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 15 N 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 15 N‐NO 3 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 15 N‐Glycine in April to more 15 N‐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 15 N‐NO 3 and 15 N‐NH4 over 15 N‐Gly possibly reflects adaptation to different N forms in temperate desert.