3.1. Variation of soil physical and chemical properties in
different vegetation types
The type of vegetation had significant effects on the soil’s basic
physical and chemical properties. The bulk density of the 0-20 cm CK
soil layer was significantly lower than both in both HR and GL (Table
2).
The contents of total nitrogen and total phosphorus in the XS 0-20 cm
layer were significantly higher than those in the other three vegetation
types (P < 0.05). The soil bulk density of the 20-40 cm layer
under all four vegetation types was higher than that in the 0-20 cm
layer, while the total porosity, total nitrogen and total phosphorus in
the 20-40 cm soil layer were lower than in the 0-20 cm layer.
3.2. Variation of soil
carbon fractions in different vegetation types
There were significant differences
in EOC, POC, and SOC under the four types of vegetation (Figure 2).
There were no significant
differences in the soil MBC content among the four types of vegetation
in the 0-20 cm layer. The MBC content in the 20-40 cm layer of HR
vegetation was significantly higher than in the other three vegetation
types. Except for the MBC contents of the HR vegetation, the MBC, EOC,
POC, and SOC contents in other vegetation types decreased significantly
as soil depth increased. At the 0-20 cm layer, the EOC contents of the
GL vegetation was 1.44, 2.82, and 2.06 g/kg higher than XS, HR, and CK,
respectively, while at the 20-40 cm layer the EOC contents was 0.63,
1.01, and 0.95 g/kg higher than XS, HR, and CK, respectively. The POC
and SOC contents in the 0-20 cm layer of XS vegetation were
significantly higher than those in the other three vegetation types. The
soil POC content in HR vegetation and the SOC content in GL vegetation
at the 20-40 cm layer were the highest. The maximum values of soil POC
and SOC were 0.37 and 1.61 g/kg higher than the minimum values,
respectively. A two-way ANOVA analysis demonstrated significant
associations between soil depth and vegetation type on organic carbon
components (MBC, EOC, POC and SOC) in all the samples measured (Table
3).