Comparative study on eco-physiological characteristics and their effects on soil water between Sophara viciifolia and Caragana korshinskii

Systematic study on eco-physiological characteristics of Sophara viciifolia (growth, photosynthesis and transpiration and water potential) and their effects on soil water was carried out for the first time, taking Caragana korshinskii - one of the local shrub with a good drought tolerance and adaptability distributed widely in the Loess Plateau - as a control. The main results are as follows: 1) the average of net photosynthetic rate of S.viciifolia during June to September is equal to that of C. korshinskii(5.12 μmol/(m²·s)), its transpiration rate(2.28 mmol/(m²·s))is 30% lower than that of C. korshinskii, its photosynthetic production has a close relationship to the amount of soil water; 2)S. viciifolia has a better drought adaptability than the C. korshinskii and it is one of promising forestation trees for the following three reasons: the water potential in branches of S. viciifolia(2.19 MPa) is higher than that of C. korshinskii(1.7 MPa), and its water potential in branches is always lower than that of C. korshinskii in the whole year; the monthly average water use efficiency (WUE) of S. viciifolia(0.002 3 g/g) is 26.1% higher than that of C. korshinskii(0.001 7 g/g), and, its leaves and biomass above ground are higher than those of C. korshinskii at the same level of evapotranspiration. S. viciifolia has a strong ability of using the deep soil water, however, the soil water in the 10 m deep soil profile does not change obviously during the two growing seasons, which shows its growth balance with local rainfall.