Abstract: To examine the effects of future rainfall change on the physiological characteristics of Sabina vulgaris, an evergreen shrub growing in the semi-arid Mu Us sandy region, a water gradient experiment was conducted at the Ordos Grassland Ecological Station in Inner Mongolia. The results showed: minimal fluorescence (Fo), variable fluorescence(Fv), Fm/Fo, Fv/Fm were not significantly affected by the water gradient, while in contrast, net photosynthesis ratio, stomatal conductance, transpiration rate, ratio of substomatal CO2 to atmospheric CO2, water use efficiency, apparent light use efficiency and apparent CO2 use efficiency were all influenced significantly by changing water status. These results indicate that while the water gradient has a significant effect on external features, such as gas exchange and resource use efficiency, it has no significant influence on the internal fluorescence features of photosynthesis system Ⅱ. The patterns of the responses of the gas exchange and resource use efficiency to water change varied with various physiological indices. Net photosynthesis rate responded most sensitively to soil water content relative to soil field capacity.

Key words: Sabina vulgaris seedlings, Semi-arid sandy region, Chlorophyll fluorescence, Gas exchange, Resource