昆欄樹的空間分布是否真有北降現象？

Is it true for“northern descent”phenomenon of Trochodendron aralioides spatial distribution?

現今孑遺於東亞的昆欄樹，臺灣是其主要的分布地，過去許多報告提及，昆欄樹在臺灣具有北降現象的分布觀察。為證實此一觀察，本文藉由生物資料庫擷取及野外植株定位，共蒐集3032 點昆欄樹之分布點，並比較昆欄樹在陽明山至塔塔加之5處山區的實際出現位置，結果顯示臺灣北部，特別是陽明山，昆欄樹之數量較多且分布海拔較低。綜合出現點資料可具體證實，昆欄樹在臺灣北部具有分布海拔較低的北降現象，而出現於陽明山之昆欄樹的生態氣候顯著異於其他山區，推論昆欄樹的適宜生育地不僅與環境熱量有關，更深受環境濕度、雲霧之影響。 The contemporary Trochodendron aralioides is relic in East-Asia, and Taiwan is its major habitat. An observation of the“northern descent”phenomenon of T. aralioides had been mentioned once in certain documents. For confirming this observation, we collected 3032 occurrence points of T. aralioides from biological database and field GPS positioning data, and compared the altitudinal positions of T. aralioides among 5 different mountain habitats. The results of comprehensive occurrence data demonstrated that the“northern descent”phenomenon of T. aralioides is a true distribution pattern in Taiwan. The rather abundant population of T. aralioides occurred in northern Taiwan, especially in Yangmingshan area with specially ecoclimatic regime. The results inferred that the suitable habitat of T. aralioides was involved with thermal regime as well as environmental humidity and cloud and fog.