Table 1.

Predicted species richness for Bacteria and Fungi and quantitative PCR of total bacterial or Gram-positive 16S rDNA in Larrea rhizosphere soil exposed to elevated or ambient [CO₂].

Phylogeny	[CO2]	No. of sequencesa	Observed No. of phylotypesb	Chao1 (SD)c	QPCR mean nanogram DNA per gram of fine roots SD (Ratio Ambient to Elelvated)
					Total	Gram-pos
Bacteria	Ambient	199	130	522 (343, 853)	2.53 ±0.37 (1.10)	34.02 ±6.69 (1.77)
	Elevated	208	164	535 (385, 788)	2.29 (±0.18)	19.20 (±3.65)
Fungi	Ambient	189	15	16 (15, 22)	N.D.	N.D.
	Elevated	182	49	64 (54, 92)	N.D.	N.D.

^aThe number of sequences used to calculate the species richness.

^bThe number of identified phylotypes (or OTUs) detected at 97% sequence similarity cut-off.

^cRelative richness employing the Chao1 (Chao, 1984) richness estimator, using single linkage clustering and 97% sequence similarity cutoff, for microbial communities under the different CO₂ treatments. (SD) = Standard deviations

N.D. = not done