臺灣中部塔塔加地區臺灣雲杉老熟林樹液流特性

Sap Flux Characteristics of Old-growth Taiwan Spruce(Picea morrisonicola Hayata)in Tataka Region, Central Taiwan

蔡孜奕(Zi-Yi Tsai)

指導教授 ： 關秉宗

共同指導教授 ： 久米朋宣(Tomonori Kume)

國立臺灣大學/生物資源暨農學院/森林環境暨資源學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.01951

摘要

林木水分利用是森林生態系水循環中一個重要的途徑，亦可影響植物之光合作用及蒸散作用狀況。臺灣雲杉（Picea morrisonicola）為雲杉屬中分布於最南端之樹種，為瞭解其水分利用狀況，本實驗於臺灣中部塔塔加鞍部選擇3株樣木，從2010年4月至2012年3月進行樹液流監測，探究（1）不同樹幹方位（東、西、南及北側）及邊材深度對樹液流速之影響；（2）水蒸氣壓差對於林木整體樹液流之影響及（3）樹幹底層與頂層之樹液流遲滯時間及儲存水利用情形。
本研究結果顯示：
(1)樹幹東側之樹液流速最大，西側則最小，東側約為西側之1.5-3.6倍，因此若僅以單側樹液流速估算樣木樹液流量會造成約19-52 %之差異。
(2)樹液流速隨邊材深度增加而減少之幅度不明顯，自邊材深度0-2 cm處到深度4-6 cm處有先降後升之現象，使不同邊材深度估算之樣木樹液流量差異普遍在10 %以內。
(3)臺灣雲杉於春季時月均樹液流速為1.33-2.87 cm3m-2s-1，夏季時為1.01-2.85 cm3m-2s-1，冬季為0.44-0.92 cm3m-2s-1，夏季流速最大值可達16.25 cm3m-2s-1。
(4)樹液流速與水蒸氣壓差之關係為一飽和曲線，藉由非線性混合效應模式分析擬合三株樣木白晝平均樹液流速與白晝平均水蒸氣壓差之結果，可知白晝平均水蒸氣壓差達0.43 kPa時，白晝平均樹液流速即達飽和(10.74 cm3m-2s-1)。
(5)時間遲滯方面，經交叉相關函數分析後，底層樹液流較頂層樹液流晚約0-30分鐘。
(6)樣木於夏季每日平均水分消耗量為7.86-12.34 kg，冬季每日平均消耗量為4.7-7.26 kg。
由上述結果做討論比較，塔塔加鞍部臺灣雲杉樹液流在樹幹不同方位之變異較不同邊材深度變異大，且每日蒸散之水分與同處於雲霧帶之鴛鴦湖臺灣扁柏（Chamaecyparis obtusa var. formosana）相當。同株林木樹幹兩高度間之樹液流遲滯時間與每日水分消耗量較某些溫帶針葉樹種少。

關鍵字

塔塔加鞍部 ； 臺灣雲杉 ； 樹液流 ； 水蒸氣壓差 ； 儲存水 ； 時間遲滯

並列摘要

Tree water usage is an important component in forest ecosystem’s water cycle, and is related to plant photosynthesis and transpiration. The main objective of this study is to understand the water usage characteristics of Taiwan spruce (Picea morrisonicola), the southernmost distributed species of the genus. The sap fluxes at different stem heights, directions, and sapwood depths of three Taiwan spruces located in the Tatachia area of central Taiwan were monitored from April, 2010 to March, 2012. This study also examined how temperature, solar radiation, and vapor pressure deficit (VPD) influenced the species sap fluxes.
The results showed that:
(1) The east side had the highest sap flux density, whereas the west had the lowest. The east side sap flux density was 1.5-3.6 times larger than that of west side. Thus, the overall sap flux density would be under-estimated by 19-52 % if based only on the west-side measurements.
(2) Minor differences in sap flux density at different sapwood depths were found. Thus, the overall sap flux density would be over-estimated by less than 10% if based solely on the outermost sapwood area measurements.
(3) The monthly average of daily sap flux density was about 1.33-2.87 cm3m-2s-1 in spring, 1.01-2.85 cm3m-2s-1 in summer, and 0.44-0.92 cm3m-2s-1 in winter. In summer, the sap flux density could reach upto 16 cm3m-2s-1.
(4) The relationship between the mean daytime sap flux density and the mean daytime VPD resembled a 1st-order asymptotic curve. Based on a nonlinear mixed-effects modeling approach, the mean daytime sap flux density would reach a mean saturation value of 10.74 cm3m-2s-1, when the mean daytime VPD reaches 0.43 kPa.
(5) Based on cross-correlation function analysis, the sap flux time lag between the basal part and the canopy was about 0-30 minutes.
(6) Based on the diurnal changes in sap flux density measured in the basal part and the canopy, the average daily water consumption was about 7.86-12.34 kg in summer, and about 4.7-7.26 kg in winter.
Overall, the variations in aspects were highter than in sapwood depths for Taiwan spruce. Compared to the previously documented results for the conifer species located in the temperate regions, the monitored Taiwan spruces consumed less water and had less lagged time between different stem heights, even with larger diameters and taller heights.

並列關鍵字

Tatachia area ； Taiwan spruce ； sap flow ； vapor pressure deficit ； storage water ； time lag

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