Background The stability of soil aggregates plays an important role in maintaining land productivity and regulating soil fertility. It is also one of the important indicators to reflect the soil structure. In order to explore the influences of different reclamation modes on the stability of soil aggregates, 5 reclamation modes of shrub (Amorpha fruticosa)forest, Ulmus pumila forest, Robinia pseudoacacia forest, mixed forests(Robinia pseudoacacia and U. pumila)and weeds in Haizhou opencast coal mine, Fuxin city of Liaoning province, were used as the research objects.

Methods The dry sieving method and wet sieving method were used to measure soil mechanical aggregates, and the stability of soil aggregate index (R_>0.25) and percentage of aggregate destruction (PAD), soil aggregate diameter index (mean mass diameter MWD, the geometric mean diameter GMD and the fractal dimension of soil the number of D) as the evaluation index, to analyze the characteristics of soil aggregate stability under different reclamation modes.

Results 1) Big aggregate content(R_>0.25)was used to reflect the soil structure of quality, big aggregate content(R_>0.25) was 58%-63% in the dry sieve of different reclamation mode, and was 17.5%-37.43% in the wet sieve. Important indicators were the diameter of the soil aggregate mean mass diameter (MWD) and geometric mean diameter (GMD). 2) In the condition of dry sieving, there were MWD (2.27) and GMD (1.3) in mixed forest, MWD (1.56) and GMD (0.96) at least grassland. Under the condition of wet screening, MWD (2.97) and GMD (2.43) of Robinia pseudoacacia forest were the most, and MWD (1.16) and GMD (0.53) were the least in the grassland. 3) In fractal dimension, the fractal dimension of the dry sieves and wet sieves was 2.23-2.35 and 2.35-2.43, respectively. The correlation coefficients were 0.949, 0.610 and 0.514 under dry screen condition, respectively, and their correlation coefficients were 0.999, 0.276 and 0.282 under wet screen conditions, respectively. The he overall trend on the surface layer of soil in different reclamation modes for aggregate stability, soil aggregate diameter and aggregate destruction rate was better than that of weeds, the soil aggregate destruction rate was the lowest in shrub land, soil aggregate diameter index was better in the Robinia pseudoacacia and mixed forest, and soil stability index MWD and GMD were better in forest land.

Conclusions The stability of soil aggregates were of positive correlation between the fractal dimension, and was positively correlated with the D value. In the process of transforming from micro aggregates (< 0.25 mm) to 5 mm, the 1.00 mm and 2.00 mm aggregates were the more critical nodes. The comprehensive experimental results show that the soil structure in the dump was seriously damaged, the climatic environment of the soil where vegetation grew was poor, and the vegetation restoration was a slow process in improving the soil.