Quantifying Typhoon Impact on Net Carbon Ecosystem Exchange in a Sub-tropical Mangrove Ecosystem

Although typhoon is a natural disturbance for mangrove forests, research of typhoon impact on net carbon ecosystem exchange (NEE) of mangrove wetlands has not reached final conclusion. In this study we investigated possible effects of typhoons with different forces on the NEE of a subtropical mangrove forest in Fujian, China (117°23'E, 23°55'N). In 2010, Typhoon Lionrock, Fanapi and Megi made landfall with a speed of 23, 35 and 38 m s^-1 near our mangrove field station in Zhangjiang Estuary National Mangrove Nature Reserve on September 2, September 20 and October 23, respectively. In October 2009, total of 16 litter traps and an eddy covariance system were instated at this field station. Litter production was monitored at the biweekly intervals while the NEE was measured continuously. The litter production and NEE values were compared before and after each typhoon landed. Strong winds and torrential rains from these typhoons caused the amount of litter production more than double over the same period a year before when there was no typhoon landing. Moreover, about 5~25% green leaves and twigs were found in the litter traps after the typhoons, indicating significant defoliation by the typhoons. Typhoon Lionrock and Fanapi did not significantly reduce NEE, while Typhoo Fanapi reduced gross ecosystem production (GEP) by about 12%. However, NEE was increased by Typhoon Megi, which resulted from lower daily ecosystem respiration (Re) following the typhoon. Our results indicate that, although theses typhoons caused significant defoliation, they had little effect on ecosystem carbon exchange over the short periods following the typhoons.