Figure 1

Geographical position of the study area and distribution of sampling sites. This figure was produced using ArcGIS 10.2 (Environmental Systems Research Institute). The background is the vegetation map according to the Editorial Committee of Vegetation Map of China (ECVMC, 2007)."

Figure 2

Box plot of soil carbon stocks (a) and their vertical distributions (b) for grassland, forest and cropland. Different letters indicate a significant difference in the total soil carbon stocks and soil carbon stocks of different depths between different land use types at the 0.05 level. NS signifies no significant difference. Bars denote standard error. Values in parentheses indicate the number of samples. Box plots display the median (solid line), mean (dotted line), interquartile range (upper and lower edge of box), 10-90 percentile (whiskers) and outliers (circles)."

Figure 3

Comparison of SOC stocks (a) and their vertical distributions (b) between grazing-excluded (GE) (GE<20a, GE≥20a) and grazed (G) grasslands. The inset panel shows the relationship between SOC stock and the duration of GE. G, GE<20, and GE≥20 represent grazed grasslands, <20 years GE, and≥20 years GE grasslands, respectively. Different letters indicate a significant difference (p<0.05) in the total SOC stocks and SOC stocks at different depths among grassland types. Bars denote standard error. NS signifies no significant difference. Values in parentheses indicate the number of samples."

Figure 4

Effects of forest stand age on SOC stocks (a) and their vertical distribution (b). The inset panel in (a) shows the relationship between SOC stocks and forest stand age. Bars denote standard error. NS signifies no significant difference. Values in parentheses indicate the number of samples."

Figure 5

Comparisons of SOC stocks (a, c) and their vertical distribution (b, d) between coniferous and broadleaf forests (a, b) and between natural forests and plantation (c, d). Bars denote standard error. NS signifies no significant difference. Values in parentheses indicate the number of samples."

Figure 6

Comparisons of SOC stocks (a) and their vertical distributions (b) between conventional (tillage) and conservation cultivation (no-tillage) croplands. Different letters indicate a significant difference in the SOC stocks of different depths between tillage and no-tillage at the 0.05 level. Bars denote standard error. NS signifies no significant difference. Values in parentheses indicate the number of samples."