在森林生態上,林木樹頂或大部分枝條死亡或瀕臨死亡且站立於林地上,通常稱為枯立木(Snags)。而根據政府間氣候變遷委員會(Intergovernmental Panel on Climate Change, IPCC) 指出全球暖化所帶來的溫度與降水量的改變,已經對高山地區的森林生態系和林木生長產生衝擊。本研究以合歡山地區為研究範圍,利用合歡山地區長期氣候資料為材料,分析合歡山地區長期氣候的變化趨勢,並探討高海拔地區氣候變遷對臺灣冷杉(Abies kawakamii (Hayata) Ito)生長之影響,另以ASD-40數值多光譜航照影像和數位高程模型(Digital Elevation Model, DEM),配合現地樣區之臺灣冷杉枯立木之調查資料,探討生態環境與地形因子,對臺灣冷杉枯死之影響,及枯立木之空間分布型態。研究結果顯示,百年來合歡山地區的氣溫呈現上升趨勢,約提升0.38℃,降水方面雖無顯著增加或減少,但降水天數呈現下降之趨勢;本研究再透過溫量指數,分析氣溫與臺灣冷杉生長之關係,結果發現目前的氣候現象,將導致合歡山地區乾旱時間增加,進而影響臺灣冷杉生長。以樣區調查枯立木資料並結合地形因子,探討不同地形對枯立木數量分布之影響,結果顯示合歡山海拔2,600-3,000 m之臺灣冷杉枯死數量較海拔3,000-3,400 m多。在枯立木之空間分布型態研究中,本研究運用平均最近鄰法進行分析,結果顯示合歡山地區的臺灣冷杉枯立木多數是呈現集落分布,僅11.06%之枯立木為均勻分布,因此本研究認為合歡山地區雖然有少數的臺灣冷杉可能是受到自我疏伐影響而產生死亡,但是大部分的臺灣冷杉則是因氣候暖化的影響,如氣溫上升、乾旱時間拉長,以及土壤水分不足等因素而導致死亡。
In forest ecology, a snag refers to a standing, dead or dying tree, often missing a top or most of the smaller branches. According to IPCC report in 2013, global warming increased the temperature and changed the patterns of rainfall at high mountain area, and that has impacted on the forest ecosystem and tree growth. In this study, we used Hohuanshan as a study area, used meteorological data to study the relationship between long-term trends of climate change and growth of Abies kawakamii, and used ADS-40 airborne multispectral images, digital elevation model and field data to analyse the terrain factor, mortality factor and spatial patterns for A. kawakamii. The results showed that temperature increase 0.38℃ and number of rain day decrease, but precipitation undiversified. Besides, we chose warmth index to analyse the relationship between temperature and growth of A. kawakamii, the results showed that climate condition of current were causing drought duration and effect on growth of A. kawakamii. An analysis of investigation data and terrain factor, the results showed that A. kawakamii of elevations between 2,600-3,000 m mortality more strongly than elevation above 3,000 m. We used average nearest neighbor to study the spatial patterns of snags, the results showed that A. kawakamii of most snags were contagious distribution, 11.06% were regular distribution. Therefore, although A. kawakamii of part mortality factor maybe is self-thinning, but A. kawakamii of most is climate warming, such as temperature increased, drought duration and soil moisture shortage.