Karstification under different land-use patterns in summer: A case study in the Qingmuguan karst valley, Chongqing

The direction and intensity of karstification could be deeply affected by soil physical and chemical variations resulted from land cover. Taking Qingmuguan karst valley area, Chongqing as an example, the total corrosion amount and corrosion amount under per unit area in 6 kinds of typical land use patterns in summer are got to study the impact of land covers on karst processes by means of limestone tablet corrosion test in the field. The results show that the corrosion rate under different land use patterns is quite different, generally, the corrosion rate decreases from tilled land, woodland exchanged from tilled land, paddy field, woodland mixed with Chinese fir-bamboo land, fallow land and bamboo land successively. It is also found that the corrosion rate largely increases with depth by means of counting up the corrosion rate at different depth. But there is obvious difference in corrosion rate among different depth under same land use pattern, especially in waste land, with the corrosion rate being 4.23 times higher under -20 cm than on the surface layer. Moreover, the CO2 increases with depth in all spot, which is better related with the regime of corrosion rate. The soil organic matter decreases with depth, which is opposite with the regime of corrosion rate but positively correlated with the corrosion rate on the surface layer. So, it is concluded that the impact of organic matter content on the corrosion rate is quite complicated.