Earthworm density differences among tallgrass prairies over time in the Ozark Highlands

Abstract

Abstract To mitigate the loss of tallgrass prairies through fragmentation and conversion to other land uses, prairie restoration efforts have been undertaken to reclaim areas that have been previously used for agricultural production. Earthworms are a key component of the soil ecology of natural, undisturbed ecosystems. However, limited research exists on earthworm populations in prairie restorations and how earthworm densities may change over time. The objectives of this study were (a) to evaluate earthworm densities in the upper 20 cm of soil over time (i.e., May 2007 and May 2019) in a native prairie and chronosequence of three prairie restorations (i.e., established in 1979, 2000, and 2002), and (b) to identify relationships between earthworm (i.e., juvenile, adult, and total) density and soil physical and chemical properties. Juvenile (P = .03) earthworm density decreased 25 and 35% and total (P = .03) earthworm density decreased by 33 and 42% in the 2000 and 2002 restorations, respectively, from May 2007 to May 2019. Adult earthworm density did not change over time (P > .05) in any prairie ecosystem. Combined across prairie sites, adult earthworm density was positively correlated (P < .05) with sand content (r = .49) and pH (r = .49) and negatively correlated (P < .05) with silt (r = –.56) and sulfur content (r = –.47). To promote earthworm densities similar to native prairies, consideration should be given to numerous soil properties for a successful restoration.