Relationship between process of sap flow of P.tabulaeformis and solar radiation

In order to investigate the relationship between time processes of solar radiation and sap flow systematically,sap flow velocity(SFV) of P.tabulaeformis and effective solar radiation(ESR) were synchronously monitored for one year in Beijing western mountains by using TDP systems(TDP30) and automatic weather station.Results showed that significant differences were found between changes of time characters of ESR and sap flow of P.tabulaeformis in sunny days of different seasons.Starting time,peak time and stopping time of sap flow were generally 03 h later than that of solar radiation while the lagged times were much longer in spring with more than 3.5 h.Duration times of sap flow showed obvious differences among different seasons that well regularity was not appeared.There exist a good quantitative correlation between time process characters(duration time of rising and falling,rising rate and peak time) of ESR and P.tabulaeformis sap flow in summer,while only the single character express a good correlation in spring and autumn.Seasonal models of sap flow velocity indicated that,it was more practical to simulate seasonal water consumption models of P.tabulaeformis from ESR especially in autumn.Furthermore,these models should be optimized later.