Earthworm differences among mound positions in native prairies in the Ozark Highlands

Mounded, tallgrass prairie ecosystems are a unique, endangered ecosystem due to severe disturbance for agricultural production and/or urban expansion. Limited research exists on earthworm (Lumbricus terrestris) dynamics in mounded, tallgrass prairies, particularly in the Ozark Highlands region of northwestern Arkansas. The objectives of this study were to evaluate the effects of soil moisture regime (SMR), landscape position (LP), and sample date on earthworm densities in the top 20 cm of soil in two mounded, native prairies in the Ozark Highlands region of northwestern Arkansas. Juvenile and total earthworm densities were five times greater (P < .05) in the udic- and aquic-inter-mound combinations than any other SMR-LP combination in October 2018 and May 2019, respectively. Adult earthworm densities were two times greater (P < .05) in the aquic-inter-mound at Searles Prairie than any other SMR-LP combination in either mounded prairie. Juvenile earthworm densities were three times greater (P < .05) in May 2019 than in May 2018 at Chesney Prairie, but adult and total earthworm density did not change over the same period of time. Combined across all data, juvenile and total earthworm densities were positively correlated (P < .05) with moisture (r = .33 and .34, respectively), Ca (r = .20 and .21, respectively), and Fe (r = .53 and .52, respectively), but negatively correlated (P < .05) with Mn (r = -.34 and -.32, respectively). Results of this study extended overall understanding of earthworm population distributions and dynamics in mounded prairie systems.