高雄市公園彩葉植物、行道樹配置應用及根害改善現況 調查研究

Abstract

本研究針對高雄市公園綠地內彩葉植物的應用、高雄市重要景觀道路行道樹常用配置模式及高雄市行道樹根害改善等進行現況調查，目的為了解高雄市公園及行道樹植栽配置缺失及如何改善，提供大高雄未來規劃公園綠地植栽配置物種的選擇及提升維護管理素質的參考。 調查高雄市20座公園內之彩葉植物配置，應用頻度最高前十名分別為黃金金露華（Duranta repens cv. Golden Leaves）、黃金榕（Ficus microcarpa. Cv.’Golden leaves’）、朱蕉（Cordyline fruticosa）、變葉木（Codiaeum variegatum）、金邊虎尾蘭（Sansevieria trifasciata cv. Laurentii.）、銀姬小蠟（Ligustrum sinense cv. ‘Variegatum’）、斑葉月桃（Alpinia speciosa cv ‘Variegata’）、紅葉鐵莧（Acalypha wilkesiana）彩葉山漆莖（Breynia nivosa cv. ‘Roseo-picat’）及海芙蓉（Crossostephium chinense）等，其中彩葉植物種類平均約佔4.75種。公園內彩葉植物應用少於3種的占大部分有11座55％，介於4-5種的有4座占20％，6種以上的有5座占25％。彩葉植物種類應用最多的前3名皆為近期開闢竣工的公園，例如：熱帶植物園彩葉植物應用達17種、勞工公園達12種及凹仔底森林公園達10種等；而崗山仔公園則全無彩葉植物配置。植物種類中，栽植面積第一名為黃金金露華315,045平方公尺，遠遠超過第二名之黃金榕的64,650平方公尺及第三名朱蕉約29,325平方公尺。整體而言，高雄市20座樣本公園內僅栽植23種彩葉植物，未來應加強推廣彩葉植物的應用。 依其生育指數將觀賞品質優劣分為五等級，整體表現較佳者依序為金邊虎尾蘭的3.5、黃金金露華的2.88、變葉木的2.78、黃金榕的2.6，以朱蕉為1.65表現最差，而高雄市公園內彩葉植物的平均生育指數為2.69並未達觀賞的最低標準。 高雄市公園內土壤硬度平均為18.93㎏/cm2，介於一般正常硬度範圍10-22㎏/cm2 內，土壤硬度低於15㎏/cm2者僅1座，硬度為15-18㎏/cm2有8座，硬度18-20㎏/cm2有4座，硬度20-22㎏/cm2有5座，其中土壤硬度超過標準值22㎏/cm2以上有2座。土壤酸鹼值平均為7.49，其中前鎮區民權公園6.39與小港區熱帶植物園為6.4皆太酸，而鼓山區凹仔底森林公園南側8.26，凹仔底森林公園北側8.2皆太鹼，不利於植物生長。一般土壤酸鹼值應為偏酸性，而高雄市的公園內土壤卻為鹼性，推斷可能的原因為土木工程施工將工程廢棄物水泥等倒入土壤內導致土壤偏鹼性。公園土壤EC值結果平均為498.3μS/㎝，屬於養分略少旳環境，其中以鼓山區凹仔底森林公園南側土壤EC值1296μS/㎝及凹仔底森林公園北側土壤EC值1224μS/㎝最佳，為適合植物生長及大部分生長中的植物，而苓雅區忠孝公園土壤EC值僅274.5μS/㎝，其次為小港區小港1號公園土壤EC值281.6 μS/㎝及前鎮區勞工公園土壤EC值292.2μS/㎝皆為土壤過於貧瘠養分略少不利植物生長。土壤EC值與公園開闢年代有關，愈是新闢的公園土壤EC值愈高。 高雄市公園土壤平均水分含量為15.98％，其中以前鎮區興仁公園31.1％水分最充足，其次為苓雅區生日公園22.5％及鼓山區凹仔底森林公園北側20.6％。水分較不足者有前鎮區民權公園的6.28％及小港區小港1號公園的9.36％，水分不足的公園現況植栽生長皆不佳，灌木類植物下位葉嚴重落葉及黃化，草皮乾枯嚴重，建議加強水分肥培管理以增進其觀賞品質。 在行道樹生長維護管理上，普遍良好，問卷調查結果顯示民眾最喜愛的植栽配置票選第一名為喬木下方規劃精緻花壇的四維三路快慢分車帶，第二名為九如一路行道樹下層栽植色彩鮮艷的季節性草花綠帶，第三名為民族二路行道樹成長形成林蔭大道下層配置多年生的綠色植栽。行道樹應用樹種以黑板樹（Alstonia scholaris）及印度紫檀（Pterocarpus indicus）栽植數量最多，其次為樟樹（Cinnamomum camphora）、大葉桃花心木（Swietenia macrophylla）、掌葉蘋婆（Sterculia foetuda）等，以上喬木共同特色為植栽苗木容易取得，生長快速及環境適應性強，後續維護管理工作較輕鬆。高雄市10條重要道路行道樹的配置模式，因應近年來高雄市政府推廣複層式栽植，行道樹下層近九成栽植黃金金露華及多年生開花的仙丹類植物，重要道路的島頭島尾加強配置季節性草花以添加色彩及道路生態多樣性及提升都市美感。 高雄市行道樹根害改善部分，其中因樟樹產生根害的四維路、民權路、民生路以植栽帶替代原植栽穴進而改善根害；因榕樹產生根害的中正路或因木棉產生根害的林森路或因印度橡膠樹產生根害的五福路、成功路、忠孝路皆以移植原植栽至市政府所屬苗圃後新植新樹種並將原植栽穴擴大或改為植栽帶，解決根害問題。經筆者訪查高雄市政府工務局養護工程處相關執行科室表示，未來將持續辦理行道樹暨人行空間改善等相關造街工程，未來高雄市因行道樹產生的根害將愈減少。

The study investigate the application of color-leaf plants in green land of parks, the layout model of common-used street trees, and the improvement of root-damage from street trees in Kaohsiung city to understand the miss-layout of park plants and street-trees and the improvement methods. Further, to provide a guideline of greening-plants selection and management / maintenance improvement to Kaohsiung city for layout of parks. We surveyed the layout of color-leaf plants of 20 parks in Kaohsiung city and indicated a top 10 color-leaf plants which were frequently used: Duranta repens cv. Golden Leaves, Ficus microcarpa. Cv.’Golden leaves, Cordyline fruticosa , Codiaeum variegatum, Sansevieria trifasciata cv. Laurentii, Ligustrum sinense cv. ‘Variegatum’, Alpinia speciosa cv ‘Variegata’, Acalypha wilkesiana, Breynia nivosa cv. ‘Roseo-picat’, and Crossostephium chinense. The using frequency of color-leaf plants in each park is equal to 4.75. The parks planted with less than 3 kinds of color-leaf plants were accounted for about 55% (11 of 20 parks), which with 4 to 5 species were about 20 % (4 of 20 parks), and which with more than 6 species were about 25 % (5 of 20 parks). The top 3 parks which used the most color-leaf plants were entirely the currently-established park, like “Tropical Botanical Garden” possessing of 17 species, “Labour Park” with 12 species, and “Aozihdi Urban Forest Park” with 10 species. Otherwise, “Gangshan Park” planted without the color-leaf plants. According to classification by plant species, the Duranta repens cv. Golden Leaves has the most planting-area about 412,245 m2 than the second species Ficus microcarpa. Cv.’Golden leaves’with 64,650 m2 and the third species Cordyline fruticosa with 29,325 m2. As a whole, totally only 23 kinds of color-leaf plants were planted in 20 parks of Kaohsiung city we were sampled. So, to enhance the application of color-leaf plants in park design is indeed necessary. The ornamental quality of color-leaf plants was categorized into 5 levels by growth index. Their quality were scored and presented sequentially in accordance with the overall growth performance: Sansevieria trifasciata cv. Laurentii.as 3.5 scores, Duranta repens cv. Golden Leaves as 2.88 scores, Codiaeum variegatum as 2.78 scores, Ficus microcarpa. Cv.’Golden leaves’ as 2.6 scores, and Cordyline fruticosa as 1.65 scores. Furthermore, all the color-leaf plants planted in park of Kaohsiung city were never to be up to the standard of watch according to their lower growth index 2.69. The soil hardness of 20 parks in Kaohsiung city were calculated and averaged into 18.93㎏/cm2 which was belonging to normal hardness range from 10 to 22㎏/cm2. Of 20 parks surveyed in Kaohsiung city, only 1 park yielded a soil hardness value under 15㎏/cm2, 8 parks yielded value 15 to 18㎏/cm2, 4 parks yielded value 18 to 20㎏/cm2, 5 parks yielded value 20 to 22㎏/cm2, and 2 parks yielded value higher than 22 ㎏/cm2that exceed standards. With regard to the soil pH, the average pH of 20 parks was 7.49. Of 20 parks, “Mincyuan Park” and “Tropical Botanical Garden” has mild-acidic soil with pH 6.39 and 6.4, separately; northern and southern part of“Aozihdi Urban Forest Park” has alkaline soil with pH 8.26 and 8.2, separately. All of these 4 parks which without reasonable pH were unfavorable to the growth of plants. Generally, soil is mild acidic, but soils in park of Kaohsiung city were alkaline. We suggested that the waste cement from civil constructions mixed into soil lead to the alkalization of soils. About EC (electrical conductivity) value of soil, average EC value of 20 parks was 498.3 μS/㎝ which was poor in nutrition. Among 20 parks, soil EC of southern part of“Aozihdi Urban Forest Park” and northern part of “Aozihdi Urban Forest Park” were the highest with value of 1296 μS/㎝ and 1296 μS/㎝, separately, which were beneficial to plant growth. Moreover, soil EC of“忠孝 Park”(274.5 μS/㎝), “Siaogang Park” (281.6 μS/㎝) , and“Labour Park” (292.2 μS/㎝) were relative lower than others, which were disadvantageous to plant growth. Therefore, soil EC value is highly correlated to constructive times that the newer park with the higher EC values. About soil water content (SWC), the average water content of soil in 20 parks of Kaohsiung city was 15.98%. Of 20 parks, “Sing Ren Park”has the highest SWC with 31.1%, and“Birthday Park” and northern part of“Aozihdi Urban Forest Park” were the second and third with 22.5% and 20.6%, separately. Conversely, “Mincyuan Park” and“Siaogang Park”were under lower SWC which with 6.28% and 9.36%, separately. Both these two parks with insufficient water content were resulted in low growth quality to plants, like serious leaf-drop and chlorosis on lower-leaf of shrubs and critical withered of turfs. Hence, it is recommended to improve the management of water and fertilizers to enhance ornamental qualities. With regard to the street trees, the maintenance and management of growth were generally well. The questionnaire results about favorite plant layouts indicated that the No.1 layout is the parterre design under the street trees in Speed separation strip in Sihwei 3nd Rd, the No.2 is the green-belt design with colorful seasonal flowers under street trees in Jiouru 1st Rd, and the No.3 is the planting of perennial green plants under boulevard in Minzu 2nd Rd. The tree species applied in street-tree layouts in Kaohsiung city were mainly use of Alstonia scholaris and Pterocarpus indicus, others included the Cinnamomum camphora, Swietenia macrophylla, and Sterculia foetuda. These above tree species were have identical characters which were obtained easily, grew rapidly, with strong adaptation ability, and maintain/manage simply. Recent years, Kaohsiung city government promoted the “multi-layer planting” to layout the street-tree in ten major roadway in Kaohsiung city. For example, open space under street-trees were planted with almost 90% of Duranta repens cv. Golden Leaves and/or perennial Ixora williamsii, two extremities of traffic island were reinforced in layout of seasonal flowers to increase the color and bio-diversity of roadways to promote the sense of urban beauty. In part of root-damage (RD) improvement in Kaohsiung city, the RD of Cinnamomum camphora in Sihwei Rd, Mincyuan Rd, and Minsheng Rd was improved by replacement of RD trees with plants the belt; RD Fious mircocarpa in Jhongiheng Rd, RD Bombax ceiba in Lin SenRd, ChenggongRd, and Zhongxiao Rd were improved by transplanting the RD trees to the nursery of Kaohsiung city government or enlarging the original plant-hole or designing into plants the belt. After inquire about and investigate to the maintenance office of bureau of public works of Kaohsiung city government, the results indicated that the street development, like improvement of street tree and pedestrian space, will continually conducted to decrease the root damage of street from street trees.