福山試驗林三種附生植物對幹流水水質影響之探討

Abstract

幹流水是雨水進入到森林生態系的形式之一，在森林的水文生態和生物地質化學上扮演著相當重要的角色。降雨多的潮濕森林常可見大量附生植物，附生植物因無法利用土壤中的水與營養故一般認為與非附生植物相比較常遭遇水及營養的逆壓。前人研究提出附生植物透過影響著幹流水的滲流、營養吸收和釋放，從而改變幹流水中營養離子濃度。台灣巢蕨基質富含有機質，幹流水流經這類附生植物，可能會淋洗溶出營養物質，但部分營養元素也會被吸收利用，至今對於有大型基質的附生植物對於幹流水水質的影響卻鮮少有研究關注。本研究於福山試驗林比較幹流水通過有大型基質的台灣巢蕨、無大型基質的書帶蕨與長葉羊耳蒜等三種附生植物前後水質的差異。實驗結果顯示幹流水通過台灣巢蕨後離子濃度和總量、水量大多減少，且pH值降低。幹流水通過其它兩種附生植物多數離子濃度亦下降，但濃度降幅低於巢蕨，反之離子總量因水量大幅下降導致下降幅度遠大於巢蕨。由研究結果推斷，和台灣巢蕨共生的附生植物可能面臨較低的水逆壓但較高的營養逆壓，即這些附生植物要在水和營養中做取捨。Stemflow is one of the main types of precipitation input to the forest ecosystem. Stemflow plays an important role on forest ecohydrology and biogeochemistry. Many moist forests are characterized with abundant epiphytes that have no direct access of water and nutrients from the soils and as such often considered to experience water and/or nutrient stress. Some studies indicate that epiphyte affect stemflow percolation and may absorb nutrients from or leach nutrients to stemflow through which affects stemflow nutrient content. Asplenium nidus (nest fern) has a large substrate that rich in nutrient. Stemflow through this large substrate may release or uptake nutrient. However, few studies examined the effects of epiphytes that is have a large substrate on stemflow chemistry. In Fushan Experimental Forest (FEF) we use three kinds of epiphytes nest fern(large substrate), Haplopteris flexuosa Fee, Liparis nakaharai Hayata to compare the effects to stemflow chemical. The results show that the stemflow ion flux, concentration, water flux and pH are lower after passing through the nest fern. The decrease of ion concentration through small epiphytes was lower than nest fern. But the flux that nest fern decrease is fewer than small epiphytes. Epiphytes that form symbiotic relationship with nest fern may have lower water stress but higher nutrient stress. That means epiphytes have trade-off between water and nutrient.