Study on the Natural Regeneration by Self-Sown Seeds in Mature Casuarina spp. Stands

試驗主要目的是探討衰老之木麻黃林分實施天然下種更新的可行性。試驗地設在雲林縣四湖海岸木麻黃純林，試驗方法除在現場設置樣區外，部分試驗則於實驗室完成。試驗結果（1）清除地表枯落物的樣區，可發現萌發大量小苗，二年後還是可以保留部分幼苗的生長；（2）林地不同光照強度會影響小苗的生長，以相對光度約40%最適宜更新小苗的生長；（3）林地土壤雖不會影響種子的發芽率，但會延長發芽時間。經本試驗結果，我們認為利用天然下種更新以維持林分是絕對可行的，惟適時移除林地枯落物，以提高成苗率，是天然下種更新成功的關鍵。Casuarina spp. is an important tree species of coastal forest in Taiwan. This species is more quickly senescent under the most stressful environment. The aim of this experiment is to focus on how to regeneration those aging stands by self-sown seeds. During two years study, we not only established plots in the field but also designed control treatment in the laboratory. The results we got (1) there are many seedlings in the plots where the litter was moved, and still having some healthful seedlings after two years; (2) the survival rate and growth of seedlings were affected by light. In the stand, the seedlings grown under 40% of relative light intensity can get the best height growth; (3) although the seed germination rate was not affected by soil, but the germination speed was lagged. Our results provide evidence that future Casuarina spp. regeneration could use natural regeneration by self-sown seeds, but the key point is to move ground litter in time