ESTIMATING WHITE PINE SITE INDEX 



consequently a somewhat higher standard 

 deviation from regression than the prediction 

 equations for estimating tree height. They 

 are 3hown graphically in Appendix C. Vari- 

 ables other than tree height and age contri- 

 buted little increased accuracy to estimates; 

 so more complex equations are omitted. 



A second objective of this study was to pro- 

 vide a means for estimating white pine site 

 index when white pine is absent, but when 

 height and age of a common associate species 

 can be measured. The equations that follow 

 have a lower coefficient of determination and 



From Western Larch Height: 



WPSI = -7.3 + 0.3(WLht) + 1,300(1/A) - 600(l/WLht) - 0.003(WLhfA) 



R 2 = 0.37; Sy = ±11.0 feet. 



From Lodgepole Pine Height: 



WPSI = + 33.3 + l.l(LPht) - 1.2(A) + 600 (1/A) 



R- = 0.51; Sy = ±12.0 feet. 



From Douglas-Fir Height: 



WPSI = - 51.5 + 0.8(DFht) + 0.6(A) + 3,400 (1/A) - 1,100 (1/DFht) 

 - 0.005 (DFhf A) 



From Grand Fir Height: 



WPSI = - 28.8 + 0.28(A) + 1,200 (1/A) + 43(GFht/A) + HT value 



R 2 = 



0.50; Sy s ±9.7 feet. 



Abies /Pachistima +>3 

 Thuja/ Pachistima 

 Thuja-Tsuga/ Pachistima —3 



R 2 = 0.51; Sy = ±10.7 feet. 



From Western Hemlock Height: 



WPSI = + 37.9 + Ll(WHht) - 1.0(A) + 500 (1/A) 



R 2 = 0.50; Sy = ±11.3 feet. 



6 



