關刀溪森林生態系干擾地更新之研究

Abstract

關刀溪森林生態系位於南投縣惠蓀林場第三林班，主要之植群組成為 原生及次生闊葉林，森林資源豐富。各種天然及人為之干擾均曾發生過， 干擾後之更新演替過程，受到天然下種、林下種子庫以及微環境的影響。 本研究探討關刀溪森林生態系經干擾後之更新情形。 於1995年11月 至1997年4月間，就關刀溪森林生態系之火燒地、崩坍地及其他人為干擾 地，設定永久樣區，調查植群的變化，並對干擾地之主要適存植物，如臺 灣二葉松、臺灣五葉松、蘇鐵蕨等標定座標，進行長期監測，而土壤中的 種子庫也同時進行研究。環境因子之測定方面，包括坡度、坡向、氣溫、 光度、相對濕度及土壤酸鹼度等。 干擾地樣區之植群調查結果，採用 Motyka之相似性指數公式，計算兩兩樣區間的相似性指數，並據以進行群 團分析作成樹形圖。各樣區間之相似性指數都在30%以下，小出山廢耕地 與小出山廢棄林道之相似性指數為29.04%，吊橋廢棄林道與木荷火燒跡地 之相似性指數為29.00%。干擾地樣區之植群以草本植物為主，隨季節而有 明顯的消長。唯其可改變干擾地的微環境，使更適合演替較後期植群的生 育。 臺灣二葉松及臺灣五葉松於火燒後大量下種，小苗之發芽及死亡 與水分有關。火燒跡地的臺灣二葉松只在火燒後初期的一兩年大量下種， 建立族群，之後便少有新苗出現；而崩坍地的臺灣二葉松，天然下種的年 期較長，但每年只有少數能夠存活下來。顯示不同的干擾地環境，植物有 不同的更新模式。 非干擾地林下土壤種子庫之發芽測試，總共鑑定 出60種植物，其種子來源較多元化，組成比較複雜，平均發芽數量 為26,579株/m2*5cm ，喬木及灌木的數量佔47.8%。干擾地之種子庫組成 主要為草本植物，發芽測試有50種小苗出現，平均發芽數量為256157株/ m2*5cm ，其中99%以上為草本植物。

The composition and development of forest vegetation are affected byvarious factors. Disturbances create various sizes of canopy gap and changevegetational succession process. Sampling plots were set up at burned sites, landslide sites and the other disturbed sites in Guandanshi forestecosystem. The plant composition and the development of well-adapted plants, sush as Pinus taiwanesis , Pinus morrisonicola and Brainea insignis ,were investigated. The seed banks of the sampling areas were also studied.The environmental factors , including temperature , relative humidity ,light intensity, and soil pH value , were also monitored. Employing the data of vegetational composition at each plot , wecalculated the Motyka similarity index of every plot pair and constructedthe dendrogram by cluster analysis. All similarity coefficients are lowerthan 30%. It indicates that those disturbed areas are all at the earlystage of secondary succession. Following a fire , many seedlings of Pinus taiwanesis and Pinusmorrisonicola occurred. Their germination and survival were affected bysoil water content. Different disturbed sites may show differentregeneration strategies. The seed banks of the undisturbed forests consisted of 60 species. Themean density of seedlings was 26,579 seedlings/m2(5cm in which 47.8% werewoody species. The seed banks of disturbed sites consisted of 50 species.The mean density of the seedlings was 256,156 seedlings/ m2(5cm in which99% were herbaceous species.