台中港區木麻黃天然更新之研究

Natural Regeneration of Casuarina spp. At Taichung Harbor Area

現今海岸造林樹種多以生長快速之木麻黃為主，但其有壽命短且不易天然下種更新之缺點，為瞭解此問題，本試驗於台中港北堤區木麻黃防風林內，依大、中、小孔隙及鬱閉林下設置樣區，藉由調查不同孔隙內種實雨、種子庫及微環境狀況，並觀察在干擾土壤與枯枝落葉層後之變化，以釐清木麻黃天然更新所需條件。結果顯示種子庫與種實雨於孔隙間累積情形相似，以大孔隙最少量，而鬱閉林下為最大量，其種實雨落下之種子量約250seeds m^（-2）month^(-1)；種實雨之種子的發芽率以播於溫室（約40%）明顯高於孔隙地內（約11%），顯示孔隙大小不同造成林分內之微環境差異所導致。各樣區於干擾處理後並未發現木麻黃天然更新小苗，但以種子直播於干擾地並給予充足之灌溉，則可產生更新小苗（小孔隙及對照組皆有15%以上之發芽率）。綜合以上結果顯示木麻黃天然更新之主要來源為種實雨，林地枯落物之累積、雜草覆蓋及水分缺乏，為台中港區木麻黃天然更新之主要限制因子。 Casuarina spp. is the major windbreak species used to afforest in coastal regions. They grow fast, but have short life and difficult to natural regenerate. In order to dispose of this problem, we set plots in large, medium, small gap and close stands at the Northern Embankment region of Taichung Harbor. To understand the mechanism of regeneration, we surveyed gap regeneration, treatment on the litter layer, microenvironment, seed rain and seed bank in this study. The result showed that the accumulation of seed rain and seed bank were similar. The smallest values were in large-gap plots and the highest values were in control plots. The number of seed rain was about 250 seeds m^(-2) month^(-1), and the germination rate in green house (about 40%) was higher than in the field (about 11%). The result showed different gap size conducted the changes of microenvironment. There were few seedlings found in plots after disturbance. After seeding and irrigating, the germination rate in small gap and control plots can reach above 15%. In conclusion, the main source of seedlings is seed rain. In the Casuarina spp. stands, the limit factors of natural regeneration were not only litterfall and weeds, but also water deficient.

Casuarina spp. is the major windbreak species used to afforest in coastal regions. They grow fast, but have short life and difficult to natural regenerate. In order to dispose of this problem, we set plots in large, medium, small gap and close stands at the Northern Embankment region of Taichung Harbor. To understand the mechanism of regeneration, we surveyed gap regeneration, treatment on the litter layer, microenvironment, seed rain and seed bank in this study. The result showed that the accumulation of seed rain and seed bank were similar. The smallest values were in large-gap plots and the highest values were in control plots. The number of seed rain was about 250 seeds m^(-2) month^(-1), and the germination rate in green house (about 40%) was higher than in the field (about 11%). The result showed different gap size conducted the changes of microenvironment. There were few seedlings found in plots after disturbance. After seeding and irrigating, the germination rate in small gap and control plots can reach above 15%. In conclusion, the main source of seedlings is seed rain. In the Casuarina spp. stands, the limit factors of natural regeneration were not only litterfall and weeds, but also water deficient.