應用物種分布模式於氣候變遷下監測樣區之篩選

Abstract

物種分布模式目前是廣泛應用於植物生態學的方法，但在台灣尚欠缺與傳統植群調查資料的整合。本研究嘗試整合模式預測、現生植群圖以及樣區調查資料，以評估物種潛在分布在氣候變遷下的變化，並藉現生棲地脆弱度評估的機制，篩選出適於長期生態監測的調查樣區。在比較基礎不同的模式�尺度不同的氣象資料組合的表現後，我們使用統計模式分類與迴歸樹（classification and regression tree, CART）與全球尺度的WORLDCLIM氣象資料，建立台灣冷杉 （Abies kawakamii）、台灣鐵杉（Tsuga chinensis var. formosana）及兩種檜木屬（Chamaecyparis）植物等數種台灣地區針葉林優勢樹種，在現生氣候下的分布模式，發現在四個氣候因子中熱量因子比水分因子更為重要。模式結果可以投影到兩種氣候變遷情境下三個不同時期，並與現生植群圖套疊，以評估物種現生棲地的可能位移與脆弱度，而脆弱度較高的調查樣區將可作為我們未來的監測對象。結果顯示各目標物種的潛在棲地會在每個時期間向上移動約兩百到三百公尺，同時會逐漸分化使交錯帶減縮。整體而言，氣候變遷對台灣冷杉的影響會大於對台灣鐵杉和檜木的影響，儘管台灣冷杉在交錯帶內仍能保有相當的競爭力。脆弱度評估顯示台灣北部對氣候變遷較為敏感，大部分的監測樣區也集中在此，顯示此區域的物種棲地遷移速率較高，同時也符合歷史文獻中提及植物物種與植群在此區域的海拔壓縮現象。

Species distribution modeling (SDM) is now widely applied in plant ecology but still lack of integration with traditional vegetation survey data in Taiwan. In this study, we try to integrate model prediction, current vegetation map, and survey plots data to evaluate the transition of species potential habitats under climate change. Moreover, we expect to find survey plots that would be appropriate for long term ecological monitoring based on the vulnerability evaluation on species current habitats. After comparing the performance of each set of different based models and climate datasets within different scale, we treat WORLDCLIM data which is within global scale to build the statistical model classification and regression tree (CART) on Abies kawakamii, Tsuga chinensis var. formosana, and two Chamaecyparis species which are dominance in coniferous forest in Taiwan under current climate. Four bioclimatic variables are treated in the model and we find that thermal factors are more important than moisture ones. The model results would be able to be projected into two different climate change scenarios within three periods, and combined with current vegetation map to evaluate the potential shift and vulnerability for each species and their ecotones. Moreover, survey plots that are vulnerable would be the long term monitoring targets. The results show that the potential habitats of each target species would shift upward about 200 to 300 m between each period, and their habitats would differentiate gradually, causing ecotones narrower. Generally speaking, the impact of climate change on Abies would be stronger than on Tsuga and Chamaecyparis, though Abies would have competitive force within ecotone areas in future. The vulnerability evaluation told that northern Taiwan is more sensitive to climate change, and most of monitoring plots would fall within, revealing the shifting speed of species under climate change in the part would be faster. The trend corresponds to the literatures that indicated the altitudinal depression of plant species and vegetation within the region.