Abstract: Background, aim, and scope Radiation research is essential for better understanding past climate change,and in various climatic factors,the amount of radiation is also an important indicator of the growth of trees. However,so far involving the tree-ring data and radiation changes in the research results are still relatively rare. Tree-rings have been considered as one of the best known archives in the past climate research field with their strong continuity,high resolution and easy access to duplicate features. In our study,we used the Chinese pine tree (Pinus tabulaeformis Carr.) from Mt. Xinglong in north-central China. Materials and methods Employing the standard methods sponsored by the International Tree-Ring Data Bank (ITRDB),we collected 44 tree cores from 22 trees in Mt. Xinglong (103°50′—104°10′E,35°38′—35°58′N,annual average radiation is 5122 MJ/m2)during November,2016. In the laboratory,the standard dendrochronological processes were employed,and the ring-widths of each core were measured with a precision of 0.001 mm. After cross-dating,the COFECHA program was used to control the quality of cross-dating. Three tree ring chronologies (STD,RES and ARS chronologies) were carried out with the ARSTAN program. To clarify the climatic conditions in our study area,the total annual radiation data from 1960 to 2016 were extracted from the Yuzhong station (104.15ºE,35.87 ºN,1875 m a.s.l.). We compared the tree-ring widths and the total annual radiation,used Pearson correlation analyses to preliminary to identify their relationship. We also explored the change of the tree-ring chronology and total radiation over time by using the sliding correlation analysis. Based on the correlation analysis,we use multivariate regression analysis to establish the conversion equation of the annual total radiation of the STD chronology. And use the conversion equation to reconstruct the annual total radiation from 1640 to 2015 in the historical period. Results In the sliding correlation analysis,the sliding window is chosen for 11 years. Since the solar sunspot activity period is 11 years,if the sunspots are relatively large,the sun activity will be more intense,the radiation sunshine hours and the solar radiation all will be increase. Therefore,the sliding correlation coefficient calculated by the 11-year sliding window can better represent the effect of radiation intensity on tree-ring width. During the study year, the correlation coefficient r (r0 = 0.338,p <0.01,n = 57) between tree-ring width and annual radiation in the region from 1960 to 2016 was tested by the confidence degree <0.01,indicating that the total annual radiation and the tree-ring width have a more significant positive correlation. The sliding correlation coefficient shows that the relationship between tree-ring width and total annual radiation is always positive correlation between 1970 and 2016. Among them,the positive correlation in 1970—1991 reached the significance level of 0.05,and the positive correlation between them was significant. It shows that the change of total annual solar radiation is always the main part of the variation of tree-ring width. From 1992 to 2016, the sliding correlation coefficient between the two tends to fluctuate between 0.3—0.5,fluctuating within this range and tends to be stable. The results showed that the factors influencing the radial growth of the width of Pinus tabulaeformis Carr. trees became more complicated. However, its relationship with the change of annual total radiation reached a steady state. It is of great significance to indicate the change of the annual total radiation of Pinus tabulaeformis Carr. trees in this region. Using multivariate regression technique to reconstruct the history of the change of annual total radiation in the study area from 1640 to 2015. During the past 376 years,the annual total amount of radiation showed significant inter-annual fluctuations. There are times below average during the reconstruction period: 1646—1668,1705—1727,1739—1751,1758—1774,1832—1846,1856—1875,1923—1944,1984—2010; There are higher periods: 1683—1704,1728—1738,1752—1757,1775—1812, 1876—1922,1945—1983.The rest of the year's values are close to the average. At the same time, there is a high frequency of extremes, of which 70 were very high and 68 were very low, accounting for 18.67% and 18.04% of the total period (1640-2016) respectively. Discussion During the study year,the relationship between tree-ring width and total annual radiation was always positively correlated. The growth of Pinus tabulaeformis Carr. was more sensitive to the change of total annual radiation. From a physiological point of view,in a certain range of radiation intensity,adequate light to make the heat required for tree growth conditions are met,will promote the plant photosynthesis,is conducive to the accumulation of organic matter,while ensuring the growth of consumption. For the next year to reserve part of the nutrients,so easy to form a wide ring. At the same time, the total annual solar radiation can affect the radial growth of trees by affecting the temperature and precipitation on the earth. According to the geographical location and climate characteristics of Xinglong Mountain, Xinglong Mountain is located in the east, the most western end of the monsoon region, the boundary between semi-arid and semi-humid areas, which is a temperate and semi-humid climate. Water is the main limiting factor of plant growth in this area. When the amount of precipitation is constant, if the amount of solar radiation increases, it will accelerate the evaporation of water and reduce the soil water content, thus limiting the normal growth of plants. In addition, changes in the total annual solar radiation will cause changes in temperature, in addition to direct changes in temperature affect photosynthesis, but also indirectly adjust the plant's respiratory and transpiration, Therefore, It also has an impact on the physical activity of trees. Therefore, the width of tree rings can truly record the favorable or unfavorable changes of solar radiation to its growth, and reflect the change of total annual solar radiation. Conclusions The tree-ring width chronology of Mt. Xinglong can indicate the change in the total amount of annual radiation in the region for a period of 1970—2016. The radial growth of Pinus tabulaeformis Carr. is more sensitive to the change of total annual radiation. It is further indicated that the tree chrono chronology has a certain significance to the total annual radiation in the study area. According to the reconstruction results in the study area from 1640 to 2015,during the past 376 years,the annual total amount of radiation showed significant inter-annual fluctuations. And there are times below average during the reconstruction period: 1646—1668,1705—1727,1739—1751,1758—1774,1832—1846,1856—1875,1923—1944,1984—2010;There are higher periods: 1683—1704,1728—1738,1752—1757,1775—1812, 1876—1922,1945—1983. The rest of the year's values are close to the average. At the same time, there is a high frequency of extremes, of which 70 were very high and 68 were very low, accounting for 18.67% and 18.04% of the total period (1640—2016) respectively. Recommendations and perspectives Due to the shortage of historical data related to annual radiation in this study area. Therefore,historical records can not be used to corroborate the reliability of this paper. Therefore, the future research on radiation in the history of the region is still very necessary.
Keywords: Xinglong Mountain; Pinus tabulaeformis Carr.; The tree ring width; The total annual solar radiation reconstruction; Correlation