Differences in maximum resistive bending moments of Pinus radiata trees grown on a range of soil types

The maximum resistive bending moments (M-b) were measured for 164 Radiata p ine (Pinus radiata D. Don) trees spanning a range of sizes and growing on s ix different New Zealand soil types. M-b was significantly and positively c orrelated with tree height, diameter at 1.4 m (DBH) and stem volume with th e latter explaining the greatest proportion of the Variation in M-b (R-2=0. 854). Trees with higher taper (lower ratio of tree height to DBH) had highe r maximum resistive bending moments than trees with low taper. Both root pl ate diameter and root plate depth were significantly and positively associa ted with M-b For trees which failed by uprooting, stem volume, height:DBH r atio and root plate width explain over 91% of the variation in M-b Differen ces in M-b were also found between soil types. Trees growing on northern ye llow-brown earths and southern yellow-grey earths had significantly greater values of M-b than those growing on yellow-brown pumice soils. A higher in cidence of stem failure was also recorded on yellow-grey and yellow-brown e arths. This type of failure could not be successfully modelled using elemen tary beam theory because of the breakdown of the uniform stress assumption and the presence of stem defects. (C) 2000 Elsevier Science B.V. All rights reserved.