Aboveground biomass and water storage allocation in alpine willow shrubs in the Qilian Mountains in China

The aboveground biomass allocation and water relations in alpine shrubs can provide useful information on analyzing their ecological and hydrological functions in alpine regions. The objectives of this study were to compare the aboveground biomass allocation, water storage ratio and distribution between foliage/woody components, and to investigate factors affecting aboveground biomass allocation and water storage ratio in alpine willow shrubs in the Qilian Mountains, China. Three experimental sites were selected along distance gradients from the riverside in the Hulu watershed in the Qilian Mountains. The foliage, woody component biomass, and water allocation of Salix cupularis Rehd. and Salix oritrepha Schneid. shrubs were measured using the selective destructive method. The results indicated that the foliage component had higher relative water and biomass storage than the woody component in the upper part of the crown in individual shrubs. However, the woody component was the major biomass and water storage component in the whole shrub level for S. cupularis and S. oritrepha. Moreover, the foliage/woody component biomass ratio decreased from the top to the basal level of shrubs. The relative water storage allocation was significantly affected by species types, but was not affected by sites and interaction between species and sites. Meanwhile, relative water storage was affected by sites as well as by interaction between sites and species type.