Ecological stoichiometry characteristics of ionic rare earth mining area soil in different management years

The mining of ionic rare earth elements causes serious ecological problems,and it has become an important issue for ecological restoration management in South China. Ecological stoichiometry,combined with the basic principles of physics,biology,and chemistry,can be used to investigate the ecological processes affecting chemical elements. It can be used to investigate soil ecosystem nutrient cycling and to identify the limiting factors on plant growth when it is used in ionic rare earth mining ecology restoration projects. The present study used ecological stoichiometry to analyze the topsoil nutrient contents at soil sampling depths of 0-10 cm and 10-20 cm over three different management years in an ionic rare earth mining area and one unexploited rare earth mine in Changting County,Fujian Province. The results showed that the soil organic carbon,total nitrogen,and total phosphorus contents were in the range of 0.69-15.7 g / kg,0.26-1.21 g / kg,and0.05-0.11 g / kg,respectively. The soil nutrient contents were higher in the 0-10 cm layer than in the 10-20 cm layer.The soil C : N,C : P,and N : P ratios were in the range of 0.89-15.42,9.50-136.46,and 4.17-20.87,respectively.The ratios first decreased, and then increased as management time progressed. The soil ecological stoichiometry characteristics were affected mainly by the organic matter content because of the residual nitrogen levels and the loss of organic matter in the early management years. In the later management years,soil ecological stoichiometry characteristics were mainly affected by nitrogen limitation due to its increased loss during the late management period. Our research suggested that stress resistant plant species should be planted to take full advantage of the residual nitrogen in the early years of management. Plant growth and soil nitrogen uptake as time progresses means that nitrogen should be applied during the late management years to overcome nitrogen limitations.