Plant function traits-driven spatial expansion processes modulate grassland species coexistence

In this dataset. Field work was conducted in the Yunwu Mountain National Nature Reserve, central Loess Plateau, China (36°13'-36°19' N, 106°24'-106°28'; 1800-2150 m above sea level). The experimental site was established within an area protected from grazing for over 30 years. The experimental site consisted of 108 permanent plots (6m × 4m), arranged as 12 replicate blocks, each receiving a factorial combination of three mowing frequencies (0, 1 or 2 clips yr-1) and three nitrogen (N) addition levels (low: 0 g N m-2 yr-1; moderate: 7.02 g N m-2 yr-1; high: 28.08 g N m-2 yr-1) from 2013. The composition of community was recorded in August 2022 and August 2023. Within each plot, a 1 m × 1 m quadrat was randomly located. For every species, we recorded percentage cover, mean height, and individual count (richness was defined as the total number of species per quadrat). The above-ground biomass collected from the harvest quadrant was first heat-treated for 30 minutes at 105°C, then dried at 65°C to a constant weight before being weighed. Dominant-species leaves for trait analysis were collected outside quadrats (≥ 25 healthy leaves species-1; > 4000 leaves in total)