Influence of the 2021 Brood X cicada emergence on near surface hydrology in forested and urban landscapes

350 210 Stroud Water Research Center

Ficklin, D., C. Kelleher, E.V. Bergan, D.T. Myers, S. Adelsperger, and E. Hardman. 2023. Hydrological Processes 37(2): e14822.

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The 2021 emergence of the 17-year Brood X cicadas (Magicicada septendecim, M. cassinii, and M. septendecula) saw billions of cicadas emerge from the soil throughout the midwestern and eastern United States. The emergence left connected burrows visible at the surface, which are hypothesized to affect near surface hydrologic processes. To investigate these processes, we used single-ring, dual head infiltrometers to measure field saturated hydraulic conductivity (Kfsn = 70) across patterns of emergence and land use in south-central Indiana, USA. Our experimental design included locations with and without cicada burrows in forested (undisturbed) and urbanized (disturbed) areas. Across undisturbed sites, we found a significant 80.8% increase in Kfs between soils with (median = 14.1 cm/hr; n = 20) and without (median = 7.8 cm/hr; n = 20) cicada burrows. At disturbed sites, we found no significant difference in Kfs between sites with (median = 4.2 cm/hr; n = 18) and without (median = 4.4 cm/hr; n = 12) cicada burrows. We found a significant correlation between the number of burrows present at the surface and Kfs rates for undisturbed sites (ρ = 0.42; p = 0.008), while no correlation was found for the disturbed sites (ρ = -0.09; p = 0.62). Our measurements suggest that the effect of burrows on Kfs is minimized in urbanized areas, potentially due to compaction and other impacts from human disturbance that mitigate the presence of macropores left by cicadas. In contrast, surface-connected macroporosity from Brood X cicada burrows in undisturbed areas act as a conduit for precipitation into the soil profile and bypass flow into deeper horizons and the shallow groundwater table, with implications for runoff dynamics, soil and groundwater recharge and quality, and nutrient cycling.