3.1 General dataset information
We established a SOC and TN database from different sampling depths and corresponding to different LUCCs. A more detailed data description is presented in Table 1. Obviously, the deeper the soil, the smaller the sample size (number of samples collected) in our meta-analysis. Therefore, appropriate adjustments were made: when the soil depth was greater than 30 cm, the sample size of shrub land was greatly reduced, so it was incorporated into the secondary forest. Similarly, when the soil depth reached 100 cm, secondary forests, plantation and fruit trees were collectively referred as other woodlands.