以臺灣赤楊種子直播進行武陵廢耕地造林之探索性研究

Exploratory research on direct seeding of Alnus formosana for reforestation of abandoned farmlands in Wuling

在退化的武陵廢耕地以臺灣赤楊實施復原造林是極為必要的，不僅可促進演替後期樹種之建立，也有助於改善土壤理化性質與養分，然臺灣赤楊一直無法於武陵廢耕地天然更新，為探索赤楊直播造林之可行性，本文嘗試於苗圃進行赤楊種子發芽及模擬試驗、於廢耕地進行種子直播造林試驗，結果顯示武陵廢耕地偏鹼性的土壤並非阻礙赤楊種子定殖的首要限制因子，赤楊更新的障礙並非發生於種源與散播階段，而是發生於發芽與建成階段；分析造成赤楊無法發芽或建成的定殖阻礙因素，主要包括：赤楊種子受雜草層隔離而無法觸及礦質土、土壤水分不足或不連續供應、繁茂雜草遮蔽日照，為此未來進行赤楊種子直播之研究設計可著重在選擇最適播種的時機、創造有利直播種子定殖的微環境、配合赤楊種苗之需求進行雜草控制、提升與維持土壤水分的供應。此外，本文也比較種子直播與苗木出栽之特徵與適用性，建議進行生態復育時宜採用最適方法或二者同時併用。

The reforestation of Alnus formosana in degraded Wuling abandoned farmland is vital to facilitate the recruitment of late successional tree species, improve the soil physical and chemical properties as well as nutrients. However, the natural regeneration of A. formosana was impede in Wuling abandoned farmland. To explore the feasibility of A. formosana direct seeding, we performed the germination and simulation test in the nursery, as well as direct seeding in the field. The results revealed that the alkaline abandoned soil was not the principal factor impede the colonization of A. formosana seed. Blocking of A. formosana regeneration did not occurred in the seed source and dispersal stages, but in the germination and establishment stages. The factors blocking A. formosana germination and establishment might include the separation of A. formosana seeds and mineral soil by weed litter layer, insufficient or discontinuous supply of soil moisture, and the most of sunlight shaded by flourishing weeds. This paper suggested the reforestation researches of A. formosana direct seeding in the future could focus on identifying optimal seeding timing, creating a microhabitat conducive to improve seed colonization, weed control, and enhancing and maintaining soil moisture. This paper also compared the characteristics and applicability of direct seeding and planting seedling. We suggested adopting the most suitable method or used both methods together in an ecological restoration project.