Spatial differentiation of soil carbonic anhydrase under different types of land use

Carbonic anhydrase (CA) plays an important role in catalyzing the reversible hydration of CO2, which connects with chemical weathering (including the carbonate rock dissolution and silicate weathering) in atmospheric CO2 sink and the mysterious missing sink in carbon cycling. In order to explore the soil CA activity by means of pH method from different types of land use in southwest China karst area, 11 sampling plots from four different karst ecosystems and 5 sampling plots from non-karst ecosystems as a contrast are selected for the study.The results show that there are larger differences in soil CA activity among different soil layers under different types of land use in southwest China karst area.Under woodland, the soil CA activity in 40 cm and 60 cm soil layers is higher than that in 20 cm. The soil CA activity under tree-shrub land, shrub land and farmland is the highest in 60 cm soil layer, but the lowest in 20 cm. However, in abandoned field, soil CA activity is the highest in 20 cm soil layer but the lowest in 60 cm. It can be seen that the land use type is the main factor affecting the soil CA activity. The soil CA activity increases with the plant root depth due to the CO2increases along with the soil depth.Moreover, karst landform is another important factor that affects the soil CA activity. For example, in the Yaji karst experimental site, the soil CA activity is controlled by the physiognomy character due to the weathering product of carbonate rock and organic matter migration from the bealock and piedmont slope to the karst depression. So, the soil microbe will be assembled, which lead to the soil CA activity in 20 cm layer at depression is 0.782 U/g and higher than those at the bealock and piedmont slope. At last, we also need to consider the effect from the change of sample sites. For the future comparison, the samples should be collected at the border of the same site. Then, the research can provides a certain theoretical basis for further study on the role of soil CA activity in karst processes.