Correlation between Non-Structural Carbohydrates and C:N:P Stoichiometric Ratio of Haloxylon ammodendron under Different Water–Salt Gradients

Abstract

Growth is restricted by both water and phosphorus (P), and balancing the relationship between non−structural carbohydrates (NSCs) and carbon: nitrogen: phosphorus (C:N:P) is essential for Haloxylon ammodendron to adapt to arid habitats. The survival and growth strategies of the dominant species H. ammodendron in a desert ecosystem were examined in order to better serve the restoration of degraded ecosystems and desertification control. Three water and salt gradients (high water and high salinity, medium water and salinity, and low water and low salinity) in the Aibi Lake Reserve were selected. We analyzed the accumulation and distribution of NSCs in the assimilation branches and secondary branches of H. ammodendron and the changes in the measurement ratio characteristics of C:N:P, as well as the soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) content. The results showed that: (1) With the decrease of soil water and salt content, the basal diameter, plant height, crown area, and NSC content of H. ammodendron significantly decreased. This morphological adjustment in the aboveground part is similar to a “self thinning” behavior, aimed at reducing transpiration area and balancing carbon distribution in the body. The carbon accumulation in the body helps the H. ammodendron to resist the dual stresses of drought and salt. (2) With the decrease of water and salt content, the C content of assimilating branches increased significantly, while there was no significant change in secondary branches. However, the N and P content of both branches decreased significantly, and the N: P of both branches was greater than 16, indicating that it was mainly limited by P. (3) The NSC of the two branches was significantly negatively correlated with C, and significantly positively correlated with N and P, and there was a strong positive correlation between the assimilation branches NSC: C: P and NSC: C: P. The synthesis and accumulation of NSC of H. ammodendron were influenced by the content and relationship of C, N, and P, and the abundance of P content transported by the root system to the aboveground portion may have an important and decisive role in regulating nutrient balance and non-structural carbon dynamics.