臺灣中部溪頭實驗林溪流水溫動態

The Dynamics of Stream Temperature at Xitou Experimental Forest, Central Taiwan

王立志(Lih-Jih Wang) ； 久米朋宣(Tomonori Kume) ； 梁偉立(Wei-Li Liang) ； 羅士福(Sih-Fu Lo) ； 魏聰輝(Tsong-Huei Wey)

《國立臺灣大學生物資源暨農學院實驗林研究報告》 24卷1期 (2010/03) Pp. 1-16

https://doi.org/10.6542/EFNTU.201003_24(1).0001

摘要

本研究自2005年1月1日起至2005年12月31日止，於中海拔溪頭實驗林巨石溪及神木溪設置自記溫度感測器，連續一年監測水溫，蒐集同時期溪頭氣象站氣溫，以分析氣溫與水溫動態。結果顯示2005年平均氣溫為15.6˚C，最低氣溫為-0.3˚C，最高氣溫為26.5˚C，冬季1月平均氣溫11.0°C，夏季7月平均氣溫19.3˚C。巨石溪年平均水溫為15.9˚C，最低水溫為10.4˚C，最高水溫為19.4˚C，冬季1月平均水溫11.0°C，夏季7月平均水溫18.3˚C。神木溪年平均水溫為16.5˚C，最低水溫為3.3˚C，最高水溫可超過30.0˚C，推判係因枯水期河床裸露，使感應器直接接受日曬之緣故，冬季1月平均水溫11.5°C，夏季7月平均水溫19.3˚C。三者溫度皆呈現明顯3月～8月（春－夏季）升溫期及9月～次年2月（秋－冬季）降溫期之季節變化。冬季1月下旬至2月中為乾涸時期，河床裸露，巨石溪與神木溪河床溫度受氣溫影響極大，直至二月下旬溪水再現，兩溪流水溫始趨向穩定。一年之中，天晴時日（如晚春5月），神木溪水升溫較大，且日變幅較大；巨石溪因森林覆蓋良好，溪水升溫較緩，且日變幅較小，濱水森林提供重要緩衝效果。另溪頭巨石溪與神木溪水溫明顯受降雨影響，然各降雨形式水溫動態不一。研究期間，溪頭遭逢百年罕見降雪，氣溫降至-0.3˚C，神木溪因缺乏濱水森林覆蓋且受輻射冷卻影響，降雪前後水溫變化幅度在3～5°C之間，溫差頗大，然巨石溪因森林覆蓋良好，水溫維持在13°C左右。6月梅雨時期，巨石溪水溫可因梅雨溫度較高而呈升溫現象，而神木溪水溫並未呈現升溫現象。夏季午後大雷雨及颱風超大豪雨皆使巨石溪水溫呈現升溫現象，而神木溪水溫則呈現降溫現象。冬季冷鋒期間神木溪溫度變化則較巨石溪為大。此些結果顯示溪頭巨石溪及神木溪水溫動態受太陽輻射、氣溫、乾旱、降水形式及濱水森林覆蓋等不同因子所影響，而其中濱水森林覆蓋可遮蔽反射太陽輻射，穩定林內氣溫，進而使巨石溪水溫穩定。

關鍵字

溪頭 ； 溪流水溫 ； 濱水森林 ； 暴雨事件

並列摘要

This study was to analyze the dynamics of stream temperature in Giant-Rock Creek and Sacred-Tree Creek in Xitou Experimental Forest, central Taiwan. Autonomous sensors were set up to monitor the stream temperatures continuously from January 1 to December 31 2005, and the air temperature of Xitou Agro-meteorological Station was collected in same period. Results revealed that due to influences from altitude and solar radiation, the minimal and maximal annual daily average temperature were 15.6˚C, -0.3˚C and 26.5˚C, with winter monthly average 11.0˚C (January) and summer monthly average 19.3˚C (July), respectively. The minimal and maximal annual daily average of stream temperature in Giant-Rock Creek were 15.9˚C, 10.4˚C and 19.4˚C, with winter monthly average 11.0˚C (January) and summer monthly average 18.3˚C (July), respectively. The minimal and maximal annual daily average of stream temperature in Sacred-Tree Creek were 16.5˚C and 3.3˚C. During dry seasons, the exposed riverbed might cause the sensors to be exposed in direct sunlight and resulted in water temperature higher than 30.0˚C. The winter monthly average was 11.0˚C (January) and the summer monthly average was 18.3˚C (July), respectively. Air temperature behavior at Giant-Rock Creek and Sacred-Tree Creek exhibited seasonal increases from March to August and decreases from September to February. Those behaviors also showed daily and diurnal fluctuation variation, influenced fundamentally by solar radiation. The occurrence of winter drought with attendant high air temperature also encouraged unusual stream temperature fluctuations both in Giant-Rock Creek and Sacred-Tree Creek. In those sunny days, the diurnal differences in stream temperature in the Sacred-Tree Creek were greater than those in the Giant-Rock Creek. The existence of riparian forest provided buffering effect to the Giant-Rock Creek. During the unprecedented snowfall events, air temperature dropped to -0.3˚C, the before-and-after temperature differences were 3-5˚C for the Sacred-Tree Creek due to the lack of riparian forest and radiant cooling effect. Yet the Stream temperature was buffered at around 13˚C for the Giant-Rock Creek with the sufficient riparian forest coverage. Stream temperature in both creeks also responded to heavy rainfall events (e.g. late spring frontal rainfall, summer thunder storms and heavy typhoon storms) variously, indicating the mixing of relative contributions from different flow paths. These results revealed that dynamics of stream temperature in Xitou Experimental Forest were influenced by solar radiation, air temperature, drought, rainfall events and coverage of riparian forest. Particularly, the riparian forest could help in maintaining the stability of stream temperature in the Giant-Rock Creek by reflecting solar radiation.

並列關鍵字

Xitou ； stream temperature ； riparian forest ； storm events