title: Experimental drought reduces the transfer of recently fixed plant carbon to soil microbes and alters the bacterial community composition in a mountain meadow.
abstract: Drought affects plants and soil microorganisms, but it is still not clear how it alters the carbon (C) transfer at the plant-microbial interface. Here, we tested direct and indirect effects of drought on soil microbes and microbial turnover of recent plant-derived C in a mountain meadow. Microbial community composition was assessed using phospholipid fatty acids (PLFAs); the allocation of recent plant-derived C to microbial groups was analysed by pulse-labelling of canopy sections with (13) CO2 and the subsequent tracing of the label into microbial PLFAs. Microbial biomass was significantly higher in plots exposed to a severe experimental drought. In addition, drought induced a shift of the microbial community composition, mainly driven by an increase of Gram-positive bacteria. Drought reduced belowground C allocation, but not the transfer of recently plant-assimilated C to fungi, and in particular reduced tracer uptake by bacteria. This was accompanied by an increase of (13) C in the extractable organic C pool during drought, which was even more pronounced after plots were mown. We conclude that drought weakened the link between plant and bacterial, but not fungal, C turnover, and facilitated the growth of potentially slow-growing, drought-adapted soil microbes, such as Gram-positive bacteria.
authors.affiliation: Department of Microbiology and Ecosystem Science, University of Vienna, Althanstr. 14, A-1090, Vienna, Austria.
authors.forename: Lucia
authors.initials: L
authors.lastname: Fuchslueger
authors.affiliation: Institute of Ecology, University of Innsbruck, Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Bahn
authors.affiliation: Institute of Ecology, University of Innsbruck, Innsbruck, Austria.
authors.forename: Karina
authors.initials: K
authors.lastname: Fritz
authors.affiliation: Institute of Ecology, University of Innsbruck, Innsbruck, Austria.
authors.forename: Roland
authors.initials: R
authors.lastname: Hasibeder
authors.affiliation: Department of Microbiology and Ecosystem Science, University of Vienna, Althanstr. 14, A-1090, Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Richter
mesh_terms: D001317:Austria; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D057486:Carbon Cycle; D002247:Carbon Isotopes; D055864:Droughts; D017753:Ecosystem; D064307:Microbiota; D008834:Microclimate; D009584:Nitrogen / Q000032:analysis; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013997:Time Factors; D014867:Water
chemical_list: D002247:Carbon Isotopes; D012987:Soil; D014867:Water; D002244:Carbon; D009584:Nitrogen
keywords: 13C pulse-labelling; carbon allocation; drought; microbial community composition; mountain grassland; mowing; phospholipid fatty acids