亞熱帶山地雲霧森林生態系統中通量模式的年際變化

Abstract

山地雲霧森林的特色為長時籠罩在雲霧條件，或樹冠及地面低雲層當中。這是因為雲霧的遮蔽效應使得入射輻射減少和蒸汽壓力不足造成的。雲霧森林的雲霧特色也使該系統具備獨特的水文輸入，為從雲霧中截取的水資源，是當地生態系統重要的水輸入和養分來源。近年來氣候變遷的議題引起了人們的關注，討論如何對不同地域造成影響，但雲霧森林的敏感性和反應仍然缺乏研究。因此我們 使用渦度協方差方法來量化霧、大氣和近地表之間的通量模式。年際尺度由於氣象原因造成的外在環境事件的變化而有顯著差異，並預計會改變地表-大氣之間的相互作用。 本研究以臺灣東北部宜蘭境內的棲蘭山雲霧森林帶為樣區，利用安裝在 24 米高的通量塔上的渦流協方差觀測系統，進行連續的通量和環境參數測量，當中資料的連續性在進行整理後劃分為 2008-2011 年及 2018-2021 年。討論的重點為分析兩個不同年際段的通量特色以及趨勢，並分析造成差異性和變化的機制改變 為何。此外，我們將嘗試填補樣區時序資料上的缺失數據，並以棲蘭樣區為出發 點將山區站的趨勢與平原站進行比較，分析區域地理的效應。從結果中我們觀察 到棲蘭樣區的溫度下降了 1.2。可感熱再跨年際後有所增加，反觀淨輻射，短波 輻射，潛熱和雨量都是下降的趨勢。造成以上通量變化的原因可能為樣區的雲霧 特性變遷或增強。

Montane cloud forest (MCF) is characterized by frequent immersion under foggy conditions and low clouds at canopy or ground tree levels. This is caused by the reduction of incident radiation and lower vapor pressure deficit. MCF is important due to the importance of the hydrological and ecological role as the main source of water input and nutrients for the ecology. As climate change raises concern, the sensitivity and response from MCF remain unclear. We used eddy covariance method to quantify flux patterns between fog, atmosphere and surface. Interannual scale represent significant differences in environmental conditions due to the meteorology and are expected to alter the surface atmosphere interactions. The study site is in northeastern Taiwan at Chi-Lan Mountain (CLM) preserve area. An eddy covariance observation system is mounted on a 24 m flux tower at 1600 m above sea level to continuously measure the flux and environmental parameters, available from 2008-2011 and 2018-2021. The focus is to quantify the shifting pattern of fluxes across different annual scales, discuss the fluxes mechanism and their relationship to climate events. In addition, we will try to fill the gap of CLM missing data and compare mountain station trend to plain stations to analyze regional geographic effect. We observed temperature at CLM region has dropped by 1.2。C accompany by decreased net radiation, mainly due to the cutting of shortwave. Sensible heat has a partial increase but latent heat (LE) increases gradually in summer. LE affects rainfall which observed significant drop in typhoon season (July-Oct). Typhoons contribute to extreme rainfall in CLM with some degree of relationship which is influenced by global ENSO. A potential reason is the changes in visibility(increased) due to fog and low cloud. Regional difference between high latitude and plain also results in opposite trend of rainfall and temperature.