13C NMR spectroscopy characterization of particle-size fractionated soil organic carbon in subalpine forest and grassland ecosystems

Botanical Studies

Table 4 CP/MAS ¹³C NMR of distribution of organic carbon functional group of whole soils in different sampling locations

Site	% of C functional groups				HI^a	AR^b
Site	Carboxyl-C	Aromatic-C	O-Alkyl-C	Alkyl-C	HI^a	AR^b
Forest	7.42	12.29	51.18	29.11	0.70	0.13
Transition	7.82	14.84	49.11	26.82	0.68	0.16
Grassland	7.63	12.72	52.39	26.52	0.63	0.14

^aHumification degree of sampling soils: alkyl-C peak area (0–50 ppm)/O-alkyl-C peak area (50–110 ppm)
^bAromaticity ratio: aromatic-C peak area (110–165 ppm)/total peak area (0–165 ppm)