| The warm temperate semi-humid monsoon climate zone Tashan forest, Fei County, south of Shandong, were selected as study area. The Pinus thunbergii Parl tree-ring stable carbon isotope ratio (513C) were taken as the study object. Through analysing tree rings sequence of different components, different directions and different aspects, we choose the optimal sequences to analyse the response mechanism of atmospheric CO2, climate factors, ENSO phenomenon and district levels of drought. The main environmental elements were tried to reconstructed. Results showed:Through analysis of the average sequence of tree rings513C, the fact that atmospheric CO2concentration increase and the stable carbon isotope ratio decrease since the industrial revolution on decades of scale were find. However, tree rings stable carbon isotope ratio (513C) has an abnormal rising trend since1976, which may be because that the cumulative effect of atmospheric CO2led to the instability of the CO2exchange between atmosphere and ocean.The influence of atmospheric CO2was removed, and the high frequency part of tree ring513C were extracted. The correlation analysis between the sample513C series and meteorological indices were performed. The tree rings513C series and temperature were presented a positive correlation, and that between tree rings513C series and precipitation and sunshine duration were presented a negative correlation seperately. There was a lagging effect of the influence of temperature, precipitation and sunshine duration on tree rings513C to some extent,namely tree ring513C can record the climate change in winter. The correlation of continuous temperature and precipitation are much better than that with a single month, which indicated that the influencing process is a long-term accumulation process. Monthly average temperature in winter and spring season has an extremely remarkable influence on tree rings513C, which can be considered as an indicator of the climate. Power spectrum analysis showed that tree ring δ13C has obvious cycles since1940, the sequence contained7.83a,3.13a～3.13a,2.68a～2.61a quasi-periodic oscillation. Among them,2.68a through the reliability test level of99%, the rest of the cycle through the reliability test level of95%. These few cycle recorded by tree ring δ13C sequence may be associated with the change of the el nino.3.13a～3.03a,2.68a～2.61a also may be associated with tropical atmosphere "quasi two years oscillation (QBO).The multiple regression was analysed, it was find that the significant contribution factor to tree ring δ13C are mainly the average temperature in winter and spring season and6-8months total sunshine, using monadic linear regression equation to rebuild the average temperature of winter and spring season (i.e., December last year to that year May) nearly70years. Analysis also showed that the rebuilded temperature sequence has an obvious rising trend alternately. |
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