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Elk, sagebrush, and saprotrophs: indirect top‐down control on microbial community composition and function
Author(s) -
Peschel Anna R.,
Zak Donald R.,
Cline Lauren C.,
Freedman Zachary
Publication year - 2015
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/15-0164.1
Subject(s) - foraging , ecology , biology , plant community , steppe , shrub , microbial population biology , detritus , ecosystem , species richness , genetics , bacteria
Saprotrophic microbial communities in soil are primarily structured by the availability of growth‐limiting resources (i.e., plant detritus), a bottom‐up ecological force. However, foraging by native ungulates can alter plant community composition and the nature of detritus entering soil, plausibly exerting an indirect, top‐down ecological force that shapes both the composition and function of soil microbial communities. To test this idea, we used physiological assays and molecular approaches to quantify microbial community composition and function inside and outside of replicate, long‐term (60–80 yr) winter‐foraging exclosures in sagebrush steppe of Wyoming, USA. Winter foraging exclusion substantially increased shrub biomass (2146 g/m 2 vs. 87 g/m 2 ), which, in turn, increased the abundance of bacterial and fungal genes with lignocellulolytic function; microbial respiration (+50%) and net N mineralization (+70%) also were greater in the absence of winter foraging. Our results reveal that winter foraging by native, migratory ungulates in sagebrush steppe exerts an indirect, top‐down ecological force that shapes the composition and function of soil microbial communities. Because ~25% of the Earth's land surface is influenced by grazing animals, this indirect top‐down ecological force could function to broadly shape the community membership and physiological capacity of saprotrophic microbial communities in shrub steppe.