Negative Correlation between Soil Salinity and Soil Organic Carbon Variability

Soil Organic Carbon (SOC) is vital for terrestrial ecosystems, affecting biogeochemical processes, and soil health. It is known that soil salinity impacts SOC content, yet the specific direction and magnitude of SOC variability of in relation to soil salinity remain poorly understood. Analyzing 43,459 mineral soil samples (SOC < 150 g kg-1) collected across different land covers since 1992, we approximate a soil salinity increase from 1 to 5 dS m-1 in croplands would be associated with a decline in mineral soils SOC from 0.14 g kg-1 above the mean predicted SOC ( = 18.47 g kg-1) to 0.46 g kg-1 below (~-430%), while for non-croplands, such decline is sharper, from 0.96 above = 35.96 g kg-1 to 4.99 below (~-620%). Although salinity’s significance in explaining SOC variability is minor (< 6%), we estimate a one std increase in salinity of topsoil samples (0 - 7 cm) correlates with respective declines of ~4.4% and ~9.26%, relative to and . The decline in croplands is greatest in vegetation/cropland mosaics while lands covered with evergreen needleleaved trees are estimated with the highest decline in non-croplands. We identify soil nitrogen, land cover, and precipitation Seasonality Index the most significant parameters in explaining the SOC’s variability. The findings provide insights into SOC dynamics under increased soil salinity, enhancing our understanding of SOC stock responses to land degradation and climate warming.The data provided in this dataset forms the foundation for the aforementioned results and helps in replicating the output.

土壤有机碳（Soil Organic Carbon, SOC）是陆地生态系统的关键组分，对生物地球化学过程与土壤健康至关重要。尽管已知土壤盐分对SOC含量存在影响，但土壤盐分与SOC变异性之间的具体作用方向及变化幅度仍未得到充分阐明。本研究分析了1992年以来在不同土地覆盖类型下采集的43459个矿质土壤样品（SOC含量<150 g·kg⁻¹），结果估算显示：农田区域土壤盐分从1 dS·m⁻¹升高至5 dS·m⁻¹时，矿质土壤SOC含量会从较平均预测SOC（均值为18.47 g·kg⁻¹）高出0.14 g·kg⁻¹的水平，下降至较该均值低0.46 g·kg⁻¹的水平（降幅约-430%）；而非农田区域的SOC下降趋势更为剧烈，SOC含量从较均值（35.96 g·kg⁻¹）高出0.96 g·kg⁻¹的水平，下降至较该均值低4.99 g·kg⁻¹的水平（降幅约-620%）。尽管盐分在解释SOC变异性中的贡献占比极小（<6%），但我们估算得出，表层土壤（0~7 cm）样品的盐分每增加一个标准差，SOC含量会分别较对应基准值下降约4.4%和9.26%。农田区域的SOC降幅以植被/农田镶嵌型土地最大，而非农田区域中，常绿针叶林覆盖土地的SOC降幅最高。本研究确定，土壤氮含量、土地覆盖类型以及降水季节指数是解释SOC变异性的最核心参数。本研究结果为土壤盐分升高背景下的SOC动态变化提供了新的认知视角，加深了我们对SOC库响应土地退化与气候变暖的理解。本数据集提供的数据为上述研究结果奠定了基础，同时可支撑该研究结果的复现工作。