Linkage between exotic earthworms, understory vegetation and soil properties in sugar maple forests

Authors: Drouin, Mélanie; Bradley, Robert; Lapointe, Line
Abstract: The comminuting and soil mixing activities of earthworms can affect soil physical, chemical and biolog-ical properties, which in turn can influence plant growth and survival. Accordingly, there is growing con-cern that the spread of exotic earthworms into northern temperate forests may compromise biodiversityand tree species recruitment. We report on a study where we sampled earthworms, soils, and understoryplants in plots established in 40 mature sugar maple stands distributed over 3 areas in the EasternTownships of Southern Québec (Canada). Earthworms were found in 19 of 40 plots, and earthworm fre-quency of occurrence (Efo) as well as the complexity of earthworm communities reflected human acces-sibility to the plots. Plant species richness decreased, and species evenness increased, withEfo. TheEfowasrelated to a decrease in the cover of 5 plant species, and to an increase in the cover of 2 other plant speciesor plant functional groups. IncreasingEfoalso correlated with higher soil pH, lower forest floor thicknessand lower soil C:N ratio. Among these 3 variables, redundancy analysis (RDA) revealed that soil pH andforest floor thickness correlated with plant community composition. Based on neutral lipid and phospho-lipid fatty acid profiles, we found that soil bacteria and fungi increased with a decrease in forest floorthickness, bacteria and arbuscular mycorrhizal fungi (AMF) increased with soil pH, whereas actinobacte-ria and AMF increased withEfo. We discuss the possible mechanisms by which earthworms might directlyor indirectly alter understory plant community composition. By considering the location and land usemanagement of each study site, our study provides further evidence that the spread of exotic earthwormsin sugar maple stands of Southern Québec may be linked to human activities, with implications for fur-ther research and conservation issues.
Document Type: Article de recherche
Issue Date: 18 January 2016
Open Access Date: 18 July 2019
Document version: AM
This document was published in: Forest ecology and management, Vol. 364, 113–121 (2016)
Alternative version: 10.1016/j.foreco.2016.01.010
Collection:Articles publiés dans des revues avec comité de lecture

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