Measurement and modelling of rainfall partitioning by deciduous Potentilla fruticosa shrub on the Qinghai-Tibet Plateau, China

Abstract. Rainfall partitioning is a key process of ecosystem water cycle which has not get enough attention in the alpine deciduous shrub. Moreover，there is no apposite analytical model that suits to estimate the rainfall redistribution of the deciduous shrub with great changes in coverage and leaf storage capacity due to foliation and defoliation. Field and laboratory experiments to assess these processes and to determine vegetation and atmospheric parameters were established for deciduous Potentilla fruticosa shrub on the Qinghai-Tibet Plateau. Based on the experimental data, a variable parameter Gash model especially for deciduous shrub rainfall partitioning which is adapted from the revised Gash model was developed to represent these processes. The performance of the variable parameters Gash model in modelling the rainfall partitioning of the deciduous shrub patches is better than that of the original model. The variable parameters Gash model treated the water captured by the stem as that captured by leaf canopy considering the low height of shrub and its low coverage in leafless period. Thus, the model developed here were perfect to represent the rainfall partitioning processes. It was found that the interception, throughfall and stemflow accounted for 21.44 %, 29.26 % and 49.30 % of gross rainfall in the shrub patches during the growing season of 2012, respectively. 42.6 % of the interception was loss by evaporation from the saturated leaf canopy during rainfall events. The results indicate that adaptations of the analytical model in this paper improved its performance and provide hypotheses more near the realities in the deciduous shrub.