Leaf demography and growth of the tree-fern Cyathea pubescens Mett. ex Kuhn in Jamaica

Leaf demography and growth of the tree-fern Cyathea pubescens Mett. ex Kuhn in Jamaica. A demographic study of the fronds of Cyathea pubescens has been made at c. 1550 m altitude in the mountains of Jamaica; a smaller study has been made for C. furfuracea and C. woodwardioides. Leaves were tagged on 119 C. pubescens in August 1979 and inspected at intervals until September 1980. Leaf scars were counted on the trunks of 39 of the 119 trees. There were many individuals < 0.4 m tall (mostly without trunks) and much smaller numbers in all other size classes (to 9.0 m tall).
Leaf production increased after periods of higher rainfall, but the mortality rate was much less variable. Mean leaf-life was about 525 days in C. pubescens , about 328 days in C. furfuracea and about 730 days in C. woodwardioides.
With increasing distance from the stem apex the numbers of leaf scars per 0.2 m of trunk decreases, and the mean length of an individual leaf scar increases, irrespective of absolute trunk height. This may indicate extension growth throughout the length of the trunk, though measurements to date have not confirmed this.
Height is a poor predictor of time for trunk growth (total age cannot be calculated because the time for establishment has not been measured). The mean rate of trunk growth, once it has started, is about 1.0 m every 15 years.