Effects of Atmospheric CO₂ Enrichment on Soil CO₂ Efflux in a Young Longleaf Pine System

Table 1

Regression parameters and statistics for relationships of total soil CO₂ efflux (g C m⁻²) over the 90-day measurement period with soil N and C content.

CO2^a	Soil profile depth	Soil elemental content (g m^−2)^b	Intercept	Variable	Significance of variable (𝑝𝑟>|𝑡|)	𝑟^2
Ambient	0–15 cm	N	163.970	1.550	0.17	0.42
	15–30 cm	N	172.578	1.516	0.17	0.41
	30–45 cm	N	136.918	2.381	0.12	0.49
	45–60 cm	N	185.687	1.101	0.30	0.26
	0–60 cm	N	165.534	0.403	0.18	0.39
Elevated	0–15 cm	N	169.059	2.805	0.07	0.60
	15–30 cm	N	179.336	2.908	0.26	0.30
	30–45 cm	N	207.544	2.197	0.22	0.35
	45–60 cm	N	220.245	1.795	0.30	0.26
	0–60 cm	N	190.030	0.633	0.18	0.39
Ambient	0–15 cm	C	57.834	0.215	0.21	0.36
	15–30 cm	C	−34.372	0.379	0.05	0.67
	30–45 cm	C	−130.076	0.499	0.04	0.69
	45–60 cm	C	−20.394	0.315	0.12	0.50
	0–60 cm	C	−142.144	0.123	0.02	0.79
Elevated	0–15 cm	C	−61.083	0.443	0.01	0.88
	15–30 cm	C	−79.153	0.528	0.08	0.57
	30–45 cm	C	75.940	0.309	0.11	0.51
	45–60 cm	C	19.100	0.356	0.14	0.46
	0–60 cm	C	−120.255	0.139	0.01	0.83

^aAmbient CO₂≈365 μmol mol⁻¹; elevated CO₂≈720 μmol mol⁻¹. ^bN: soil nitrogen; C: soil carbon.