溪頭地區六種台灣原生闊葉樹種葉部特性及昆蟲植食程度之研究

Abstract

本研究自2009年4月24日至11月28日在台大實驗林溪頭苗圃進行，針對6種台灣原生闊葉樹種(紅楠、青剛櫟、烏心石、櫸木、楓香及無患子)3到4年生之苗木進行施肥及遮蔭處理，以破壞性取樣及連續性調查了解不同演替階段樹種間葉面積損失率(量化昆蟲植食程度)及葉部特性的反應，探討葉面積損失率及葉部特性間的關係。 葉面積損失率在樹種間有顯著差異，可依樹種的演替階段作區隔。演替初期樹種(櫸木、楓香、無患子)的葉面積損失率較高，演替晚期樹種(紅楠、青剛櫟、烏心石)較低，且演替初期樹種之葉片硬度較低、葉部氮濃度較高，而葉部總酚類濃度的變異較大，在演替階段間沒有明顯的趨勢。施肥處理會顯著提高葉片之氮濃度並降低總酚類濃度及比葉重，但對葉面積損失率沒有顯著影響。遮蔭處理下，葉部氮濃度較高，總酚類濃度、比葉重較低，而第2採樣階段的葉面積損失率顯著降低。 破壞性取樣中，僅在第1採樣階段葉面積損失率與葉部氮濃度有顯著正相關，與總酚類濃度、比葉重及葉片硬度有顯著負相關；連續性調查的最大葉面積損失率與葉部氮濃度有顯著正相關，與總酚類濃度沒有顯著相關性，與比葉重及葉片硬度有顯著負相關。葉部氮濃度與總酚類濃度呈負相關，比葉重與葉部氮濃度有負相關，與總酚類濃度在第1採樣階段有正相關。 總結而言，演替前期的物種因葉片硬度低且葉部氮濃度高，受植食損失的情況較嚴重，施肥與遮蔭處理會影響葉部特性，未來可考慮差異較大的施肥與遮蔭處理進行試驗或延長調查時間，以期更確定植食程度與葉片特性之間的關係。

From April to November, 2009, we investigated the leaf area loss (LAL, to quantify insect herbivory) and leaf traits in the seedlings of 6 native hardwood species, Machilus thunbergii, Cyclobalanopsis glauca, Michelia compressa var. formosana, Zelkova serrata, Liquidambar formosana and Sapindus mukorossii in Chitou nursery of the Experimental Forest, National Taiwan University. Fertilization and shading were applied to examine the effects of light regime and nutrient supply on these 6 species of different successional stages. Compared to the late-successional species (Mac. thunbergii, C. glauca, Mic. compressa var. formosana), the early-successional species (Z. serrata, L. formosana and S. mukorossii) were higher in LAL and leaf N and lower in leaf toughness. Leaf total phenols were also significantly different between species, but the difference was not consistent with successional stages. Fertilization had no significant effect on LAL, but resulted in higher leaf N, lower leaf total phenols, and lower leaf mass per area (LMA). Shading lowered LAL in the 2nd sampling, leaf total phenols, LMA, and toughness, but increased leaf N. There was significantly positive correlation between LAL and leaf N, and negative correlations between LAL and total phenols, LMA, and leaf toughness in the 1st sampling. In the continuous monitoring, the maximum of leaf area loss was in significantly positive correlation with leaf N, and in negative correlation with LMA and leaf toughness. There was negative correlation between leaf N and total phenols, positive correlation between LMA and leaf N, and positive correlation between LMA and total phenols in the 1st sampling stage. In conclusion, fertilization and shading treatments would affect leaf traits. The early-successional species with lower leaf toughness and higher N suffered higher loss of herbivory. The effects of fertilization and shading on herbivory were not conclusive in this relatively short-term study.