南仁山熱帶低地雨林白榕冠層及林下植物的光合作用

Photosynthesis of a Tropical Canopy Tree, Ficus benjamina, and Understory Species in a Lowland Rain Forest in Nanjenshan, Taiwan

郭耀綸(Yau-Lun Kuo)

《台灣林業科學》 15卷3期 (2000/09) Pp. 351-363

https://doi.org/10.7075/TJFS.200009.0351

摘要

本研究在1995年11月至1997年2月間，測定南仁山低地雨林白榕樹冠上層、中層及林下九節木及大葉樹蘭的光合作用日變化與季節變化。白榕樹冠上層葉的光合作用率在夏季會受強光抑制，但在冬季則不會。光合作用率及氣孔導度在夏日高溫強光條件下有明顯的中午抑制現象。冬季寒流期間，在飽和光量下，光合作用率隨葉溫提高而增加。白榕樹冠上層葉瞬間最大光合作用率可達17.17μmol m^(-2)s^(-1)，一日碳收穫量平均為275mmol m^(-2)d^(-1)，換算成CO2重量為12gCO2m^(-2)d^(-1)。白榕樹冠中層葉及林下植物的光合作用率因光量低而受限制，一日碳收穫量分別為白榕上層葉的30%及7-11%。白榕上層葉一日碳收穫量的季節變化與白天總光量並無顯著相關性，但與白天平均葉溫有顯著相關。合併不同冠層葉的日變化資料，發現最大光合作用率及在上午9時所測得的光合作用率二項，與當日碳收穫量都有極顯著相關，決定係數分別為0.920及0.976。據此推測，藉上午9時短時聞的光合作用率測定值，可方便又準確的估算白榕不同冠層的一日碳收穫量。

關鍵字

一日碳收穫 ； 氣體交換 ； 最大光合作用率 ； 中午抑制 ； 熱帶森林

並列摘要

Diurnal and seasonal patterns of photosynthesis of canopy leaves of Ficus benjamina L. and 2 understory species, Psychotria rubra (Lour.) Poir and Aglaia elliptifolia Merr, were studied under natural conditions in a lowland rain forest of Nanjenshan, southern Taiwan. Measurements were conducted from November 1995 to February 1997. Photosynthetic light responses were inhibited under high Light in summer but not in winter. During hot summer days, net photosynthesis and stomatal conductance were greatly reduced at noon. During a cold period, photosynthetic rates increased as leaf temperature rose under saturated light conditions. For the upper canopy leaves of the Ficus tree, the maximum rate of photosynthesis was 17.l7μmol m^(-2)s^(-1), and the averaged daily carbon gain was 275 mmol m^(-2)d^(-1) (12g CO2 m^(-2)d^(-1)). Photosynthetic rates of both the middle canopy of Ficus and the understory species were light limited and were only 30% and 7-11%, respectively, as compared to those of the upper canopy. Seasonal patterns of daily carbon gain of the upper canopy did not significantly correlate with daily total light intensity, but had a significant correlation with diurnal mean leaf temperature. For all canopy levels combined, both the maximum rate of photosynthesis and the photosynthetic rates measured at 0900 h showed a significant correlation (r^2=0.920 and 0.976, respectively) with daily carbon gain. Due to the high correlation, it would be an easy and accurate prediction for daily carbon gain of the Picas canopy to simply measure the photosynthetic rates at 0900 h.

並列關鍵字

daily carbon gain ； gas exchange ； maximum rate of photosynthesis ； midday depression ； tropical forest