Abstract

Airborne light detection and ranging (LIDAR) measurements derived before and after Hurricanes Katrina and Wilma (2005) were used to quantify the impact of hurricanes and lightning strikes on the mangrove forest at two sites in Everglades National Park (ENP). Analysis of LIDAR measurements covering 61 and 68 ha areas of mangrove forest at the Shark River and Broad River sites showed that the proportion of high tree canopy detected by the LIDAR after the 2005 hurricane season decreased significantly due to defoliation and breakage of branches and trunks, while the proportion of low canopy and the ground increased drastically. Tall mangrove forests distant from tidal creeks suffered more damage than lower mangrove forests adjacent to the tidal creeks. The hurricanes created numerous canopy gaps, and the number of gaps per square kilometer increased from about 400~500 to 4000 after Katrina and Wilma. The total area of gaps in the forest increased from about 1~2% of the total forest area to 12%. The relative contribution of hurricanes to mangrove forest disturbance in ENP is at least 2 times more than that from lightning strikes. However, hurricanes and lightning strikes disturb the mangrove forest in a related way. Most seedlings in lightning gaps survived the hurricane impact due to the protection of trees surrounding the gaps, and therefore provide an important resource for forest recovery after the hurricane. This research demonstrated that LIDAR is an effective remote sensing tool to quantify the effects of disturbances such as hurricanes and lightning strikes in the mangrove forest.

Highlights

  • Mangrove forests along tropical and subtropical coasts are frequently altered by disturbances from hurricanes, frost, lightning, and insects [1,2,3]

  • Lugo and Snedaker [9] argued that the maximum biomass and structural dimension that mangrove forests can develop in a hurricane zone are limited by storm activity, because mangrove forests usually reach maturity in 20-25 years, a period that coincides with the frequency of hurricanes

  • During our visit to the study area on March 21, 2007, we found resprouting A. geminans or L. racemosa around hurricane-induced gaps many branches of the trees were snapped by hurricane winds

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Summary

Introduction

Mangrove forests along tropical and subtropical coasts are frequently altered by disturbances from hurricanes, frost, lightning, and insects [1,2,3]. Lugo and Snedaker [9] argued that the maximum biomass and structural dimension that mangrove forests can develop in a hurricane zone are limited by storm activity, because mangrove forests usually reach maturity in 20-25 years, a period that coincides with the frequency of hurricanes. Mangrove forests in these regions are cyclically replaced by young forests of similar structural properties through hurricane disturbances and subsequent regeneration, rather than by proceeding to another vegetation community through succession; they can be considered as a steady-state system at the landscape scale [10]

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