Short-term effect of invasive plant species on soil nematode fauna

1. Short-termeffectofinvasiveplantspecies on soilnematode fauna MarekRenčo, Zuzana Kumpálová, Marek Gális • Introduction • Invasive plant species belong to the most influential threats for natural ecosystems and humans have been proven as a main vector in the distributing of that species throughout the world. These species can cause considerable problems in environment, nature conservation, economy and human health and their control is estimated costly worldwide. It is widely accepted that invasive plants have negative effect on native plant communities by altering resource dynamics andinterspecific interactions and many times these species completely exclude native species, form monocultures and becoming dominant. Invasion can modify soil organic matter dynamics and other soil properties, water loss, nutrient enrichment and cycling through biomass production, changed fire regimes but also can alter native biota such as arthropods, microbes, bacteria or soil free-living and plant parasitic nematodes.Moreover, from the aspect of agricultural production invasive alien plant pests such as fungus can by spread and introduced to new areas. • Methods • The investigation was carried out in the south-western part of Slovakia in the river bank of Nitra River with sandy wet soil in the rural zone of NitrianskaStreda village (IG1 and IP1) andSolčanyvillage (IG2) and oakforest in cataserof Krnča village (IP2). • Soilcollectionatall localities was started in 2009 where the soil samples from native vegetation Populusnigrawith undergrowth of Urticadioica(IG2, IG2, IP1) and QuercusroburwithundergorwthofPoamemoralisandsomeherbswere taken not so far from invasive plant current position (20 meters). Two and threeyears later (2011-2012) after invasion of native vegetation by invasive species atallsiteswhere they became dominant, soil sampling were repeated from the same places like in 2009. Soil collection has been made at the beginning of June. • We chose at each site, foursampling sites(1 x 1 m square).Of this squares(1m2), 5 randomised sub-samples were collected, one from the each corner of square and one in its centre to have one representative average soil sample (1kg). Sampling was made by garden trowel up to the depth of 0-20 cm. Total, four representative soil samples were takenfromeach site.Thenematodeswereexctractedfrom 100g ofsoil by combination of Cobb sieving (Cobb 1918) and modified Baermann funnel method (van Benzoijen 2006) using a set of two cotton-propylene filters. • Thenematodeabundance, numberofspecies and genera, occurrenceofnematodespecies, proportionofnematodetrophicgroups and basalecologicalanddiversityindicesbased on nematodetrophicstructurewereevaluated to investigatetheeffectofinvasiveplantspeciesestablishment on theseecosystems. • Data from the study were subjected to analysis of variance (ANOVA) and means compared by Student´s t Test. Statistical analysis were performed using the PlotIT program. • Researchpurpose • The aim of this study was to contribute to the research of impact of non-native plants invasions on natural ecosystems worldwide by the following of their grown on soil nematode communities by describing of taxonomical and functional diversity of nematode communities before (native ecosystems) and after invasions. • We ask: Do invasive plant species vary in their effect on species diversity of soil nematodes? If so, what is the range of this effect and what are the major determinants of this impact? • Results • Altogether 115nematode species belongs to 66nematode genera in a set of 36329nematode individuals were identified during our investigations.Threeof them: Eudiplogasterrobinicola, Mesorhabditisinarimensis, Paramphideluslaetificans (all bacteriovores) are new for Slovak nematofauna, thus increasing the total number of previously recorded species (723) to 726. • The changes in nematode communities underImpatiens parviflora • The changes in nematode communities underImpatiensglandulifera • A total nematode numberincreasedat IP1 site (river bank) butdecreasedat IP2 site (oakforest) afterI. parviflora invasion (Table 3). Hovewer, totalnumberofgenerawaslowerafterinvasionatbothsites, similartotalnumberofspeciesat site IP2. Similar to I. glanduliferasites, genus Rhabditiswere found aseudominant, which increased in total abundance after invasion. A similar behaviour at some other eudominant and dominant nematode species were found e.g. A. nanus, C. persegnis, B. dubius, H. digonicus. • I. glandulifera alter nematode community structures at both investigated places (Table 1). There were found a significant higher total number of nematodes, total number of nematode species and genera in soil under invasive plant in comparison to native plant (P=0.05).At both investigated sites the BF nematodes of the genus Rhabditiswere found as eudominant with higher total abundance under I. glandulifera than U. dioica. Table 1Nematode population density and number of species, genera and non- identified individuals associated with twoinvestigated sites before (2009) and after I. glanduliferainvasion (2011, 2012) Table 3Nematode population density and number of species, genera and non- identified individuals associated with twoinvestigated sites before (2009) and after I. parviflorainvasion (2011, 2012) (1) Each value is a sum of 4 replications (1) Each value is a sum of 4 replications • The analysis of the trophic groups based on number of nematodes showed that bacteriovoreswere dominant trophic group at both sites under native and invasive plant followed by plant parasites, fungal feeders, omnivores, root-fungal feeders and predators (Fig1,2). • At site 1, the proportion of FF, RFF and Pnematodes significantly increasedbutproportionof O nematodedecreasedunder I. glandulifera compared with native U. dioica.Proportionof BF was no changed(P=0.05). • At site 2, a similar trend was found when numberof FF, RFF andPP nematodesincreasedunder I. glandulifera,ominivoresdecreased and BF and Pnematodes were no changed afterinvasion (P=0.05). • Bacteriovores were found as dominant trophic groups as well, followed by PP, O, F, FF and P nematodes at site IP1 and F, RFF, O, PP and P at site IP2. To describe the changes in nematode community structure based of trophic groups after I. parviflora invasion is problematic because of showed variable results. E.g., PP nematodes significantly increased after invasion at site IP1 but decreased at site IP2. Only RFF nematodes showed the higher abundance after invasion at both sites (Fig 3,4). a a a a a b b b a a ab b b b a b b a a a a ab a a a a a a a b b b a a b c a a b b ab b b b a a a b b a a a b b a b a c a b a b b b a b a a a a a a a a a Each value is an average of 4 replications, Data flanked forindividualtrophicgroupsby the same letter are not statistically different according to Least Significant Difference’s Test (P=0.05) Each value is an average of 4 replications, Data flanked forindividualtrophicgroupsby the same letter are not statistically different according to Least Significant Difference’s Test (P=0.05) • Valuesof Maturityindices (MIand∑MI)significantly decreasedafter invasion by I. parvifloraat both sites. PPI significantly increasedat IP1 butdecreasedat IP2 afterinvasionassociatedwithdifferentabundanceof PP nematodes (Table 4). Significantplant species effect was found to thevaluesoftaxonomic diversity indices (TD andH´spp)aswellasvalues of EI, SI and CI indices whichwere always similarat site IP1, butsignificantlyincreased (EI, SI) or decreased (CI) at site IP2 afterinvasion. • Evaluation of resultsby ecological and diversity indices showed a significant plant species effect on soil nematode communities (Table 2). All Maturityindices (MI,∑MI and MI2-5)significantly decreasedafter invasion by I. glandulifera at both sites. Significantplant species effect on the valuesoftaxonomic diversity indices (TD and H´spp)at both investigate siteswasfoundwhenthosedecreasedafterI.glanduliferaivasion. The values of EI, SI and CI indices were always significantly different between native and invasive plant at both sites. • Conclusion Table 2Nematodecommunitystructureindicesassociatedwithtwoinvestigated sites before (2009) and after I. glanduliferainvasion (2011, 2012) Table 4Nematodecommunitystructureindicesassociatedwithtwoinvestigated sites before (2009) and after I. parviflorainvasion (2011, 2012) • Deterioration of native vegetation by the invasive I. glanduliferaand I.parviflora plantswhich became dominant on space showed significant effects on soil nematode communities. • Though, the further investigations of impact of in this study followed invasive weeds or others one at different type’s ecosystems (e.g. forest, grass stands, parks etc.) or established at different soil types throughout Slovakia are needed, as well as to compare the soil nematode communities after removal of alien plants to those before and after invasion. Acknowledgements: Thisstudy wassupported by the VEGA scientific grant agency, grant No. 2/0079/13 (0.5) and project "Application Centre to protecthumans, animals and plantsagainstparasites“ (Code ITMS: 26220220018) based on thesupportoftheOperationalProgramme "Research and DevelopmentfundedfromtheEuropeanRegionalDevelopmentFound (0.5) Each value is an average of 4 replications, Dataflanked by the same letter are not statistically different according to Least Significant Difference’s Test (P=0.05) Each value is an average of 4 replications, Data flankedby the same letter are not statistically different according to Least Significant Difference’s Test (P=0.05)