Spatial Pattern Of Diameter Class Larix Gmelinii Radial Growth To Climate Factors Under Latitude Gradient In Daxing’an Mountains,Northeast China

The region of Daxing’an Mountains,has shown a significant warming trend since the1980 s,is one of the most sensitive areas to climate change.Larix gmelinii is a typical species in the Daxing’an Mountains,which plays an important role in maintaining climate change,increasing carbon sink,conserving water sources and soil,protect biodiversity and ecosystem service.Although the radial growth of Larix gmelinii and its regulatory factors have been systematically understood,it is unclear that the difference of the main driving factors in radial growth of different diameter class and its response to climate warming under latitude gradient In this study,tree ring samples were collected at Chaoyuan(CY,-2.9 ℃),Wue’rqihan(WQ,-4.15 ℃),Shangyangqi(SY,-4.61 ℃)and Mangui(MG,-5.25 ℃)along the latitude gradient in the north of the Daxing’an Mountains.Explored the differences of the main driving factors of tree radial growth under latitude gradient according to tree ring theoretical and method.The result show that:(1)The driving factors of Larix gmelinii radial growth are obviously different in latitude gradient.The influence of water on radial growth is stronger than that of temperature,and the temperature in summer significantly inhibits tree radial growth at SY sample site.The available water in spring and summer promotes radial growth in lower latitude region(CY,WQ and SY).Precipitation weakly promotes tree radial growth in MG.The interaction effect of climate factors intensely impacts on tree growth in higher latitude region(SY and MG).The available water is more and more important for radial growth in higher latitude regions(SY and MG)as climate warm.On the contrary,the main driving factors of tree growth changing weakly in lower latitude region(CY and WQ).(2)There are differences in chronology parameters of smaller size and larger size Larix gmelinii.Smaller diameter class and larger trees have significantly different growth trends in regions with lower latitude(CY),while the consistent trend in higher latitude regional.Both younger and older trees in lower latitude regional were promoted by summer,autumn,and winter PDSI,while the driving factors of smaller diameter class and larger trees were significantly different in latitude region.With the regional latitude decrease,the interaction effect of climate factors increasing influence on larger diameter class Larix gmelinii and decreasing influence on smaller trees.In lower latitude regionals(CY and WQ),smaller Larix gmelinii has lower resistance and higher recovery.On the contrary,there are no significant difference in the adaptability of smaller diameter class and larger trees to drought in higher latitude regionals.This study proved that available water was the main driving factor for radial growth of Larix gmelini in Daxing’an Mountains.Tree growth in higher latitude arear will face severe drought stress with the future climate warming.The growth trend of younger and larger diameter class Larix gmelinii and its main influencing factors have obvious spatial differences.With the increasingly serious extremely drought events,smaller diameter class trees may face further severe challenges than larger trees in lower latitude regionals.