- 期刊
棲蘭山地區柳杉人工林行列疏伐更新之研究
Regeneration Development after Row Thinning in Cryptomeria Japonica Plantations at Chi-Lan-Shan Area
摘要
本研究在棲蘭山柳杉人工林進行行列疏伐，配合栽植檜木苗、檜木種子撒播與集約整地除草處理，嘗試瞭解試區在疏伐後之更新情形與各處理作業之間的關係，以尋求最佳作業方式。試驗在2007年1月完成疏伐作業，同年4月完成操作處理，總試區面積約3ha，調查時間為2年，項目包括檜木栽植苗之生長與存活率、種子發芽率及成苗密度及天然更新數量等。初步結果認為，棲蘭山柳杉人工林行列疏伐作業，佐以檜木栽植處理，2年存活率約66~68%，可成功改變林相為檜木人工林。2種檜木栽植苗的生長表現以紅檜較佳，尤其是基徑的生長，存活率在2者之間則無顯著差異。若執行撒播作業，可成功提高檜木苗的比例，成為檜木與闊葉樹混合更新之形態，紅檜、台灣扁柏及闊葉樹苗平均密度分別為0.84、0.46及0.56(n/平方公尺)，唯分布不均勻，在經營上是個缺點。整地除草作業初步觀察對更新苗的密度無顯著效應，對後續生長及競爭是否造成影響仍需持續觀察。目前僅發現台灣扁柏小苗，可在部分蕨類植物覆蓋下存活，檜木、闊葉樹種與草生地被彼此之競爭關係尚未釐清。疏伐區之天然更新，以闊葉樹為主，平均密度高達8200株／ha，檜木及柳杉的種子則來源不足。營林者可依據經營之目的，在柳杉疏伐後採取不同的處理，以達所期望之組成。目前國內木材生產成本高，且大面積的伐採亦不可行，針對棲蘭山地區，建議以小單位行列疏伐柳杉純林後，採針闊葉混合之更新，彈性分配樹種比例，並開發闊葉樹種利用性，以提高經濟價值，可在長伐期高價檜木的林分中分散市場風險並保持伐期中間收入。
並列摘要
This study examined the development of both naturally regenerated and planted seedlings and sowed seeds of two Chamaecyparis spp. In order to select the best operation strategy, seeds and seedlings were planted after row thinning with intensive soil and weed preparation in plantated Cryptomeria japonica stand. Total thinning sites was about 3 ha; row thinning was completed in January 2007 and treatments operation was completed in April 2007. The whole experiment took two years. During this period of time, we measured the growth and survive rate of planted Cypress seedlings, germination percentage, survival rate of the seeds and all regenerated seedling density within each thinning row. The preliminary results showed that Cypress seedling had no difficulty to grow after slash row thinning of Cryptomeria plantation. The survival rate was around 66~68% over two years period after thinning. This operation success-fully changed the stand structure from Cryptomeria forest to Cypress plantation forest. We found planted seedling of Chamaecyparis formosensis has better growth performance than C. obtusa, especially in growth of collar diameter. There was no significant difference of the survival rate between two Chamaecyparis spp. We also found that if we sow seeds the Cryptomeria stand, we could increase the percentage of cypress seedling establishment and transfer the stand into a mixture stand of regenerated cypress and broadleaf trees. The densities of C. formosensis, C. obtusa and broad leaved trees of this new stand were 0.84, 0.46 and 0.56 (n/m^2). Because of this uneven distribution, it could be a weakness in management. Weeding did not affect germinated seedling density during this experimental period, but further observation was needed to ensure the impacts of weeds on seedling growth and competition currently, we only observed that some of C. obtusa and C. formosensis individuals could survive under the coverage of ferns. Detail competition among cypress, broad leaved trees and herb was still not clear. After row thinning, the recruitment of natural regeneration was dominated by broad leaf species with a density of 8200 (n/ha). Seed Source of Cypress and C. japonica was insufficient. Based on the purpose of the management, the manager can have different treatments after row thinning to meet their goals of desired species combination. Currently in Taiwan, the timber production cost is high, and it is impossible to harvest large area in Chi-Lian mountain. Here we suggested to use the row thinning silviculture in small unit and then regenerate with both conifer and broad leave mixed species. The regeneration process would focus on Cypress; accompany with proper proportion of broad leaved species. Meanwhile, we should develop new technique to improve the utility of the broad leaf species and to add economic values of them. If we do so, we could disperse the risk from those high-value but long rotation Cypress and also keep extra incomes between rotations.