{"id":"chojnacky-2014-picea-spg-lt-035","source":{"id":"chojnacky-2014","citation":"Chojnacky, D.C., Heath, L.S., Jenkins, J.C. (2014). Updated generalized biomass equations for North American tree species. Forestry, 87(1), 129–151.","title":"Updated generalized biomass equations for North American tree species","authors":["Chojnacky, D.C.","Heath, L.S.","Jenkins, J.C."],"year":2014,"venue":"Forestry: An International Journal of Forest Research","doi":"10.1093/forestry/cpt053","url":"https://doi.org/10.1093/forestry/cpt053","read_url":"https://research.fs.usda.gov/download/treesearch/45402.pdf","access":"open","checked_at":"2026-11-01","status":"current"},"name":"North American taxa group: Picea < 0.35 spg (Table 5)","output":{"quantity":"agb"},"expression":"exp(-3.03 + 2.5567 * ln(D))","published":{"expression":"exp(-3.03 + 2.5567 * ln(dbh))","units":{"dbh":"cm"},"variables":{"dbh":"D"},"output_unit":"kg"},"taxon":{"level":"mixed","name":"Picea < 0.35 spg (Picea engelmannii, P. sitchensis)","family":"Pinaceae","group":"conifer","members":["Picea engelmannii","Picea sitchensis"],"members_complete":true},"region":{"scope":"national","countries":["US"],"place":"United States (equations compiled from US and Canadian studies)","biomes":["temperate"]},"stand":"mixed","fit":{"dbh_min_cm":3,"dbh_max_cm":283,"r2":0.81,"method":"Weighted regression of ln(biomass) on ln(dbh) fitted to 128 pseudodata points generated from 8 published equations; no back-transform correction"},"evidence":[{"field":"expression","quote":"ln(biomass) = β0 + β1 ln(diameter)","locator":"Table 5 caption, p. 140"},{"field":"expression","quote":"Picea < 0.35 spg 0.33 −3.0300 2.5567 128 8 dbh 3–283 0.81","locator":"Table 5 row, p. 140"},{"field":"taxon","quote":"Picea engelmannii Spruce, Engelmann 93 0.33 5","locator":"Table 2, p. 135"},{"field":"fit.cf","quote":"we did not include a correction (Baskerville, 1972) for underestimation","locator":"Methods, p. 139"}],"check":[{"inputs":{"D":30},"expected":288.8309,"origin":"computed","note":"computed from the published form at dbh = 30 cm"}],"verification":"original_read","checked_at":"2026-11-03","notes":"Western low-specific-gravity spruces: Engelmann and Sitka. Median specific gravity of the group: 0.33. Diameter range is that of the pseudodata. R² is the published 'R²-statistic'."}