Data from: Exotic invasive plants increase productivity, abundance of ammonia-oxidizing bacteria, and nitrogen availability in intermountain grasslands

1. Exotic plant invasion is often associated with dramatic increases in
above-ground net primary productivity and soil nitrogen. However, most
evidence for these increases comes from correlative studies of single
species, leaving open the question of whether invasive plants drive these
processes and if they are consistent among invaders. 2. We combined field
surveys and measurements within experimental plantings to examine how
plant productivity, soil nitrogen, and the abundance of ammonia-oxidizing
bacteria (AOB) change in response to invasions by four exotic species. 3.
The relationship between plant productivity and soil nitrate differed
among native and invasive species, suggesting a fundamental disparity in
the effects of natives and invaders on ecosystem processes. In field
surveys, dense patches of all invasive species had higher abundances of
AOB than native-dominated sites. Three of the four invasive species had
higher productivity, soil nitrate concentrations, and rates of potential
nitrification as compared to nearby native-dominated communities. In our
experimental plantings we found that two invasive species drove increases
in soil nitrate and one invader caused increased productivity after a
single season. 4. Synthesis:Our results highlight the importance of the
N-cycling soil microbial community in how exotic invasive plants alter
ecosystem function and show that shifts in function can occur rapidly.