Drought consistently alters the composition of soil fungal and bacterial communities in grasslands from two continents

TitleDrought consistently alters the composition of soil fungal and bacterial communities in grasslands from two continents
Publication TypeJournal Article
Year of Publication2018
AuthorsOchoa-Hueso R, Collins SL, Delgado-Baquerizo M, Hamonts K, Pockman WT, Sinsabaugh RL, Smith MD, Knapp AK, Power SA
JournalGlobal Change Biology
Date Published01/2018
Accession NumberSEV.799

The effects of short-term drought on soil microbial communities remain largely
unexplored, particularly at large scales and under field conditions. We used seven
experimental sites from two continents (North America and Australia) to evaluate
the impacts of imposed extreme drought on the abundance, community composition,
richness, and function of soil bacterial and fungal communities. The sites
encompassed different grassland ecosystems spanning a wide range of climatic and
soil properties. Drought significantly altered the community composition of soil bacteria
and, to a lesser extent, fungi in grasslands from two continents. The magnitude
of the fungal community change was directly proportional to the precipitation gradient.
This greater fungal sensitivity to drought at more mesic sites contrasts with the
generally observed pattern of greater drought sensitivity of plant communities in
more arid grasslands, suggesting that plant and microbial communities may respond
differently along precipitation gradients. Actinobateria, and Chloroflexi, bacterial
phyla typically dominant in dry environments, increased their relative abundance in
response to drought, whereas Glomeromycetes, a fungal class regarded as widely
symbiotic, decreased in relative abundance. The response of Chlamydiae and Tenericutes,
two phyla of mostly pathogenic species, decreased and increased along the
precipitation gradient, respectively. Soil enzyme activity consistently increased under
drought, a response that was attributed to drought-induced changes in microbial
community structure rather than to changes in abundance and diversity. Our results
provide evidence that drought has a widespread effect on the assembly of microbial
communities, one of the major drivers of soil function in terrestrial ecosystems.
Such responses may have important implications for the provision of key ecosystem
services, including nutrient cycling, and may result in the weakening of plant–microbial
interactions and a greater incidence of certain soil-borne diseases.