Data from: Smooth brome invasion increases rare soil bacterial species prevalence and alters soil bacterial community composition

Plant and soil communities are tightly linked, but the mechanisms by which
the invasion of an exotic plant and the resulting shifts in plant
diversity and productivity influence soil bacterial community structure
remain poorly understood. We investigated the effects of invasive smooth
brome (Bromus inermis) on grassland soil bacterial community structure
using massively-parallel sequencing of the 16S rRNA gene to determine
bacterial community richness, evenness, composition, and beta diversity
(UniFrac indices) of soils collected along a gradient of smooth brome
abundance. We evaluated several hypotheses including: a) that the declines
in native plant diversity associated with smooth brome invasion would
cause declines in bacterial community diversity, and b) that mechanisms
driving smooth brome effects on bacterial community structure involved
altered soil edaphic properties rather than preferential invasion in areas
of high soil nitrogen and distinct soil microbial communities. Smooth
brome invasion led to increased soil nitrogen, soil carbon and root
biomass. Bacterial evenness and bacterial richness increased with
increasing smooth brome cover, while bacterial beta diversity declined. We
found no evidence of a dominant direct link between the alteration of soil
edaphic properties by brome and the changes in the soil bacterial
community. Rather, the main controls on the soil bacterial community were
direct effects of pH and smooth brome that could not be linked to the
edaphic changes. The most important effect of brome on the bacterial
community was the selective suppression of dominant bacterial species,
which allowed rarer bacteria to increase in relative abundance. Synthesis:
Here we show that plant community composition influences bacterial
community structure at a very fine scale, but that these changes are not
due to altered soil total nitrogen or carbon content. The dominant direct
effect of smooth brome invasion on soil communities suggests non-edaphic,
i.e. inter and intra-trophic, interactions among smooth brome and
non-bacterial components of the soil ecosystem are key drivers of soil
community structure. Some of the data in this repository were also
reported in the following paper: Piper, C.L., Lamb, E.G. &
Siciliano, S.D. (In Press) Smooth brome changes gross soil nitrogen
cycling processes during invasion of a rough fescue grassland. Plant
Ecology. doi:10.1007/s11258-014-0431-y