C-N Isotope Coupling along the vertical profiles under different land use in a typical karst area, Guizhou, southwest China

The soil stable carbon and nitrogen isotopic compositions characterize its fate and identify the different land use. In this study, carbon concentration and isotope component, nitrogen concentration and isotope component, and C/N ratios in soils collected from Puding, southwest of China were determined. The carbon and nitrogen content data range from 7.92% to o.48%, and 0.77% to 0.05%, respectively. Soil delta C-13 ranged from -25.49 parts per thousand to -17 parts per thousand, soil delta N-15 varied from 1.11 parts per thousand to 9.46 parts per thousand. The concentrations of SOC and SON decrease with depth along the vertical profiles. In addition, combined the SOC and delta C-13 or SON and delta N-15 could obtained the possibility of distinguish the replaced of C3 and C4 plants. However the pattern of distribution in soil organic delta C-13 is different from that in soil organic delta N-15 at the subsoil (deeper than 30cm). With correlation analyses with C/N ratios and delta C-13, it reveals that subsoil carbon microbial derived carbon due to root activity. (C) 2014 Published by Elsevier B.V.