Photosynthetic characteristics and water use efficiency of Tamarix ramosissima in shelterbelt and natural communities in south fringe of Taklamakan Desert, China.

The growth and reproduction of shelterbelt plants in arid regions is mainly limited by water availability, which can be alleviated by drip irrigation. We measured water use efficiency (WUE), leaf gas exchange and carbon isotope composition of Tamarix ramosissima in shelterbelt and natural communities in south fringe of Takelamakan Desert to investigate water use efficiency and photosynthetic properties of T. ramosissima differed in water sources. Compared to natural community, T. ramosissima in the drip irrigation community had low water potential due to irrigation and soil salinity. For natural community, T. ramosissima had lower predawn and midday water potential than other plants, indicating that T. ramosissima suffered serious water stress. The net photosynthe-tic rate (P_n), stomatal conductance (g_s), intercellular carbon dioxide concentration (C_i) and maximum photosynthesis rate (P_{n max}) of T. ramosissima in the drip irrigation community were significantly lower than that in the natural community, indicating the photosynthesis of T. ramosissima in the drip irrigation community was weaker. Compared to the natural community, T. ramosissima in the drip irrigation community had higher long-term water use efficiency, which was related to salt stress caused by irrigation. We concluded that the current irrigation model could meet the water needs of shelterbelt plants. However, the technical defects and soil salt accumulation might affect long-term stability of the shelterbelt community.