Effect of long‐term nighttime warming on carbon storage and nitrogen retention of calcareous soil profiles in wheatland

Abstract The effects of warming on the buildup and depth‐related distribution of soil organic carbon (SOC) and nitrogen (N) in agricultural soil profiles remain incompletely understood. Using a long‐term field experiment initiated in 2012 in North China, we aimed to clarify whether warming would modify SOC and N accumulation and distribution in wheatland soil profiles. However, warming tended to boost wheat ( Triticum aestivum L.) aboveground biomass but reduced root biomass and root‐to‐shoot ratios by 25.5%–66.7% and 26.9%–57.6%, respectively, from 2016 to 2024. Since 2020, it decreased SOC, total nitrogen (TN), and C/N ratios in the 0–20 cm layer. Warming significantly increased SOC levels by 16.1% in the 20–40 cm layer but reduced them by 15.8% and 23.6% in the 0–20 cmand 40–60 cm soil depths, respectively. TN content rose significantly by 12.8% and 33.3% in the 20–40 cm and 60–80 cm soil layers, respectively. However, inorganic nitrogen (IN) content increased by 36.8%–166.5% across depths. C/N ratios declined by 9.7%–28.3% in 0–20 cm, 40–60 cm, and 60–80 cm. Consequently, warming enhanced C and N contents in the 20–80 cm soil layer, though this came with a decrease in topsoil C and N stocks. In the 1 m soil profile, long‐term warming significantly curtailed SOC storage by 10.8%, primarily due to topsoil depletion, while elevating IN accumulation by 54.8%. These insights are pivotal for understanding how warming influences C and N storage and distribution within a 1 m wheatland soil profile under anticipated future warming scenarios.