[Water sources of Nitraria sibirica and response to precipitation in two desert habitats].

Nitraria sibirica usually exists in a form of nebkhas, and has strong ecological adaptability. The plant species has distinctive function for wind prevention and sand fixation, and resistance drought and salt. However, the water condition is still a limiting factor for the plant survival and development. In order to understand the water use strategy of the plant in different desert habitats, we selected the N. sibirica growing in sandy desert habitat and gravel desert habitat to study the seaso-nal variation of plant water sources and response to precipitation at the edge of the oasis of Linze in the Hexi Corridor. We measured the oxygen stable isotope of the plant stem water and the different potential water sources (precipitation, soil water and ground water), and used the IsoSource model to calculate the proportion of water sources from the potential water. The results showed that there were significant seasonal variation characteristics of δO value and water source of stem water for the plant in the two habitats. In the sandy habitat, the plant used more ground water in the less precipitation seasons including spring and fall, and more than 50% of the water sources absorbed from ground water. However, under the condition of gravel habitat, the plant could not achieve the ground water level depth of 11.5 m, and its water source was controlled by precipitation, which had large seasonal variability. The water sources of N. sibirica had significant responses to the change of precipitation in the two desert habitats. Following the rapid decrease of soil water content after the precipitation events, the plant in the sandy habitat turned to use the abundant ground water as the main sources of water, while the plant in the gravel habitat only used the less water from precipita-tion infiltration to the deep soil. Therefore, different water use strategies of the plant in the two habitats were the main reason for the difference in growth characteristics, and it had a strong ability of self-adjustment and adaptation.