Impacts of tropical cyclones on hydrochemistry of a subtropical forest
- 1Department of Geography, National Taiwan University, Taipei 10617, Taiwan
- 2Environmental Defense Fund, 257 Park Avenue South, New York, NY 10010, USA
- 3Taiwan Forestry Research Institute, Taipei 10066, Taiwan
- 4Department of Atmospheric Sciences, National Central University, Chung-Li 32001, Taiwan
- 5Taiwan Endemic Species Research Institute, Nantou 55244, Taiwan
- 6School of Forestry and Resource Conservation, National Taiwan University, Taipei 10617, Taiwan
- 7Department of Life Science, National Taiwan Normal University, Taipei 11677, Taiwan
Abstract. Tropical cyclones (typhoons/hurricanes) have major 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 characterised the impacts of 14 typhoons over six years on hydrochemistry of a subtropical forest plantation in Taiwan, a region 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 precipitation poses a challenge with respect to managing the impacts 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 (except nitrogen) during an average 9.5 day yr−1 period, resulting in nutrient input/output rates an order of magnitude greater than during non-typhoon months. Nitrate output balanced input during the non-typhoon period, but during the typhoon 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 response to typhoons, resulting in minimal loss of nutrients.