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GLIWICE RADIOCARBON LABORATORYCarbon isotopes in tree-ringsTREE RINGS MEASUREMENT IN GLIWICE TREE RINGS LABORATORYTrees are the perfect material for isotopic measurements of the environmental changes. In temperate climate the trees growth in one year cycle (Robertson and Waterhouse 1998), produce two kind of wood in single year. The first kind produced in spring and early summer is called earlywood. The second one is latewood which is produced in summer and autumn. The differences between these two kinds of wood are recognized for each species of tree individually but generally the earlywood has a lower density and higher width than latewood. The most popular tree species used for isotopic investigations are: pine (Pinus Sylvestris), oak (Quercus Robur L.) and fir (Abies). In the case of pine all single year growth (earlywood and latewood) represents the isotopic record in given calendar year. It is possible because isotopic record in single year growth in pine is the average record from all calendar year. Another situation is presented in oak. The isotopic record is clearer in latewood of single year growth because of vegetation period. The oak possesses leafs in the vegetation period only and pine has needles all the year. As we know trees in vegetation period need a light, water, oxygen and atmospheric CO2 for photosynthesis process and finally for growth. The trees make a possibility of environment changes monitoring by measurements of the isotope ratios of hydrogen, oxygen, carbon, nitrogen, sulfur and others. Of course we must prepare the tree for isotopic research. In first step the tree trunk is dendrochronologically dated for construct the chronology of calendar years. In Gliwice Tree Rings Laboratory we used the special device LINTAB produced by Frank Rinn Company in Germany used for tree rings width measurement. Additionally the device is equipped with microscope LEICA GZ6 for observation and counting of tree rings and computer with software TSAPWin Basic 1.15b for registration of measurement results. The measurement steps: (1) moving the tree slice on the special LINTAB platform by the micrometric screw, (2) observation the single tree rings in the microscope, (3) marking each single tree growth by mouse clicking in its end, (4) preparation of dendrochronologically plots using the measurement results. Measurement precision of LINTAB device is 0,01 mm. Dendrochronologically plots should be compare with tree standards for the results correction and for matching the three to the chronology (we must know the calendar years period which is represented by investigated tree). Now we can separate the single tree rings and measure the isotope ratios mentioned above by mass spectrometer. For radioactive compounds like 14C we can use the known measurement methods: GPC (Gas Proportional Counting method), LSC (Liquid Scintillation Counting method) or AMS (Accelerator Mass Spectrometry method).
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