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 HR and GL (Table 2). The
soil bulk density of the CK plot in the 20-40 cm layer was the smallest,
but the difference has not reached a significant level. Moreover, the
contents of total N and total P in the XS 0-20 cm layer were
significantly higher than those in the other three vegetation types (P
< 0.05). The maximum total N content of the soil in the 20-40
cm layer appeared in the HR plot, and the maximum total P content
appeared in the GL plot, but the difference in vegetation type to soil
total N and total P content did not reach a significant level. 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 N
and total P 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 (Fig.
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
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 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).