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標題: 惠蓀林場三種原生樹種木質部水勢及養分分析研究
Analysis of Xylem Sap and Xylem Water Potential of Three Native Tree Species in Hui-Sun Experiment Forest
作者: 李苑瑋
Li, Yuan-Wei
關鍵字: xylem water potential;木質部水勢;xylem sap;木質部汁液
出版社: 森林學系

The purposes of this study were to investigate the variation of both xylem water potential and xylem sap of Schima superba var. superba, Michelia compressa var. formosana and Cinnamomum kanehirai at the native tree species area in Hui-Sun experiment forest from June 2004 to April 2005. The result showed that the xylem water potential fluctuation had its regularity in the diurnal change. The predawn xylem water potential of the three tree species was all the highest before dawn, and all the lowest at noon. The variations in xylem water potential during a day were apparently related to environment factors, particularly to the relative humidity factor. The dynamic relationship between the rates of water loss and uptake depended on plant water status. In the three tree species, the minimum of xylem water potential was -1.65MPa, of Schima superba var. superba at noon. It indicated that Schima superba var. superba had better ability on water uptake and drought resistant than Michelia compressa var. formosana and Cinnamomum kanehirai had.
The xylem water potential, season, species phenology of plant and soil chemistry influencing on the ion concentrations in xylem sap were discussed. From the analysis of the anion and cation concentrations in xylem sap, we found that the xylem sap nutrient concentration at noon were higher than those in the morning. Xylem sap nutrient concentrations in drought season were lower than in wet season. When leaf emergence or bloom, xylem sap nutrient concentrations also increased, especially to Michelia compressa var. formosana. In the plant growth period, xylem sap provided more information on tree nutrient status than either soil extracts or foliar analyses. Therefore, xylem sap analysis not only provided plant and soil nutrient balance, but also to indicate the degree of tree water stress and stored energy.
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