Table 1. Specialist taxa identified by indicator species analysis, which calculates the product of relative frequency and relative average abundance of a given OTU (Dufréne and Legendre, 1997).

Treatment	Location	Phylum	Family	Indicator value	P-value
Autochthonous DOC	Above treeline	Proteobacteria	Oxalobacteraceae	0.3823	0.009
		Proteobacteria	Oxalobacteraceae	0.3469	0.032
	Below treeline	Bacteroidetes	Chitinophagaceaea	0.381	0.003
		Verrucomicrobia	Spartobacteria	0.3673	0.014
		Proteobacteria	Pseudomonadaceae	0.3361	0.009
		Bacteroidetes	Cytophagaceaea	0.3111	0.004
		Proteobacteria	Alcaligenaceaea	0.3061	0.032
Allochthonous DOC	Around treeline	Bacteroidetes	Flavobacteriaceae	0.3034	0.008
	Below treeline	Bacteroidetes	Chitinophagaceaea	0.5357	0.002
		OD1a	OD1a	0.4396	0.002
		Bacteroidetes	Flavobacteriaceae	0.439	0.002
		Bacteroidetes	Chitinophagaceae	0.4286	0.001
		Bacteroidetes	Chitinophagaceae	0.3968	0.002
		Bacteroidetes	Flavobacteriaceae	0.3613	0.012
		Proteobacteria	Comamonadaceae	0.3571	0.015
		Proteobacteria	Oxalobacteraceae	0.3333	0.027
		Proteobacteria	Oxalobacteraceae	0.3183	0.008
		Firmicutesa	Pasteuriaceaea	0.3143	0.009
		Proteobacteria	Polyangiaceaea	0.3117	0.016
		Proteobacteria	Hyphomicrobiaceaea	0.3014	0.01

Abbreviations: DOC, dissolved organic carbon; OTU, operational taxonomic unit.

In total, 876 OTUs, all belonging to the active communities, were included.

^aClassification reliability below a confidence of 80%.