In this article, the distribution characteristics, stability and erodibility of soil
aggregate in three zones of forest, forest-steppe and steppe on the Loess Plateau are studied
with the Le Bissonnais (LB) method. The effect of vegetation and slope aspect on the
characteristics and erodibility of soil aggregate is also discussed. The results show that: 1) for
the surface soil (0-20 cm) in different vegetation zones, both the content of soil aggregate
(R0.2) and the mean weight diameter (MWD) are less on sunny slopes than on shady slopes,
while the soil erodibility factor K is a little bigger on sunny slopes than on shady slopes with no
significance. This implies that both the stability and erodibility of soil aggregate are slightly
higher on the shady slope than on the sunny slope in the three vegetation zones in hilly loess
region, but the differences are not significant. 2) In the surface layer (0-20 cm) under different
vegetation, R0.2 and MWD decrease as follows: forest > forest steppe > steppe, while soil
erodibility factor K decreases in the following order: steppe> forest- steppe > forest. This
suggests that the stability and anti-erosion ability of soil aggregate in the forest vegetation zone
is the highest. 3) Under processes of WS (wet-stirring sieving method) and FW (fast-wetting
sieving method), there are significant difference between samples in forest zone and in steppe
zone in both the soil stability and the soil erodibility (R0.2, MWD, K value), especially under
the process of FW. The stability and erodibility of soil in forest-steppe zone are in between. A
conclusion can be drawn that in the hilly loess zone, the stability and the anti-erosion ability of
soil aggregate is ever increasing from north to south. The stability and the anti-erosion ability
of soil aggregate is significantly higher in the southern forest zone than in the northern steppe
zone.
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