Fig. 4
Redundancy analysis for the fluorescence fractions of soil dissolved organic matter (DOM) in response to soil properties and DOM spectral indices. SOM soil organic matter, TN total nitrogen, TC total carbon, DOC dissolved organic carbon, DON dissolved organic nitrogen, CEC cation-exchange capacity, FI fluorescence index, HIX humification index, BIX biological index. Red circle, paddy soils; red square, red soils in croplands; green square, red soils in natural lands; red diamond, chernozem soils in croplands; green diamond, chernozem soils in natural lands; red triangle, cinnamon soils in croplands; green triangle, cinnamon soils in natural lands