- Hyperaccumulator
- A plant that concentrates a trace element in its living above-ground tissue to a level orders of magnitude above what most species tolerate — above a defined element-specific threshold — while growing in its natural habitat.
- Hyperaccumulation threshold
- The foliar dry-weight concentration above which a plant is classed as a hyperaccumulator of a given element. Thresholds are element-specific (e.g. 1,000 µg g⁻¹ for Ni, 100 µg g⁻¹ for Cd) and follow van der Ent et al. (2013).
- Obligate hyperaccumulator
- A species (or population) in which essentially all individuals hyperaccumulate the element wherever they occur, independent of soil concentration.
- Facultative hyperaccumulator
- A species that hyperaccumulates only in part of its range — typically on metalliferous soil — while non-accumulating populations exist on normal soil.
- Ultramafic (serpentine) soil
- Soil derived from ultramafic rock such as serpentinite; naturally rich in Mg, Fe, Ni, Co and Cr and poor in Ca, K and P. The main natural habitat of nickel hyperaccumulators.
- Calamine soil
- Soil naturally or anthropogenically enriched in zinc, lead and cadmium, typically over ore bodies or around historical mining and smelting — the classic habitat of Zn/Cd hyperaccumulators.
- Agromining (phytomining)
- Cultivating hyperaccumulator crops on metal-rich or mineralised soil and harvesting the biomass to recover the metal — for example farming Odontarrhena or Phyllanthus for nickel.
- Phytoextraction
- Using living plants to remove contaminants from soil or water and concentrate them in harvestable tissue, a remediation strategy for metal-polluted land.
- Dry-weight concentration (µg g⁻¹)
- Mass of element per mass of oven-dried tissue, in micrograms per gram, equivalent to parts per million (ppm). The standard unit for reporting hyperaccumulation.
- Rare earth elements (REE)
- The fifteen lanthanides plus yttrium and scandium, often split into light (LREE) and heavy (HREE) fractions. Reported here as total REE (ΣREE).
- Verification level
- This database's provenance flag for each concentration: primary-measured (cited from the primary study that measured it), review-cited (compiled from an authoritative review), or hypothesized (reported but not yet independently confirmed).