| The marginal distribution of species is very sensitive to climate change.The plantation ecosystem of Pinus tabulaeformis,a special species in China,is more vulnerable to the threat of climate change.Based on the P.tabulaeformis as the research object and using the method of dendrochronology,the paper has measured the ring width of 1227 trees,this included 2552 cores from 55 sampling sites in the north of the distribution of P.tabulaeformis.And negative index and linear fitting were used to de-trending and standardization,to understand the growth of P.tabulaeformis under different climate gradients,the P.tabulaeformis plantation growth situation and the response of climate factors to P.tabulaeformis,and to discuss the suitable climate region of P.tabulaeformis growth.Finally,three kinds of standardized chronologies(STD;ring chronologies(RW),earlywood chronologies(EW)and latewood chronologies(LW))were developed.Each of which were 50.The STD and BAI was used to study the(radial)growth changes of P.tabulaeformis,and combine temperature,precipitation,and vapor pressure difference(VPD)to analyze the response of P.tabulaeformis growth and climatic factors in different climate backgrounds.The main results are as follows:(1)The study found the quality of all chronologies could reach the study standard of dendrochronology.The three kinds of chronologies had relatively consistent regularity.The mean sensitivity and standard in the middle east of Inner Mongolia which was relatively arid was less than that in the northeast and the north of north China which was moist.It could be seen that there was a strong correlation between each type of 50 chronologies,and the correlation of the ring width chronologies and earlywood chronologies was stronger than that of latewood chronologies.(2)There were local differences in radial growth of trees.The proportion of the decline in the northern region was much larger than that in the southern region.The radial growth of trees indicated by BAI showed an upward trend in 86% sampling sites.The drier areas of central Inner Mongolia and most of western Liaoning had lower average BAI,which was not good for tree growth.And the wetter areas of south of Chengde and northeast China had larger average BAI,which was beneficial to the growth of trees.(3)The correlation between RW,EW and climate factors was similar: Precipitation in April,May,June and July was beneficial for EW and RW.And the correlation coefficients of EW and RW with precipitation.Temperatures from May to July were not conducive to the growth of EW and RW,and VPD from March to July was not conducive to the growth of EW and RW.Moreover,the correlation coefficient between temperature and VPD of EW and RW at most sampling points in these months was less than-0.38(p<0.05).LW was relatively less sensitive to climatic factors.Only the combination of the main growing season(May-July)of precipitation,temperature and VPD could significantly affect the growth of LW: The effect was the same as that of RW and EW: Precipitation was good for LW growth,and temperature and VPD were not good for LW growth.(4)The response of EW and RW to climate factors showed a spatial gradient change in early spring(March and April)in the study area(p<0.05),and the response of LW to climate factors in the late growth season(after August)showed a spatial gradient(p<0.05).And with the increase of spatial precipitation and the decrease of VPD in the main growing season,precipitation could promote the growth of trees.With the increase of spatial temperature in the study area,temperature could inhibit the growth of trees.Therefore,the drought stress caused by rising temperature in the study area was the main reason to restrict the growth of P.tabulaeformis.In the future,the P.tabulaeformis in arid regions may decline with climate change,and there were suitable planting areas.There was a trend of regional movement in northeast China and south of Chengde,Hebei with better water and heat conditions.. |
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