Effect of simulated nitrogen deposition on the seed germination of Seriphidium transiliense

Seriphidium transiliense, a dominant species of sagebrush deserts in Xinjiang, was used to study the effects of nitrogen (N) addition rates 0, 0.4, 0.8, 1.2, 1.6 g·(m²·a)⁻¹) and frequencies (once and thrice) on seed germination by simulating nitrogen deposition with urea. The results indicated that the nitrogen addition rate and frequency had no significant effects on the germination rate, germination potential, and germination index of S. transiliense seeds, which ranged from 84.75% to 89.50%, 81.50% to 88.50%, and 16.14 to 19.17, respectively. However, nitrogen addition had significant effects on the root length, shoot length, and dry weight of seedlings (P < 0.01), which decreased with increase in nitrogen levels. The minimum nitrogen addition conditions for growth inhibition were one-time addition of 0.4 g·(m²·a)⁻¹ and three-time addition of 1.2 g·(m²·a)⁻¹, and the inhibitory effect under single nitrogen addition was higher than that under three-time addition. There were significant differences in the S. transiliense response to addition frequencies at higher addition rates (P < 0.05). In conclusion, the level of nitrogen deposition (within the experimental treatment range) did not affect the seed germination and emergence of S. transiliense; however, it did inhibit seedling growth and development, which reduced after multiple additions of nitrogen at the same nitrogen addition rate.