Aims Seed traits are of great significance for clarifying plant population reproduction and regeneration strategies. Exploring responses of Artemisia ordosica seed traits to nitrogen and water addition can improve our understanding of desert plant community succession in the context of global change.
Methods The study was conducted based on a 8-year field water and nitrogen control experiment (2015-2022) in Mu Us Desert. A full factor interaction experiment of ambient precipitation, 20% water increase, 40% water increase and 0, 20, 60 kg N·hm−2·a−1 were carried out to determine the morphological, physiological, chemical and germination traits of A. ordosica seed. Seed germination traits under each treatment at two temperatures (25 °C/15 °C and 20 °C /10 °C) were explored by using the petri dish germination experiment and calculating the germination indexes by observing the number of seedling emergence.
Important findings (1) Nitrogen and water addition, as well as their interactions, significantly influenced A. ordosica seed morphological traits, including seed mass, length, width, curvature, volume, form coefficient and other traits. Water addition resulted in smaller seeds while nitrogen alone led to larger seeds. However, 20% water increase mitigated the effect of nitrogen increase on seed size. Conversely, with a 40% water increase, nitrogen addition caused smaller seeds. (2) Germination percentage was higher at normal temperature (25 °C /15 °C) than that at low temperature conditions (20 °C /10 °C). At low temperature, seed germination traits were more affected by water and nitrogen addition experienced by parental organisms, and when only adding 20% and 40% water, A. ordosica had higher germination percentage. (3) Under the treatments of water and nitrogen addition, the morphological traits such as seed length, width, quality jointly regulated function of dispersal and establishment while form coefficient, 2 h water absorption, germination percentage and germination speed jointly regulated ecological function of germination timing. Adding water or nitrogen alone tent to the variation of only one function (seed dispersal and seedling establishment or seed germination) of A. ordosica seeds, while simultaneous addition of water and nitrogen led to the variation of both functions of A. ordosica seeds. These findings demonstrate that populations of A. ordosica possessed a great adaptability in response to global climate change by altering their functional strategies of seed dispersal, seedling establishment and seed germination.