dust contamination of samples. These groups are tracked with deliberate caution and flagged where relevant.
Vendor neutrality
Hyperaccumulate promotes no product, company, or service. It links to primary literature and public taxonomic resources only. The dataset is released under CC BY 4.0 with attribution to the cited primary sources, so anyone can reuse and cite it.