Table 2. Relationship between C functional group contents (y) and C contents in physical subfractions (x) in macroaggregates and microaggregates.^a.

Subfraction	C functional groups	Macroaggregates (>250 μm)		Microaggregates (53–250 μm)
		Equation	R2	Equation	R2
Coarse iPOM	Alkyl C	y = 10.206e0.305x	0.743	–	–
	Methxoyl/N-alkyl C	y = 1.961lnx−4.393	0.865*	–	–
	O-alkyl C	y = 10.096e0.137x	0.599	–	–
	di-O-alkyl C	y = 10.091e0.388x	0.612	–	–
	Aromatic C	y = 8.199e0.289x	0.585	–	–
	Phenolic C	y = 1.752lnx−4.044	0.872*	–	–
	Carboxyl C	y = 2.837lnx−6.449	0.687	–	–
Fine iPOM	Alkyl C	y = 1.562e0.766x	0.399	y = 2.151x+2.749	0.197
	Methxoyl/N-alkyl C	y = 0.514lnx+0.206	0.696	y = 2.686lnx+6.183	0.396
	O-alkyl C	y = 0.797e0.555x	0.837*	y=3.684lnx+2.891	0.600
	di-O-alkyl C	y = 0.836e1.526x	0.807*	y = 3.585lnx+6.877	0.632
	Aromatic C	y = 0.304e1.226x	0.898*	y = 2.625x+1.526	0.364
	Phenolic C	y = 0.419lnx+0.125	0.585	y = 2.939lnx+7.314	0.520
	Carboxyl C	y = 0.194lnx+0.406	0.534	y = 0.258e0.242x	0.670
Silt + clay subfraction	Alkyl C	y = 1.101e1.318x	0.848*	y = 3.463x+4.559	0.513
	Methxoyl/N-alkyl C	y = 0.46lnx+0.105	0.780*	y = 6.231x+3.911	0.838*
	O-alkyl C	y = 1.08e0.584x	0.663	y = 2.350x+3.660	0.688
	di-O-alkyl C	y = 1.24e1.522x	0.575	y = 7.161x+3.585	0.785
	Aromatic C	y = 0.471e1.205x	0.621	y = 4.415e0.445x	0.650
	Phenolic C	y = 0.398lnx+0.002	0.735	y = 8.429x+4.012	0.847*
	Carboxyl C	y = 0.776lnx-0.145	0.842*	y = 0.187x-0.564	0.609

^aThe data for C content in physical subfractions are cited from Yu et al.²⁰, and iPOM is the abbreviation for intra particulate organic matter. *P < 0.05; **P < 0.01.