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Earthworm invasion causes declines across soil fauna size classes and biodiversity facets in northern North American forests

Citation

Jochum, Malte et al. (2021), Earthworm invasion causes declines across soil fauna size classes and biodiversity facets in northern North American forests, Dryad, Dataset, https://doi.org/10.5061/dryad.0p2ngf20r

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.

Methods

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.

Usage Notes

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).

Funding

H2020 European Research Council, Award: 677232

Deutsche Forschungsgemeinschaft, Award: FZT 118, 202548816; TH 2307/1-1, 2-1

German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig

German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig, Award: NA

German Centre for Integrative Biodiversity Research Halle-Jena-Leipzig