2.3 Plant sampling
The dominant plant species, S . krylovii , was chosen to examine the effects of N and P addition upon seed production in this study. Being a widespread perennial tussock grass in typical temperate steppe, it is an important fodder species used in China, Mongolia, Kazakhstan, and Russia (Ronnenberg et al., 2011; Wu & Raven, 2006). The vegetative and reproductive tillers of S . krylovii can attain heights of 50 cm during the growing season (Li et al., 2017).
In the experiment, three plant individuals were selected in each plot to measure tiller number per individual, inflorescence number per individual, and seed number per inflorescence in late August, from 2015 to 2017. Meanwhile, maximum plant height and density were investigated in a randomly selected subplot (1 m × 1 m) within each plot. Seed production per individual was calculated as the product of seed number per inflorescence and inflorescence number per individual (Brys et al., 2005).