Simple, inexpensive, and rapid approach to detect changes in the structure of soil free-living nematodes.

A general limitation of ecological investigations based on nematodes is related to the difficult and time-consuming taxonomic identification of species. Therefore, nematologists are investing many efforts to develop alternative approaches as proxies applicable in biomonitoring assessment. Recently, an alternative method that combines morpho-functional traits was proposed for detecting assemblage changes of marine nematodes. In view of the promising results, it was tested the same approach to document taxonomic structure changes of soil free-living and plant parasitic nematodes. Specifically, this attempt was carried out using three data sets that include studies from various European regions and different types of ecosystems: forests, grasslands and maize crops. Multivariate statistical analysis revealed that the simple combination of the four traits (i.e., buccal cavity cuticularization occurrence, amphideal fovea size and shape, morphology of the cuticle and pharynx) in a single code number perfectly mirrors the taxonomic structure trends of the nematode assemblage at genus level. Therefore, we predict that similar results can be also obtained by directly encoding nematode specimens with the selected traits and we point to new important advances if this procedure can be coupled with advanced machine learning.

The Effect of Soil Type and Ecosystems on the Soil Nematode and Microbial Communities.

Integrated studies are required to better understand the relationships between groups of soil microfauna under the influence of various biotic and abiotic factors that drive and characterise ecosystems. We analysed soil nematode communities and microbial diversity and the properties of three soil types to assess the effect of these environmental variables on biological diversity in natural (forest), semi-natural (meadow), and managed (agriculture) habitats of the Slovak Republic. The type of ecosystem and soil and the interaction of both factors had considerable effects on most monitored abiotic and biotic soil properties. The forest with a Chernozem soil had the most nematode species, highest nematode diversity, highest abundance of nematode within functional guilds, best values of ecological and functional indices, highest microbial biomass, highest microbial richness and diversity, and the highest values of various soil properties, followed by meadows with a Cambisol soil. The agricultural ecosystem with a Stagnosol soil had the lowest biological diversity and values of the soil properties. Several nematode species were new for Slovak nematode fauna. Sampling date and the interaction of all three factors (ecosystem × soil × date) had minor or no effect on most of the parameters, except soil moisture content, microbial richness, nematode channel ratio, nematode maturity index, and plant parasitic index. Both the biological indicators and basic soil properties indicated that the natural forest with a Chernozem soil was the best habitat from an ecological point of view. This ecosystem is thus the most appropriate for ecological studies.

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

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.

Short-term effects of forest disturbances on soil nematode communities in European mountain spruce forests.

The nematode communities in spruce forests were compared with the short-term effects of forest damage, caused by windstorm, wildfire and management practices of forest soils. Soil samples were collected in June and October from 2006 to 2008 in four different sites: (1) forest unaffected by the wind (REF); (2) storm-felled forest with salvaged timber (EXT); (3) modified forest affected by timber salvage (wood removal) and forest fire (FIR); and (4) storm-felled forest where timber had been left unsalvaged (NEX). Nematode analysis showed that the dominant species in all four investigated sites were Acrobeloides nanus and Eudorylaimus silvaticus. An increase of A. nanus (35% of the total nematode abundance) in the first year in the FIR site led to the highest total abundance of nematodes compared with other sites, where nematode abundance reached the same level in the third year. In the FIR site bacterial feeders appeared to be the most representative trophic group, although in the second and third year, after disturbance, the abundance of this trophic group gradually decreased. In the NEX site, the number of nematode species, population densities and Maturity Index were similar to that recorded for the FIR site. In EXT and NEX sites, the other dominant species was the plant parasitic nematode Paratylenchus microdorus. Analyses of nematodes extracted from different forest soil samples showed that the highest number of species and diversity index for species (H'spp) were in the REF site. Differences between the nematode fauna in REF and other localities were clearly depicted by cluster analysis. The greatest Structure Index and Enrichment Index values were also in REF. In the EXT site, the number of nematode species, their abundance, H'spp and Maturity Index were not significantly different from those recorded in the reference site.