Browsing by Author "Huang, Jr-Chuan"

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    On the seasonality of long-range transport of acidic pollutants in East Asia
    (IOP, 2022-08-07) Chang, Chung-Te; Wang, Lixin; Wang, Lih-Jih; Liu, Chiung-Pin; Yang, Ci-Jian; Huang, Jr-Chuan; Wang, Chiao-Ping; Lin, Neng-Huei; Lin, Teng-Chiu; Earth and Environmental Sciences, School of Science
    East Asia currently has the largest SO2 and NOx emissions in the world. The long-range transport (LRT) of acidic pollutants in this region is of great concern but the extent is not well understood. Here results from combined long-term (⩾20 years) atmospheric deposition monitoring and air trajectory analysis in East Asia were reported. The results showed that despite the large decrease of SO2 and NOx emissions in Taiwan, annual deposition of non-sea-salt sulfate (nss-SO2−4 ) in northern Taiwan showed no decreasing trend during 1994–2020. However, when divided seasonally, both nss-SO2−4 and nitrate (NO−3 ) deposition had a significant decreasing trend in the summer but not in the winter. Similar patterns were found for Japan and Korea. Air trajectory models in combination with a regional emission map indicate that LRT from eastern China contributed up to 70% of the winter deposition of nss-SO2−4 and NO−3 in Taiwan and up to 50% in Japan and Korea. The results indicate that LRT obscured the efficacy of local pollution control measures in East Asia and suggest that transboundary air pollution regulations are required to combat acid deposition.
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    Precipitation controls on nutrient budgets in subtropical and tropical forests and the implications under changing climate
    (Elsevier, 2017-05) Chang, Chung-Te; Wang, Lih-Jih; Huang, Jr-Chuan; Liu, Chiung-Pin; Wang, Chiao-Ping; Lin, Neng-Huei; Wang, Lixin; Lin, Teng-Chiu; Department of Earth Sciences, School of Science
    Biological, geological and hydrological drivers collectively control forest biogeochemical cycling. However, based on a close examination of recent literature, we argue that the role of hydrological control particularly precipitation on nutrient budgets is significantly underestimated in subtropical and tropical forests, hindering our predictions of future forest nutrient status under a changing climate in these systems. To test this hypothesis, we analyzed two decades of monthly nutrient input and output data in precipitation and streamwater from a subtropical forested watershed in Taiwan, one of the few sites that has long-term nutrient input-output data in the tropics and subtropics. The results showed that monthly input and output of all ions and budgets (output – input) of most ions were positively correlated with precipitation quantity and there was a surprisingly greater net ion export during the wet growing season, indicating strong precipitation control on the nutrient budget. The strong precipitation control is also supported by the divergence of acidic precipitation and near neutral acidity of streamwater, with the former being independent from precipitation quantity but the latter being positively related to precipitation quantity. An additional synthesis of annual precipitation quantity and nutrient budgets of 32 forests across the globe showed a strong correlation between precipitation quantity and nutrient output-input budget, indicating that strong precipitation control is ubiquitous at the global scale and is particularly important in the humid tropical and subtropical forests. Our results imply that climate change could directly affect ecosystem nutrient cycling in the tropics through changes in precipitation pattern and amount.
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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.