Continental scale drivers of microbial biomass and community composition

Background/Question/Methods

Soil microbes play an integral role in ecosystem functions by supporting plant growth, cycling nutrients, and sequestering carbon. But there is a lack of consensus regarding the drivers of microbial biomass across space and time due to an absence of standardized data at continental scales. The recent availability of open and standardized data from the National Ecological Observatory Network (NEON) provides an opportunity to quantify the drivers at continental scale. We used phospholipid fatty acid (PLFA), litter, land cover, and soil physicochemical data to identify the most important drivers of microbial biomass across 41 NEON sites in the United States.

Results/Conclusions

Our results show that soil moisture, longitude, and acidity are the top predictors for microbial biomass based on random forest analysis. Percent vegetative coverage is not an important predictor, but the land cover types show significant impact on microbial biomass. For example, dwarf/scrub and herbaceous sedge plots had the highest levels of biomass while pasture hay, cropland, and shrub scrub plots had the lowest biomass levels. The importance of moisture and acidity corroborates previous microbial biogeography studies, but our results suggest that carbon and nitrogen levels are not strong predictors of microbial biomass as expected. Our findings highlight the biogeography and drivers of microbial biomass at the continental scale and emphasize the need to consider how soil microbial communities will respond to changing land cover and climate.