Ash and Sycamore Regeneration and the Phenomenon of their Alternation

A survey of ash and sycamore regeneration patterns was conducted in six woods in Oxfordshire and Gwent during the summer of 1990 in order to investigate suggestions that canopy tree replacement in stands of the two species tends to proceed in cyclic rather than serial fashion. It was shown that the regeneration under either canopy species is dominated, normally to the extent of well over 80 per cent, by individuals of the other species. The pattern was consistent across the size classes of regeneration, manifesting itself early in the life cycles of the two tree species. It is concluded that alternation of regeneration is a real phenomenon for these two species. The degree of threat that sycamore poses to the British ash woods is questioned and the necessity for a more realistic attitude to sycamore is emphasized.