關刀溪森林火燒後植物演替與土壤中協生性生物固氮活性之關係

Plant Succession and Root-associative Dinitrogen Fixation Activities in the Kuandaushi Forest Soils after a Fire

本試驗所選定的試區為惠蓀林場關刀溪集水區小出山山頂附近火燒區與其鄰近未火燒過之區域，以瞭解火燒對森林土壤之生物固氮活性之影響。火燒區於1995年12月經火燒後，到1997年11月已復育生長33種樹物。經根據調查火燒跡地各種植物之重要值指數﹝i樹種之重要值指數 = i樹種之相對優勢度 + i樹種之相對頻度﹞，選取重要值較高之巒大蕨、山胡椒、五節芒，與重要值較低之栗蕨，與非火燒區台灣杜鵑林之優勢植物台灣杜鵑及木荷，做為供測植物，探討不同演替階段植物與其根圈協生性生物固氮活性之關係。結果顯示：（1）森林經火燒過後，植物之根圈協生性生物固氮活性皆較非火燒區植物的根圈協生性生物固氮活性高。且在二次演替之植群復育過程中，演替初期重要值較高之巒大蕨、山胡椒、五節芒，其協生性生物固氮活性比較晚入侵火燒區重要值較低之栗蕨協生性生物固氮活性高。（2）協生性生物固氮活性與植群重要值指數之迴歸結果顯示，兩者間有顯著之相關（r=0.836*）。此結果顯示植物之協生性生物固氮活性的高低，與該植物在植群復育演替的過程中，能否取得優勢地位有著重要之關係。 A burned area and an unburned area nearby the top of SheauChu hill in the Kuandaushi forest were selected to investigate the effect of burning on the root-associative dinitrogen fixation activities in the forest soils. By November in 1997, thirty-three plant species have replanted and grown on the soil which was burned in 1995. Among those species, Pteridium aquilinum, Litsea cubeba, Miscanthus floridulus had higher importance value indices, (the importance value index of species i = the relative dominance of species i + the relative frequency of species i), and Histiopteris incisa had lower importance value. On the other hand, Rhododendron formosanum had higher importance value at unburned area. The purposes of this research were to investigate the relationship between the associative nitrogen fixation activity with the plant development during secondary succession. The result shows that root-associative dinitrogen fixation activities in burned soils were higher than unburned. During the secondary succession the associative dinitrogen fixation activities of P. aquilinum, L. cubeba, M. floridulus, which had higher important values, were higher than that in later invader such as H. incisa with lower important value. The associative dinitrogen fixation activities were significantly correlated (r = 0.836*) with the important values of the flora. This result shows that associative dinitrogen fixation activity was one of the factors that decided whether it could get vantage in the plant succession after burning.

A burned area and an unburned area nearby the top of SheauChu hill in the Kuandaushi forest were selected to investigate the effect of burning on the root-associative dinitrogen fixation activities in the forest soils. By November in 1997, thirty-three plant species have replanted and grown on the soil which was burned in 1995. Among those species, Pteridium aquilinum, Litsea cubeba, Miscanthus floridulus had higher importance value indices, (the importance value index of species i = the relative dominance of species i + the relative frequency of species i), and Histiopteris incisa had lower importance value. On the other hand, Rhododendron formosanum had higher importance value at unburned area. The purposes of this research were to investigate the relationship between the associative nitrogen fixation activity with the plant development during secondary succession. The result shows that root-associative dinitrogen fixation activities in burned soils were higher than unburned. During the secondary succession the associative dinitrogen fixation activities of P. aquilinum, L. cubeba, M. floridulus, which had higher important values, were higher than that in later invader such as H. incisa with lower important value. The associative dinitrogen fixation activities were significantly correlated (r = 0.836*) with the important values of the flora. This result shows that associative dinitrogen fixation activity was one of the factors that decided whether it could get vantage in the plant succession after burning.