| Diurnal and monthly changes of annual shoot water potentials of dominant tree species Populus pruinosa and Populus euphratica under the different depths of groundwater level were measured by pressured chamber in desert region,Tarim,XingJing province.The results showed that diurnal and monthly changes of shoot water potential were "V" curves,the minimum value of day and year emerged in 14∶00 and August,respectively.Monthly changes of predawn and middy water potentials were "V" curves,with big change of the different month and the average water potential of months in such a order June>July>September>August.The diurnal change range of water potential and monthly change range of middy water potential of P.pruinosa were higher than that of P.euphratica and average water potentials of P.euphratica were higher than that of P.pruinosa under the different depths of groundwater level.Variance analysis showed that water potentials of two tree species were not significance,but it was extreme significance among the different depths of groundwater level.The osmotic potential at turgor loss point(Ψ0),maxium osmotic potential at water saturation point(Ψ100),relative content of apoplastic water(AWC) and relative osmotic water loss(Ψ100-Ψ0)of P-V water parameters of P.euphratica were lower than that of P.pruinosa and relative osmotic water content at turgor loss point(ROWC),relative water content at turgor loss point(RWC) and osmotic adjustment ability(VP/V0) were higher than that of P.euphratica,all above indicated that two dominant tree species adopted different physiological ecology strategy to adapt desert drought environment in the long time.The average,predawn and middy water potential decreased gradually with declining of depths of groundwater level,the depths of groundwater level effected directly water potential of trees. |