Light interception and its relation to structural differences in three Australian rainforest canopies

Relative diflerences in the seasonality o f light penetrating the canopies of three Australian i.ainforests were tt~easured directly n,ith a quanturn rneter and indirectbl ~rsing hemispherical photographs. The tnossy rnicrophyll~fern .forest had higher incident light levels (100-200 pEinstcin r , 1 2 per s) and tnore sky visible (21.8%) at ground level than the sitnple (5-20 pEinsteiti nli ' per s with 11.2°0 slkylight) and c o r n p l ~ ~ ~ (510 pEinstein m 2 per s with 10.8% skylight) notophyll vine ,forests. There brvre nosignificant changes in atnounts of shy visible through the canopy over tirne (10 rnonths) .for anjl canopy, despite the ,fact that Icafl,fall ~vas a seasonal event. Profile diagratns ~verc constructed at each site to illustrate the depth and stratification of the canopy, and the differences in these structural features were related to the variation in light attenuation. Ecological aspects of' light interception through rainforest canopies are discussed, including tree branch growth patterns and leafing phenologies, and seedling regeneration on the,forcst ,/loor.