Response characteristics of the closed desert wetland vegetation to ecological water transport in arid regions

The population distribution of water-utilizing vegetation in arid areas, the water source of the vegetation in the seasonal banks of the terminal wetland in the arid zone, the water source of the plant, and the soil moisture content all exhibit delayed response characteristics to seasonal water delivery. After determining the plots and sample sites for the field experiment, samples of soil water, groundwater, precipitation, and vegetation stem water taken at different distances from the existing water source were analyzed for the stable isotope of deuterium oxygen. The ISOSOURCE model was used to examine the contribution rates of various water sources and provided a comprehensive analysis of how riparian vegetation (Nitraria tangutorum) responds to artificial water delivery. The characteristics of the vegetation water source vary depending on the distance between the sample plot and surface water, the effect of precipitation, the influence of supplied surface water on the soil water content of the adjacent sample plots with varying distances, and the response characteristics of the N. tangutorum communities before and after artificial water delivery. The results show that the soil water content of the N. tangutorum plots 0～200 m from the surface water decreased with the increase in distance between the plot and the surface water. The soil water content of plots 200～1 000 m from the river water did not change regardless of the distance to the water surface. Using the same sample plots, we found that the main water absorption layers of the N. tangutorum root systems before and after the rain were different, and the proportion of water absorption in deep soil decreased after precipitation. The results show that the water absorption mechanism of the N. tangutorum communities was responsive to both artificial water delivery and precipitation. As the distance between each monitored plot and the delivered surface water increased in the first year, the frequency of the N. tangutorum communities decreased in each plot. Under the influence of the cumulative artificial water delivery over many years, the species distribution area decreased, and the xerophytic vegetation community changed into a water-loving vegetation community. These findings can provide a basis for the prevention of vegetation degradation, soil desertification, and salinization in wetlands.