Original Article

The ISME Journal (2015) 9, 2477–2489; doi:10.1038/ismej.2015.58; published online 15 May 2015

Temporal variation overshadows the response of leaf litter microbial communities to simulated global change

Kristin L Matulich1, Claudia Weihe1, Steven D Allison1,2, Anthony S Amend3, Renaud Berlemont2, Michael L Goulden1,2, Sarah Kimball4, Adam C Martiny1,2 and Jennifer BH Martiny1

  1. 1Department of Ecology and Evolutionary Biology, University of California-Irvine, Irvine, CA, USA
  2. 2Department of Earth System Science, University of California-Irvine, Irvine, CA, USA
  3. 3Department of Botany, University of Hawaii, Honolulu, HI, USA
  4. 4Center for Environmental Biology, University of California-Irvine, Irvine, CA, USA

Correspondence: KL Matulich, Department of Ecology and Evolutionary Biology, University of California-Irvine, 321 Steinhaus Hall, Irvine, CA 92697-2525, USA. E-mail: kristin.matulich@uci.edu

Received 19 December 2014; Revised 6 March 2015; Accepted 13 March 2015
Advance online publication 15 May 2015

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Abstract

Bacteria and fungi drive the decomposition of dead plant biomass (litter), an important step in the terrestrial carbon cycle. Here we investigate the sensitivity of litter microbial communities to simulated global change (drought and nitrogen addition) in a California annual grassland. Using 16S and 28S rDNA amplicon pyrosequencing, we quantify the response of the bacterial and fungal communities to the treatments and compare these results to background, temporal (seasonal and interannual) variability of the communities. We found that the drought and nitrogen treatments both had significant effects on microbial community composition, explaining 2–6% of total compositional variation. However, microbial composition was even more strongly influenced by seasonal and annual variation (explaining 14–39%). The response of microbial composition to drought varied by season, while the effect of the nitrogen addition treatment was constant through time. These compositional responses were similar in magnitude to those seen in microbial enzyme activities and the surrounding plant community, but did not correspond to a consistent effect on leaf litter decomposition rate. Overall, these patterns indicate that, in this ecosystem, temporal variability in the composition of leaf litter microorganisms largely surpasses that expected in a short-term global change experiment. Thus, as for plant communities, future microbial communities will likely be determined by the interplay between rapid, local background variability and slower, global changes.