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 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Diurnal Dynamics of Stand Transpiration and Stomatal Conductance in Rubber (Hevea brasilliensis Muell. Arg.)) ผู้เขียน: Sumit KUNJET, Philippe Thaler, Frederic Gay, บุญธิดา โฆษิตทรัพย์, Pisamai Chuntuma,  ดร.กุมุท สังขศิลา, รองศาสตราจารย์ , ดร.พูนพิภพ เกษมทรัพย์, รองศาสตราจารย์ สื่อสิ่งพิมพ์:pdf AbstractTranspiration at the leaf and stand level is mainly controlled by climatic conditions. The diurnal dynamics of stand transpiration and stomatal conductance were analyzed in rubber trees. The experiment was conducted using 13 yr-old rubber trees from clone RRIM 600 under natural conditions at the Chachoengsao Rubber Research Center during January to December 2007, with sampling in the dry season, the rainy season and early in the dry season. At the stand level, the stand transpiration was monitored using sap fl ow measurement and estimated evapotranspiration from meteorological data. At the leaf level, the stomatal conductance was measured using a portable photosynthesis system on the leaves exposed to the sun. The leaf water potential was measured using a pressure chamber and the soil water content was measured by the gravimetric method. Climatic measurements were recorded using a weather station above the canopy. The plant water status was correlated with the climatic conditions and soil water content. The diurnal dynamics of stand transpiration and stomatal conductance were mainly controlled by the vapor pressure defi cit and net radiation. The stomatal conductance was more sensitive to climatic variations than stand transpiration. There were different time lags between the stomatal conductance and stand transpiration throughout the year. The relationship between the climatic factors and transpiration varied throughout the year. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Modeling for Radial Distribution of Sap Flow in Rubber (Hevea brasiliensis Muell. Arg.) Trees) ผู้เขียน:Sumit KUNJET, Philippe Thaler, Pisamai Chuntuma, ดร.กุมุท สังขศิลา, รองศาสตราจารย์, ดร.พูนพิภพ เกษมทรัพย์, รองศาสตราจารย์ สื่อสิ่งพิมพ์:pdf AbstractThis research improved the model for the radial distribution of the sap flux density in rubber trees. The objective of the study was to describe the radial variability of xylem sap flux in rubber trunks. The experiment was conducted in mature rubber trees aged 13 yr from clone RRIM 600, in a non-traditional planting area at the Chachoengsao Rubber Research Center from January to December 2007. The sap flow was measured by the heat dissipation method using home-made radial probes and then calibrated with the cut stems of rubber tree in the laboratory. The radial variability was modeled as a function of the depth into the xylem. Regression analysis was carried out using data on the sap flux density and depth into the xylem. The model used two basic assumptions: (1) young xylem (0–4 cm) has the maximum sap flux density and is stable and (2) sap flux density decreases linearly with the depth into the xylem (and thus older xylem) toward the center of the stem. The results showed that the model for radial distribution can be used to predict the sap flux density and to estimate the tree transpiration of different trunk diameters in rubber trees. The tree transpiration was highly variable with different girths of the rubber trees. |
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