DECAY RATE OF PICEA ABIES LOGS AND THE STORM GAP THEORY: A RE-EXAMINATION OF SERNANDER PLOT III, FIBY URSKOG, CENTRAL SWEDEN

Abstract
One of the sites (Plot III) used by Sernander (1936) in developing the ‘storm-gap theory’ of cyclic change in Picea ablest forests on unstable soils has been located in Fiby urskog, near Uppsala. Re-mapping has facilitated calculation of the time elapsing between the fall of the trunk and its complete disintegration, which varies according to individual circumstances: the original estimate of 90 years proves something of an over-estimate. The results confirm the validity of the storm-gap theory; indicating that the size of gaps is often increased by further falls in subsequent years and that dwarf trees play an important role in regrowth. Small spruce saplings are concentrated on boulders and logs, where they are less vulnerable to competition from the field layer. Few occur where the shade is deep.