Assessing restoration potential in relict wetland soils: investigating the effect of wetland hydrology on soil microbial community composition and denitrification potential

Wetland restoration;legacy sediments;denitrification;microbial community function;soil transplants

Koval, Jason ; Kent ; Angela D.

关键词: Wetland restoration;    legacy sediments;    denitrification;    microbial community function;    soil transplants;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/29438/Koval_Jason.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Microbial communities are known to strongly influence rates of biogeochemical cycling inwetland ecosystems; specifically, they are strong determinants of rates of denitrification typicallyobserved. Human induced land use changes have significantly reduced the acreage of wetlandhabitats, with dam building in the eastern United States figuring prominently in these losses.Wetlands located behind these dams turned into ponds, and this ecosystem alterationsignificantly lowers denitrification potential. Due to these ecosystem land use changes, higherexports of anthropogenic nitrate continue to leach off the land, ultimately ending up in openbodies of water. The damming and subsequent ponding of these floodplain systems have causedradically altered environmental conditions for relict wetland soils. Microbial communities areresistant to change, and may undergo periods of dormancy when conditions are not conducive toactivity, but it is uncertain how long they can withstand the effects of ecosystem alteration. Byremoving the dam and the depositional sediments, wetland restoration efforts attempt tostimulate higher rates of denitrification observed at the site. However, understanding if themicrobial 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) isimportant when studying sites targeted for restoration. This thesis attempts to address wetlandrestoration potential with two studies. In the first part, the hydric soil from Big Spring Run (a sitetargeted for wetland restoration) was surveyed for both denitrification potential and microbialcommunity composition. Big Spring Run (BSR) was the site of a floodplain wetland prior toEuropean settlement; however, in the 1800s, a dam was erected downstream, filling the wetlandto create a mill pond. The dam was removed in the mid-1900s; however the relict wetland soilremained buried under settled pond sediments. The relict wetland soil at BSR was surveyed tosee if the microbial communities present in the relict hydric soil (which has been buried for over200 years) are still functional. Results indicate that the current buried hydric soil performsdenitrification at significantly lower rates than any of the surveyed reference wetlands (Nov 2010F[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 toperform denitrification. The second part of this thesis attempts to determine if the microbialcommunity contained within relict hydric soil will perform high rates of denitrification againiiwhen dynamic wetland hydrology is restored. Soil from the altered BSR site was transplanted tonearby wetland ecosystems and denitrification rates and microbial community composition wereassessed before and after transplanting. Results indicate that when stable wetland environmentalparameters dominate, the microbial communities perform higher rates of denitrification in thetransplanted sites than in their current altered conditions (F[5,66]= 8.459, p<0.0001). Howeverthese denitrification rates, while improved over their current conditions, are still significantlylower than any of the surveyed reference wetland sites. Results were mixed when otherenvironmental 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 doshow slight improvements in denitrification potential after transplanting, the soil microbialcommunity at BSR seems resistant to a full recovery of denitrifying potential.