In Nitrate-Rich Soil, Fallopia x bohemica Modifies Functioning of N Cycle Compared to Native Monocultures

Abstract

The effects of invasive species at the ecosystem level remain an important component required to assess their impacts. Here, we conducted an experimental study with labeled nitrogen in two types of soil (low and high nitrate conditions), investigating the effects of (1) the presence of Fallopia x bohemica on the traits of three native species (Humulus lupulus, Sambucus ebulus, and Urtica dioica) and (2) interspecific competition (monoculture of the invasive species, monoculture of the native species, and a mixture of invasive/native species) on nitrification, denitrification, and related microbial communities (i.e., functional gene abundances). We found that the species with the higher nitrate assimilation rate (U. dioica) was affected differently by the invasive species, with no effect or even an increase in aboveground biomass and number of leaves. F. x bohemica also decreased denitrification, but only in the soil with high nitrate concentrations. The impacts of the invasive species on nitrification and soil microorganisms depended on the native species and the soil type, suggesting that competition for nitrogen between plants and between plants and microorganisms is highly dependent on species traits and environmental conditions. This research highlights that studies looking at the impacts of invasive species on ecosystems should consider the plant–soil–microorganism complex as a whole.

Nitrification inhibition by polyphenols from invasive Fallopia japonica under copper stress

“…In general, TPC, emodin, and resveratrol in plant tissues in our study were similar to or slightly lower than the reported values by Stefanowicz et al (2021). A reason for these observed differences could be related to growing conditions (Kovárová et al, 2010), for example, natural versus artificial soil (Parepa & Bossdorf, 2016), plant age as well as the absence of competitive plants (Cantarel et al, 2020).…”

“…The PNR was less than half in soil grown with F. japonica compared to the unplanted controls (Figures 4 and 5), confirming the inhibiting effect of F. japonica on nitrification (H3). This observation is in line with Dassonville et al (2011) and Cantarel et al (2020). We hypothesized that nitrification is mainly inhibited in the rhizosphere compared to the non-rooted soil (H3).…”

“…(2011) and Cantarel et al. (2020). We hypothesized that nitrification is mainly inhibited in the rhizosphere compared to the non‐rooted soil (H3).…”

“…Several plant species are able to inhibit nitrification, a process called biological nitrification inhibition (Subbarao et al., 2007), generating a larger pool of ammonium rather than nitrate. Biological nitrification inhibition is discussed as one of the invasion strategies used by the Fallopia species complex (Cantarel et al., 2020; Dassonville et al., 2011) from the knotweed family (Polygonaceae), which are among the world's most successful invasive plant species (Holden et al., 2022; Lowe et al., 2000). In our context, Fallopia spp.…”

Salt Marsh Elevation Drives Root Microbial Composition of the Native Invasive Grass Elytrigia atherica

“…For this, the bulk soil and rhizosphere samples were normalized to 10,118 and 4520 sequences, respectively, to increase sampling depth in more diverse communities. Differences on the predicted functional profiles among elevations in each compartment were assessed by a Welch t -test using a “t.test” function in R. Potential denitrification activity was measured following [ 51 ] in collaboration with the University of Lyon.…”