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).本研究于2024年植物生长季的三个关键生育期采集土壤样品：分别为生长初期（5月15日，EG）、生长中期（7月17日，MG）与生长后期（9月15日，LG）。每个采样时间点均采用土钻，按照每个样地内的“S”形布点模式进行分层采样，采样深度分别为0–10 cm、10–20 cm及20–40 cm。采集后的样品立即置于无菌袋中并运送至实验室。针对每个样地的各深度土层，将采集的土芯混合并均质化处理。混合后的样品被分为两份子样品：其中一份经2 mm孔径筛网过筛后，保持新鲜状态，用于测定土壤含水量（soil water content, SWC）、微生物量碳（microbial biomass carbon, MBC）与微生物量氮（microbial biomass nitrogen, MBN）、铵态氮（ammonium nitrogen, NH₄⁺）以及硝态氮（nitrate nitrogen, NO₃⁻）；另一份置于暗处风干，经0.15 mm孔径筛网过筛后，用于测定土壤有机碳（soil organic carbon, SOC）、全氮（total nitrogen, TN）与全磷（total phosphorus, TP）。