Effects of nitrogen addition on the root morphology and biomass characteristics of ephemeral plants in a cold desert

Increased nitrogen deposition has a huge influence on terrestrial ecosystems. Desert ecosystems are more fragile than other ecosystems and are more sensitive to global change such as nitrogen deposition. In this study, three desert ephemeral species (Plantago minuta, Nepeta micrantha, and Eremopyrum distans) were used as the research subjects. Five nitrogen addition treatments were utilized to study the effects of aboveground and belowground biomass and root traits. The results showed that (1) 1.5, 3, 6, and 12 g·(m²·a)⁻¹ concentrations of nitrogen had a significant effect on the root characteristics of the three ephemeral plants (P < 0.05). (2) Nitrogen addition of 1.5, 3, and 6 g·(m²·a)⁻¹ concentrations significantly increased the aboveground and belowground biomass accumulation of the three desert ephemeral plants (P < 0.05); however, the 12 g·(m²·a)⁻¹ treatment inhibited the biomass accumulation of P. minuta and N. micrantha, whereas it had no significant inhibitory effect on E. distans (P > 0.05). (3) The aboveground and belowground biomass characteristics of the three ephemeral species were correlated with plant root morphological characteristics. The root characteristics of various diameters were different from the aboveground and belowground biomass correlations, and there were also large distinctions between the different species. Therefore, the continuous increase of nitrogen deposition in desert areas might cause changes in the survival strategies and community structure of ephemeral species, and further affect the synusia structure of ephemeral plants.