Original Article

Subject Category: Microbial population and community ecology

The ISME Journal (2013) 7, 1102–1111; doi:10.1038/ismej.2013.11; published online 14 February 2013

Changes in assembly processes in soil bacterial communities following a wildfire disturbance

Scott Ferrenberg1, Sean P O'Neill1,2, Joseph E Knelman1,2, Bryan Todd1, Sam Duggan1, Daniel Bradley1, Taylor Robinson1, Steven K Schmidt1, Alan R Townsend1,2, Mark W Williams2,3, Cory C Cleveland4, Brett A Melbourne1, Lin Jiang5 and Diana R Nemergut2,6

  1. 1Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA
  2. 2Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA
  3. 3Department of Geography, University of Colorado, Boulder, CO, USA
  4. 4Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT, USA
  5. 5School of Biology, Georgia Institute of Technology, Atlanta, GA, USA
  6. 6Environmental Studies Program, University of Colorado, Boulder, CO, USA

Correspondence: DR Nemergut, Institute of Arctic and Alpine Research, Environmental Studies Program, University of Colorado, Boulder, CO 80309-0450, USA. E-mail: Diana.Nemergut@colorado.edu

Received 1 May 2012; Revised 28 December 2012; Accepted 9 January 2013
Advance online publication 14 February 2013

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Abstract

Although recent work has shown that both deterministic and stochastic processes are important in structuring microbial communities, the factors that affect the relative contributions of niche and neutral processes are poorly understood. The macrobiological literature indicates that ecological disturbances can influence assembly processes. Thus, we sampled bacterial communities at 4 and 16 weeks following a wildfire and used null deviation analysis to examine the role that time since disturbance has in community assembly. Fire dramatically altered bacterial community structure and diversity as well as soil chemistry for both time-points. Community structure shifted between 4 and 16 weeks for both burned and unburned communities. Community assembly in burned sites 4 weeks after fire was significantly more stochastic than in unburned sites. After 16 weeks, however, burned communities were significantly less stochastic than unburned communities. Thus, we propose a three-phase model featuring shifts in the relative importance of niche and neutral processes as a function of time since disturbance. Because neutral processes are characterized by a decoupling between environmental parameters and community structure, we hypothesize that a better understanding of community assembly may be important in determining where and when detailed studies of community composition are valuable for predicting ecosystem function.

Keywords:

niche vs neutral processes; community assembly; 16S rRNA gene pyrosequencing; Betaproteobacteria; Firmicutes; beta diversity