عنوان مقاله [English]
نویسنده [English]چکیده [English]
Background and objectives: During recent few decades several denderoclimatological studies have been done in different places of the world and researches using denderoclimatology methods extracted the climatic related information from the tree ring and reconstructed past climatic variations. The purpose of this study was to investigate the potential of Siberian elm wood (zelkova carpinifolia) in reconstruction of precipitation and temperature using tree ring width and vessel lumen area chronologies.
Materials and methods: In this study we built zelkova carpinifolia ring width and vessel lumen area chronologies. We extracted 20 cores from intact trees using Swedish increment borer. After preparation the samples were scanned using a 4800 dpi scanner. After scanning ring width and vessel lumen area was measured by image j software. Afterwards ring width and vessel lumen area time series was drowning by Excel software. Standardization of time series was performed by Fritts method (1976). Chronologies characteristics including mean sensitivity, first autocorrelation, express population signal and GLK coefficient was calculated. Correlation coefficient was calculated between ring width and vessel lumen area indexes and neighboring meteorological station precipitation and temperature data. We used Ramian meteorological station data. It was 5 kilometers far from Dland Park. Variations with the most important correlations were used for temperature and precipitation reconstruction. Reconstruction performed by split – sample calibration verification method. For testing validity of reconstruction we used sign test and reduction of error (RE) statistics.
Results: Correlation coefficients analysis indicated that at seasonal scales ring width was significantly, positively correlated with previous year spring and fall precipitation and vessel lumen area was correlated with previous year autumn precipitation. About temperature the only important correlation was observed in August month. Ring width and vessel lumen area were negatively correlated with previous year August temperature. The validity of reconstruction by sign test and reduction of error statistics indicated that reconstruction of previous year spring precipitation using ring width variation and reconstruction of previous year fall precipitation by vessel lumen area variation in this region is successful, but reconstruction of temperature was not successful.
Conclusion: It seems that at low elevation reconstruction of precipitation by ring width and vessel lumen area variation is successful but reconstruction of temperature perhaps needs other tree ring variable such as maximum late wood density or late wood ring width. Also at this region the effect of previous year climatic conditions on ring width and vessel lumen area is more important than current year climatic conditions.