Based on the fractal theory

soil fractal features of five types of vegetation in the Ziwuling forest area were studied on contrast to the 6-year abandoned farmland.Results show that the aggregate fractal dimension

the pore fractal dimension

and the mean weight diameter of aggregates can indicate soil structure stability.The aggregate fractal dimension and pore fractal dimension are highly correlated to the content of 0.25 mm aggregates

the content of soil organic carbon

and soil bulk density.So they can be used as the indexes to evaluate soil structure stability.The mean weight diameter does not have significant correlations with the content of soil organic carbon and soil bulk density and however

it has significantly positive correlations with the content of 0.25 mm aggregate and the content of 5 mm aggregates.The mean weight diameter can only be used as the index to evaluate the content of large soil aggregates.As contrasted to the abandoned farmland

soil structure is improved under other four types of vegetation.