Seasonal changes of physiological and biochemical characteristics of four shrub species in Chaiwopu Lakeshore desert area of Xinjiang, China.

We investigated the physiological characteristics of four shrub species in the coastal desert area of Chaiwopu Lake in spring (May), summer (July), and autumn (September), including Calligonum junceum, Zygophyllum xanthoxylum, Caragana leucophloea, and Caragana roborovskyias. The results showed that from spring to autumn, leaf moisture content of all the four species showed a decreasing trend, while the water saturation deficit showed an increasing trend. The activity of superoxide dismutase, proline, and soluble protein content all showed a trend of first increasing and then decreasing, indicating that all the four shrub species could enhance their adaptation to arid environments by regulating antioxidant and osmotic regulation systems. In summer, the activities of superoxide dismutase and catalase in C. leucophloea were significantly higher than those in the other three species. The increase in soluble protein and soluble sugar content was the highest, 2.1 and 3.7 times that of spring, respectively, reflecting the relatively strong antioxidant and osmotic regulation abilities of C. leucophloea. From spring to summer, the abscisic acid levels of all the four species significantly increased. Among them, the abscisic acid levels of C. leucophloea and C. roborovskyi increased significantly, by 4.0 and 5.9 times, respectively compared to spring, indicating a more pronounced activation of their stress response mechanisms. Compared with spring, the non-structural carbohydrate content of C. leucophloea and C. roborovskyi significantly increased in summer, with higher total chlorophyll content, indicating stronger carbon assimilation. The total chlorophyll content of C. junceum and Z. xanthoxylum in summer increased by 1.2 and 1.7 times respectively, while the content of soluble sugars, non-structural carbohydrates, and starch significantly decreased, indicating that carbon budget of these two shrubs was limited, with carbon consumption greater than carbon supply. In summary, the four desert shrubs in the study area could respond to and adapt to changes in natural habitats through osmotic and antioxidant regulation systems. Their drought resistance was ranked in the order of C. leucophloea > C. roborovskyi > C. junceum > Z. xanthoxylum. Two species of Caragana plants (C. leucophloea and C. roborovskyi) could be used as the preferred dominant shrubs for ecological restoration in the Chaiwopu lakeside desert area.