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Title:Assessing restoration potential in relict wetland soils: investigating the effect of wetland hydrology on soil microbial community composition and denitrification potential
Author(s):Koval, Jason
Advisor(s):Kent, Angela D.
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Wetland restoration
legacy sediments
microbial community function
soil transplants
Abstract:Microbial communities are known to strongly influence rates of biogeochemical cycling in wetland ecosystems; specifically, they are strong determinants of rates of denitrification typically observed. Human induced land use changes have significantly reduced the acreage of wetland habitats, with dam building in the eastern United States figuring prominently in these losses. Wetlands located behind these dams turned into ponds, and this ecosystem alteration significantly lowers denitrification potential. Due to these ecosystem land use changes, higher exports of anthropogenic nitrate continue to leach off the land, ultimately ending up in open bodies of water. The damming and subsequent ponding of these floodplain systems have caused radically altered environmental conditions for relict wetland soils. Microbial communities are resistant to change, and may undergo periods of dormancy when conditions are not conducive to activity, but it is uncertain how long they can withstand the effects of ecosystem alteration. By removing the dam and the depositional sediments, wetland restoration efforts attempt to stimulate higher rates of denitrification observed at the site. However, understanding if the microbial community inhabiting the relict hydric soil has a high restoration potential (e.g., capability of performing higher rates of denitrification when wetland hydrology is returned) is important when studying sites targeted for restoration. This thesis attempts to address wetland restoration potential with two studies. In the first part, the hydric soil from Big Spring Run (a site targeted for wetland restoration) was surveyed for both denitrification potential and microbial community composition. Big Spring Run (BSR) was the site of a floodplain wetland prior to European settlement; however, in the 1800s, a dam was erected downstream, filling the wetland to create a mill pond. The dam was removed in the mid-1900s; however the relict wetland soil remained buried under settled pond sediments. The relict wetland soil at BSR was surveyed to see if the microbial communities present in the relict hydric soil (which has been buried for over 200 years) are still functional. Results indicate that the current buried hydric soil performs denitrification at significantly lower rates than any of the surveyed reference wetlands (Nov 2010 F[4,31] = 13.75, p<0.0001; March 2011 F[4,42] = 84.6, p<0.0001; June 2011 F[4,35] = 71.89, p<0.0001). Bacterial community composition was also distinct between all of the sites sampled (ANOSIM R=0.693, p<0.001) indicating that no specific community composition is needed to perform denitrification. The second part of this thesis attempts to determine if the microbial community contained within relict hydric soil will perform high rates of denitrification again ii when dynamic wetland hydrology is restored. Soil from the altered BSR site was transplanted to nearby wetland ecosystems and denitrification rates and microbial community composition were assessed before and after transplanting. Results indicate that when stable wetland environmental parameters dominate, the microbial communities perform higher rates of denitrification in the transplanted sites than in their current altered conditions (F[5,66]= 8.459, p<0.0001). However these denitrification rates, while improved over their current conditions, are still significantly lower than any of the surveyed reference wetland sites. Results were mixed when other environmental parameters (e.g., cold temperatures, persistent flooding, and high stream flow) affected the results. Further work is needed to test the long term implications of these findings; however the preliminary results indicate that while the hydric soil microbial communities do show slight improvements in denitrification potential after transplanting, the soil microbial community at BSR seems resistant to a full recovery of denitrifying potential.
Issue Date:2012-02-01
Rights Information:Copyright 2011 Jason Koval, Angela Kent
Date Available in IDEALS:2014-02-01
Date Deposited:2011-12

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