Impacts of tropical cyclones on hydrochemistry of a subtropical forest

Tropical cyclones (typhoons/hurricanes) have ma- jor impacts on the biogeochemistry of forest ecosystems, but the stochastic nature and the long intervals between storms means that there are limited data on their effects. We charac- terised the impacts of 14 typhoons over six years on hydro- chemistry of a subtropical forest plantation in Taiwan, a re- gion experiencing frequent typhoons. Typhoons contributed 1/3 of the annual rainfall on average, but ranged from 4 to 55 %. The stochastic nature of annual typhoon related pre- cipitation poses a challenge with respect to managing the im- pacts of these extreme events. This challenge is exacerbated by the fact that typhoon-related rainfall is not significantly correlated with wind velocity, the current focus of weather forecasts. Thus, little advance warning is provided for the hydrological impacts of these storms. The typhoons we studied contributed approximately one third of the annual input and output of most nutrients (ex- cept nitrogen) during an average 9.5 day yr 1 period, re- sulting in nutrient input/output rates an order of magnitude greater than during non-typhoon months. Nitrate output bal- anced input during the non-typhoon period, but during the ty- phoon period an average of 10 kg ha 1 yr 1 nitrate was lost. Streamwater chemistry exhibited similarly high variability during typhoon and non-typhoon periods and returned to pre- typhoon levels one to three weeks following each typhoon. The streamwater chemistry appears to be very resilient in re- sponse to typhoons, resulting in minimal loss of nutrients.