Cells Characteristic In Xylem Of Three Hardwood And Its Relationship With Climate In The Southern Part Of Northeast China

Tree growth is affected by a variety of climatic factors.Compared with the annual tree-ring width,changes of xylem cell growth of trees have recorded more detailed climate information obtained from the cellular levels of trees and it is of great significance for the research of climatic changes on the forest ecosystem.The paper analyzes the various responses of the xylem cells of the three broad-leaved hardwoods(Fraxinus mandshurica;Juglans mandshurica;Phellodendron amurense)to the meteorological factors in NE China by the paraffin section preparation technology and micro-tree-core-sampling approach according to dendrochronology theories.We have carried out sample-taking experiments from the three broad-leaved hardwood forests in the tree sample sites established in central and southern Chang Baishan Mountain and analyzed the correlations between the anatomical parameters of the tree-rings of the three broad-leaved hardwoods and the meteorological factors together with the response analysis among them through consistently correlated analysis,investigated and clarified the various responses of the secondary xylems of the three broad-leaved hardwoods to the climatic factors in NE China.Both Fraxinus mandshurica and Phellodendron amurense belong to the ring-porous wood which are classified into early woods and late woods.Ducts of Fraxinus mandshurica(with diameter of 119.67±18.59um)are mainly concentrated in the early woods(with diameter of 267.15±24.07um)whereas those ducts of the late woods(with diameter of 46.95±7.15um)are also distributed but getting smaller(with diameter of 46.95±7.15um).Ducts of Phellodendron amurense have distributions throughout the entire tree-rings,of which the ducts in the early woods gradually become smaller(with diameter of 191.62±35.89um)whereas those ones in late woods tend to form polygon pore clusters.There are no early or late woods in Juglans wmandshurica.Its ducts are similar to those in broad-leaved diffuse-porous woods of which the ducts gradually decrease in the entirely inner tree-rings.In response to the climate changes,all the three broad-leaved hardwoods tend to reduce the number of ducts and increase the diameters of ducts in similar strategy,and reduce density of the fiber cells and latewood percentage.The experiment shows the decrease in the width of the latewood tends to reduce the width of the tree-ring for that year.There is a significantly positive correlation between the number of the duct cells of Fraxinus mandshurica with the average temperature in April,which is negatively correlated with the average temperature in May;Density of the fiber cell is significantly negatively correlated with the temperature in March and in April.There is a significantly negative correlation between the number of cell ducts in Phellodendron amurense and the mean minimum temperature in March,April and the temperature in September;There are apparently some negative correlations between the density of its fiber and the minimum temperature in March,April and May whereas there is an obviously negative correlation with the temperature and precipitation in September.It's apparent that the number of duct cells of Juglans mandshurica are negatively correlated wth the mean minimum temperatures in March,April,May and the temperature in September as well as its density of fiber cells with the mean temperature,minimum temperature in February and the maximum temperature in September.Among the three tree species,there are much more significantly negative correlations(p<0.05)between the characteristics of xylems in Fraxinus mandshurica and monthly PDSI,but an apparently positive correlation(p<0.05)between those in Phellodendron amurense and monthly PDSI whereas there is no any significant correlation between the cell characteristics of xylems of Juglans mandshurica and the monthly PDSI.All the anatomic parameters of tree-ring of Phellodendron amurense are suitable for the reconstruction of PDSI while those parameters of Juglans mandshurica are much more suitable for the climate reconstruction with the temperature as the limiting factor because it's affected by the temperature.