Effects of elevated atmospheric CO₂ on rhizosphere microbial community of Pinus densiflora (Korean red pine)

Figures & data

Figure 1. Cumulative heights and root diameters of Korean red pine from three different CO₂ concentration treatment chambers. OTC1: Elevated CO₂ level as 1.4x (approximately 560 ppm), OTC2: elevated CO₂ level as 1.8x (approximately 680 ppm), and OTC3: ambient CO₂ level (approximately 380 ppm).

Figure 2. Rarefaction curves for bacterial operational taxonomic units (OTUs; 97% sequence similarity) in each sampling chamber associated with the rhizosphere of pine tree. In the rarefaction curves, the number of OTUs increased with the number of sequencing reads. OTC1: elevated CO₂ level as 1.4x (approximately 560 ppm), OTC2: elevated CO₂ level as 1.8x (approximately 680 ppm), and OTC3: ambient CO₂ level (approximately 380 ppm).

Table 1. Comparison of the estimated OTU richness and diversity indexes in the rhizosphere of Korean red pine according to CO₂ concentration.

Sample	Valid reads	OTUs	Ace	Chao1	Jackknife	NPShannon	Shannon	Simpson	Goods Lib. coverage
OTC1	13,569	2045	3013.8	2730.3	2911.1	6.45	6.22	0.0112	91.8
OTC2	16,179	2874	3761.5	3500.0	3853.5	7.41	7.20	0.0018	92.2
OTC3	15,989	2524	3400.5	3122.6	3401.3	7.07	6.88	0.0032	93.2

Figure 3. Similarity of phylogenetic diversity at the phylum level (97% sequence similarity) for bacterial communities. The hierarchical relationship was obtained via the unweighted pair group method with arithmetic mean (UPGMA) clustering dendrogram. OTC1: elevated CO₂ level as 1.4x (approximately 560 ppm), OTC2: elevated CO₂ level as 1.8x (approximately 680 ppm), and OTC3: ambient CO₂ level (approximately 380 ppm).

Figure 4. Relative distribution (%) of the main bacteria taxa detected in the rhizosphere of Korean red pine tree according to CO₂ concentration. OTC1: elevated CO₂ level as 1.4x (approximately 560 ppm), OTC2: elevated CO₂ level as 1.8x (approximately 680 ppm), and OTC3: ambient CO₂ level (approximately 380 ppm).

Table 2. Chemical properties of Korean red pine leaves according to CO₂ concentration.

Sample	Total organic carbon (%)	Nitrogen (%)	Phosphate (ppm)
OTC1	45.44 ± 1.27 ns	1.30 ± 0.07 a	0.49 ± 0.05 ns
OTC2	43.18 ± 1.55 ns	1.14 ± 0.06 ab	0.39 ± 0.08 ns
OTC3	41.78 ± 1.07 ns	1.08 ± 0.02 b	0.42 ± 0.03 ns

Different lowercase letters indicate statistically significant difference at 5% level in columns. ns: not significant.

Table 3. Soil chemical properties in the rhizosphere of Korean red pine according to CO₂ concentration.

Sample	pH	OM (%)	TN (%)	TP (mg kg^−1)	CEC (cmol kg^−1)	K^+(mg kg^−1)	Na^+(mg kg^−1)	Ca^2+ (mg kg^−1)	Mg^2+(mg kg^−1)	EC (dS m^−1)
OTC1	6.73 ± 0.03 a	0.35 ± 0.04 ns	0.01 ± 0.00 a	28.30 ± 1.01 a	1.98 ± 0.04 a	0.08 ± 0.00 ns	0.06 ± 0.00 ns	2.81 ± 0.01 a	0.48 ± 0.03 ns	0.07 ± 0.00 a
OTC2	6.07 ± 0.03 b	0.36 ± 0.05 ns	0.09 ± 0.00 a	16.13 ± 2.21 b	1.27 ± 0.15 b	0.08 ± 0.01 ns	0.05 ± 0.00 ns	1.60 ± 0.13 b	0.44 ± 0.05 ns	0.05 ± 0.00 b
OTC3	5.90 ± 0.15 b	0.39 ± 0.06 ns	0.11 ± 0.00 b	18.23 ± 2.91 b	1.56 ± 0.21 ab	0.07 ± 0.00 ns	0.05 ± 0.00 ns	1.78 ± 0.18 b	0.42 ± 0.01 ns	0.06 ± 0.00 b

Different lowercase letters indicate statistically significant difference at 5% level in columns. ns: not significant.