Abstract
Mangroves are key resources of tropical and subtropical coastal environments because of their ability to buffer hurricane effects such as severe winds, surge flooding, and heavy erosion. Because of their critical role in protecting the shoreline, maintaining ecosystem functions, and providing habitat, mangrove community recovery post-hurricane disturbance is a concern to coastal areas. We examined the effects of hurricane disturbance within four regions along a decreasing wind intensity gradient and the effects of altered hydrology on mangrove post-hurricane recovery via tidally "restricted" and "unrestricted" locations. Data was collected on seedling densities, seedling recruitment, growth rates, litter fall, and canopy closure. Tidal amplitude was quantified to confirm tidal restriction. Results confirmed tidally restricted locations as having significantly lower ( 11 .07 cm) tidal amplitude than unrestricted locations (2 1.68 cm). Three years following Hurricane Charley our data suggest significantly lower mean seedling densities in tidally restricted locations (10.2 seedlings m·2) compared to unrestricted locations (32.0 seedlings m·2 ) and significantly lower mean seedling densities in regions of higher hurricane wind intensity (Captiva, 6.3 seedlings m"2; North Sanibel, 9.2 seedlings m·2; Central Sanibel, 29.94 seedlings m"2 ; East Sanibel, 42.80 seedlings m"2 ) . Mean seedling recruitment for both the third and fourth reproductive seasons post Charley (2004) were higher in unrestricted locations (3'd, 16.6 seedlings m·2; 4'h, 28.15 seedlings m·2) than in restricted locations (3'd, 6.9 seedlings m·2, 4'h, 9.1 seedlings m·2), with the difference significant in 2007. For the third reproductive season post Charley, mean seedling recruitment displayed significant regional differences (Captiva, 5.5 seedlings m·2 ; North Sanibel, 4.8 seedlings m"2; Central Sanibel, 16.3 seedlings m"2; East Sanibel, 21 .8 seedlings m"2). Unrestricted locations (AGR 0.11 cm·yr"1 , RGR 0.08 cm·yr-1) had significantly higher growth rates than restricted locations (AGR 0.04 cm·yr"1 , RGR 0.03 cm·yr-1) and significant regional differences (Captiva, AGR 0.09 cm·yr"1 , RGR 0.06 cm·yr" 1; North Sanibel, AGR 0.09 cm·yr"1 , RGR 0.07 cm·yr-1; Central Sanibel, AGR 0.14 cm·yr·1, RGR 0.10 cm·yr"1 ; East Sanibel, AGR 0.03 cm·yr"1 , RGR 0.02 cm·yr"1) . The dry weight and ash free dry weight of litter fall displayed similar trends, with unrestricted locations (OW 154.04 g·m·2·yr"1, AFDW 133. 11 g·m·2·yr-1) having significantly higher litter fall than restricted locations (DW 41.78 g·m·2·yr"1 , AFDW 35.33 g·m·2·yr" 1 ) and significantly lower litter fall in regions of higher hurricane wind intensity (Captiva, OW 26.37 g·m·2·yr·1, AFDW 22.85 g·m·2·yr" 1; North Sanibel, DW 79.33 g·m·2·yr"\AFDW 68. 14 g·m·2·yr"1; Central Sanibel, OW 12 1.48 g·m·2·yr"1, AFDW 107.49 g·m·2·yr"1; East Sanibel, OW 170.67 g·m·2·yr"1; AFDW 143.77 g·m·2·yr-1) . Three years after Hurricane Charley percent canopy closure revealed a significant regional trend of increasing means with decreasing wind intensity (Captiva, 30.9 %; North Sanibel, 33.2 %; Central Sanibel, 62. I %; East Sanibel, 86. I %). Our results indicate that both tidal influence and hurricane wind intensity impact post hurricane mangrove recovery with measures of productivity and stand structure decreasing with hurricane intensity and tidal restriction. These results provide insight into the mangrove recovery dynamics, and are useful to both restoration and land use planning which are essential in the sustainable management practices of barrier island systems.