The Research Of Tree-ringδ~13cazimuth Variation Rules And Causes For Pinus Thunbergii And Other Conifers In Tashan Mountain, Shandong Province

Taking Tashan, a branch of Mengshan Mountain, which is located in Fei County,Shandong Province as the area and the tree-ring carbon isotope ratio(δ^13C)of Pinusthunbergii and P.tabulaeformis, which are growing in the slope of east, south, west and north, asthe proxy of case study, we analyze the tree ringδ^13C azimuth distribution and the regularpattern of the spatial-temporal variation ofδ^13C extremum of different slopes in turn. We alsoprobe into the causes of tree ringδ^13C azimuth distribution. The main contents and conclusionsare as follows:Firstly, we have compared the difference of azimuth extremum, average and inter-annualchanges ofδ^13C sequences from each slope. As a result, the amount level of tree ringδ^13Cazimuth variation is similar to that of inter-annual variation, and the study of tree ringδ^13Cazimuth variation and inter-annual variation are equally important. Variance analysis werecarried out forδ^13C value sequences of each azimuth in each slope, and the result indicates thatthe azimuth change ofδ^13C values in Tashan mountain are significantly different at differentlevels: 0.01 level for the east, south and north slope and 0.05 level for the west slope. Theextremum ofδ^13C for different aspects in each slope is not synchronous, but is lead-lag for 2 or3 years. Similarly, the azimuth of tree-ringδ^13C extremum emergence is not immobile, butchanges with the variation of site slope and year. As the slope changes from east side to southside, the most likely aspect for extreme values emergence of tree ringδ^13C turns 90°clockwisecorrespondingly. And then with the slope turns to west side, the most likely aspect turns 180°clockwise correspondingly. As the slope changes from west side to north side, the most likelyaspect for maximum and minimum value turns 270°and 90°clockwise respectively.Secondly, correlations between tree ringδ^13C series of four aspects for each slope, as wellas between theirδ^13C high-frequency sequence and climate factors, such as monthly meantemperature, monthly extreme maximum temperature, monthly extreme minimum temperature, monthly rainfall, monthly time of sunlight and average annual evaporation have been analyzed,and qualitative analysis to various factors that may lead to changes in tree ringδ^13C azimuthdistribution, such as the mixed number of tree ring cores, solar radiation changes in differentdirections of canopy, soil and ambient humidity, soil nutrients in different slope, wind speed anddirection, atmospheric CO2concentration and itsδ^13C and the combined effects of allecological factors, have been carried out. At last, we draw a conclusion that the regionalenvironmental factors impacting on tree ringδ^13C azimuth variation of different slopes aresimilar, and the difference of different slopes is the determining factor for the variation of treeringδ^13C azimuth distribution. In addition, the differences of sunshine time and intensity indifferent directions of canopy, the differences of slope position and their impact on water andnutrient are main factors. Furthermore, the mixed number of tree ring cores is also veryimportant.