Composition and fractal features of soil macro-aggregate under different abandoned lands in the loess hilly region of West Henan

The distribution，stability and fractal features of topsoil macro-aggregate were studied for abandoned arbor，shrub，orchard，grassland and wasteland about 10 years. The results showed that：> 2 mm aggregate dominated in the soil aggregate structure，the 2-5 mm and 1-2 mm aggregate contents in shrub，arbor land and wasteland soil increased significantly than those of the cultivated land；the contents of > 5mm and 2-5 mm water stable aggregate in the arbor，shrub，orchard，grassland and wasteland in the topsoil significantly increased than those of cultivated land. The mean weight diameter and geometrical mean diameter by dry sieving and wet sieving in the arbor，shrub，grassland and wasteland significantly increased，but the fractal dimension decreased significantly than that of cultivated land，this 4 kinds of soil structurs were improved significantly，but the orchard soil structure improvement was not obvious. The soil aggregate fractal dimension can describe the distribution of soil aggregate better and has close relationship with soil physiochemical properties