SUBCANOPY GAPS IN TEMPERATE AND TROPICAL FORESTS

We present a model of gaps in the vertical structure of forest vegetat ion. The traditional model of a forest gap assumes the existence of a 'hole' in the uppermost canopy layer, often extending down to near the ground. The present model extends the concept to gaps at any level, i ncluding those in lower layers below an intact canopy or subcanopy. It assumes that gaps at any level represent spaces with unused resources , especially favourable for plant growth and survival. Evidence from t emperate and tropical forests indicates that gaps in the subcanopy and understorey layers below intact canopies are common, and that plants have higher growth rates in them than in non-gap sites. We also extend this model to below-ground gaps in the root zone.