利用梯度提升樹建構玉山國家公園台灣黑熊(Ursus thibetanus formosanus)棲地選擇模型

Habitat Selection by Boosted Regression Trees for Formosan Black Bears (Ursus thibetanus formosanus) in Yushan National Park, Taiwan

葉子維(Yeh Zi-Wei)

指導教授 ： 黃美秀

國立屏東科技大學/獸醫學院/野生動物保育研究所/碩士(2020年)

https://doi.org/10.6346/NPUST202000382

摘要

儘管有關台灣黑熊(Ursus thibetanus formosanus)研究文獻不斷累積增加，但礙於地形和研究技術等條件限制，我們對台灣黑熊(以下簡稱黑熊)如何使用棲息地環境資源的了解仍十分有限。筆者利用黃美秀等人於2014-2018年在玉山國家公園捕捉繫放的9隻黑熊(6雌3雄)的人造衛星定位數據，分析其活動範圍，並透過梯度回歸樹(BRT, Boosted Regression Trees)進行第二階層棲息地選擇分析，依據棲息地選擇的最佳模型繪製預測分布圖。棲息地選擇分析考量的環境變數包含海拔、坡度、坡向、道路最近距離、植被類型、河流最近距離以及植生指標，時間變數則包含大分青剛櫟結果季節與年份，並考量棲息地選擇的性別差異。由於大分為本研究樣區目前唯一已知的密集青剛櫟純林，結果量影響黑熊的移動，故考量黑熊與其之距離以釐清大分青剛櫟林對黑熊的吸引效應。研究結果發現公熊活動範圍大於母熊，活動範圍主要集中在國家公園東境大分至登山口一帶，追蹤期間有半數以上個體(n=5)曾移動至國家公園之外範圍。黑熊的棲息地選擇不僅在性別上有所差異，於櫟實季與非櫟實季亦有所不同。在櫟實季，黑熊對大分青剛櫟優勢林有明顯的偏好，影響棲息地選擇的顯著因子包含道路(40.2%)、海拔(34.4%)、大分距離(15.4%)、植生指標(8.5%)與性別(1.4%)；非櫟實季的顯著因子包含海拔(38.5%)、道路最近距離(27.6%)、植生指標(16.1%)、河流最近距離(12.6%)以及性別(5.2%)。整體而言，黑熊對植生指標的選擇呈正相關，即偏好高植生指標，且偏好500至2,000公尺間的海拔高度，並且遠離道路。此外，本研究也發現雄性似乎比雌性對高海拔(>2,500公尺)有更高的利用程度，可能與其廣泛的活動範圍有關。在預測分布圖上，黑熊除了在低海拔的花東縱谷平原(高度開發區)以及高於2,500公尺的山區幾乎無分布外，於整個研究樣區均有分布，可見人為干擾和食物資源分布對黑熊分布的影響。另根據過往的研究和通報資料比較，預測圖顯示此區黑熊似乎有向園區外圍擴散的趨勢。本研究凸顯完整而連續的森林環境、關鍵食物資源以及避免人為干擾對於保育台灣黑熊的重要性。

關鍵字

台灣黑熊 ； 棲地選擇 ； 梯度提升樹 ； 全球定位系統

並列摘要

Despite a growing body of research literature about Formosan black bears (Ursus thibetanus formosanus), we seemingly have a limited understanding of how bears use habitats due to terrain and technical issues. Baead on recent applications of GPS satellite telemetry in Yushan National Parkm, we futher analyzed the location data collected during 2014-2018 for home range of 9 bears (6 females and 3 males). Besides, we also used boosted regression trees to develop a predictive model of 2nd order habitat selection for bears, and further a predictive distribution map based on the best-fitted habitat selection model. The environmental variables analyzed included altitude, slope, aspect, distance to road, distance to Dafen (the only known high-denity oak forest), type of vegetation, distance to river, and NDVI. The time variables included oak season and year. Sex differences were also taken into the account. The results showed that bears were mainly concentrated in eastern part of the park, and 5 of 9 tracked individuals have traveled beyond the park. Male generally had larger home range than females. Our results indicated some differences in habitat selection according to seasons and sexes. During the acorn season, bears preferred Dafen area, and the significant factors of the model included roads (40.2% of relative importance), elevation (34.4%), Distance to Dafen (15.4%), NDVI (8.5%) and sex (1.4%). But During the non-acorn season, the significant factors included elevation (38.5%), road (27.6%), NDVI (16.1%), river (12.6%), and sex (5.2%). Generally, bears prefered thicker vegetative cover, elevation between 500 to 2,000 m, and tended to avoid roads. Besiseds, there was a sex difference in the utilizationd of elevational range where males tended to use high elevation (>2,500 m) more often than females. The predictive distribution map revealed that bears distributed in whole study areas except for the low-elevational plain of East Rift Valley (highly developed area) and the mountainous areas above 2,500 m. This indicated the critical impact of human interference and food resource distribution on bears. This study represents the most in-depth study of bear habitat use to date, and also highlights the importance of the forest landscape continuity, critical food resource and low human disturbance for cornservation of endangered Formosan black bears.

並列關鍵字

Ursus thibetanus formosanus ； habitat selection ； Boosted Regression Trees ； Global Position System

參考文獻

參考文獻

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