Seasonal nitrogen uptake strategies in a temperate desert ecosystem depends on N form and plant species

• Symbiotic plants might be able to regulate a limited nitrogen (N) pool, thus avoiding and reducing competition for resources, through the uptake of different chemical N forms. Our aim was to see whether coexisting herbs showed preference for different forms of N in a temperate desert.
• We conducted a situ experiment using the ¹⁵N labeling method in the Gurbantunggut Desert of Northwestern China dominated by Erodium oxyrrhynchum, Hyalea pulchella, Nonea caspica and Lactuca undulata during their growing period (April and May).
• Four desert herb species preferentially relied on ¹⁵N‐NO₃ for their N nutrition. Multi‐factor analysis of variance (ANOVA) analysis results showed that species, N forms, months, and soil depths strongly affected N uptake rate. The uptake rate by herbs was higher in May than in April, and higher at 0–5 cm than at 5–15 cm soil layers. Erodium oxyrrhynchum, N. caspica and L. undulata showed different preference on N form over months. Erodium oxyrrhynchum and L. undulata changed their uptake preference from more ¹⁵N‐Glycine in April to more ¹⁵N‐NH4 in May.
• Although the N uptake rate of four desert herbs varied across different soil depths and months, all species absorbed more inorganic N compared with organic N. The higher preference for ¹⁵N‐NO₃ and ¹⁵N‐NH4 over ¹⁵N‐Gly possibly reflects adaptation to different N forms in temperate desert.