人工林之多目標經營模式研究(5/5) Studies on the models of sustainable management for plantations (5/5)

處在21世紀，生態環境和天然林之保護為當前之趨勢，因此，天然林將繼續禁伐，在此環境下，永續與集約經營人工林，透過多元化育林或撫育等策略，變成為重要課題。長伐期林業經營目標是將人工林延長伐期，即由目標樹之選育，並透過一系列多元化育林撫育措施（如選擇疏伐、塊狀伐採、天然更新和人工促進天然更新及撫育等），同時將人為的干擾降低到最小，並且不影響森林的結構和景觀，使同齡純林逐步接近天然的複層異齡混交林，即近自然林，並且要求林地上持續地有林冠覆蓋，且不斷的有木材收穫，培育大徑高品質及高價目標樹，做為終伐收穫之標的。因此，此永續經營之森林將達到社會、文化、生態和經濟需求之平衡。本計畫已完成六龜試驗林45年生之香杉、台灣杉，及蓮華池57年生台灣肖楠人工林長伐期目標樹、干擾樹、生態樹、一般樹之標訂，及干擾樹之砍伐，並和傳統之下層疏伐及未疏伐之對照區進行比較分析。結果顯示。林下地被植物在疏伐作業過後並未顯現明顯影響，喬木天然更新方面，疏伐作業初期確實對於林下天然更新的小樹造成破壞，但疏伐後新增加之空間產生了極大量的天然更新小樹，數量遠大於疏伐作業所造成的小樹之損害。
To reach 21th century, the protection of ecological environments and conservation of natural forests are the current trend on the earth. Therefore, the ban of natural forest cut is still a continuing tendency. Under the circumstance, it is important that sustainable and intensitiving management of man-made forests through a breeding desired trees and a series of alternative silvicultural tending strategies (such as dispersed thinning, tree selection, aggregated (gap or cluster) cutting, natural regeneration and planting or tending) to approach the long-term rotation plantation management that is to establish multi-stories and uneven aged, mixed-species plantations to reach sustainable forestry. In the meantime, reduces the disturbed manipulations to minimum, furthermore, uneffect the forest structure and landscapes. And pure even-aged plantations were gradually transformed into natural multi-stories and uneven aged mixed-species forest i.e. close to natural forest. Those forests are claimed to maintain that can produce wood sustainability and continuous cover forestry. Moreover, the breeding target trees can possess big diameter, good quality and high value will be harvested at the extended rotations. Therefore, that sustainable forest could balance social, cultural, ecological and economic needs. This study was conducted in Luanta-fir (Cunninghamia konishii Hayata), Taiwania (Taiwania cryptomerioides Hayata), 45-yr-old and Taiwan Incense-cedar (Calocedrus formosana), 57-yr-old plantations located at the Lioukuei and Lienhuachih research centers in southern and central Taiwan, respectively. The stands have finished marking 4 parts, such as, target trees, disturbed trees, ecologic trees and general trees, The long-term target trees area, the general thinning from below area, and unthinned area (control) were established to compare and analyize the difference among growth, structure and diversity.The results showed that there were no significant effect ground-layer vegetation after thinned area. The natural regeneration trees, which were damaged by thinned operations at first, but promote large amount of natural regenerated trees because of increasing spaces after thinned. Therefore, the numbers of natural regeneration trees have more than that of mortally by thinned operation. There were no difference between long-term trees area and the general thinning from below area.