MORPHOLOGY AND ECOLOGICAL SIGNIFICANCE OF INTRAANNUAL RADIAL CRACKS IN LIVING CONIFERS

Intra-annual radial cracks were studied on 294 cross-sections of Norwa y spruce sampled at two forest sites in the eastern Alps (Italy) and f rom seven isolated trees in the Jura region (Switzerland). Cracks were occasionally accompanied by traumatic resin canals in the wood that w as formed after the cracking. Most of the cracks, however, were withou t such canals. Traumatic resin canals are not significantly more abund ant in tree rings formed after cracking, and their occurrence is not r elated to the cracking. Cracks developed when the cambium was inactive . Water imbalances during the early spring, due to transpiration losse s and inadequate moisture supply from very cold roots, are the likely cause of these cracks.