Changes in plant community composition and reduced precipitation have limited effects on the structure of soil bacterial and fungal communities present in a semiarid grassland

Abstract

To assess the impacts of precipitation and plants on soil bacterial and fungal communities, precipitation was reduced and plants were removed from experimental plots in a semiarid grassland. For plots with reduced precipitation, rainout shelters were constructed using clear, corrugated polycarbonate panels. Plant removal plots had plants extracted manually to remove both above- and belowground portions, and these plots were kept free of vegetation for the duration of the experiment. High-throughput sequencing of the 16S rRNA gene and fungal ITS region was used to assess the response of soil microbial communities to experimental manipulations. Soil moisture content, inorganic nitrogen concentrations, and aboveground plant biomass were also examined in these experimental plots. Soil moisture in plots with reduced precipitation was on average 40 % lower than that in control plots, while soil moisture in plant removal plots resembled that of control plots. No significant differences in available nitrogen were observed among treatments. Plots with reduced precipitation contained significantly less aboveground biomass than control plots, and also displayed a significantly higher occurrence of Russian thistle, an annual exotic. Soil bacterial and fungal communities were impacted by reduced precipitation, plant removal, and time, though these differences were subtle. Climate-change associated reductions in precipitation and vegetation will not cause large shifts in soil microbial communities on short time scales.