Figure 1.
Soil sampling locations from our survey and the extracted dataset of Yang et al.
[2].
Table 1.
The study area, distribution of sampling sites and soil organic carbon density by grassland type in the Three River Source Region.
Figure 2.
Mean SOC stocks with uncertainty estimates (95% confidence intervals) for alpine grasslands in the Three Rivers Source Region from our data, the dataset of Yang et al.
[2], and the pooled dataset.
Figure 3.
Probability (power) of detecting a 10% uncertainty in soil organic carbon density with a 0.05 level of significance for grassland types at three soil depths.
The numbers above each bar represent the number of sampling sites needed to be taken at three depths for each alpine grassland to detect the tolerated uncertainty with 90% probability.
Figure 4.
Predicted SOC densities by kriging of our data against observed values of Yang et al.
[2].
Figure 5.
Comparisons of soil organic carbon concentration (A) and density (B) between present and previous studies.
The present SOC values (open squares) were extracted from our kriged prediction map. The dark grey circles (A) indicated the measured SOC concentration values from previous study, while the previous corresponding SOC densities (B) were re-calculated using different bulk density values derived from pedotransfer functions of Yang et al. [22] (dark circles) and Zhong et al. [23] (gray circles), since bulk density was not measured in the previous study [21].