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<p>Soil organic carbon stocks (SOCS) play a vital role in sustaining ecosystem functions and regulating regional carbon cycling and climate in the Inner Mongolia Autonomous Region (IMAR), which is characterized by extensive grasslands and diverse ecological zones that are sensitive to climate change and anthropogenic activities. However, the spatiotemporal dynamics of SOCS and their drivers in this fragile region remain insufficiently understood. In this study, we quantified changes in SOCS within the top 1-metre soil depth across the IMAR from 2001 to 2022 and identified their drivers by combining field measurements with multiple environmental datasets using Quantile Regression Forest (QRF) modelling. QRF was selected for its ability to build on the robust prediction performance of Random Forests (RF) while directly quantifying prediction uncertainty, particularly in sparsely sampled regions. The results showed that the total SOCS ranged from 10.9 ± 0.3 to 12.3 ± 0.3 Pg C during the period 2001–2022, with a mean of 11.49 Pg C. The total SOCS exhibited significant interannual variability and a significant (<i>P</i> &lt; 0.05) decreasing trend at a rate of 0.03 Pg C yr<sup>− 1</sup>. Spatially, SOCS displayed marked spatial heterogeneity, decreasing from east to west, which was consistent with land use types and climatic gradients. Significant changes were observed in 27.3% of the regions, with approximately 23.9% showing a significant decline. This observed decline was primarily attributed to climate warming and intensified grazing intensity over the past few decades. These findings emphasized the vulnerability of SOCS to climate change and grazing in the IMAR region. Consequently, the implementation of moderate rotational grazing strategies was essential for restoring SOCS. This study provided key evidence to support ecological restoration strategies and policy intervention in this region.</p> Graphical Abstract <p></p> <p>This graphical summary presented a simulation study of soil organic carbon stocks (SOCS) in the Inner Mongolia Autonomous Region (IMAR). The region encompassed largest geographical extent and diversity ecological zones. In recent years, SOCS has been significantly impacted by substantial changes in temperature, precipitation, and grazing intensity. This study employed Quantile Regression Forest (QRF) model was applied to quantify the spatiotemporal dynamics and driving mechanisms of SOCS in the top 1-m soil layer from 2001 to 2022. The model integrated field observations with multi-source environmental covariates, including topography, climate, biophysical attributes, human activities, and soil properties. Results showed that total SOCS fluctuated range from 10.9±0.3 to 12.3±0.3 Pg C, with an overall declining trend. Climate warming and intensified grazing were identified as the main contributors to SOCS reduction. And implementing moderate rotational grazing strategies was crucial for restoring SOCS. This study provided scientific insights into regional carbon cycling and supported ecological restoration strategies.</p>

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Widespread Decline in Soil Organic Carbon Stocks Linked To Warming and Grazing in Inner Mongolia (2001–2022)

  • 期刊论文

  • 发表日期：

    2026年2月21日

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  • Liya Ma,
  • Shaobo Sun,
  • Dandan Zhao,
  • Zhaoliang Song,
  • Yong Liu,
  • Xiaolei Yang,
  • Xiangyu Zhu,
  • Tianqi Zhao,
  • Shuo Li

摘要

Soil organic carbon stocks (SOCS) play a vital role in sustaining ecosystem functions and regulating regional carbon cycling and climate in the Inner Mongolia Autonomous Region (IMAR), which is characterized by extensive grasslands and diverse ecological zones that are sensitive to climate change and anthropogenic activities. However, the spatiotemporal dynamics of SOCS and their drivers in this fragile region remain insufficiently understood. In this study, we quantified changes in SOCS within the top 1-metre soil depth across the IMAR from 2001 to 2022 and identified their drivers by combining field measurements with multiple environmental datasets using Quantile Regression Forest (QRF) modelling. QRF was selected for its ability to build on the robust prediction performance of Random Forests (RF) while directly quantifying prediction uncertainty, particularly in sparsely sampled regions. The results showed that the total SOCS ranged from 10.9 ± 0.3 to 12.3 ± 0.3 Pg C during the period 2001–2022, with a mean of 11.49 Pg C. The total SOCS exhibited significant interannual variability and a significant (P < 0.05) decreasing trend at a rate of 0.03 Pg C yr− 1. Spatially, SOCS displayed marked spatial heterogeneity, decreasing from east to west, which was consistent with land use types and climatic gradients. Significant changes were observed in 27.3% of the regions, with approximately 23.9% showing a significant decline. This observed decline was primarily attributed to climate warming and intensified grazing intensity over the past few decades. These findings emphasized the vulnerability of SOCS to climate change and grazing in the IMAR region. Consequently, the implementation of moderate rotational grazing strategies was essential for restoring SOCS. This study provided key evidence to support ecological restoration strategies and policy intervention in this region.

Graphical Abstract

This graphical summary presented a simulation study of soil organic carbon stocks (SOCS) in the Inner Mongolia Autonomous Region (IMAR). The region encompassed largest geographical extent and diversity ecological zones. In recent years, SOCS has been significantly impacted by substantial changes in temperature, precipitation, and grazing intensity. This study employed Quantile Regression Forest (QRF) model was applied to quantify the spatiotemporal dynamics and driving mechanisms of SOCS in the top 1-m soil layer from 2001 to 2022. The model integrated field observations with multi-source environmental covariates, including topography, climate, biophysical attributes, human activities, and soil properties. Results showed that total SOCS fluctuated range from 10.9±0.3 to 12.3±0.3 Pg C, with an overall declining trend. Climate warming and intensified grazing were identified as the main contributors to SOCS reduction. And implementing moderate rotational grazing strategies was crucial for restoring SOCS. This study provided scientific insights into regional carbon cycling and supported ecological restoration strategies.