Browsing by Subject "typhoon"

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    Forests affected by frequent and intense typhoons challenge the intermediate disturbance hypothesis
    (Wiley, 2019-11) Wang, Lixin; Lin, Teng-Chiu; Earth Sciences, School of Science
    Tropical cyclones (hurricanes and typhoons) are extreme disturbances that have a significant impact on ecosystem structure and processes. The intermediate disturbance hypothesis (IDH) generalizes disturbance–diversity relationships but its validity is hotly debated. The IDH has been challenged both theoretically and with results from experimental studies; however, few studies have empirically tested the proposed mechanisms of IDH using results from the actual ecosystems. In this commentary, based on empirical observations from studies on the interactions between tropical cyclones and forest dynamics, we outlined seven possible outcomes of gap dynamics and tree diversity as a result of different frequency and intensity combinations. We argue that the lack of distinction and differentiation between disturbance intensity and severity, and the overlooked role of tree mortality, seedling recruitment, and tree adaptations limit the applicability of IDH in predicting the disturbance–diversity relationship. In the era of climate change characterized with more frequent climate extremes and natural disturbances, we should move beyond the generalizations and directly address the processes leading to the observed disturbance–diversity relationships to make reliable predictions.
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    Shifts in stream hydrochemistry in responses to typhoon and non-typhoon precipitation
    (European Geosciences Union, 2018-04-19) Chang, Chung-Te; Huang, Jr-Chuan; Wang, Lixin; Shih, Yu-Ting; Lin, Teng-Chiu; Earth Sciences, School of Science
    Climate change is projected to increase the intensity and frequency of extreme climatic events such as tropical cyclones. However, few studies have examined the responses of hydrochemical processes to climate extremes. To fill this knowledge gap, we compared the relationship between stream discharge and ion input–output budget during typhoon and non-typhoon periods in four subtropical mountain watersheds with different levels of agricultural land cover in northern Taiwan. The results indicated that the high predictability of ion input–output budgets using stream discharge during the non-typhoon period largely disappeared during the typhoon periods. For ions such as Na+, NH+4, and PO3−4, the typhoon period and non-typhoon period exhibited opposite discharge–budget relationships. In other cases, the discharge–budget relationship was driven by the typhoon period, which consisted of only 7 % of the total time period. The striking differences in the discharge–ion budget relationship between the two periods likely resulted from differences in the relative contributions of surface runoff, subsurface runoff and groundwater, which had different chemical compositions, to stream discharge between the two periods. Watersheds with a 17–22 % tea plantation cover showed large increases in NO−3 export with increases in stream discharge. In contrast, watersheds with 93–99 % forest cover showed very mild or no increases in NO−3 export with increases in discharge and very low levels of NO−3 export even during typhoon storms. The results suggest that even mild disruption of the natural vegetation could largely alter hydrochemical processes. Our study clearly illustrates significant shifts in hydrochemical responses between regular and typhoon precipitation. We propose that hydrological models should separate hydrochemical processes into regular and extreme conditions to better capture the whole spectrum of hydrochemical responses to a variety of climate conditions.