- 學位論文
應用合歡山冷杉樹輪穩定氧同位素重建台灣高山232年氣候
Reconstruction of 232 Years Montane Climate of Taiwan from Stable Oxygen Isotope Ratios in Abies kawakamii Tree Ring
摘要
本世紀因全球升溫和降雨頻率、強度改變，使得許多地區乾旱發生頻率增 加，導致森林大規模死亡。其中，高山生態系對氣候變遷非常敏感，其可能衝擊受到普遍關注。重建歷史氣候為回答相關生態議題之重要步驟，在古氣候的研究上，樹輪穩定氧同位素被認為較傳統樹輪學使用輪寬資料，能提供更為單純的氣候訊號。本研究於合歡山採集144支臺灣冷杉樹芯樣本，經交叉定年後，建立三種輪寬年表，並從中挑選9支建立樹輪穩定氧同位素時間序列(1780-2011)。氣候資料來自高山測站及臺灣氣候變遷推估與資訊平台計畫(Taiwan Climate Change Projection & Information Platform, TCCIP)等，經定態拔靴法(stationary bootstrap)重新估計平均值及標準差。結果顯示輪寬與穩定氧同位素分別反映不同季節的氣候資訊。輪寬與生長季前(三月至五月)日照時數呈現正相關(r = 0.421, p < 0.05)，與降雨呈現負相關(r = -0.461, p < 0.01)，穩定氧同位素則與生長季(五至十月)多項氣候因子有關。利用冷杉穩定氧同位素重建合歡山區過去232年氣候其解釋變異量分別為：生長季溫度33.1% (r = 0.575)、降雨變異度38.4% (r = 0.620)、降雨22.9% (r = -0.479)以及乾旱指標(Palmer Drought Severity Index, PDSI)36.7% (r = -0.606)。透過重建的資料顯示臺灣高山環境的氣候在19世紀並沒有顯著趨勢變化，然而到了20世紀降雨顯著下降，溫度、降雨變異度以及乾旱的發生頻率與時間長度均顯著提高。本研究提供了臺灣高山的氣候重建資訊，有助於了解東南亞地區的氣候變化趨勢，以及氣候變遷對於高山生態系的影響。
並列摘要
Increasing global temperature, drought events, and changes of precipitation regimes have been related to high level of forest mortality and concerns rise over the vulnerability of mountain ecosystem. Paleoclimate reconstruction is important to address these issues. Both tree-ring widths and stable isotopes have been widely adapted in dendroclimatology and the latter may yield better climatic signals. I developed the first tree-ringδ18O chronology in Taiwan using Taiwan fir (Abies kawakamii) in Mt.Hehuan. I collected and cross-dated 144 tree cores of Taiwan fir and selected 9 cores to obtain δ18O chronology. Climate data were from mountain weather station and Taiwan Climate Change Projection and Information Platform (TCCIP). I applied stationary bootstrap to re-sampled climate and stable oxygen isotope data and estimate mean and standard deviation at each data point. Ring width and δ18O were correlated with different climate factors of different seasons. Ring widths were positively correlated with sun hour (r = 0.421, p < 0.05) and negatively correlated with precipitation (r = -0.461, p < 0.01) of pre-growing season (Mar-May). I applied tree-ringδ18O chronology to reconstruct 232 years climate (1780-2011). The δ18O chronology accounts for 33.1% of variance of growing-season (May to October) temperature (r = 0.575), 38.4% of standard deviation of precipitation (r = 0.620), 22.9% of precipitation (r = -0.479) and 36.7% of Palmer Drought Severity Index (r = -0.606). No significant climate change was detected in Taiwan mountain areas in the 19 century, but in the following century, rapid decrease in precipitation,and dramatic increases of temperature, precipitation variance, and drought events were observed. The mountain ecosystem in Taiwan may undergo stress with global climate change.