Coupling Relationships Of Hydraulic And Economic Traits Of Leaf-stem-root For 10 Tree Species In The Temperate Forest Of Northeastern China

Exploring co-ordinated relationships between plant hydraulics and economic traits is important in modeling carbon-water relations,understanding the mechanisms of water/carbon investments,and extending the leaf economic spectrum.Using 10 tree species[White birch(Betula platyphylla),Korean aspen(Populus davidiana),Amur linden(Tilia amiirensis),Machurian ash(Fraxinus mandshurica),Mongolian oak(Quercus mongolica),Manchurian walnut {Juglans mandshurica),Korean pine(Pinus koraiensis),Korean spruce(Picea koraiensis),Mongolian pine(Pinus sylvestris var.mongolica),Dahurian larch(Larix gmelinif)]with different phylogenetic groups(angiosperm vs.gymnosperm)in Chinese temperate forest,we measured the hydraulics,photosynthesis,nutrient and structural traits and photosynthetic resource use efficiencies of leaf,stem and root organs,which could help in exploring an integrated whole-plant co-ordinated relationships beween hydraulics and economic traits.The main results were bellows:(1)There were no significant differences in leaf hydraulics traits(TLP、π0、Kleaf_area and P501eaf)between the angiosperms and gymnosperms(P>0.05;except for Kleaf_mass).There were significant differences in stem hydraulics traits(Kss、KSL、P50stem and HV)and root hydraulics traits(Kroot and P50root),and the values of these tratis were higher in angiosperms than gymnosperms(except for HV).Kleaf mass was negatively correlated with P50leaf,and Kss was also negatively correlated with P50stem(P<0.05),while there was no significant relationship between Kroot and P50root,suggesting that trade-offs between hydraulic efficiency and safety exists in leaf and stem,but not in root.Leaf hydraulic conductance(Kleaf area and Klear_mass)was negatively linearly co-ordinated with TLP or π0(P<0.05).Among the leaf,stem and root,Kleaf area was positively correlated with Kroot(P=0.01),but there were no significant relationships between Kleaf_area and Kss,and also between Kss and Kroot.There were significant positive relationships in vulnerability to embolism among leaf,stem and root(P<0.05),and the vulnerability to embolism of root is higher than leaf and stem.The difference in vulnerability to embolism between stem and their terminal leaves is positive in gymnosperms,while the value in angiosperms is close to zero,or even negative,suggesting that vulnerability segmentation is evidently common for gymnosperms species,but not necessarily the case for angiosperms species in this region.(2)There were significant differences in leaf key economics traits between the angiosperms and gymnosperms(P<0.05),and the values of photosynthetic capacity(Amass),leaf nitrogen concentration(Nmass),specific leaf area(SLA),photosynthetic resource use efficiencies(WUEi、PNUE and PPUE)were higher in angiosperms than gymnosperms.There were no significant differences in stem density(TD)and root density(RD)between the angiosperms and gymnosperms.Amass was positively correlated with Nmass and SLA(P<0.05).SLA increased with increasing Nmass,whereas leaf density(LD)and leaf dry mass content(LDMC)decreased(P<0.01).Although TD was positively related to RD(P = 0.005),both TD and RD were unrelated to leaf key economic traits.(3)Leaf hydraulic conductance(Kleaf_mass)was positively correlated with photosynthetic rate(Amass),specific leaf area(SLA),leaf nitrogen concentration(Nmass),photosynthetic resource use efficiencies(WUEi and PNUE),suggesting co-ordinations between leaf hydraulics and economic traits.Both stem sapwood-specific hydraulic conductivity(Kss)and root embolism vulnerability(P50root)were strongly related to leaf key economic traits,suggesting that co-ordinated relationships between hydraulic and economic traits could be extended to stem and root.Principal component analysis(PCA)further revealed that co-ordinated correlations between economic and hydraulic traits among leaf,stem and root by pooling the data across the 10 species.The PCA axis 1 showed strong positive loadings for Kleaf_mass,FSS,Amass,Nmass,SLA,and photosynthetic resource use efficiencies(WUEi and PNUE),but negative loadings for LD,C/N,HV and hydraulic vulnerability(P50leaf、P50stem and P50root).The PCA axis 2 had positive loadings for root hydraulic conductivity(Kroot),but negative loadings for wood density(TD and RD).The 10 species were distributed along the axis 1.PCA results provided supports for the ’fast-slow’ economics spectrum.Species displaying the "fast" strategy tended to have higher photosynthetic rates,leaf and stem hydraulic conductivity and photosynthetic water and nutrient use efficiencies;however,they also faced a greater risk of embolism;while the "slow" strategy species showd the contraty traits.These findings indicated that plant hydraulics,economics and resource uses together play an important role in determining species ecological strategies.In addition,wood economic traits(stem density and root density)were orthogonal to leaf,stem and root traits,suggesting that the decoupled relationship between wood economic traits and leaf traits.This study quantified the variability in hydraulic and economic traits and their co-ordinated relationships in leaf,stem and root of 10 tree species with different phylogenetic groups(angiosperm vs.gymnosperm)in a Chinese northeatern temperate forest.This work not only extended the theory of ecological strategy on co-occurring temperate tree species,but also provided evidence for developing an integrated whole-plant economics spectrum,including carbon-nitrogen-water resources and leaf-stem-root hydraulic transport system,which will help revealing ecophysiological mechanisms of plant structure-functional coupling,carbon sequestration and water use.