Historical and contemporary drivers of greenhouse gas emissions from upland soils

Precipitation events are increasing in intensity in the Midwestern United States due to climate change, leading to ponding in depressional areas within fields that can feed back on climate change by altering soil greenhouse gas (GHG) emissions. Ponding of soils can temporarily decrease soil O2 concentrations, creating conditions conducive for anaerobic biogeochemical reactions that produce and consume nitrous oxide (N2O) and carbon dioxide (CO2). In addition to the contemporary effects of ponding on soil O2 concentrations, repeated ponding of soils in depressional areas can alter soil biotic and biotic properties, establishing soil drainage legacy effects associated with microtopography that may control variation in soil CO2 and N2O emissions at the field scale. The role of soil drainage legacy on the response of soil GHG dynamics to intense precipitation events has not been previously explored, yet it may be important in accurately predicting soil GHG feedback effects on climate change. I demonstrate that soil drainage legacy effects lead to different controls on soil CO2 and N2O emissions. Specifically, ponding of upslope soils triggered pulses of N2O emissions caused by stimulation of gross N2O production by denitrifiers. In contrast, depressional soils only had high net N2O emissions between large rain events, and gross N2O production was inhibited following ponding. Greater abundance of Fe reducing microorganisms in depressional soils may facilitate the production of CO2 from dissimilatory Fe reduction under ponded conditions. Additionally, Fe reduction produces Fe(II) compounds that stimulate N2O via chemodenitrification, potentially fueling N2O emissions from depressional soils that harbor persistent anaerobic microsites. Finally, incorporating variables related to soil drainage failed to explain much variation in field-scale N2O emissions. Early in the spring, cold conditions constrain soil N2O emissions by slowing the depletion of soil O2 concentrations by microbial respiration. Later in the growing season, soil drainage legacy effects can counteract patterns in soil N2O emissions that might otherwise be expected as a result of the distribution of soil moisture across microtopographic gradients. Accounting for soil drainage legacy effects may be necessary to predict how soil GHG emissions will respond to rainfall intensification and feedback on climate change in the future.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Ecol, Evol, Conservation Biol

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2019

Author dc:creator

• Krichels, Alexander Howard

Contributors dc:contributor

• Yang, Wendy H
• Kent, Angela D
• DeLucia, Evan H
• Fraterrigo, Jennifer M

• nitrous oxide
• denitrification
• nitrification
• soil drainage
• global warming
• soil oxygen
• soil redox
• carbon dioxide

Statement dc:rights

• Copyright 2019 Alexander Krichels

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/105861

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/105861