. 2011 Mar 18;6(3):e17961. doi: 10.1371/journal.pone.0017961

Table 1. Summary of regression analyses between petroleum concentration (X) and soil properties (Y).

Soil properties (Y)	Stage	b ₁	b ₀	R²	P	Soil properties (Y)	Stage	b ₁	b ₀	R²	P
DOC	EVG	0.659	33.703	0.506	<0.001	DON	EVG	0.219	8.575	0.26	<0.01
	LVG	0.746	19.795	0.444	<0.001		LVG	-0.011	5.896	0.004	NS
	REP	1.883	32.694	0.546	<0.001		REP	0.08	8.163	0.132	NS
	EVG vs. LVG	<0.001	NS				EVG vs. LVG	<0.001	<0.01
	EVG vs. REP	<0.001	<0.01				EVG vs. REP	<0.001	NS
	LVG vs. REP	<0.001	<0.01				LVG vs. REP	<0.001	NS
DIN	EVG	0.019	10.307	0.006	NS	NNM	EVG	-0.117	0.277	0.127	NS
	LVG	0.122	6.625	0.461	<0.001		LVG	-0.527	7.612	0.523	<0.001
	REP	0.088	7.098	0.213	<0.05		REP	-0.542	7.232	0.536	<0.001
	EVG vs. LVG	<0.001	NS				EVG vs. LVG	<0.001	<0.001
	EVG vs. REP	<0.001	NS				EVG vs. REP	<0.001	<0.001
	LVG vs. REP	<0.001	NS				LVG vs. REP	<0.001	NS

Equations are in the form Y = b ₁X + b ₀. Differences among plant developmental stages were also tested using ANCOVA. NS means non-significant. EVG: the early stage of vegetative growth; LVG: the late stage of vegetative growth; and REP: the reproductive stage.

DOC: dissolved organic carbon; DIN: dissolved inorganic nitrogen; DON: dissolved organic nitrogen; NNM: net nitrogen mineralization.