123 SummaryThe paper presents research findings on the influence of windfall and wildfire on nematode communities in Lariceto-Piceetum forest in the High Tatras in Slovakia.Comparison was made of an intact (REF), affected and extracted (EXT), non-extracted (NEX) and burnt (FIR) forest stand. A total of 55 species belonging to 36 genera were found. The EXT locality harboured the majority of the identified species, but the highest abundance of nematodes was observed in the FIR locality. Bacterial feeders were the dominant trophic group in all investigated plots. In the REF bacterial feeders were followed by root-fungal feeders, fungal feeders and omnivores, in the EXT by omnivores and plant parasites, in the FIR by omnivores and root-fungal feeders and in the NEX by fungal feeders and omnivores. The MI and SI were higher in the REF and the EXT compared to those in the FIR and the NEX, the highest B/F ratio was observed in the FIR and the highest EI was found in the REF. We can conclude that disturbance of forest vegetation and soil has had a clear and demonstrable impact on nematode communities.

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.

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.

Nematodes are omnipresent in composts and are active in virtually all stages of the composting process. Major shifts in species composition, life strategies, and feeding behavior occur during the composting process. Due to the heat peak, nematodes can be virtually absent, but several taxa appear immediately when the temperatures drop. These comprise both taxa present before the heat peak and new taxa. However, it is not known how nematodes populate the compost. In this study, we aimed to assess the survival and colonization capacity of nematodes in compost. Our results showed that composting processes inaccessible to insects or not in contact with soil did not significantly influence nematode succession during composting. However, differences between treatments were found for some specific taxa (i.e., for Acrostichus sp., Neodiplogasteridae sp., Nygolaimoides sp., and Rhabditidae sp. 1), illustrating the importance of insects for the dispersal of nematodes to compost. Experiments in the lab with the blue bottle fly as a possible carrier demonstrated actual transport of nematodes isolated from compost by the fly (i.e., Halicephalobus cfr. gingivalis, Diploscapter coronatus, Diplogasteritus sp., Acrostichus sp., and Mesorhabditis sp.). Juveniles and dauer stages of Aphelenchoides sp., Panagrolaimus sp., and rhabditids survived an experimentally induced temperature peak, while members of Tylenchidae did not. In conclusion, our results indicate that the rapidly changing nematode community in compost is the result of both differential survival and colonization capacities.

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Soil nematodes were studied in 11 meadow sites in the White Carpathians. In total, 155 species and 86 genera were found but the composition of nematode assemblages in eastern and western side of the mountains differed. Most nematode species belonged to the orders Tylenchida (52), Dorylaimida (35) and Rhabditida (16), and to the trophic groups bacterivores (47), plant parasites (29) and omnivores (25). In individual sites and sampling dates the number of species varied in range 18 -68, genera 18 -52, H'spp 1.32 -3.50, H'gen 1.31 -3.21, T 1.79 -5.70, MI 2.32 -3.63, PPI 2.03 -2.98, and ΣMI 2.20 -3.50. Composition of nematode assemblages and their matrix classification indicated a low degree of anthropogenous disturbance to the meadows.

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