Fig 1.
The elevation of Tongken river basin and distribution of the sampling cites.
Fig 2.
(a) The soil types in Tongken basin; (b) The land use types in Tongken basin.
Table 1.
Driving factors of SOC dynamic used in this study.
Fig 3.
(a) Trends of annual average temperature from 2013 to 2023; (b) Trends of annual precipitation from 2013 to 2023; (c) Trends of NDVI from 2013 to 2023; (d) Trends of NPP from 2013 to 2023; (e) Trends in population density from 2013 to 2023; (f) Changes in land use types from 2013 to 2023.
Table 2.
Descriptive statistics of SOC content and SOC density.
Fig 4.
Soil organic carbon (SOC) content in different land use types (a) and different soil types (b).
Fig 5.
Semi-variogram for SOC data in 2013 (a) and SOC data in 2023 (b).
Fig 6.
Spatial distribution of SOC content in 2013 (a) and 2023 (b), along with the corresponding standard error distributions in 2013 (c) and 2023 (d), and the spatial distribution of SOC variation map (e) and the standard error distribution of SOC variation values (f).
Fig 7.
Performance of the random forest models in predicting SOC of train set (a) and test set (b).
Fig 8.
The importance ranking chart of influencing factors with the number representing the percentage of significance.
Fig 9.
Spearman correlation between drivers and SOC variation.
Fig 10.
(a) Relationship between annual average precipitation (MAP) and SOC content and (b) relationship between annual precipitation change slope (PRE_SL) and SOC variation (dSOC).
Fig 11.
(a) Relationship between annual average temperature (TMP) and SOC content and (b) relationship between annual temperature change slope (TMP_SL) and SOC variation (dSOC).