臺灣都市林種植原生樹種之現況與展望

Current status and prospects of planting native tree species in Taiwanese urban forests

種植原生種與重視生物多樣性為近年都市林建造的2大趨勢，本研究為瞭解臺灣都市林使用原生樹種之情況，蒐集過去相關調查報告，將都市林分為行道樹、校園植栽、公園及其他綠地等3類，並逐一下載臺北市、臺中市之行道樹資料庫，分析其原生樹種之種類與株數百分率。首先，本研究剖析相關文獻，將都市林惠益區分為環境－生態、社會－經濟－文化2大面向，並羅列其各項惠益。彙整文獻分析結果顯示，3類都市林種植原生種之種數比例差異不大（35.6－37.0％），而株數比例差異較大（36.0－46.9％），並以行道樹之原生種株數比例最高，臺灣整體都市林之原生種種數比例為36.1％、株數比例為39.7％。行道樹資料庫分析結果顯示，臺北市行道樹之原生種種數明顯低於臺中市（75 vs 126），然其原生種株數比例明顯高於臺中市（63.7％ vs 45.6％），臺中市行道樹外來種黑板樹株數達10.0％亟待處理；兩市不論在種、屬、科中基本上均已符合Santamour提議的10／20／30基準，明顯優於世界主要城市都市林的多樣性。未來，臺灣都市林應至少考量適地、適種、適人，優先選用臺灣原生種，並釐清影響種樹成敗的環節，以達都市林的綜合惠益。

Planting native species and emphasizing biodiversity are two major trends in urban forest construction in recent years. To realize how native trees were used in Taiwanese urban forests, we surveyed relevant literatures and divided them into 3 categories (street trees, campus plantings, parks and other green spaces), and downloaded the street tree databases of Taipei and Taichung cities to analyze the species and number percentages of the native trees. First, we compiled relevant literatures of urban forests and divided its benefits into environment-ecological and social-economic-cultural, 2 major aspects, and various other benefits were listed as well. The results of the literature analysis showed that the species proportion of native trees in the 3 urban forest categories were similar (35.6-37.0%), while the number proportion of native trees was different (36.0-46.9%) with street trees had highest native number proportion. The species and number proportions of native trees in Taiwanese urban forests were 36.1% and 39.7% respectively. The analysis results of the street tree databases reveal that the number of native trees in Taipei was significantly lower than that of Taichung (75 vs 126), but the number proportion of native trees was significantly higher than that of Taichung (63.7% vs 45.6%). The number of the alien tree species Alstonia scholaris accounted for 10.0% and needs to be addressed urgently. The urban forests of two cities generally meet the 10/ 20/ 30 guideline proposed by Santamour in terms of species, genus, and family levels, which is significantly better than the diversity of urban forests in major cities of the world. In the future, Taiwanese urban forests should be assessed for the suitability among environment, species, and people. Native species should be prioritized, and factors that are critical to the planting performances should be identified in order to achieve the comprehensive benefits of urban forests.