Selective alteration of soil food web components by invasive giant goldenrod Solidago gigantea in two distinct habitat types

Abstract

Apart from relatively well‐studied aboveground effects, invasive plant species will also impact the soil food web. So far, most research has been focusing on primary decomposers, while studies on effects at higher trophic levels are relatively scarce. Giant goldenrod Solidago gigantea, native to North America, is a widespread and common invasive species in most European countries. We investigated its impact on plant communities and on multiple trophic levels of the soil food web in two contrasting habitats: riparian zones and semi‐natural grasslands. In 30 pairs of invaded and uninvaded plots, floristic composition, pH, fungal biomass and the densities of 11 nematode taxa were determined by using a quantitative PCR‐based method. In the two habitats, the invader outcompeted both rare and dominant plant species. Belowground, S. gigantea invasion reduced pH, increased overall fungal biomass as well as the density of a single lineage of fungivorous nematodes, the family Aphelenchoididae. The densities of two other, phylogenetically distinct lineages of fungivorous nematodes, Aphelenchidae and Diphtherophoridae, were unaffected by the local increase in fungal biomass. Apparently this plant species induces a local asymmetric boost of the fungal community, and only Aphelenchoididae were able to benefit from this invader‐induced change. The alternative explanation – the results are explained by a subtle, S. gigantea‐induced 0.1–0.2 units decrease of pH – seems unlikely, as pH optima for nematode taxa are relatively broad. Thus, apart from readily observable aboveground effects, the invasive plant species S. gigantea affects fungal biomass as well as a specific part of the fungivorous nematode community in a soil type‐independent manner.

Species-specific effects of plant invasions on activity, biomass, and composition of soil microbial communities

“…Both plant species increased mycorrhizal frequency but decreased species richness of AMF (Zubek et al unpublished). Our results agree with those of Scharfy et al (2009Scharfy et al ( , 2010 and Quist et al (2014) who found that S. gigantea invasion had no influence or decreased soil respiration, bacterial biomass, or phosphomonoesterase activity but increased fungal biomass and/or fungal:bacterial ratio. S. gigantea litter may support fungal rather than bacterial growth as it has lower tissue concentrations of most nutrients and higher C:N ratio than adjacent native vegetation Thorn and Lynch 2007;Dassonville et al 2008).…”

“…It was proved that invasive plants can alter the abundance or species composition of soil and sediment invertebrates, including fungivorous or bacterivorous nematodes, collembola, enchytraeids, and mites (Talley and Levin 2001;Yeates and Williams 2001;Quist et al 2014;Rusterholz et al 2014). These changes would possibly influence microorganisms as, depending on species and grazing intensity and selectivity, soil invertabrates can inhibit or stimulate mycelial growth and alter species dominance and composition within microbial communities (Hedlund and Augustsson 1995;Crowther et al 2011).…”

Differential influence of four invasive plant species on soil physicochemical properties in a pot experiment

“…Most previous studies on the effects of I. glandulifera, R. japonica, and/or S. gigantea included only a single invasive species, a single or few study sites and the results obtained were inconsistent, indicating increases, decreases, or no change in soil properties under a particular invader in comparison to uninvaded soil Vanderhoeven et al 2006;Dassonville et al 2007;Scharfy et al 2009;Aguilera et al 2010;Tharayil et al 2013;Mincheva et al 2014;Quist et al 2014;Ruckli et al 2014b;Stefanowicz et al 2017). To our knowledge, information on the effect of R. laciniata on soil physicochemical properties is scarce (Stefanowicz et al 2017).…”

“…Overall, total and available forms of N (N-NO 3 , N-NH 4 ) and P (Olsen), S-SO 4 , exchangeable K, and Mg contributed the most to the discrimination of soils under different plant species. The influence of invasive I. glandulifera, R. japonica, and S. gigantea on soil has been estimated earlier in numerous field studies Vanderhoeven et al 2006;Dassonville et al 2008;Scharfy et al 2009;Maurel et al 2010;Tharayil et al 2013;Quist et al 2014;Ruckli et al 2013Ruckli et al , 2014bStefanowicz et al 2017), but experiments concerning this problem are rare (Scharfy et al 2010(Scharfy et al , 2011Bardon et al 2014Bardon et al , 2016. Previous studies focused mainly on invasion-induced changes in different forms of N and P in soil and found that these properties responded variably to the presence of I. glandulifera, R. japonica, or S. gigantea, and so did some exchangeable cations, for example K and Mg (ChapuisLardy et al 2006;Hejda and Pyšek 2006;Vanderhoeven et al 2006;Dassonville et al 2007;Scharfy et al 2009Scharfy et al , 2010Scharfy et al , 2011Tharayil et al 2013;Ruckli et al 2014b;Stefanowicz et al 2017).…”

“…To our knowledge, information on the effect of R. laciniata on soil physicochemical properties is scarce (Stefanowicz et al 2017). Moreover, overwhelming majority of studies was conducted in the field, making pairwise comparisons of soils under patches of invasive species with those under neighboring native vegetation (ChapuisLardy et al 2006;Vanderhoeven et al 2006;Dassonville et al 2007;Aguilera et al 2010;Tharayil et al 2013;Mincheva et al 2014;Quist et al 2014;Ruckli et al 2014b;Stefanowicz et al 2017). Although such space-for-time substitution approach provides a valuable wealth of information, it suffers from drawbacks such as the possibility that potential differences between invaded and native stands existed prior to the invasion.…”