銀合歡種子發芽及小苗更新特性

Characteristics of Seed Germination and Seedling Regeneration of Leucaena leucocephala

林其臻(Chi- Chen Lin)

指導教授 ： 郭耀綸

國立屏東科技大學/農學院/森林系所/碩士(2011年)

https://doi.org/10.6346/NPUST.2011.00195

摘要

摘要
學號：M9712016
論文題目：銀合歡種子發芽及小苗更新特性 總頁數：52頁
學校名稱：國立屏東科技大學 系別：森林系
畢業時間及摘要別：九十九學年度第二學期碩士學位論文摘要
研究生：林其臻 指導教授：郭耀綸
論文摘要內容：
銀合歡為世界百大入侵物種之一，在恆春地區入侵程度極為嚴重，且形成大面積純林，為暸解銀合歡更新時所需的光環境，本研究分別將銀合歡種子及小苗置於8種不同光量條件，比較各處理間銀合歡種子的發芽率及小苗的生長量及生物量分配。此外，為暸解銀合歡在不同林分的天然更新狀況，本研究在恆春西海岸10個銀合歡林分調查土壤種子庫的銀合歡種子數量，並設樣區監測銀合歡小苗在不同月份的出生死亡動態變化。
銀合歡種子以熱水浸泡處理可縮短發芽時間，但種子若有蟲蛀其發芽率則維持約30%。於2009年10月在8種光環境下進種子發芽試驗，結果發現銀合歡種子在100%及70%的環境下發芽率分別為33.5及29.5%，顯著低於在40~0.2%相對光量下的發芽率(43.0~54.5%)。然而，在當年12月的相同試驗，卻發現以全光處理的銀合歡種子發芽率顯著高於其它7個較低光量的處理，兩個試驗結果並不一致，不同月份的溫度可能與處理時的光量有交感作用，使種子發芽率有不同的表現，另種子品質有可能為影響之原因之一。銀合歡小苗的遮陰試驗結果，發現低於相對光量20%的環境，小苗的存活率降低，在0.2%的極低光條件小苗2個月即全部死亡。銀合歡小苗在70%光量處理有顯著較高的苗高、地徑及全株生物量，全光處理的銀合歡小苗形體生長並非最大，低於40%光量的小苗生長亦不利。
在恆春西海岸10處銀合歡林分土壤種子庫的調查，發現土壤表層銀合歡種子密度為40~950粒m-2；土層5 cm範圍每m2可有70~1,020粒種子，兩層合計最高可有1,900粒 m-2銀合歡種子。小苗密度方面，大圓山試區銀合歡小苗密度為所有試區中最高，在2010年7月可達145株m-2，其餘9個試區皆低於40株m-2。調查期間乾雨季銀合歡小苗密度差異很大，雨季時新生苗雖可大量萌發，但到8月時小苗密度即快速降低。銀合歡新生苗數與土壤種子庫數量分析顯示具有正相關。

關鍵字

銀合歡 ； 入侵種 ； 種子發芽 ； 土壤種子庫

並列摘要

Abstract
Student ID: M9712016
Title of Thesis: Characteristics of Seed Germination and Seedling Regeneration of Leucaena leucocephala
Total Page: 52
Name of Institute: Department of Forest, National Pingtung University of Science and Technology
Graduate Date: July 8, 2011 Degree Conferred: Master
Name of student: Chi- Chen Lin Adviser: Dr. Yan-Lun Kuo
The Contents of Abstract in This Thesis:
Leucaena leucocephala is among the 100 of the World's Worst Invasive Alien Species, and its invasiveness in Hengchun is extremely severe—with large areas of pure forest being formed. In order to understand the required light conditions for L. leucocephala regeneration, seeds and seedlings of L. leucocephala were placed under 8 different light treatments, and seed germination ratio, seedling height growth and seedling biomass allocation were compared among different light treatments. In addition, to understand the natural regeneration at different stands we investigated the amount of L. leucocephala seeds in soil seed banks from 10 L. leucocephala stands along the Hengchun west coast, while sample areas were set to monitor the dynamics of seedling survival in different months.

Germination time of L. leucocephala can be reduced by soaking seeds in hot water, but if affected by worm bites the percentage of seed germination will be reduced to around 30%. Seed germination experiments were carried out in October 2009, under 8 different light treatments. Result showed that germination percentage of L. leucocephala seeds under 100% and 70% full-sun was 33.5% and 29.5%, respectively. These were significantly lower than germination percentage of 40~0.2% full-sun treatments (43.0~54.5% germination). However, same experiment carried out in December 2009 showed that full-sun condition resulted in significantly higher seed germination than the other 7 lower light treatment s. These two results contradict with each other. Possible explanations include variations in temperature of different month interact with light conditions—which affect seed germination performance—and seed quality.
From shading experiments of L. leucocephala seedlings, we found that seedling survival was lowered under 20% full-sun, and death within two months under extremely low light of 0.2%. L. leucocephala seedlings had significantly higher height, ground diameter, and biomass under 70% full-sun, whilst 100% full-sun condition didn’t produce the tallest seedlings. In addition, 40% full-sun or lower was not favorable for seedling growth.

Soil seed banks investigation in 10 L. leucocephala stands along west coast of Hengchun showed that the density of L. leucocephala seed on surface soil was 40~950 seeds per m-2; the 5 cm-thick subsoil contained 70~1,020 seeds per m-2. In total, these two soil horizons contained 1,900 L. leucocephala seeds per m-2 to the most. As for seedling density of L. leucocephala, Dayuanshan stand had the highest seedling density among all stands—145 seedlings per m-2 in July 2010—with all the other nine stands under 40 seedlings per m-2 each. There were major differences in L. leucocephala seedling density between dry and wet seasons: the seeds underwent mass sprouting during wet season, but seedling density was rapidly lower when it came to August. Results showed that there was a positive correlation between the numbers of L. leucocephala seedling and seed counts from soil seed banks.

並列關鍵字

Leucaena leucocephala ； invasive species ； seed germination ； soil seed banks

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