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Table 2 Characteristics and model statistics of four Sitka spruce ( Picea sitchensis (Bong.) Carr.) trees at Cefn Du (plot 1), Clocaenog Forest (North Wales, UK)

From: Methods of modelling relative growth rate

Tree # dbh (cm) b c Volume (m 3 ) Total height (m) Stem diameter ( dbh )
Min. Max. Bias RMSE m 1 RMSE m 2 RMSE
2000 6.4 32.2 −0.05251 6.12877 0.00303 0.02478 2.82205 0.01309 1.07431 0.02211
3000 4.2 28.3 −0.05057 6.44977 0.00307 0.01646 2.63452 0.00633 1.04791 0.01835
4000 4.9 32.6 −0.04667 6.40575 0.00249 0.02401 2.78971 0.01296 1.13672 0.01294
5000 6.6 38.7 −0.00822 3.68512 0.00024 0.01248 2.66006 0.01105 1.17268 0.01218
  1. dbh – stem diameter at breast height at 1.3 m above ground level; b, c – model parameter of the Chapman-Richards model of relative growth rate; m 1, m 2 – allometric coefficients for estimating the relative growth rates of total height and stem diameter, respectively. Bias and RMSE relate to estimates of relative growth rates.