台灣原生或本地植物做為農田綠籬之可行性評估

Abstract

綠籬(hedgerow or hedge)，又稱田籬，是指由人為在耕地邊緣或農路兩側將各種樹木或灌木以條狀且成排的方式種植，包括其植冠下方之草本植物所組成之帶狀植物群，用以劃分農田邊界及圈養牲畜。綠籬在自然環境保育、生物多樣性之復育以及鄉村休閒景觀等方面皆可做為轉型至生態系統服務型農業最好的載體與指標。本研究挑選19種台灣原生或本地種灌木，種植於國立台灣大學農業試驗場水稻田周圍，觀察並記錄其生長狀況、外觀型態以及開花期等性狀，用以評估是否適合作為農田綠籬；同時於其中挑選六種植株木質化程度較發達之樹種種植於單筒滲漏計中進行試驗，透過植株之生物量及土壤有機碳含量評估各樹種碳封存之能力；另外，將19種灌木之地上部萃取液進行發芽試驗，以評估各植物中是否具有相剋物質。經過1年之田間觀察結果顯示，各植物之植冠高度隨著時間的推移而增長，但部分植物之生長速度受到季節影響，且植株於冬季之生長速度及生長勢普遍優於夏季，大部分植物花期皆集中於1-6月，且花期多持續2-3個月；僅少數植物其花期在夏季或冬季。各植物之土壤有機碳量含量並未相差太多，多在28 g kg -1上下，土壤有機碳於各土層中之含量皆大致呈現由上層表土往下層底土遞減之趨勢，大部分10 cm土層之有機碳含量皆顯著高於其他土層，各植物每年每株可固定之CO2介於0.19-0.56 kg之間，以每平方公尺15株之種植密度換算，每年可固定28.5-84.0 t CO2 ha-1。19種植物之不同濃度地上部萃取液在發芽試驗中種子之生長並無明顯隨著萃取液濃度之增加而被抑制，各植物萃取液中總酚含量之高低與種子發芽試驗中之各參數並無絕對之關聯性。期望透過本試驗挑選出符合台灣農田環境且耕作便利之綠籬樹種，增加農民種植意願，以期達到友善耕作，推廣生態農業之目標。

Hedge or hedgerow is any kind of trees or shrubs planted in linear pattern on the edge of fields or on the both sides of the country road. Hedge included herbaceous plants under canopy of trees or shrubs. The main purposes of hedge are built the boundaries of farmland and confinement rearing livestock. For the ecosystem service, hedge is one of the indicators for natural environment conservation, biodiversity remediation and rural area landscape. In this study, nineteen shrubs origin from Taiwan or local varieties planted in Taiwan were chosen and planted on the edges of rice paddy field of National Taiwan University Farm, Taipei, Taiwan. Several plant parameters (ex. growth, morphology and flowering date, etc.) of these shrubs were measured to assess the suitability of being hedge of field. Furthermore, six shrubs plants with highly lignified traits were chosen and planted in the roll infiltrator to measure their biomass and the content of soil organic carbon to evaluate the ability of carbon sequestration of these shrubs. In addition, the aboveground plant tissue extractions of these nineteen shrubs were tested in germination bioassay to assess inhibition ability. After a year of field survey, the height of these nineteen shrubs increased with time, but the growth rate of some of shrubs affected by season which plants would growth faster in winter than summer. The flowering time of most hedge plants are from January to June and last for two to three months. Only a few have flowering in summer or winter. There is no significant of soil organic carbon content within six shrubs plants which contain approximately 28 g kg-1 across species. The soil organic carbon content of these shrubs plants is decreasing with depth. The 10 cm soil layer of organic carbon content is significantly higher than other layers. Each shrub plant could fix 0.19-0.56 kg of CO2 every year. With the density of 15 plants per square meter, 28.5-84.0 tons of CO2 per hectare could be fixed. For the germination bioassay, there is no positive correlation for the inhibition ability with concertation of plant tissue extracted. In addition, there is no correlation between total phenol content of plant tissue extraction with germination bioassay. The main purpose of this study is to find the shrubs plants suitable for the field management in Taiwan which would increase planting willingness for farmers and further achieve the concept of ecological agriculture.