Table 1.

Summary of the datasets included in the meta-analysis

Dataset	Description	Successional age range and number of samples (N)	Soil pH range	Primer pair and targeted variable region	Sequencing platform and average length of sequencing reads (bp)	Rarefied sequence depth	Total number of OTUs observed	Data source
Systematically sampled across short-term succession	Austre Lovénbreen glacier chronosequence, Svalbard, Norway (AL)	2–142 years (N = 38)	6.5–8.0	27F/519R (V1–V3)	454-Pyrosequencing (472-bp)	438	2922	Kim et al. [22]
	Midtre Lovénbreen glacier chronosequence, Svalbard, Norway (ML)	2–87 years (N = 39)	7.8–9.4	Bakt_341F/ Bakt_805R (V3–V4)	Illumina Miseq (241-bp)	7148	15,075	This study
	Damma glacier chronosequence, Switzerland (DM)	10–110 years (N = 33)	4.8–6.2	27F/519R (V1–V3)	454-Pyrosequencing (261-bp)	3840	12,053	Rime et al. [24]
	Easton glacier chronosequence, Washington, USA (ES)	0–80 years (N = 13)	3.9–5.6	27F/338R (V1–V2)	454-Pyrosequencing (242-bp)	95	1118	Castle et al. [23]
Systematically sampled across long-term succession	Wilderness Park sand-dune soil chronosequence, Michigan, USA (SD)	0–4010 years (N = 85)	3.1–8.1	27F − YM + 3/ 515R-NK (V1–V3)	454-Pyrosequencing (162-bp)	485	4750	Williams et al. [27]
	Franz Josef Glacier chronosequence, South Island, New Zealand (FJ)	10–120,000 years (N = 42)	3.7–7.1	27F − YM + 3/ 515R-NK (V1–V3)	454-Pyrosequencing (228-bp)	576	2035	Jangid et al. [26]
Sampled without regard for successional age	Global scale sampling of soil across a range of biomes	— (N = 130)	3.6–8.9	27 F/338 R (V1–V2)	454-Pyrosequencing (213-bp)	514	13,950	Lauber et al. [31] and Chu et al. [29]