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<p>Detecting the spatial heterogeneity of soil carbon and its key driving factors is critical for soil management. However, this remains poorly understood in saline–alkali arable soils at a large scale. In this study, geostatistical analysis combined with statistical analysis was employed to investigate the key drivers of the spatial heterogeneity of soil total carbon (TC), soil organic carbon (SOC), soil inorganic carbon (SIC), and SOC forms in the 0–20&#xa0;cm and 20–40&#xa0;cm soil layers in saline–alkaline soils of Da’an city (496&#xa0;km<sup>2</sup>), Northeast China. (1) TC, SIC, SOC, soil dissolved organic carbon (DOC), soil mineral-associated organic carbon (MAOC), and soil particulate organic carbon (POC) exhibited distinct spatial aggregation patterns across the study area (<i>P</i> &lt; 0.05). SIC constituted a large proportion of TC (53.7–58.0%), and MAOC dominated SOC (57.3–66.0%). SOC significantly decreased from the 1980s to 2024 (<i>P</i> &lt; 0.05) at 0–20&#xa0;cm (29.4%) and 20–40&#xa0;cm (25.2%). (2) All carbon forms were correlated between the surface and subsurface layers at the regional scale (<i>P</i> &lt; 0.05). High concentrations of most ions and elevated bulk density sustained high TC via SIC and DOC, particularly under conditions of high pH and fine soil particles. These conditions also reduced SOC through the depletion of MAOC and POC, especially in paddy fields and wetlands. The SIC distribution was influenced mainly by temporal changes in pH (1980s–2024) but not by spatial changes in pH. Furthermore, soil ferric oxide was positively related to SIC but not to SOC. (3) Drylands at high elevations favored MAOC-driven SOC accumulation (53.4–52.3% of TC) but suppressed SIC and DOC, whereas wetlands at low elevations acted as TC sinks via SIC accumulation (67.0–73.4% of TC). Nitrogen fertilization maintained high concentrations of TC via SIC accumulation and SOC mineralization, but the positive effect of fertilization on SOC has been modulated by thresholds of soil total nitrogen (TN) change since the 1980s. Structural equation modeling revealed that the heterogeneity of SIC, SOC, and SOC forms was determined mainly by TN and saline–alkali ions, which were influenced primarily by land use, tillage method and elevation. These findings highlight that soil carbon heterogeneity across saline–alkali soil at a large scale is driven by land use and topography through their control of ion dynamics and soil physical properties, with nitrogen fertilization optimized according to TN change thresholds to increase carbon sequestration while protecting SOC stocks.</p>

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Topography and land management influence soil carbon heterogeneity by altering the physicochemical properties of saline–alkaline soil in Northeast China

  • 期刊论文

  • 发表日期：

    2026年5月14日

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  • Shaoliang Zhang,
  • Xingjian Shi,
  • Shizhan Li,
  • Pengke Yan,
  • Xiaoguang Niu,
  • Haijun Zhang,
  • Ziliang Xiao,
  • Mingming Wang

摘要

Detecting the spatial heterogeneity of soil carbon and its key driving factors is critical for soil management. However, this remains poorly understood in saline–alkali arable soils at a large scale. In this study, geostatistical analysis combined with statistical analysis was employed to investigate the key drivers of the spatial heterogeneity of soil total carbon (TC), soil organic carbon (SOC), soil inorganic carbon (SIC), and SOC forms in the 0–20 cm and 20–40 cm soil layers in saline–alkaline soils of Da’an city (496 km2), Northeast China. (1) TC, SIC, SOC, soil dissolved organic carbon (DOC), soil mineral-associated organic carbon (MAOC), and soil particulate organic carbon (POC) exhibited distinct spatial aggregation patterns across the study area (P < 0.05). SIC constituted a large proportion of TC (53.7–58.0%), and MAOC dominated SOC (57.3–66.0%). SOC significantly decreased from the 1980s to 2024 (P < 0.05) at 0–20 cm (29.4%) and 20–40 cm (25.2%). (2) All carbon forms were correlated between the surface and subsurface layers at the regional scale (P < 0.05). High concentrations of most ions and elevated bulk density sustained high TC via SIC and DOC, particularly under conditions of high pH and fine soil particles. These conditions also reduced SOC through the depletion of MAOC and POC, especially in paddy fields and wetlands. The SIC distribution was influenced mainly by temporal changes in pH (1980s–2024) but not by spatial changes in pH. Furthermore, soil ferric oxide was positively related to SIC but not to SOC. (3) Drylands at high elevations favored MAOC-driven SOC accumulation (53.4–52.3% of TC) but suppressed SIC and DOC, whereas wetlands at low elevations acted as TC sinks via SIC accumulation (67.0–73.4% of TC). Nitrogen fertilization maintained high concentrations of TC via SIC accumulation and SOC mineralization, but the positive effect of fertilization on SOC has been modulated by thresholds of soil total nitrogen (TN) change since the 1980s. Structural equation modeling revealed that the heterogeneity of SIC, SOC, and SOC forms was determined mainly by TN and saline–alkali ions, which were influenced primarily by land use, tillage method and elevation. These findings highlight that soil carbon heterogeneity across saline–alkali soil at a large scale is driven by land use and topography through their control of ion dynamics and soil physical properties, with nitrogen fertilization optimized according to TN change thresholds to increase carbon sequestration while protecting SOC stocks.