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| 108年度墾丁國家公園社頂高位珊瑚礁生態保護區森林更新調查計畫 |
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一、計畫緣起
社頂高位珊瑚礁生態保護區，具有獨特的喀斯特地形，交錯的礁岩與經冲積的谷地，形成多樣的棲地。森林木本植物於小苗階段的生長與存活，與森林更新的過程息息相關，對於維繫森林的物種多樣性與生態系過程，具有持續且深遠的影響。瞭解森林更新的過程，為發展森林保育策略的重要基礎。本計畫評估社頂高位珊瑚礁生態保護區物種小苗與稚樹在不同棲地的多樣性、群聚組成、存活與更新，並分析環境因子與群聚組成的關係，進而鑑定高位珊瑚礁森林的重要棲地。除此之外，本計畫整合現有長期小苗監測資料，推估高位珊瑚礁森林的動態趨勢。
二、研究方法與過程
本團隊於2019年3-4月間，於10公頃的社頂高位珊瑚礁生態保護區的礁頂、過渡帶與谷地等三類型棲地，設立45個樣區。在2019年4月與九月，在每一個小苗樣區（3 m x 3 m）內，調查所有胸高徑小於1公分的木本植物，記錄物種、高度、存活狀態與位置。在2019年6月，則在稚樹樣區（10 m x 10 m）內，調查胸高徑介於1-10 cm之稚樹，記錄物種與胸高徑。除此之外，本團隊於2019年4月，記錄每個樣區內之礁岩覆蓋度、凋落物覆蓋度、林下光環境與梅花鹿排遺，並在每類棲地，選擇兩個樣區，架設自動相機，比較梅花鹿於三類棲地的活動。
三、重要發現
2019年4月與9月所進行的小苗調查，各發現木本植物小苗42種，1673株與2340株。在兩季的小苗調查中，紅柴為最優勢物種，廣泛分布於礁頂、過渡帶與谷地三類棲地。在2019年6月的稚樹調查，記錄胸高徑介於1-10公分之稚樹725株，共34種，最優勢物種為黃心柿。無論小苗或稚樹，均在礁頂棲地之密度最高，過渡帶次之，谷地最低。小苗物種組成在三類棲地，呈現顯著差異，且與稚樹物種組成，顯著不同。小苗與稚樹於物種組成的差異，可能源自於小苗物種組成之改變。此種結果與小苗長期監測樣區所得之結果一致。自2007年7月至2019年7月，社頂高位珊瑚礁生態保護區木本植物小苗數量降低約45%，物種豐富度降低。優勢物種中，黃心柿的密度，大幅降低，而鐵色與樹杞之小苗密度，雖然呈現較大的年間波動，但近年來，小苗密度亦減少。
本研究顯示社頂高位珊瑚礁生態保護區，在過去十餘年間，小苗與稚樹之組成，呈現大幅改變。梅花鹿啃食，應為造成小苗與稚樹群聚組成改變的主要原因。
四、主要建議事項
建議一
監測梅花鹿圍籬植被復原狀況:立即可行建議
主辦單位：墾丁國家公園管理處
在社頂高位珊瑚礁生態保護區，梅花鹿活動於谷地棲地，最為頻繁，應為保育重點區域。目前墾管處，已於谷地棲地，建構梅花鹿圍籬，對於自然植被恢復，具有重要效果。建議針對梅花鹿圍籬之植被恢復，進行持續監測。
建議二
控制梅花鹿數量:中長期可行建議
主辦單位：墾丁國家公園管理處
梅花鹿啃食作用，為影響社頂高位珊瑚礁生態保護區小苗密度、物種多樣性與植物群聚組成的重要因素，建議適度控制梅花鹿數量，以降低梅花鹿對於社頂高位珊瑚礁生態保護區森林植被的影響。
計畫類別：[植物生態]
英文摘要：The Shirding Uplifted Coral Reef Nature Reserve is associated with karst topography and characterized by limestone outcroppings interrupted by depressions of thick soils. Understanding the processes governing forest regeneration is critical for developing conservation strategies for forest ecosystems. This project studied species diversity and community composition of seedlings and saplings in different habitats in the Shirding Uplifted Coral Reef Nature Reserve. Relationships between environmental factors and community compositions were explored. In addition, this project incorporated existing long-term data to evaluate the patterns of forest dynamics in the Shirding Uplifted Coral Reef Nature Reserve.
We established 45 quadrats in three different habitats during March-April in 2019 in the Shirding Uplifted Coral Reef Nature Reserve. A 3 m x 3 m seedling plot was established within each quadrat. All woody seedlings with DBH smaller than 1 cm were identified, tagged and mapped in April and September, 2019. In June 2019, saplings with DBH of 1-10 cm within the 10 m x 10 m quadrats. Species identity and DBH were measured. In addition, we studied light environments, deer feces and coverages of limestone and litters in each quadrat. Two automatic cameras were established in each of the three habitats to quantify deer activities in the three habitats.
We identified 1673 and 2340 seedlings of 42 species in April and September 2019, respectively. Aglaia formosana is the most dominant species in both seedling censuses, widely distributed in the ridge, transition and valley habitats. In the sapling census in June 2019, we detected 725 saplings of 34 species. Density of both seedlings and saplings were highest in the ridge habitat and lowest in the valley habitat. Species composition of seedlings differed significantly among the three habitats. Furthermore, species composition of seedlings and saplings varied significantly. Such differences may be attributed to temporal changes in species composition of seedlings. The findings of this study were consistent with a long-term study of seedling monitoring. Seedling abundance reduced by 45% and species richness decreased substantially during 2007-2019. Among the dominant species, seedling density of Diospyros maritima reduced greatly in the past 13 years. Meanwhile, density of Ardisia sieboldii and Drypetes littoralis decreased in the recent years despite temporal fluctuations in density during 2007-2019.
This study indicated that species composition of seedlings and saplings altered substantially in the past decade. Herbivory by Formosan sika deer was suggested to be the key factor driving temporal changes in species composition of seedlings and saplings. Based upon the findings of this study, we have two management suggestions. First, deer activities were concentrated in the valley habitat. Valleys should be the target areas for vegetation protection. The existing deer exlosure is critical for seedling conservation. Long-term monitoring of vegetation recovery in the deer exclosure is important. Second, deer herbivory cast significantly impacts on seedling density, species richness and diversity in the Shirding Uplifted Coral Reef Nature Reserve. Population controls of Formosan sika deer may be necessary for the conservation of forest vegetation.
辦理單位：東海大學
計畫屬性：本處委託研究
執行年度：108
計畫主持人：林宜靜
中文關鍵字：高位珊瑚礁森林、梅花鹿啃食、棲地效應
英文關鍵字：Karst forest, deer herbivory, habitat associations