The Hydraulic Architecture Of Whole Branch And Their Parts For The Major Tree Species In The Eastern Region Of Northeast China

Water shortage has become a global problem.The hydraulic characteristics of trees are key determinants of plant competitive ability and distribution.However,a question about hydraulic conductance of whole branch and their parts(leaf blade,petiole,and leafless branch)is not well understood,especially for coniferous species.In the present study,whole branch(Kwb),leaf blades(Klb),petioles(Kp),and leafless branch(Kb)hydraulic conductances,hydraulic relative resistance(the inverse of conductance)were determined in the quasi-steady-state mode using the high pressure flow meter(HPFM)in three conifers(Pinus koraiensis Sieb.,Picea koraiensis Nakai,Larix gmelinii(Rupr.)Kuzen.)and four deciduous broadleaved tree species(Betula platyphylla Suk.,Acer mono Maxim.,Ulmus japonica(Rehd.)Sarg.,Quercus mongolica Fisch)commonly found in the eastern region of Northeast China.We analyzed hydraulic resistance distribution of the whole branch,compared hydraulic conductances within the same part of the branch among different tree species,wood properties or leaf habits,and established the relationship between hydraulic traits and wood properties or leaf habits.The main results were bellows:The branches and their parts of the seven tree species have obvious seasonal variation characteristics.The Klb for P.koraiensis Sieb.was about 4 times as much as Kwb and Kb wheareas the Klb and Kwb for the rest six species were similar,and significantly lower than those of Kb.The leaf-blade relative resistance(Rlb)in P.koraiensis Sieb.accounted for 20%of the branch total hydraulic resistance(Rwb)while the Rlb,leafless branch(Rb),and petiole(Rp)relative resistance contribution to the Rwb were more than 50%,about 20%,and less than 10%for the rest tree species,respectively.This indicates that whole branch or leaf blade with petiole could be used to measure Klb for all tree species except P.koraiensis Sieb.The Kwb were significant positively correlated with Klb or Kb while the Klb were not correlated with Kb.This indicates that the leaf and leafless branch segments have relatively independent water transport.The results of leaf area-or leaf mass-based hydraulic conductance(Klb-area and Klb-area)among the tree species with different wood types were different.The Klb-area of the non-porous species were greater than those of the diffuse-porous and ring-porous species,which the latter two functional groups showed no significant differences in Klb-area.The Klb-area of broadleaved tree species was significantly lower than that of coniferous species.No differences were found in terms of the Klb-mass among the tree species with different wood types or leaf habits.A tradeoff relationship was evident between Klb and Kb in the conifers.Klb-area and Klb-mass were positively correlated to the density and diameter of the primary leaf veins while the Klb-mass were not correlated with the diameter of the primary leaf veins.The leaf area-based hydraulic conductances were positively correlated with LMA or LDMC while the leaf mass-based hydraulic conductances were negatively correlated with LMA and LDMC.The Klb-area and Klb-mass showed a strong and a weak relationship with leaf traits,respectively.The relationship between leaf mass-based hydraulic conductance and leaf traits(LMA and LDMC)is consistent with previous research results using branches instead of leaves,so Klb-mass can faithfully reflect the relationship between leaf hydraulic conductance and leaf traits of coniferous and broad-leaved trees.The differences were observed in terms of leaf area-or sapwood area-based branch hydraulic conductance(Kwb-area and Kwb-sa)among the tree species with different woody properties.The Kwb-sa and sapwood area-based leafless branch hydraulic conductance(Kb-sa)were similar among the tree species with different woody properties and leaf habits.In addition,the correlation between branch hydraulic traits and xylem anatomy were weak.The Kb was significantly positively correlated with vessel diameter,while Kb-area and Kb-sa were significantly negatively correlated with wood density.Leafless branch hydraulic traits are suitable for studying the effects of xylem anatomy on water transport efficiency.