Reineke Stand Density Index
Stand density index and its percent of the species maximum: the thin-now metric.
Example
You enter
- Trees per acre (live stems) 300
- Quadratic mean diameter (in) 10
- Species maximum SDI (0 to skip) 400
You get
- Stand Density Index 300
- Percent max 75
Checked against published worked examples from: Reineke Stand Density Index (Reineke 1933, USDA FS RMRS).
Details, formula, and sources
ScopeThe thin-now metric: SDI = TPA x (QMD/10)^1.605 and its percent of the species maximum (under 35% below the onset of competition, 35-55% lower management zone, 55-100% upper management zone and a thinning candidate, 100% and over self-thinning). Uses the QUADRATIC mean diameter (the diameter of the tree of average basal area, always >= the arithmetic mean); a plain average understates density and thins too late.
Formula or tableSDI = TPA x (QMD / 10)^1.605; percent_max = SDI / SDI_max x 100.
Source and editionReineke Stand Density Index (Reineke 1933; USDA FS RMRS), by name.
Free accessThe Reineke SDI relation is a public forest-mensuration result; the maximum SDI is species-specific from published tables.
What governsEstimate. AHJ and licensed professional govern.
API field namestrees_per_acre, qmd_in, sdi_max, sdi, percent_max
- Quadratic mean diameter QMD = sqrt(sum(d^2)/n); always >= the arithmetic mean; the arithmetic mean understates SDIforest mensuration
- Self-thinning slope the 1.605 exponent is Reineke's empirical maximum-density slope; SDI_max is species-specificReineke 1933