Characteristics of Seed Germination and Seedling Regeneration of Leucaena leucocephala

• Main Authors: Chi- Chen Lin, 林其臻
• Other Authors: Yan-Lun Kuo
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/47947821078106423878

碩士 === 國立屏東科技大學 === 森林系所 === 99 === 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.