Research on the Woodland Soil Enzyme Activities in Coal Mining Subsidence Area

Soil enzyme is involved in nutrient cycling and availability to plants and can be used as an index of soil function. Underground coal mining results in large-scope land subsidence, farmland damage and soil fertility decline. In this paper, Hanwang coal mining subsided area in Jiaozuo city, Henan province, China, was taken as an example to study on the soil enzyme activities in different sites and layers. The results show that: firstly, the activities of the hydrogen peroxidase, sucrase and dehydrogenase of the reference points exceed that of the points in the settlement zone. Similarly, the urease activity of the reference points except from the range within 0 to 5 cm is higher than that of the points in the settlement zone; By contrast, the difference of phosphatase activity between the reference points and the points in the settlement zone is not significant. Secondly, the variation of polyphenol oxidase, hydrogen peroxidase, dehydrogenase and urease from the points in the settlement zone is unconspicuous; there is some diversity of phosphatase activity between the points in the settlement zone, the significance of difference of invertase activity of the sampling points between No. 4 within the range of 5 to 15 cm and other sampling points in the settlement zone is great. Thirdly, there is no significant difference between the reference points with the hydrogen peroxidase and divertase activity in the stratum; by contraries, the differences in some stratum of the settlement zone was significant. There is some difference of between the hydrogen peroxidase and invertase activity of the reference points; by contrast, the diversity of the phosphatase and urease activity in the stratum in the settlement zone is increasing. The distribution of the dehydrogenase activity between the reference points and the points in the settlement zone is opposite to each other; the activity difference of the reference points within the range of 20 to 40 cm is the maximum, the difference is the maximum within the range of 0 to 5 cm in the ground surface. Fourthly, the ground surface subsidence is caused by the coal mining that the soil is contaminated by heavy metals and polycyclic aromatic hydrocarbons; consequently, the enzyme activity is depressed and the soil quality is degenerated, so that the soil output is reduced.