Patterns of Denitrification and Methanogenesis Rates from Vernal Pools in a Temperate Forest Driven by Seasonal, Microbial Functional Gene Abundances, and Soil Chemistry

Due to their relatively small sizes, temperate forest vernal pools are less studied than other wetlands, despite being potential biogeochemical hotspots in landscapes. We investigated spatial and temporal factors driving N 2 O and CH 4 emission rates from vernal pools in a temperate forest. We determined higher N 2 O (3.66 ± 0.53 × 10 −6 , μg N 2 O/m 2 /h) and CH 4 (2.10 ± 0.7 × 10 −3 , μg N 2 O/m 2 /h) rates in spring relative to fall (~50% and 77% lower for N 2 O and CH 4 rates, respectively) and winter (~70% and 94% lower for N 2 O and CH 4 rates, respectively). Soil organic matter, nitrate content and bacterial 16S rDNA, nirS , and norB gene abundances emerged as significant drivers of N 2 O rates, whereas, soil pH, organic matter content and mcrA abundance were significant drivers of CH 4 rates. Denitrification gene abundances were negatively correlated with N 2 O rates, whereas mcrA abundance correlated positively with CH 4 rates. Results suggest that CH 4 rates may be directly coupled to methanogen abundance, whereas N 2 O rates may be directly impacted by a variety of abiotic variables and indirectly coupled to the abundance of potential denitrifier assemblages. Overall, additional studies examining these dynamics over extended periods are needed to provide more insights into their control.