Soil Biogenic Volatile Organic Compound Flux in a Mixed Hardwood Forest: Net Uptake at Warmer Temperatures and the Importance of Mycorrhizal Associations

• Published in: Journal of geophysical research. Biogeosciences 2020-04, Vol.125 (4), p.n/a
• Main Authors: Trowbridge, A. M., Stoy, P. C., Phillips, R. P.
• Format: Article
• Language: English
• Subjects: Aerosols; Air pollution; Arbuscular mycorrhizas; Atmosphere; Atmospheric chemistry; Atmospheric models; biogenic volatile organic compounds; biogenic volatile organic compounds, mycorrhizae, methanol, soil, PTR‐MS; Biogeochemistry; Biological activity; Cycles; Decay rate; Deciduous forests; Deciduous trees; Dynamics; Ecosystems; Ectomycorrhizas; Emission analysis; Emission measurements; Emissions; Environment models; Environmental impact; ENVIRONMENTAL SCIENCES; environmental sciences & ecology; Fluctuations; Fluxes; Forests; Fungi; geology; Growing season; Hardwoods; Leaves; methanol; Mineral nutrients; Mixed forests; Moisture content; mycorrhizae; Nutrient cycles; Organic compounds; Organic soils; Plant species; PTR-MS; Soil; Soil characteristics; Soil dynamics; Soil microorganisms; Soil moisture; Soil temperature; Soil water; Soils; Species; Temperate forests; Trees; Uptake; VOCs; Volatile organic compounds; Water content
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2019JG005479

Biogenic volatile organic compounds (bVOCs) play important roles in ecological interactions and Earth system processes, yet the biological and physical processes that drive soil bVOC exchanges remain poorly understood. In temperate forests, nearly all tree species associate with arbuscular mycorrhizal (AM) or ectomycorrhizal (ECM) fungi. Given well‐established differences in soil biogeochemistry between AM‐dominated and ECM‐dominated stands, we hypothesized that bVOC exchanges with the atmosphere would differ between soils from the two stand types. We measured bVOC fluxes at the soil‐atmosphere interface in plots dominated by AM‐ and ECM‐associated trees in a deciduous forest in south‐central Indiana, USA during the early and late vegetative growing season. Soils in both AM‐ and ECM‐dominated plots were a net bVOC sink following leaf‐out and were a greater bVOC sink or smaller source at warmer soil temperatures (Ts). The flux of different bVOCs from ECM plots was often related to soil water content in addition to Ts. Methanol dominated total bVOC fluxes, and ECM soils demonstrated greater uptake relative to AM‐dominated plots, on the order of 170 nmol m−2 hr−1 during the early growing season. Our results demonstrate the importance of soil dynamics characterized by mycorrhizal associations to bVOC dynamics in forested ecosystems and emphasize the need to study bidirectional soil bVOC uptake and emission processes. Plain Language Summary Plants and soils emit and absorb complex carbon‐containing molecules in ways that remain poorly understood. These molecules—called “biogenic volatile organic compounds,” or bVOCs—mediate ecological interactions, including plant defense, and also impact atmospheric chemistry, including aerosol formation. We are becoming more aware of the importance of “mycorrhizal associations” as indicators of biogeochemical variation in forests. Tree species that associate with arbuscular mycorrhizal fungi typically have fast‐decaying leaf litters and faster nutrient cycling relative to tree species that associate with ectomycorrhizal (ECM) fungi, which generally have slow‐decaying leaf litters and slower nutrient cycling. As such, we hypothesized that forest plots dominated arbuscular mycorrhizal‐ versus ECM‐associated trees would differ in their bVOC emissions. We measured soil bVOC flux in a deciduous forest in Indiana, USA, and noted that soils that were dominated by ECM fungi had greater bVOC uptake, especially when soils were warmer.