Abstract
Anthropogenic pressures alter the biodiversity, structure and organization of biological communities with severe consequences for ecosystem processes. Species invasion is such a human‐induced ecosystem change with pronounced impacts on recipient ecosystems. Around the globe, earthworms invade habitats and impact abiotic soil conditions and a wide range of above‐ and belowground organisms. In northern North America, where earthworms have been largely absent since the last glaciation period and most earthworm species present today have only been (re‐)introduced a few hundred years ago, invasion impacts have been intensively studied. However, despite several studies assessing impacts of invasive earthworms on soil fauna, studies have rarely investigated the simultaneous responses of different soil‐fauna size groups and biodiversity facets which might respond differently to earthworm invasion and independently affect ecosystem processes. Our study goes beyond previously‐established knowledge on earthworm‐invasion effects by simultaneously assessing differences in four biodiversity facets, namely the abundance, biomass, richness and Shannon index of soil invertebrate macro‐, meso‐ and microfauna communities between high‐ and low‐invasion status plots (n = 80) and in relation to invasion intensity measured as earthworm biomass across four northern North American forests sampled between 2016 and 2017. Across forests and soil‐fauna groups, we found reduced abundance (−33 to −45%) and richness (−18 to −25%) in high compared to low‐invasion status areas. Additionally, meso‐ (−14%) and microfauna biomass (−38%) and macro‐ (−7%) and microfauna Shannon index (−8%) were reduced. Higher invasion intensity (earthworm biomass) was additionally related to reduced soil‐fauna biodiversity. While the studied biodiversity facet was important for the soil fauna response, soil‐fauna size group was comparably unimportant. Given the global ubiquity of earthworm invasion and the importance of soil fauna for key ecosystem processes, our observational results help to assess future impacts of this invasion and the consequences for anthropogenically‐altered ecosystem functioning.
Highlights
Human society depends on nature for a wide range of ecosystem services (Reid et al 2005, Díaz et al 2018, IPBES 2019)
Our study goes beyond previously-established knowledge on earthworm-invasion effects by simultaneously assessing differences in four biodiversity facets, namely the abundance, biomass, richness and Shannon index of soil invertebrate macro, mesoand microfauna communities between high- and low-invasion status plots (n = 80) and in relation to invasion intensity measured as earthworm biomass across four northern North American forests sampled between 2016 and 2017
We studied the impacts of earthworm invasion on soil-fauna communities and found a consistent negative association between earthworm invasion and soil-fauna responses across three size groups and four biodiversity facets
Summary
Human society depends on nature for a wide range of ecosystem services (Reid et al 2005, Díaz et al 2018, IPBES 2019). Despite the high number of important global-change drivers (Sala et al 2000, Reid et al 2005, Maxwell et al 2016, IPBES 2019) and their variable impact on different ecosystem properties, compartments such as above- and below-ground systems, and organisms of differing body size, most studies focus on the effects of specific drivers on single or few facets of biodiversity for specific organism groups or ecosystem properties (Rillig et al 2019). This certainly is the case for so-called ecosystem engineers in soil ecosystems (Jones et al 1996, Jouquet et al 2006) which have dramatic consequences for belowground biodiversity and ecosystem functioning (Wardle et al 2011, Bardgett and van der Putten 2014)
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