Xylem Anatomical Characteristics Of Main Tree Species In The East Of Northeast China And Their Response To Climate Change

The dense forest in the east of northeast is a typical region of temperate forests in China,it is very important to maintain the ecological security of northeast China and even the whole northeast Asia.The relationship between xylem formation and climate is the premise to reveal the response of trees to climate change,which is conducive to a better understanding of the macro growth-climate relationship.Under the background of climate warming,this study uses the dendroanatomic method to explore the response patterns of the xylem anatomical traits of twelve main tree species in the region to climate change,in order to provide theoretical and scientific basis for predicting the dynamics of forest vegetation,productivity and the process of community succession,and for accurately evaluating the impact of climate change on forest ecosystems.The main results are as follows:There are obvious differences in the anatomical structure of different wood species:the earlywood and latewood boundaries of the four ring-porous species are obvious,and the transition of conduit size from earlywood to latewood is rapid,especially Quercus Mongolia and Ulmus davidiana;for the semi-ring-porous of Juglans mandshurica,the early and late wood boundaries were not obvious,and the size of vessel gradually decreased from earlywood to latewood,and the transition was even;there was no early and late wood boundary in 4 diffuse-porous species,and the vessel size changed irregularly;the tracheid arrangement of 3 diffuse-porous species was regular and the characteristic transition process was clear,and early wood and latewood could be distinguished.There was a significant positive correlation between ring width(RW)and number of vessel(NV),total vessel area(TVA),and a negative correlation between RW and percentage of vessel area(PC),vessel density(VD).The TVA(water conducting structure)depends on NV rather than MVA,and determines the RW,which also verifies the Carbon-Water coupling relationship in the growth process to a certain extent.The correlation between NV and MVA or MVA and VD varies with tree species,and both positive and negative.The ring width,number of tracheid,average tracheid area and tracheid cell wall thickness of coniferous trees in the earlywood and latewood and the whole year were all positively correlated,which indicated that the tracheid formation was relatively regular in the year,even though there might be significant differences in the annual tracheid traits.Temperature plays an important role in xylem formation,followed by precipitation.Precipitation has a positive correlation with the width of different porous wood species(especially from May to July),and a negative correlation with the vessel traits(growing season);while temperature has a positive correlation with the ring width of ring-porous species and to the vessel traits(except for spring elm PC and VD),and a stronger positive correlation with the vessel traits,and a stronger positive correlation with the diffuse-porous(Tilia amurensis)RW,NV and TVA were negatively correlated with MVA,PC and VD.The response of humidity is similar to precipitation.For the three diffuse-porous species,the correlation between each index and low temperature and humidity in each season is weak and most of them are not significant.The mean tracheid area(MTA)and cell wall thickness(CWT)of Pinus koraiensis were positively correlated with precipitation and significantly correlated in most seasons.RW and number of tracheid(TN),MAT and CWT of Pinus sylvestris were significantly negative correlated with precipitation in non-growth season,and mainly negative correlated with precipitation in growth season(especially from May to July).Some anatomical features can record the climate information which is stronger or even different from the traditional ring-width,which provides a new idea for climate reconstruction.After warming up(1980s),the changes in macro and micro tree grow-climate relationship of different wood species may be related to the ’Warm-dry Phenomenon’ caused by warming.If climate warming continues or worsens,relatively speaking,the decline of non-porous tree(Pinus koraiensis)and diffuse-porous trees to climate warming may be more obvious.The trade-off between the safety and efficiency of the hydraulic transmission of the main tree species in the temperate forest in the east of northeast China is not obvious.The hydraulic strategy of"efficiency first" that the ring-porous and diffuse-porous tree species preferentially improve the hydraulic efficiency and ignore the hydraulic safety can maximize the benefits brought by global warming and CO2 fertilization;while the diffuse-porous tree species increase MVA and VD,but reduce NV hydraulic strategy,leading to TVA reduction seems to be inappropriate for the current environment.