臺灣屏東地區欖仁、印度紫檀人工林樹液流特性之研究

Characteristics of Sap Flow in Terminalia catappa and Pterocarpus indicus Plantation in Pingtung, Taiwan

徐唯恩(Wei-En Hsu)

指導教授 ： 王亞男

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(2014年)

https://doi.org/10.6342/NTU.2014.02840

摘要

本研究應用樹液流法探討台灣屏東地區欖仁與印度紫檀的蒸散特性，已有許多研究報告指出樹液流在林木個體內的空間分布差異將造成以樹液流估算個體蒸散量時產生誤差。因此，本試驗在台灣屏東萬隆農場平地造林地自2013年9月至2014年8月配合環境因子監測進行為期一年的樹液流量測，配合環境因子監測，目的在了解兩樹種 (1) 樹液流速率日變化與季節變化的主要影響因子。(2) 樹幹不同方位樹液流變異的情形及 (3) 樹液流變異情形在推算個體蒸散量時造成的影響。
　　研究結果顯示：年均樹液流速率欖仁 (4.77 cm h-1) 與印度紫檀 (4.81 cm h-1) 相近，兩樹種均呈現明顯的季節性變化，濕季 (5-9月) 時樹液流速率較快；乾季時樹液流速率較慢，且欖仁與印度紫檀林地土壤水分降低至15%、13% 以下時，土壤水分成為兩樹種蒸散作用的限制因子。兩樹種於季節間蒸散特性不同，印度紫檀在7-11月樹液流速率較欖仁快；欖仁在2-4月間樹液流速率較印度紫檀快速。環境因子中以飽和蒸氣壓差為影響兩樹種樹液流日變化最重要的影響因子，淨輻射值與溫度次之，土壤水分與風速影響較小。而除了環境因子外，欖仁及印度紫檀的葉面積變化同為樹液流速率的重要影響因子。
樹液流速率在樹幹不同方位存在顯著差異，但並無某一方位明顯較快或較慢的趨勢，欖仁四個方位的樹液流變異係數介於15-19% (平均16.6%)；印度紫檀為10-30% (平均19.5%)。若忽略樹液流在樹幹不同方位的變異在欖仁、印度紫檀蒸散量推估時，將分別產生17.3%、15.7%的誤差。將樹幹不同方位的樹液探針樣本數從1支增加為2或3支時，推算欖仁蒸散量誤差分別下降了6.4%、5.1%；印度紫檀為7%、3.5%，由此可知不同樹種最適合的樹液探針樣本數可能不同。

關鍵字

蒸散作用 ； 樹液流 ； 平地造林 ； 欖仁 ； 印度紫檀

並列摘要

The main purpose of this study was to measure the seasonal change of sap flow on the transpiration rate in two tree species (Terminalia catappa and Pterocarpus indicus) at Wanlong Farm in Pingtung. Nowadays, sap flow measurement could be the robust technique for measuring the transpiration of individual tree-scale. However, previous studies reported that significant spatial variations in sap flow within-tree would increase the difficulties to estimate the transpiration of individual tree. This study was conducted from September of 2013 to August of 2014, in order to (1) clarify the main factor which effect sap flow velocity (V), (2) examine the azimuthal variations in sap flow, and (3) determine the impact of azimuthal variation on the tree-scale transpiration estimations (ET).
The average annual rate of sap flow in T. catappa (4.77 cm h-1) and P. indicus (4.81 cm h-1) were similar, and there is a significant seasonal variation. For both species, V was faster in wet season (May to September). Soil moisture content during the dry season was lower than that in the wet season. We inferred that soil moisture was the most important limiting environmental factor of T. catappa and P. indicus transpiration while the soil water content is below 15% and 13%. The two species differ in transpiration characteristic, P. indicus V was faster than the T. catappa from July to November; T. catappa V was faster than P. indicus from February to April. Among the environmental factors the saturated vapor pressure difference is the most important factor which affects the daily sap flow variation of the two species, followed by net radiation and temperature, while soil moisture content and wind speed play only a slight significant role. In addition to environmental factors, variety of LAI between two species is an important factor of V.
There was no clear pattern in the direction in which the lowest and highest V occurred in all individuals. The coefficient of variation (CV) of the sap flow velocities measured at four directions ranged from 15% to 19% (mean=16.6%) in T. catappa, while in P. indicus ranged from 10% to 30% (mean=19.5%). The experimental results showed that omitting azimuthal variations in V would effect the ET estimations by 17.3% in T. catappa, and 15.7% in P. indicus. The sample size of sap flow velocity probe which estimated the evapotranspiration increased from 1 to 2 and 3 would decrease the errors to 6.4% and 5.1%, respectively in T. catappa, and 7%, 3.5%, respectively in P. indicus. Thus, the most suitable numbers of sap flow velocity probe would vary between different species.

並列關鍵字

transpiration ； sap flow ； afforestation at the plain area ； T. catappa ； P. indicus

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