64 Emerging Voices in Soil and Paleosol Science (Posters)

This session promotes research from students at all levels that are investigating soils and paleosols. We invite submissions from field, laboratory, and modeling studies that leverage or examine pedogenic processes and archives, from deep-time through modern systems.

Sunday, 19 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

Composition of Soil Microbial and Fungal Communities of a Bottomland Forest in the Tennessee River Basin, Kentucky

Paper number: 64-7
Program: Technical Sessions
Time: 8:30 AM – 8:30 AM

Authors

Abstract

Bottomland forests can be a significant source of methane, a potent greenhouse gas. The microbes in these forest soils play a major role in the development, function, and regulation of chemical and physical processes that impact the atmosphere. Yet, limited information is available about the composition, distribution, and role of fungi in these environments. We examined the composition of microbial and fungal communities along a bottomland channel to floodplain gradient of Dunn Slough, in Clark River National Wildlife Refuge, to establish connections between these microbes and wetland soil processes. Soil samples were collected at depths of 10 and 40 cm along three transects in the fall of 2024. Transects were composed of sites with low- and high-density cypress knees in the channel, and on the hardwood floodplain. The extracted genomic DNA was sequenced for 16S and ITS rRNA genes, followed by bioinformatics to classify the microbial and fungal communities. These results were compared between the transect sites and by depth.

 

Ascomycota and Basidiomycota were the dominant fungal phyla at all sites. While high heterogeneity was observed at the genus level among sites, about 10% of the unique fungal amplicon sequence variants (ASVs) were mycorrhizal at both depths in floodplain samples, and their relative abundance ranged from 20 to 94%. The channel samples were dominated by saprophytic and endophytic fungi, with less than 1% relative abundance of mycorrhizal fungi and no direct evidence of mycorrhizal colonization of bald cypress. Methanogens were present in all channel samples at the order level, with the highest relative abundance in the deep samples (0.25-1.25%). However, on the floodplain, only the deep samples had methanogens (< 0.25%). These bottomland soils are often methane sinks, but our monitoring confirmed methane emissions from bald cypress knees throughout the year, which could be aided by the presence of methanogens in the deeper soils. Methanotrophs were present in all samples. The highest relative abundance (2%) and diversity at the genus level were found at the shallow, low-density cypress knee sites. In the floodplain samples, only one methanotroph family was identified. Our next steps will include analyzing the relationship among microbes, fungi, hydrology, soil processes, and greenhouse gas fluxes in these wetlands.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412898

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