46 Temporal response of the soil microbial community to prescribed fall fire in the tallgrass prairie

Thursday, August 6, 2009
Exhibit Hall NE & SE, Albuquerque Convention Center
Amanda M. Anderson , Emporia State University, Emporia, KS
Brenda A. Koerner , Department of Biological Sciences, Emporia State University, Emporia, KS

Microbial diversity is of ecological interest because various microorganisms in soil communities impact the function of ecosystems.  Microbes play pivotal roles in the biochemical cycling in soil communities and organic matter decomposition. Environmental disturbances often have dramatic effects on microbial diversity and abundance.  This study aimed to determine how prescribed fire affects soil microbial diversity and abundance in the tallgrass prairie and encroaching shrub islands.  We predicted that the microbial biomass of the soil community would be significantly reduced in the short term as a result of the prescribed burning. We also predicted that microbial diversity would decrease as a result of the burn.   Different types of microbes have very different functions within the soil community and removal of any one type may have a detrimental impact on the productivity of the soil.An area of native tallgrass prairie at the Ross Natural History Reservation, located 15 miles Northwest of Emporia, Kansas was used in this study.   Sixteen 30m X 30m plots were burned under controlled conditions in the fall of 2008.  Eight of these plots were shrub dominated and eight were graminoid dominated.  Soil samples were taken prior to the burn, three days after the burn, and 21 days after the burn from experimental and control plots.

Fire temperature was measured on the soil surface in all of the experimental plots using ceramic tiles marked with temperature sensitive paint.  Surface fire temperature in graminoid dominated plots (99.9 ± 4.1 °C) was not significantly different from temperatures in shrub dominated plots (96.5 ± 6.6 °C). The lack of temperature difference between the two plot types shows fire temperature was not a factor in the differences observed in the microbes present between the two plot types.  Microbial abundance was determined using microbial biomass following the fumigation incubation method.  Results from this method showed an initial increase in microbial biomass possibly due to increased surface temperature following burning. To determine soil microbial diversity, soil samples were analyzed using denaturing gradient gel electrophoresis (DDGE). DDGE separates polymerase chain reaction generated DNA products isolated from the soil samples according to the degree of denaturing. All samples were analyzed for the presence of eubacteria and fungi using primers of DNA that match a sequence commonly found in these microbes.  Electrophoresis results showed a difference in microbial diversity between the two plots types as well as samples taken before and after the fire.

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