Xylem embolism characteristics and hydraulic safety risks of nine tree species in Qinling Mountains
Aims Climate warming exacerbate vulnerability of forest ecosystem in the Qinling Mountains,leading to increased forest mortality,and declined ecological function.The objectives of this study were to investigate xylem embolism vulnerability and hydraulic safety margin of nine tree species in the Qinling Mountains.Methods In this study,nine tree species of the Qinling Mountains,Betula albosinensis,Corylus ferox,Acer davidii,Acer maximowiczii,Quercus acutissima,Quercus aliena,Pinus armandii,Picea asperata and Larix principis-rupprechtii in two different forest sites,Xunyangba village in mid altitude and Pingheliang ridge in high altitude,were studied.Cochard centrifugation and Sperry centrifugation methods were used to establish vulnerability curves(VCs),which was defined as the percentage loss of hydraulic conductivity(PLC)vs.xylem water potential.The xylem maximum hydraulic conductivity(Kmax)of branches was measured by low pressure flowmeter.The midday xylem water potential(Pmd)was determined by the pressure chamber,which was used to obtain the hydraulic safety margin(HSM)to assess the risk of hydraulic failure for each tree species in natural conditions.Important findings 1)Xylem embolism vulnerability of nine species was ranked as Picea asperata＜Larix principis-rupprechtii＜Pinus armandii＜Acer davidii＜Acer maximowiczii＜Betula albosinensis＜Quercus aliena＜Corylus ferox＜Quercus acutissima.The HSM was ranked as Picea asperata＞Pinus armandii＞Acer davidii＞Acer maximowiczii＞Quercus aliena＞Larix principis-rupprechtii＞Betula albosinensis＞Corylus ferox＞Quercus acutissima.2)The six broadleaf species in the Qinling Mountains had less negative 50％PLC water potential(P50)and narrower HSM in average than the three conifer species,and therefore were under greater risk of hydraulic failure.3)The HSM of B.albosinensis,C.ferox and Q.acutissima were close to 0,which indicated an extremely high risk of xylem embolism.In conclusion,broadleaf species in Qinling Mountains had higher water transport efficiency than conifer species,in the cost of higher risk of xylem embolism and hydraulic failure.
万方数据
维普
