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Table 3 Characteristics and model statistics of four British Douglas fir ( Pseudotsuga menziesii (Mirb.) Franco) yield tables (Edwards and Christie 1981 ) relating to initial spacing 1.7 m × 1.7 m and crown thinning

From: Methods of modelling relative growth rate

Yield class dg (cm) b c Volume (m 3 ∙ha −1 ) Top height (m) Mean diameter ( d g)
Min. Max. Bias RMSE m RMSE RMSE
24 12.8 76.7 −0.03240 5.68749 0.00011 0.00185 3.64234 0.00153 0.00658
18 12.2 60.9 −0.03147 5.65227 0.00014 0.00181 3.46283 0.00151 0.00560
12 12.4 43.5 −0.02988 5.43637 0.00004 0.00075 3.20122 0.00124 0.00793
8 11.7 32.5 −0.03095 6.16601 −0.00003 0.00072 3.06830 0.00092 0.00757
  1. dg – quadratic mean stem; b, c – model parameter of the Chapman-Richards model of relative growth rate; m – allometric coefficient for estimating the relative growth rate of top height. Bias and RMSE relate to relative growth rates.