HEARTWOOD AND SAPWOOD DEVELOPMENT AND ITS RELATIONSHIP TO GROWTH AND ENVIRONMENT IN PINUS-CANARIENSIS CHR SM EX DC

Pinus canariensis yields a coloured resinous heartwood which has been widely used for centuries in the Canary Islands. Nowadays, although it reaches a high commercial value, very little is known about the influ ence of environmental, silvicultural and genetic factors on heartwood development in this species. Thus, the influence of environment and st em growth factors on heartwood and sapwood development was investigate d in Pinus canariensis 20-200 years old. Samples were taken in natural stands from La Palma and Tenerife islands. The number of growth rings , diameter under bark and radius to the 25th ring were the growth fact ors most strongly related to heartwood radius. Best prediction (r2=0.9 1) for average heartwood radius was obtained with a function of number of growth rings and radius to the 25th ring. Environmental parameters (annual water surplus and influence of Trade Winds) were found to be related more to sapwood width and diameter growth rates than to heartw ood width. Stand density, estimated as the number of trees per hectare , was negatively correlated with heartwood and sapwood width, radius t o the 25th ring, and average diameter growth rate. It is concluded tha t good site conditions improve both heartwood and sapwood development in Pinus canariensis.