Table 5 Effects of elevated CO₂ concentration (C) and N addition (N) on plant biomass and nitrogen content.

Treatment	Total biomass (mg)	Shoot biomass (mg)	Root biomass (mg)	Root:shoot ratio	Nitrogen concentration (mg g⁻¹)	Nitrogen content (mg pot⁻¹)
AN0	466.67 ± 51.32a	280.87 ± 23.58a	185.8 ± 27.83a	0.66 ± 0.05a	4.75 ± 0.32a	2.21 ± 0.11a
AN1	1013.33 ± 247.86b	581.22 ± 153.55b	432.11 ± 97.7a	0.75 ± 0.08ab	5.37 ± 0.38b	5.46 ± 1.31b
AN2	2716.67 ± 358.38d	1473.87 ± 110d	1242.79 ± 249.93c	0.84 ± 0.11bc	5.31 ± 0.44ab	14.42 ± 1.83d
EN0	686.67 ± 75.06ab	406.55 ± 68.04ab	280.12 ± 18.14a	0.70 ± 0.10ab	4.77 ± 0.12a	3.28 ± 0.44a
EN1	1733.33 ± 94.52c	879.59 ± 54.56c	853.74 ± 41.76b	0.97 ± 0.03c	5.27 ± 0.34ab	9.12 ± 0.51c
EN2	4103.33 ± 290.23e	1966.89 ± 285.25e	2136.44 ± 178.17d	1.10 ± 0.19d	5.40 ± 0.26b	22.18 ± 1.73e
P values of two-way ANOVAs
C	<0.001	<0.001	<0.001	0.005	0.969	<0.001
N	<0.001	<0.001	<0.001	0.002	0.009	<0.001
C × N	<0.001	0.130	0.002	0.201	0.841	<0.001

Different letters within a column indicate significant differences (P < 0.05) based on Duncan’s multiple range test. Significant P values are highlighted in bold. AN0, ambient CO₂ and no N added; AN1 ambient CO₂ and N supply at a rate of 2.5 g N m⁻² y⁻¹; AN2^, ambient CO₂ and N supply at a rate of 5 g N m⁻² y⁻¹; EN0^, elevated CO₂ and no N added; EN1, elevated CO₂ and N supply at a rate of 2.5 g N m⁻² y⁻¹; EN2^, elevated CO₂ and N supply at a rate of 5 g N m⁻² y⁻¹.

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