Impact of the invasive plant Solidago gigantea on soil nematodes in a semi-natural grassland and a temperate broadleaved mixed forest

Abstract

Relationships between alien plant species and their aboveground effects have been relatively well studied, but little is known about the effects of invasive plants on belowground faunal communities. Nematodes are abundant, ubiquitous and diverse soil biota, and alterations of their community compositions can illustrate changes in belowground ecosystems. In 2016 and 2017, we determined the response of species diversity, community composition and trophic composition of the soil nematode communities to invasion by the alien plant Solidago gigantea in two ecosystems, forest and grassland, where invasion takes place. Nematode abundance was higher and number of identified nematode species was lower at invaded than uninvaded sites, indicated by lower species diversity, regardless of ecosystem. Herbivorous nematodes were the most affected trophic group. Herbivore abundance was higher at invaded than uninvaded sites and in grassland than forest. The herbivorous species Boleodorus thylactus, Geocenamus sp., Helicotylenchus spp., Paratylenchus bukowinensis, Pratylenchoides crenicauda and Rotylenchus robustus were more abundant at the invaded sites. Abundances of nematodes in the other tropic groups were limited or not affected. The invasion did not significantly affect the ecological and functional indices, except for the Channel Index in 2016. Differences were observed in values of Enrichment Index (indicator of resource availability), Channel Index (indicator of ascendant bacterial/fungal decomposition channel) and Basal Index (indicator of depleted-perturbed soil food webs) between grassland and forests. We can thus conclude that invasion by S. gigantea significantly alters nematode community indicators (abundance, species diversity and specific trophic groups); however, this effect seems to be significantly influenced by the type of ecosystem where invasion takes place.

A case study of soil food web components affected by Fallopia japonica (Polygonaceae) in three natural habitats in Central Europe

“…wetland with F. japonica WF; c-p value of colonizer-persister nematode species from 1 to 5 according to Bongers (1990).…”

“…The activities of acid and alkaline phosphatase were determined by the modified method of Grejtovský (1991) using p-nitrophenyl phosphate as a substrate with incubation at 37°C for 24 hr. Urease activity was determined using urea as a substrate with incubation at 37°C for 3 hr as described by Chazijev (1976), and invertase activity was determined using sucrose as a substrate with incubation at 37°C for 24 hr as described by Schinner and Vonmersi (1990). The control measurements for enzymatic activity did not use the substrate.…”

“…Basic ecological indices were used to assess the status of the soil habitats using nematode communities. The maturity index (MI) for free-living taxa and the plant parasite index (PPI) for plant-parasitic taxa (Bongers, 1990), the enrichment (EI), structural (SI), channel (CI) (Ferris et al, 2001), and basal (BI) indices (Berkelmans et al, 2003) were calculated using the online program 'NINJA: An automated calculation system for nematode-based biological monitoring' (Sieriebriennikov et al, 2014; http://spark.rstudio.com/bsierieb/ninja).…”

“…are largely understudied. Dassonville et al (2010) found that Fallopia spp. decreased potential denitrification enzyme activity by reducing soil moisture, denitrifying bacteria density in the soil and potential ammonia and nitrite oxidizing bacteria enzyme activities.…”

“…Soil nematodes are an important group of soil biota, constituting an essential trophic link between primary decomposers, such as soil microflora, and larger animals and are recognized as useful bioindicators of soil conditions (Ritz et al, 2009) due to their abundance, diversity, and trophic structure (Bongers, 1990;Yeates et al, 2009). Root tissues and soil microorganisms such as bacteria and fungi represent a primary energy sources for nematode communities, and the quantitative variation of these resources may affect the structural and trophic diversity of nematode communities (Biederman and Boutton, 2009;Ciobanu et al, 2015). Different ecosystems have specific compositions of soil microbial and nematode communities.…”