Warming weakens the effect of nitrogen addition on N2O emissions from saline-alkali grassland in the Hexi Corridor

Soil samples were collected during the early growth stage (May 15, EG), mid-growth stage (July 17, MG), and late growth stage (September 15, LG) of the 2024 plant growth season. At each time point, soils were sampled at three depths (0–10 cm, 10–20 cm, and 20–40 cm) using a soil auger, following an "S"-shaped sampling pattern within each plot. Samples were immediately placed in sterile bags and transported to the laboratory. For each depth and plot, soil cores were composited and homogenized. The composite sample was then divided into two subsamples. One portion was sieved through a 2 mm mesh and used fresh for analysis of soil water content (SWC), microbial biomass carbon and nitrogen (MBC and MBN), ammonium nitrogen (NH₄⁺), and nitrate nitrogen (NO₃⁻). The second portion was air-dried in the dark, sieved through a 0.15 mm mesh, and used for the determination of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP).