Table 3.

Multiple regression analysis between functional gene level and TC, TN, and successional age as independent factors.

Parameters	Standardized coefficient (β)a			Model P value
	TC	TN	Age
nifH level	0.82∗∗	0.085	0.018	0.00
AOA level	-0.40	-0.55∗∗	0.57∗∗	0.001
AOB level	0.81∗∗	0.067	0.056	0.001
nirS level	0.74∗∗	0.48∗∗	0.39	0.01
nirK level	0.56∗	0.04	-0.85	0.001
nosZ level	0.74∗∗	0.78∗∗	0.41	0.01

^aSignificance levels (p) of the multiple regression model are as follows: ^∗p< 0.05; ^∗∗p < 0.01.