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The distribution and impacts of non-native earthworms are poorly documented in Atlantic Canada meaning that we have limited knowledge about the relationship between earthworms and forest properties. To address this knowledge gap, we surveyed earthworms and sampled the soil organic layer in 41 forest stands located in New Brunswick to investigate their relationship with forest properties and impact on organic layer thickness and carbon content. We found earthworms at 39 % of the sites that we surveyed. Earthworms were more common in hardwood stands than softwood stands, at low elevations, and near current or historical human activity. Sites with earthworms had thinner organic layers and less carbon in the soil organic layer. A simple two-pool Lotka-Volterra model described the relationship between earthworm abundance and organic layer carbon well. The model predicted that earthworm invasions take about a decade to reach numbers typical of invaded sites and half a century to reach carrying capacity. Together these data suggest that, despite their long-term regional presence, much of the Acadian Forest that is not adjacent to human activity remains unimpacted and vulnerable to the effects of non-native earthworms. • Non-native earthworms were found at 39 % of sites studied in New Brunswick. • Earthworms were most common in hardwood stands at low elevation near human activity. • Modelling predicted earthworm invasions take ten years to reach 100 m−2. • Modelling predicted earthworms reach a carrying capacity of 172 m−2 in 60 years. • Earthworms correlated with a 65 % loss in organic layer carbon maybe to mineral soil. [ABSTRACT FROM AUTHOR]

Earthworms can act as ecosystem engineers by altering soil structure, which impacts other organisms and ecosystem functioning. Jumping worms (family Megascolecidae) originating in Asia have been spreading in North America, extending their northern range limits to Ontario, Canada in the last decade and to New Brunswick in 2021. At the northern limits of their current range, little research has been done to examine the effects of jumping worms in these new habitats since their recent establishment. Our objectives were to evaluate: (1) how jumping worms impact soil nitrogen and soil carbon; (2) how their presence impacts the abundance of non-native European earthworms (family Lumbricidae); and (3) whether two sampling methods (i.e., mustard solution and wooden discs) are equally effective at detecting jumping worms. We sampled a residential property in Oromocto, New Brunswick, which was the first location where jumping worms were found in the province. Jumping worms did not have significant impacts on the abundance and biomass of European earthworms or soil carbon content in the top 5 cm of the soil, but they did significantly affect soil nitrogen levels. Both sampling methods were equally effective at detecting the presence of jumping worms. Further research is needed in managed landscapes, urban areas, and forests to determine the ecosystem impacts and invasion dynamics of jumping worms in Canada as this invasion progresses. • Potential for non-linear effect of jumping worm abundance on soil nitrogen content. • No significant impact of jumping worms on European earthworm abundance or biomass. • No significant impact of jumping worms on total soil carbon content. • Mustard extraction and wood discs were equally effective at detecting jumping worms. [ABSTRACT FROM AUTHOR]