PS 92-210 - Groundwater depth overrides tree-species effects on the structure of soil microbial communities involved in nitrogen cycling in plantation forests

Friday, August 16, 2019
Exhibit Hall, Kentucky International Convention Center
Tiehang Wu1, Tiehang Wu1, Tiehang Wu1, Tiehang Wu1, Bolanle Osi Efa1 and Doug P. Aubrey2, (1)Department of Biology, Georgia Southern University, Statesboro, GA, (2)Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA
Background/Question/Methods

Microbial communities found in soil ecosystems play important roles in decomposing organic materials and recycling nutrients. A clear understanding on how biotic and abiotic factors influence the microbial community and its functional role in ecosystems is fundamental to terrestrial biogeochemistry and plant production. The purpose of this study was to investigate microbial communities and functional genes involved in nitrogen cycling as a function of groundwater depth (deep and shallow), tree species (pine and eucalypt), and season (spring and fall). Soil fungal, bacterial and archaeal communities were determined by Length Heterogeneity-Polymerase Chain Reaction (LH-PCR), and soil ammonia oxidation archaeal (AOA) amoA gene, ammonia oxidation bacterial (AOB) amoA gene, nitrite oxidoreductase nrxA gene, and denitrifying bacterial narG, nirK, nirS and nosZ genes were further studied using PCR and Denaturing Gradient Gel Electrophoresis (DGGE).

Results/Conclusions

Soil fungal and bacterial communities determined by LH-PCR remained similar between tree species and groundwater depths respectively regardless of season. Soil archaeal communities determined by LH-PCR remained similar between tree species, but differed between groundwater depths in the spring only. Archaeal amoA for nitrification and bacterial nirK and nosZ genes for denitrification were detected in DGGE, whereas bacterial amoA, nrxA for nitrification and bacterial narG and nirS genes for denitrification were undetectable. The detected nitrification and denitrification community varied significantly with groundwater depths. There was no significant difference of nitrifying archaeal amoA or denitrifying nirK community between different tree species regardless of season. The seasonal difference in microbial communities and functional genes involved in nitrogen cycling was obvious and suggests microorganisms exhibit seasonal dynamics that likely impact relative rates of nitrification and denitrification.