No apparent effect of invasive alien goldenrod on soil microbial communities or soil fauna feeding activity

Abstract

Invasive alien species spreading in abandoned agricultural landscape may negatively affect native organisms, including plants and soil biota. This study assessed the effects of invasion by Solidago sp. (goldenrod) in southern Poland on soil fauna feeding activity and on soil microorganism activity, biomass, and functional and taxonomic diversity, in a comparisons of paired plots: goldenrod-invaded plots and nearby non-invaded plots of semi-natural grassland. Goldenrod-invaded plots had fewer vascular plant species (paired t-test) than non-invaded ones, and showed a distinct plant community composition (ANOSIM). Non-invaded and invaded plots did not differ in a range of measured soil physicochemical parameters. No differences were observed between non-invaded and invaded plots in soil fauna feeding activity (measured in the field using bait-lamina test), nor in soil microbial activity (basal respiration rate) and biomass (substrate-induced respiration rate). Goldenrod invasion also did not affect soil bacterial activity and functional diversity as assessed using Biolog® ECO plates, nor bacterial and eukaryotic taxonomic diversity as assessed using Illumina 16/18S rDNA gene fragment sequencing. Bacterial community functional structure (CLPP pattern) and the taxonomic structure of bacteria and eukaryotes (OTUbact and OTUeuk patterns) were not observed to differ between non-invaded and invaded plots. None of the measured soil microbial indices or soil fauna feeding activity were related to the number of vascular plant species (alpha diversity) as tested by simple regressions. The altered vegetation diversity and composition (beta diversity) was not reflected in the CLPP, OTUbact and OTUeuk patterns (Mantel tests). The reduced alpha and beta plant diversity resulting from goldenrod invasion was not reflected in soil microbial community parameters. Results of the effects of goldenrod invasion on soil organisms should be interpreted with caution, as the effects may not be so pronounced as the effects on aboveground organisms.