Abstract:Legumes are important pioneer species in arid ecosystems such as deserts, and are also the main source of available nitrogen in ecosystems. In order to clarify the relationship between desert legumes and habitat soil factors, this study took Astragalus flexus and Astragalus arpilobus as materials, which are widely distributed in the Gurbantunggut Desert. The physicochemical properties of different soil depths (0-5, 5-10, 10-15 cm) were measured, and the relationship between the stoichiometric characteristics and soil factors of the two desert legumes was compared and analyzed. The results showed that: (1) the carbon (C), nitrogen (N) and phosphorus (P) contents of A. flexus were 373.35, 25.66 and 1.03 mg·g-1, respectively, which were higher than those of A. arpilobus, 331.53, 19.59, and 0.66 mg·g-1, and the contents of N and P were significantly different (P<0.05); the C∶P and N∶P of A. flexus were 374.38 and 25.75, respectively, which were significantly higher than those of A. arpilobus, 166.09 and 10.12 (P<0.01), while the C∶N of A. flexus (14.62) was lower than that of A. arpilobus (16.99), but there was no significant difference in C and C∶N between the two plants. (2) The organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents of the legume habitat soil in the 0-5 cm soil layer were the highest, and gradually decreased with the deepening of the soil layer; the soil stoichiometric ratio SOC∶TN and SOC∶TP increased gradually with the deepening of the soil layer, while the value of TN∶TP gradually decreased with the deepening of the soil layer; the lower N content and TN∶TP indicated that the soil in this area belonged to the type of N deficiency. (3) The correlation between the two desert legumes and the soil stoichiometric characteristics at different levels was not consistent, among which: there was a negative correlation between TN and N∶P, and a very significant negative correlation between TP and P. And there was a positive correlation between TP and C∶N, and a very significant positive correlation between SOC∶TN and N∶P in 0-10 cm soil layer of A. flexus. In soil layers 10-15 cm, there was a positive correlation between SOC∶TN and N∶P. Only P in A. arpilobus had a very significant positive correlation with the SOC∶TP in the 0-5 cm soil layer, while most of the stoichiometric characteristics showed no correlation. (4) There was a very positive correlation between the phytostoichiometric index P of A. flexus and the electrical conductivity (EC) in the 5-10 cm soil layer, there was a positive correlation between the available potassium (AK) and N in the 10-15 cm soil layer. The A. arpilobus was negatively correlated with available phosphorus (AP) and N, AP and N∶P in 0-5 cm soil layer, but not with other soil layers. The research showed that the soil N content and TN∶TP ratio in the Gurbantunggut Desert were relatively low, the soil N element was poor, and the nutrient content of the leguminous soil in this area was generally low; the main limiting element for the growth of A. flexus in this area was P, The main limiting elements for the growth of A. arpilobus were N and P; and the phytochemistry characteristics were not directly determined by soil nutrient characteristics, the significant interspecific differences showed the importance of plant genetic traits in the coupling relationship between soil and plant quantitative traits.