Long-term changes in mangrove forests and cays following hurricanes at Turneffe Islands, Belize

• Main Author: Chi, Faustino
• Language: English
• Published: University of British Columbia 2012
• Online Access: http://hdl.handle.net/2429/42484

Fringing cays develop on the back-reef sediment apron in exposed reef environments. Long-term datasets that document disturbance and long-term recovery are rare. In this study, patterns of disturbance and recovery of the fringing cays on Turneffe Islands, Belize were examined focusing on the interaction between cay geomorphology and vegetation, and the role of mangroves. Historic aerial photos and field observations taken before and after catastrophic Hurricane Hattie in 1961 were combined with contemporary imagery and permanent and temporary plot data. Some cays were devegetated during Hurricane Hattie and subsequently revegetated. However, there was a 26% loss of vegetated cays between 1945 and 2008. Devegetated cays have revegetated in the same general location, but have shifted an average of 18 m away from the reef toward the west-northwest. Cay vegetation has changed from dominance of Cocos nucifera L. before Hurricane Hattie to mangrove forest dominated by Rhizophora mangle L. However, much of the vegetated area in 2008 was inundated by tides. Remeasurements of permanent sample plots indicated that there was significant increase in mangrove biomass on two of the three sampled cays between 2002 and 2008. Leaf litter was the dominant fraction in the litter fall with a mean residence time of 2.5 months. Factors that played an important role on the distribution of vegetation on the fringing cays included: exposure to wave energy, tidal inundation, substrate elevation and distance to the reef. I identified three distinct geomorphic-habitat zones on the fringing cays: sheltered leeward, ridge, and exposed reefward, each had distinctive substrates and plant communities. Rhizophora mangle dominated the leeward zone and has a competitor-stress tolerator plant strategy. It was also the most abundant species in the reefward zone, but typically did not reach large sizes. In the absence of permanent human settlements, the vegetation on fringing cays has the capacity to recolonize in the same general location following a hurricane. Once vegetation was established on or adjacent to reforming fringing cays, these plants promoted further sediment accumulation and stabilization, indicating a self-reinforcing system. Given the exposure of these cays to recurrent hurricane damage, development of these cays seems unwise. === Forestry, Faculty of === Graduate