雪山東峰亞高山草生地火燒後植群之回復

Vegetation Recovery after Fire of Subalpine Grassland on the East Peak of Mt. Shei

火燒是影響植物生長與植群演替的主要因子之一。雪山東峰玉山箭竹草生地於2001年發生火燒，本研究在火燒後設置10個樣區於4個不同時期進行植群調查。植物社會恢復過程中，共計調查到25科41屬43種維管束植物，蕨類商數為2.56；火燒後4個時期調查之物種數分別為27、33、32及 33種，顯示火燒後6個月，大部分的草生地植物種類即出現，而物種多樣性則隨著火燒後植群恢復時間的增加而有增加趨勢。植物種類全部為多年生植物，其中36.36%為常綠植物，63.64%植物屬於冬枯。雪山東峰草生地在火燒後約2年可回復至火燒前的植被覆蓋狀態，但植群高度回復則約須3年後才能接近火燒前之原有高度。由DCA分析結果顯示，火燒後植群演替具時序的變化，物種組成差異來自火燒干擾初期的物種消失，以及火燒後期非萌蘖種類的新增。雪山東峰玉山箭竹草生地火燒後，玉山箭竹、褐毛柳等木本植物之地上部死亡，但在火後地際再度萌蘖；臺灣冷杉稚樹不耐火燒而死亡，成株亦因樹皮燒傷而剝落，並導致生長勢逐漸衰退，然在火燒跡地邊緣未受火燒傷害的臺灣冷杉稚樹生長良好。本研究發現，玉山箭竹草生地若發生火燒則將維持其原有形相，但長期無火燒的情況下，雪山東峰草生地將緩慢恢復至本地的潛在自然植群—臺灣冷杉林。 Fire is one of the most critical factors affecting plant growth and vegetation succession. This study established 10 plots on the east peak of Mt. Shei, which burned in 2001 and investigated the post-fi re vegetation recovery of Yushania niitakayamensis grassland at four stages. A total of 43 vascular plant species were recorded at four stages with 27, 33, 32, and 33 species. The results revealed that after 6 months, most species of Y. niitakayamensis grassland occurred in the burned area, and the species diversity increased with the post-fi re time. All of the species were perennial plants, among which 36.36% were evergreen plants and 63.64% were winter-withered plants. The coverage of the grassland was rehabilitated within approximately 2 years after the fi re, whereas the recovery of the original height and appearance of the grassland required 3 years. A detrended correspondence analysis revealed that sequential changes in vegetation succession occurred after the fi re. The composition ofplant differences resulted from a decrease in species at an early stage after the fi re and an increase in species at a later stage after the fi re. The aboveground part of Salix fulvopubescens was burned after the grassland fi re, and caespitosa shoots then sprouted from the surface. The saplings of Abies kawakamii were not resistant to fi re, and the growth of adult A. kawakamii after the fi re declined. At the marginal zone of fi re, A. kawakamii saplings grew well. These phenomena confi rmed that Y. niitakayamensis grasslands subject to periodic fire remain the grassland community, whereas grasslands transform into potential natural vegetation, an A. kawakamii forest, if no fi re disturbance blocks succession.