Growth and Photosynthetic Responses of Understory Saplings of Three Hardwood Species to Small Patch Thinning in a Cryptomeria Japonica Plantation

柳杉人工林林下三種闊葉稚樹生長及光合作用對小區塊疏伐的反應

郭耀綸(Yau-Lun Kuo) ； 曾繁絢(Fan-Hsuan Tseng) ； 楊月玲(Yeh-Lin Yang)

《台灣林業科學》 28卷3期 (2013/09) Pp. 113-128

https://doi.org/10.7075/TJFS.201309_28(3).0001

摘要

本研究探討台灣中部地區的柳杉人工林，在疏伐後的三處不同光環境下，琉球雞屎樹、山龍眼及細枝柃木三種闊葉樹稚樹的生長及生理表現。三處環境包括疏伐孔隙區、疏伐林分的非孔隙區及未疏伐林分的對照區。此三種稚樹在上述三處環境白天分別可接受到約27、15及4%的相對光量。山龍眼及細枝柃木在光量較高的孔隙及非孔隙兩區，其光飽和光合作用率均會顯著高於生長在對照區的同種植株，有明顯的生理馴化表現，而琉球雞屎樹則無此表現。藉由一年12次的光合作用日變化測定，得知細枝柃木及山龍眼生長於孔隙及非孔隙兩區的植株，光合作用日變化年平均值皆顯著高於對照區的同種植株。相反的，琉球雞屎樹該數值在三處環境間則無顯著差異。這三種樹種所有植株的光合作用日變化年平均值，與各植株接受到的光量間，都有極顯著直線正相關，但山龍眼該迴歸式的斜率最高。山龍眼在孔隙區植株，葉綠素螢光反應Fv／Fm值在0.75以上，未遭光抑制，而琉球雞屎樹在該環境則會遭輕微光抑制。疏伐後一年，在孔隙區樹高相對生長率最大的是山龍眼，而葉面積相對生長率最大的是細枝柃木。山龍眼與細枝柃木所有植株的樹高及葉面積相對生長率，與各植株接受到的光量間，均具有極顯著直線正相關，而琉球雞屎樹則否。本研究發現此三種植物雖然都是耐陰的樹種，但山龍眼及細枝柃木在生理上有馴化高光的能力，在疏伐形成的孔隙環境不易遭光抑制，且較能有效利用疏伐後提高的光資源，提高光合作用率，因而有較高的相對生長率。琉球雞屎樹在生理不具馴化高光能力，在孔隙環境不能顯著增加生長。

關鍵字

馴化 ； 光合作用日變化 ； 光環境 ； 光抑制 ； 相對生長率

並列摘要

The growth and photosynthetic responses to different light environments created with small patch thinning in a Cryptomeria japonica plantation in central Taiwan of 3 hardwood species, Lasianthus fordii Hance, Eurya loquaiana Dunn., and Helicia formosana Hemsl., were investigated. Three different light environments included a gap site in a thinned stand, a non-gap site next to the gap site, and an unthinned control site. The respective average light intensities received by understory saplings were 27, 15, and 4% of full sunlight in the gap, non-gap, and control sites. For H. formosana and E. loquaiana, the light-saturated photosynthetic rates (Asat) were all significantly higher in the gap and non-gap sites than in the control site, showing obvious physiological acclimation. This acclimation was not detected in saplings of L. fordii. For H. formosana and E. loquaiana, the mean annual diurnal photosynthetic rates (Amean) were all significantly higher in the gap and non-gap sites than in the control site, whereas for L. fordii, no significant differences in Amean were found among the 3 sites. There were significant linear relationships for all 3 species between the Amean and light intensity, with H. formosana having the highest slope. The mean chlorophyll fluorescence value (Fv/Fm) of H. formosana was ≥ 0.75 in the gap site, which indicates no sign of photoinhibition, while Fv/Fm values of L. fordii indicated mild photoinhibition in the gap and non-gap sites. One year after the thinning operation, in the gap site, H. formosana had the highest relative rate of height growth, while E. loquaiana had the highest relative rate of leaf area growth. For H. formosana and E. loquaiana, both the height and leaf area growth had significant positive relationships with light intensity. In spite of their shade-tolerance, saplings of H. formosana and E. loquaiana possessed the ability to acclimate to elevated light intensities without suffering photoinhibition. With increasing light intensities, these 2 species raised their photosynthetic rates and growth. In contrast, saplings of L. fordii did not perform as well when exposed to elevated light intensities.

並列關鍵字

acclimation ； diurnal photosynthesis ； light environments ； photoinhibition ； relative growth rate