COS 283-5 - The impacts of soil aeration following periodical cicada emergence on soil and ecosystem respiration varies across tree mycorrhizal type

Abstract: Periodical cicadas alter host physiology, resource availability, and species interactions following their emergence from the soil, yet their effects on environmental conditions and ecosystem fluxes are lesser known. We investigated the degree to which billions of emergence holes created by Brood X cicadas (Magicicada septendecim, M. cassinii, and M. septendeculain) altered gas fluxes from hardwood forests during the summer of 2021. We hypothesized that increases in soil aeration (which promotes autotrophic and heterotrophic respiration), would outpace increases in water infiltration (which temporarily saturates soils creating anerobic microsites that limit CO2 exchange), and that CO2 fluxes would be elevated to the greatest degree in soils with low ambient fluxes and the largest number of emergence holes. Specifically, we asked: How do emergence hole densities affect chamber-based soil respiration (RS), and to what degree do such effects differ among forest plots dominated by trees associating with arbuscular mycorrhizal (AM) versus those that associating with ectomycorrhizal (EcM) fungi? We measured soil temperature, moisture, and R_S at the Morgan-Monroe State Forest AmeriFlux site (US-MMS) and Griffy Woods in southern Indiana using respiration collars (N = 128) with zero, one, or two cicada holes. Collars were placed across gradients in mycorrhizal dominance and across landscape positions to account for variation in forest composition and topography. Additionally, sixteen years of US-MMS data and chamber-based flux data was used to quantify the temperature sensitivity (Q₁₀) of R_S and nighttime ecosystem respiration (R_ECO) for cicada emergence events in 2004 and 2021.

Our hypothesis was supported as cicada holes increased R_S in AM stands by 16% and 58% for collars containing one or two cicada holes, respectively. Alternatively, EcM stands were not influenced by cicada holes densities which could be attributed to the 16% greater R_S rate relative to AM dominated stands. Across the entire landscape, scaled estimates of R_S were expected to increase by 2-3%. Moreover, soils containing cicada holes had a 34% increase in Q₁₀ suggesting soil aeration enhanced soil metabolic processes. Similarly, R_ECO sensitivity to temperature increased by 30% and 22% during the cicada emergence events of 2004 and 2021 relative to the 16-year average. These data provide a unique perspective on the influence of cicada-induced soil aeration that control soil carbon fluxes across diverse forests as trees and microbial communities benefit differently from increases in soil oxygenation and water infiltration.