Fig 1.
Vegetation map of the 36 sampling sites in the alpine grasslands on the Tibetan Plateau, selected from the Vegetation Map of China [30].
Black triangles represent the sampling sites.
Fig 2.
Comparisons of SOCCNS and SOCMWB (a), SOCCNS and STC (b).
Solid line is a linear regression passing through the origin. SOCCNS, the difference between STC and SIC; SOCMWB, SOC determined by the MWB method.
Fig 3.
Relationships between the modified Walkey-Black recovery and soil CaCO3 content (a) and pH (b) in all 712 soil samples.
Fig 4.
Boxplots of CaCO3 content (a) and pH (b) in 0–5 cm, 5–10 cm, 10–20 cm, 20–30 cm Soils, and pH (c) in soils of alpine meadow and steppe.
Solied lines within the boxes give the median, dotted lines give the mean, boxes the 25th and 75th percentile. The whiskers are the 5th and 95th percentile and the outliers are closed circles.
Table 1.
Results of three-ways ANOVAs on the effects of soil depth, vegetation type, soil type and their interactions on the modified Walkley-Black recovery.
Table 2.
Regressional relationships of SOC and STC determined between by the elemental analyzer and by the modified Walkley-Black (MWB) method in four soil depths on the Tibetan Plateau using a linear regression passing through the origin.
Fig 5.
Comparisons of SOCCNS and SOCMWB, SOCCNS and STC for alpine medow (a, c) and steppe (b, d).
Solid line is a linear regression passing through the origin. SOCCNS, the difference between STC and SIC; SOCMWB, SOC determined by the MWB method.
Fig 6.
Relationships between CaCO3 content (±SE, a) and pH (±SE, b) and the modified Walkey-Black average recovery (±SE) in 9 soil types (accroding to the GSCC, Genetic Soil Classification of China) on the Tibetan Plateau.
Equations, linear fits (R2) and significant levels (P) were obtained when ‘frigid frozen soils (FFS)’ was excluded from the analyses.
Table 3.
Regressional relationships of SOC and STC determined between by the elemental analyzer and by the modified Walkley-Black (MWB) method in 9 soil types (accroding to the GSCC, Genetic Soil Classification of China) on the Tibetan Plateau using a linear regression passing through the origin.