2001年桃芝颱風蓮華池人工林及天然林集水區溪流水化學之比較
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Date
2007-03-01
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國立臺灣大學生物資源暨農學院實驗林管理處
Abstract
2001年7月30日侵台之桃芝颱風(Typhoon Toraji)為近10年來對蓮華池地區影響最大颱風之一。本文探討桃芝颱風期間，蓮華池4號（杉木人工林）與5號（天然闊葉林）兩試驗集水區溪流水化學之變動。桃芝颱風期間，蓮華池試驗林累積雨量為390mm，分別於4號與5號試驗集水區溪流中形成1,440及1,792 LPS之最大洪峰流量。颱風期間蓮華池溪流水化學變化可歸納為下列三種形式：(1)與流量成負相關，即濃度隨流量升高而下降，如電導度、pH、Ca(上標 2+)、Mg(上標 2+)、Na(上標 +)、Cl(上標 -)、SO4(上標 2-)、HCO3(上標 -)等；(2)與流量成正相關，即濃度隨流量升高而上升，如懸浮質及NO3(上標 -)；(3)與流量無顯著相關，即濃度沒有明顯之變化趨勢，如NH4(上標 +)、K(上標 +)等。颱風期間4號集水區溪水中Ca(上標 2+)、Mg(上標 2+)、SO4(上標 2-)及HCO3(上標 -)的平均濃度分別為5號集水區的4.6、1.7、2.0及4.5倍，可能顯示與林相變更有關。
Typhoon Toraji in 2001 was the most influential typhoon event in central Taiwan during recent decades. The purpose of this paper was to compare with streamwater chemistry between Lien-hua-chi watershed No. 4 and No. 5 during the typhoon Toraji. The area of watershed No. 4 is 5.86 ha with China-fir plantation, while the area of watershed No. 5 is 8.39 ha with natural broadleaf forests. Total rainfall was 390 mm during typhoon Toraji event, and the highest peak flow rates were 1, 440 and 1, 792 LPS in watershed No. 4 and No. 5, respectively. Results showed that conductivity, pH, and concentrations of Mg(superscript 2+), Na(superscript +), Cl(superscript -), SO4(superscript 2-) and HCO3(superscript -) in streamwater decreased with increasing discharge. However, suspended solid and concentration of NO3(superscript -) increased with increasing discharge. Ionic concentrations of Ca(superscript 2+), Mg(superscript 2+), SO4(superscript 2-) and HCO3(superscript -) in watershed No. 4 were obviously higher than those in watershed No. 5 indicating possible influence from the last forest alternation.
Typhoon Toraji in 2001 was the most influential typhoon event in central Taiwan during recent decades. The purpose of this paper was to compare with streamwater chemistry between Lien-hua-chi watershed No. 4 and No. 5 during the typhoon Toraji. The area of watershed No. 4 is 5.86 ha with China-fir plantation, while the area of watershed No. 5 is 8.39 ha with natural broadleaf forests. Total rainfall was 390 mm during typhoon Toraji event, and the highest peak flow rates were 1, 440 and 1, 792 LPS in watershed No. 4 and No. 5, respectively. Results showed that conductivity, pH, and concentrations of Mg(superscript 2+), Na(superscript +), Cl(superscript -), SO4(superscript 2-) and HCO3(superscript -) in streamwater decreased with increasing discharge. However, suspended solid and concentration of NO3(superscript -) increased with increasing discharge. Ionic concentrations of Ca(superscript 2+), Mg(superscript 2+), SO4(superscript 2-) and HCO3(superscript -) in watershed No. 4 were obviously higher than those in watershed No. 5 indicating possible influence from the last forest alternation.