DOI: 10.5061/dryad.0p2ngf20r
title: Earthworm invasion causes declines across soil fauna size classes and biodiversity facets in northern North American forests

description: 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.
description: For full methods and details, please refer to the methods section
 and supplementary material of the published paper (Jochum et al. 2021,
 Oikos). In short, samples have been taken between 2016 and 2017 in four
 northern North American forests (3 in Alberta, Canada; 1 in Minnesota,
 USA). In each forest, we sampled 10 plots in a low-earthworm invasion area
 and a 10 plots in a high-invasion area, respectively (pre-determined by
 earthworm sampling in the whole area to establish the local invasion
 front). On each plot, we sampled earthworms (digging and mustard
 extraction), surface-dwelling soil invertebrate macrofauna (by hand and
 litter sieving), and we extracted soil mesofauna (Collembola and Acari)
 and soil nematodes from soil cores (5 cm diameter, 10 cm depth). Animals
 were counted, identified and measured for body length in the lab. We
 processed these data and calculated earthworm, macro-, meso-, and
 microfauna (nematode) species richness, biomass, abundance, and shannon
 index (four community properties / biodiversity facets). Subsequently we
 used these data to analyze the impact of earthworm invasion status (low
 vs. high invasion, see paper for details) and intensity (earthworm
 biomass) on the four listed community properties for each of the size
 groups. Additionally, we determined whether community property identity or
 size group had any effect on the response to earthworm invasion.
description: This dataset is related to Jochum et al. 2021, Oikos, and
 includes data and R-code to re-run the main analyses of the paper, create
 statistical output (in tables), and plot the main figures.
 For metadata of data files, please refer to the README.txt
 file. For further information, please refer to the
 paper and supporting information (open access).