The effect of plant invasion on soil microbial carbon-use efficiency in semiarid grasslands of the Rocky Mountain West

1. Grassland ecosystems invaded by exotic plant species often exhibit substantially higher aboveground productivity and soil nitrogen (N) than the native communities they replace. These shifts are likely associated with altered microbial carbon (C) and N cycling, but we know surprisingly little about how these processes change with plant invasion.

2. Targeting four invasive plant species common in the Rocky Mountain West, we collected soils from invaded and adjacent uninvaded grassland field plots, as well as from an experimental garden. We used a laboratory incubation of soils with 13C- and 15N-labelled substrates to examine how microbial C respiration, C assimilation, and N cycling differed among plant communities. To assess how these rates corresponded with plant productivity and microbial communities, we measured aboveground plant biomass and characterized bacterial and fungal communities using Illumina sequencing.

3. In the paired observational plots, soil microbial communiti...