Characterization of soil organic matter in perhumid natural cypress forest: comparison of humification in different particle-size fractions

Botanical Studies

Table 3 Relative distribution of integrated peak areas of chemical shift regions in the CP/MAS ¹³ C NMR spectra of partially decomposed materials collected from 3 organic horizons at 3 topographic positions

Topographic position	Horizon	C functional group (%)					A/ O-A ratio^a	Aromaticity^b
		alkyl	O- alkyl	di- O-alkyl	aromatic	carboxyl
Summit	Oi	34.1	30.5	15.0	13.7	6.7	0.75	0.15
	Oe	33.7	30.5	13.5	16.4	5.9	0.77	0.17
	Oa	33.5	30.0	12.5	16.2	7.8	0.79	0.18
Footslope	Oi	26.7	31.6	15.4	18.3	8.0	0.57	0.20
	Oe	28.2	30.9	14.9	18.2	7.8	0.61	0.20
	Oa	27.8	30.1	14.4	19.9	7.7	0.62	0.22
Lakeshore	Oi	30.9	26.4	15.4	19.9	7.4	0.74	0.21
	Oe	31.0	26.1	14.6	20.4	7.8	0.76	0.22
	Oa	31.3	25.9	14.2	20.7	7.9	0.78	0.22

^aalkyl-C peak area (0–50 ppm)/( (O-alkyl-C + di-O-alkyl C) peak area (50–110 ppm) ).
^baromatic C peak area (110–165 ppm)/ ((alkyl-C + O-alkyl-C + di-O-alkyl C + aromatic C) peak area (0–165 ppm)).