Cascading effects of earthworm invasion increase graminoid density and rodent grazing intensities

• Published in: Ecology
• Main Authors: Jonsson, Hanna, Olofsson, Johan, Blume-Werry, Gesche, Klaminder, Jonatan
• Format: Article in Journal/Newspaper
• Language: English
• Published: UmeÃ¥ universitet, Institutionen för ekologi, miljö och geovetenskap 2024
• Subjects: earthworms; grazing; Lumbricidae; non-native; plant community; soil moisture; tundra; Ecology; Ekologi; Tundra
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-218292; https://doi.org/10.1002/ecy.4212

Human-mediated dispersal of non-native earthworms can cause substantial changes to the functioning and composition of ecosystems previously earthworm-free. Some of these earthworm species have the potential to “geoengineer†soils and increase plant nitrogen (N) uptake. Yet the possible consequences of increased plant N concentrations on rodent grazing remains poorly understood. In this study, we present findings from a common garden experiment with two tundra communities, meadow (forb dominated) and heath (shrub dominated), half of them subjected to 4 years of earthworm presence (Lumbricus spp. and Aporrectodea spp.). Within four summers, our earthworm treatment changed plant community composition by increasing graminoid density by, on average, 94% in the heath vegetation and by 49% in the meadow. Rodent winter grazing was more intense on plants growing in soils with earthworms, an effect that coincided with higher N concentrations in plants, indicating a higher palatability. Even though earthworms reduced soil moisture, plant community productivity, as indicated by vegetation greenness (normalized difference vegetation index), was not negatively impacted. We conclude that earthworm-induced changes in plant composition and trophic interactions may fundamentally alter the functioning of tundra ecosystems.