Abstract: Aims Nitrogen is a key nutrient element for maintaining species diversity in plant communities. In nitrogen-limited desert ecosystems, it remains unclear how interspecific interactions affect nitrogen uptake rate and proportion among different functional groups of plants. Methods A field experiment was conducted in the Mau Us Sandy Land, northern China, with two treatments: removal of Artemisia ordosica and a control retaining A. ordosica. The uptake rate and proportion of nitrate nitrogen, ammonium nitrogen, and glycine by three functional groups of herbaceous plants (annual herbaceous, perennial grasses, and perennial forbs) and the overall herbaceous community, were measured using 15N isotope labeling. Environmental factors such as soil ammonium nitrogen, nitrate nitrogen, total nitrogen, soluble organic nitrogen content, soil moisture, and plot light were determined. The relationships between nitrogen uptake rate, proportion, and environmental factors for each functional group and the herbaceous community were also analyzed. Important findings Inorganic nitrogen and micromolecular organic nitrogen were effective nitrogen sources for herbaceous plants in A. ordosica community. The nitrogen proportion of herbaceous plants followed the order: nitrate nitrogen, ammonium nitrogen, and micromolecule organic nitrogen. After the removal of A. ordosica, the nitrogen uptake rate of annual herbaceous, perennial grasses, and the overall herbaceous community increased by 48.32%, 129.77%, and 55.53%, respectively, with perennial grasses showing a 10.65% increase in nitrate nitrogen uptake proportion. A. ordosica affected the nitrogen uptake rate of herbaceous plants by altering the microenvironment, particularly by reducing plot light and soil nitrate nitrogen content. Nitrogen uptake rate and proportion among different functional groups of herbaceous plants were influenced by various environmental factors, and perennial grasses demonstrating flexible nitrogen source plasticity and higher nitrogen use efficiency. The study showed that the differentiated nitrogen acquisition strategies of herbaceous plants may be a crucial mechanism underlying that herbaceous plants in A. ordosica community coped with interspecific nitrogen competition and resource scarcity, thereby enhancing community stability and resilience. Perennial grasses, with flexible nitrogen source utilization and efficient absorption capabilities, may gradually become the dominant functional group with community succession. These findings may enhance the understanding of nutrient competition and species coexistence mechanisms in the typical sand-fixed community, which would provide scientific evidence for vegetation restoration and management in desertificated areas.

Key words: plant-plant interaction, Artemisia ordosica, nitrogen uptake rate, nitrogen uptake proportion, Mau Us Sandy Land