Growth and survival of aerial roots of hemiepiphytes in a lower montane tropical moist forest in Panama

Hemiepiphytic plants grow for part of their life as true epiphytes, then be come terrestrial through the production of aerial roots that grow from the canopy to the ground. Long-term measurement of growth, dieback and mortalit y of aerial roots of hemiepiphytic plants in a lower montane moist tropical forest in western Panama was used to elucidate life-history strategies of hemiepiphytes from two families. The fates of 156 aerial roots of five spec ies of Clusiaceae and Araceae were followed for 10 mo. Some roots were cut to experimentally study the effect of injury on resprouting and survival. A erial roots of Araceae grew more than twice as fast as those of Clusiaceae but had a much greater mortality rate. Roots of both families grew much fas ter during the wet than dry season. Even for the fastest growing roots, gro wth and survival models suggest that only 18% of Araceae roots were likely to survive long enough to reach the ground from a branch 10 m high, whereas 87% of roots of Clusiaceae were likely to do so. This suggests that only t hose Araceae hemiepiphytes that produce a large number of aerial roots or a re located close to the ground are likely to reach the soil.