Keywords

Soil microbes; Microbial respiration; Amendment additions; MAOM formation; Wetlands; Carbon cycle

Abstract

Wetlands play a critical role in the global carbon cycle by acting as carbon sinks, where the flooded anaerobic conditions cause slow microbial respiration compared to other soils. Comparatively more carbon is stored in the soil as organic matter than is released as carbon dioxide (CO2). Making wetland pools of soil organic matter less available to microbes for respiration could reduce overall atmospheric CO2 and slow global warming. This study examined the effect of kaolinite, goethite, and lime on microbial respiration rates in wetland soils under alternating hydrologic conditions. Homogenized soil from a cypress dome was separated into microcosms and amended or left untreated as a control. The CO2 flux rate was then measured while the soil was either saturated or dry. Lime-amended soils exhibited greater CO2 flux rates (0.320 ± 0.022 μmol m⁻² s⁻¹) compared to the control (0.184 ± 0.019 μmol m⁻² s⁻¹) (p < 0.0001 while saturated, p = 0.0118 while dry), whereas kaolinite and goethite treatments slightly lowered CO2 flux (0.141 ± 0.004 μmol m⁻² s⁻¹ and 0.147 ± 0.005 μmol m⁻² s⁻¹, respectively), but was not significant. Lime also had an impact on soil pH (a 30.8% increase relative to initial soil pH), which may have created more favorable conditions for microbial respiration. Changes in water level only impacted the lime treatment (37.5% higher flux rate when saturated). These findings suggest lime accelerates respiration and is an undesirable amendment for the promoting of carbon storage. The potential for kaolinite and goethite to preserve soil organic carbon requires additional study. Adding amendments to reduce CO2 flux rates in organic-rich wetland soils could be a climate-smart strategy for enhanced terrestrial carbon storage.

Thesis Completion Year

2026

Thesis Completion Semester

Spring

Thesis Chair

Chambers, Lisa

College

College of Community Innovation and Education

Thesis Discipline

Environmental Studies

Access Status

Open Access

Length of Campus Access

None

Campus Location

Orlando (Main) Campus

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