Frequent, low-amplitude disturbances drive high tree turnover rates on a remote, cyclone-prone Polynesian island

Abstract

Aim How important are frequent, low-intensity disturbances to tree community dynamics of a cyclone-prone forest? We tested the following hypotheses concerning the 'inter-cataclysm' period on a remote Polynesian island: (1) tree turnover would be high and recruitment rates would be significantly higher than mortality; (2) low-intensity disturbance would result in a marginal increase in tree mortality in the short term; (3) turnover would vary among species and would be associated with plant traits linked to differences in life history; and (4) mortality and recruitment events would be spatially non-random. Location Tutuila, a volcanic island in the Samoan Archipelago, Polynesia. Methods We censused the tree (stem diameter ≥10cm) community in 3.9ha of tropical forest three times over a 10-year period, 1998-2008. We calculated annual mortality, recruitment and turnover rates for 36 tree species. We tested for non-random spatial patterns and predictors of mortality, and non-random spatial patterns of tree recruitment. A 2004 cyclone passing within 400km allowed us to measure the effects of a non-cataclysmic disturbance on vital rates. Results Annual turnover was 2.8% and annual recruitment was 3.6%; these are some of the highest rates in the tropics, and likely to be a response to a cyclone that passed