The impact of invasive plants on soil ecosystems in the last decades has attracted world-wide attention. Exotic plant invasions often have dramatic impacts on the resident vegetation by modifying its composition and structure (Levine et al., 2003). Invasive plants have been reported to alter abiotic properties (Rahmonov et al., 2014; Suseela et al. 2016; Stefanowicz et al., 2017), nutrient availability, organic carbon content (Bardon et al., 2014), soil microbiota (Scharfy et al., 2010; Coats and Rumpho, 2014), and soil mesofauna (Quist et al., 2014; Sterzyńska et al., 2017), with special references to variability and composition of arthropods (Moroń et al., 2009; Lenda et al., 2013; Baranová et al., 2014).
The clonal Japanese knotweed,
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. Estimating the status of and related changes in the structures of microbes and soil nematode communities after the establishment of the invasive plant
To our knowledge, this is the first study observing the impact of
The experiment was conducted in a valley near the village of Opátka in South Eastern Slovakia, Central Europe. This region has a temperate climate, with an annual average of 40 summer days per year and a warm, moderately dry sub-region with a mild winter. The average daily temperature in January ranges from 1.5 to 4.0°C, the average daily temperature in July ranges from 16.0 to 18.5°C, while the average annual temperature ranges from 5.0 to 7.0°C. The mean annual precipitation is 650 to 700 mm. The soils are characterized as Fluvisols, and the vegetation zone is characterized as Carpathian oak-hornbeam forest. The landscape is patchy, with deeply undulating uplands (Miklós, 2002). The first
For studying the impact of
Forest (F) (48°47.63′N, 21°03.43′E; 455 m a.s.l.): covered by a natural, undisturbed, 100 years old deciduous Querco-Fagetea forest, mainly consisting of
Forest edge invaded by
Grassland (G) (48°48.14′N, 21°03.40′E; 392 m a.s.l.): covered with indigenous multispecies vegetation dominated by
Grassland edge invaded by
Wetland (W) (48°48.34′N, 21°03.35′E; 386 m a.s.l.): covered by
Wetland edge invaded by
We selected a 25 m × 25 m area of the three different habitats (F, G, and W) which was not yet colonized by
The soils were sampled using a garden trowel to depths of 0 to 20 cm in May 2016. A quadrat sampling method was used. Five soil subsamples were collected from each quadrat (1 m2), one from each corner and one from the center. The subsamples from each quadrat were then bulked to obtain five representative soil samples (1 kg) for each area. The soil samples were transferred to the laboratory in plastic bags. The bags were stored at 5°C until processing (storage time of soil samples were no longer than one week). Each sample was gently homogenized manually before processing
Soil pH was determined for air-dried soil samples in a 1:3 solution of soil: 0.01 M CaCl2 using a pH meter inoLab pH 720-WTW GmbH, Weilheim, Germany. Soil moisture content was measured gravimetrically after the soil had been dried to a constant weight in an oven at 105°C for 24 hr. All determinations were performed in triplicate.
Soil microbial respiration (SMR) was measured by the amount of CO2 released from 100 g of field-moist soil and absorbed by NaOH (μg C-CO2/g soil) in hermetically sealed bottles (Alef and Nannipieri, 1995) at 25°C for 24 hr. Microbial biomass carbon (MBC) content was determined using the method of Islam and Weil (1998), as oven-dried equivalent (ODE) of field-moist soil adjusted to 80% water-filled porosity was irradiated twice by microwave (MW) energy at 400 J g-1 ODE soil to kill the microorganisms. The time settings and MW oven power depended on the total amount of soil in the MW oven. After cooling, soil samples were extracted with 0.5 M K2SO4. Carbon content (Cirradiated) in the extract was quantified by the oxidation with K2Cr2O7 dissolved in H2SO4 and titrimetrically by (NH4)2Fe(SO4)2. The same procedure was done with a non-irradiated sample (Cnon-irradiated). The microbial biomass carbon was then determined as MBC = (Cirradiated-Cnon-irradiated)/KME, whereby extraction efficiency factor KME = 0.213. 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. The activity of all enzymes was measured spectrophotometrically by create a reference curve.
Nematodes were isolated from 100 g of the mixed fresh soil samples by a combination of Cobb sieving and decanting (Cobb, 1918) and a modified Baermann techniques (Van Bezooijen, 2006). Nematodes were extracted from aqueous soil suspensions using a set of two cotton-propylene filters. Subsamples were removed after extraction for 48 hr at room temperature. The aqueous suspensions containing nematodes were examined under a stereomicroscope, excessive water was removed, and the nematodes were fixed in hot fixative 99:1 solution of 4% formaldehyde: pure glycerol and evaluated on permanent glycerine slides (Southey, 1986). All isolated nematodes were microscopically examined at 100, 200, 400, 600, and 1,000 × magnification, identified from permanent glycerine slides mostly to species level (juveniles were identified to genus level) using an Eclipse 90i Nikon, Japan light microscope, with original species descriptions, and several taxonomic keys: Brzeski (1998), Loof (1999), Siddiqi (2000), Andrássy (2005, 2007, 2009), and Geraert (2008, 2010).
Cysts of
Nematode species were assigned to trophic groups: bacterivores, fungivores, omnivores, predators, plant parasites, root-fungal feeders, and insect parasites, according to Yeates et al. (1993) and Wasilewska (1997).
The total number of species, total nematode abundance, mean number of nematodes per trophic group, and the Shannon and Weaver species diversity index (H’spp.) (Shannon and Weaver, 1949) were determined. 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;
The differences in nematode characteristics (total nematode abundance, abundance of nematodes per trophic group, and species diversity) and basic ecological characteristics (MI, PPI, EI, SI, CI, and BI) were analyzed with two-way ANOVA with ‘ecosystems’ (F, G, and W), ‘invasion status’ (invaded, uninvaded), and their interactions as factors. To meet the assumptions of these parametric tests, Box-Cox transformation was applied with the maximum likelihood approach and Golden Search iterative procedure on. If there was an interaction between ‘ecosystem’ and ‘invasion status’ (total nematode abundance and mean number of bacterivores), post hoc Fisher LSD test was applied separately for each ecosystem to determine the effect of ‘invasion status’. Otherwise, main factor ANOVA with two factors (without interaction) was applied. Consequently, in the case of confirmed significance of ‘ecosystem’, post hoc Fisher LSD test was used.
As untransformed soil physical and microbial properties (pH, SMR, MBC content, and enzymatic activities) were not normally distributed (Shapiro–Wilk test) and transformation did not improve normality, nonparametric statistics were applied. Differences among six combinations of ‘ecosystem’ and ‘invasion status’ were tested separately with Kruskal–Wallis ANOVA, followed by a post hoc multiple comparisons.
The above mentioned statistical analysis were performed using Statistica Cz, version 12.0 (Statsoft, Inc., 2013) and significance of all tests was determined at
Relationships between plots, nematodes, and selected environmental characteristics (soil pH and soil microbial respiration as constrained variables) were analyzed by ordination techniques. Redundancy analysis (RDA) was performed using Canoco 5 (Ter Braak and Šmilauer, 2012), because response data were compositional and had a gradient of 1.7 standard deviations. The significance of the axis was tested by a Monte Carlo permutation test.
Non-metric multidimensional scaling (NMS) ordination was used to examine any changes in the structure of nematode community for the invaded and the uninvaded habitats. A three-dimensional solution was executed by Autopilot, with the slow and thorough mode and Sørensen (Bray-Curtis) distance (recommended for community data). PC-ORD (McCune and Grace, 2002; McCune and Mefford, 2011) was used for the NMS analysis.
The soil physical properties, soil moisture, and pH differed substantially (Kruskal–Wallis statistics with
Means and standard errors (SD) of the soil physical properties, microbial respiration, microbial biomass carbon, and enzymes in different ecosystems: forest F; forest with
F | FF | G | GF | W | WF | ||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Soil Indices | H | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | ||||||
Soil moisture (%) | 21.93*** | 9.1 | 0.04 | c | 14.0 | 0.55 | ab | 9.5 | 0.35 | ac | 11.7 | 0.06 | abc | 12.4 | 0.94 | abc | 21.5 | 0.98 | b |
Soil pH (CaCl2) | 22.30*** | 5.2 | 0.06 | a | 6.4 | 0.06 | ab | 6.1 | 0.06 | ac | 6.8 | 0.06 | ab | 6.8 | 0.05 | bc | 7.2 | 0.06 | b |
Soil microbial respiration | 21.86*** | 139.6 | 7.37 | abc | 185.1 | 8.14 | bc | 58.0 | 14.67 | a | 123.5 | 7.28 | abc | 90.4 | 15.30 | ad | 147.8 | 14.84 | bcd |
Microbial biomass carbon | 17.18** | 344.0 | 33.52 | ab | 370.6 | 11.99 | a | 289.9 | 10.93 | b | 297.5 | 12.6 | b | 309.5 | 8.59 | ab | 351.0 | 16.15 | ab |
Urease | 35.15***,1 | 1.5 | 0.03 | a | 1.3 | 0.02 | ab | 1.2 | 0.11 | ab | 1.4 | 0.08 | a | 0.9 | 0.26 | b | 0.6 | 0.04 | b |
Acid phosphatase | 21.79*** | 60.0 | 1.43 | a | 53.1 | 2.78 | ab | 58.2 | 0.75 | ac | 57.5 | 1.00 | ab | 34.1 | 4.24 | bc | 24.1 | 1.54 | b |
Alkaline phosphatase | 21.37*** | 26.1 | 0.65 | b | 38.3 | 1.18 | ab | 31.7 | 4.57 | ab | 44.2 | 1.31 | a | 34.4 | 2.23 | ab | 26.2 | 0.73 | b |
Invertase | 27.80***,2 | 39.9 | 1.13 | c | 33.9 | 2.91 | ac | 21.2 | 0.99 | b | 25.5 | 0.77 | ab | 31.1 | 1.20 | ab | 28.2 | 0.28 | ab |
Note: H means statistics H (5, N = 24) from Kruskal–Wallis test (For 1N = 42 and for 2N = 30). Significant differences from multiple post hoc comparisons of site characteristics between ecosystems are indicated by different lowercase letters (a,b,c,d) in every row with p less than 0.05. Significance level: ***0.001; **0.001 levels, respectively.
SMR and MBC content were higher (but not significantly) in all plots with
A total of 9,452 individual nematodes were isolated and identified. The total number of species and genera of soil free-living and plant-parasitic nematodes was higher in the uninvaded (58 and 46) than in the invaded plots (49 and 40). The species found in the uninvaded (F, G and W) but absent in the invaded plots were as follows: six bacterivores
List of identified nematode species and their mean abundance in ind./100 g of soil (
F | FF | G | GF | W | WF | |||||||||
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Nematode species/trophic groups | Abbr. | c-p | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD |
|
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|
Acyl | 2 | – | – | – | – | 3.6 | 5.7 | – | – | 0.2 | 0.4 | – | – |
|
Anan | 2 | 5.4 | 5.0 | 3.0 | 1.9 | 2.6 | 3.4 | 11.2 | 9.5 | 18.4 | 9.4 | 5.0 | 5.5 |
|
Apri | 4 | 9.6 | 2.9 | 2.2 | 1.1 | 2.2 | 3.2 | 4.0 | 3.1 | 7.0 | 5.0 | 0.6 | 0.9 |
|
Cper | 2 | 0.8 | 1.8 | – | – | 9.6 | 8.6 | 1.8 | 1.8 | 14.6 | 14.4 | 3.2 | 4.0 |
|
Cvex | 2 | 3.6 | 4.3 | – | – | – | – | 1.4 | 2.1 | – | – | – | – |
|
Eoxy | 2 | – | – | – | – | 0.8 | 1.8 | – | – | – | – | – | – |
|
Estr | 2 | – | – | 1.0 | 1.4 | 6.4 | 4.8 | 0.4 | 0.9 | 6.8 | 5.2 | 6.2 | 7.1 |
|
Cpro | 2 | 0.6 | 1.3 | 0.4 | 0.5 | 0.2 | 0.4 | 1.0 | 0.7 | 0.4 | 0.9 | 0.2 | 0.4 |
|
Msp. | 1 | 0.4 | 0.9 | – | – | – | – | – | – | – | – | – | – |
|
Prig | 1 | – | – | – | – | – | – | – | – | 0.2 | 0.4 | 0.8 | 1.3 |
|
Ppar | 2 | 5.0 | 6.2 | 0.4 | 0.9 | 1.4 | 2.1 | 0.2 | 0.4 | 4.8 | 3.6 | 1.0 | 1.2 |
|
Ppai | 2 | 3.8 | 3.4 | 1.6 | 2.5 | 5.4 | 3.9 | 3.0 | 2.2 | 7.8 | 6.1 | 4.0 | 3.3 |
|
Pten | 2 | 0.2 | 0.4 | – | – | 1.2 | 2.7 | – | – | – | – | – | – |
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Pdol | 3 | – | – | – | – | 2.8 | 3.9 | – | – | – | – | – | – |
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Pint | 3 | 58.8 | 59.0 | 7.8 | 11.7 | 4.2 | 3.3 | 6.2 | 4.1 | 3.6 | 2.3 | 1.0 | 1.2 |
|
Psp. | 3 | 0.6 | 1.3 | – | – | – | – | – | – | – | – | – | – |
|
Rspp | 1 | 27.8 | 18.0 | 39.4 | 17.3 | 37.4 | 24.5 | 77.6 | 33.0 | 146.6 | 104.5 | 38.8 | 26.4 |
|
Tter | 3 | 2.6 | 2.1 | 2.6 | 3.6 | 1.8 | 2.7 | 1.4 | 2.6 | – | – | – | – |
|
Wsch | 2 | 2.6 | 4.2 | 2.2 | 2.3 | 0.8 | 1.3 | 4.4 | 4.3 | 0.6 | 0.9 | 1.2 | 2.2 |
|
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Acom | 2 | 0.2 | 0.4 | 0.6 | 0.9 | 2.2 | 3.2 | 1.4 | 2.1 | 0.6 | 0.5 | – | – |
|
Amin | 2 | 0.2 | 0.4 | – | – | 3.6 | 3.8 | 0.4 | 0.5 | – | – | – | – |
|
Arit | 2 | – | – | – | – | 0.6 | 1.3 | 0.2 | 0.4 | 3.4 | 4.6 | 2.4 | 1.9 |
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Aave | 2 | – | – | 0.6 | 0.9 | 6.2 | 3.9 | 6.0 | 6.4 | 19 | 29.1 | 4.0 | 3.8 |
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Dzee | 4 | – | – | 0.2 | 0.4 | 4.4 | 6.2 | 5.2 | 9.5 | 7.6 | 11.2 | 1.2 | 1.8 |
|
Tste | 4 | – | – | – | – | 4.0 | 8.4 | – | – | – | – | – | – |
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Aobt | 5 | – | – | – | – | 0.4 | 0.9 | – | – | – | – | – | – |
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Acor | 5 | – | – | – | – | – | – | 0.4 | 0.5 | – | – | – | – |
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Dcom | 3 | – | – | – | – | 8.2 | 8.8 | – | – | 26.2 | 21.9 | 2.2 | 2.9 |
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Emac | 4 | 1.4 | 1.9 | 0.6 | 1.3 | 13.6 | 6.8 | – | – | – | – | 1.0 | 1.4 |
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Espp | 4 | 10.8 | 6.0 | 1.4 | 1.7 | 7.4 | 2.7 | 1.2 | 1.1 | 9.0 | 7.0 | 6.0 | 4.7 |
|
Esil | 4 | 7.6 | 4.3 | 1.0 | 1.7 | 3.6 | 6.1 | – | – | – | – | – | – |
|
Mbas | 5 | 0.8 | 1.8 | 0.4 | 0.9 | 0.6 | 0.9 | 0.6 | 1.3 | 9.4 | 3.5 | 0.4 | 0.5 |
|
Mpar | 4 | – | – | 2.6 | 2.6 | 0.8 | 1.3 | 11.8 | 18.2 | 6.4 | 5.9 | 6.8 | 6.0 |
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Atri | 4 | 0.6 | 0.9 | 1.0 | 1.7 | – | – | 0.8 | 1.1 | 1.0 | 1.2 | 1.2 | 1.8 |
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Cpar | 4 | 5.2 | 3.7 | – | – | – | – | – | – | – | – | – | – |
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Czsc | 4 | – | – | – | – | – | – | 1.2 | 2.2 | – | – | – | – |
|
Mbra | 4 | 1.2 | 1.8 | 2.6 | 4.0 | 3.0 | 2.7 | 2.2 | 1.5 | 3.6 | 4.4 | 1.2 | 1.8 |
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Tfil | 3 | 5.4 | 11.0 | 2.0 | 4.5 | 0.2 | 0.4 | – | – | – | – | – | – |
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Tset | 3 | 11.2 | 11.0 | 7.4 | 7.8 | 1.0 | 1.0 | 7.4 | 11.6 | – | – | – | – |
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Tmon | 3 | – | – | – | – | – | – | – | – | – | – | 2.6 | 4.7 |
|
Tett | 4 | 2.0 | 2.4 | – | – | 3.0 | 3.0 | – | – | – | – | – | – |
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Bdub | 3 | – | – | 12.8 | 24.8 | 10.2 | 4.4 | 13.2 | 15.0 | 17.2 | 14.8 | – | – |
|
Hdig | 3 | 0.8 | 1.3 | 11.0 | 13.2 | 80.8 | 51.2 | 62.2 | 61.1 | 69.8 | 25.9 | 31.0 | 25.3 |
|
Hdih | 3 | – | – | – | – | 9.2 | 5.8 | 16.0 | 28.6 | 2.2 | 2.9 | 2.6 | 3.6 |
|
Htyp | 3 | – | – | – | – | – | – | – | – | – | – | 6.0 | 11.2 |
|
Hhor | 3 | – | – | – | – | 1.8 | 2.5 | – | – | – | – | – | – |
|
Hsp1 | 3 | – | – | 0.8 | 1.8 | – | – | – | – | – | – | – | – |
|
Hsp2 | 3 | – | – | – | – | – | – | – | – | 1.6 | 0.4 | ||
|
Mhap | 3 | – | – | – | – | 1.0 | – | – | – | – | – | – | |
|
Mcur | 3 | 0.2 | 0.4 | – | – | 2.4 | 0.9 | – | – | 0.2 | 0.4 | 0.6 | 0.5 |
|
Pbuk | 2 | – | – | 2.0 | 2.3 | 24.6 | 22.9 | 30.6 | 44.7 | – | – | – | – |
|
Pstr | 2 | 153.0 | 160.0 | 0.2 | 0.4 | 0.2 | 0.4 | 6.4 | 6.4 | 28.0 | 20.2 | 20.8 | 33.4 |
|
Pcre | 2 | – | – | – | – | 5.0 | 6.4 | 0.4 | 0.5 | 1.6 | 2.6 | – | – |
|
Ppra | 3 | – | – | 0.6 | 0.9 | 8.4 | 3.8 | 0.6 | 0.9 | 15.6 | 24.6 | 3.4 | 4.7 |
|
Rrob | 3 | – | – | 4.0 | 2.1 | 1.4 | 3.1 | 6.8 | 7.0 | 3.2 | 4.1 | 8.4 | 6.4 |
|
Tspa | 4 | 33.0 | 19.0 | 2.2 | 4.9 | – | – | – | – | 14.4 | 14.0 | – | – |
|
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Aagr | 2 | 25.6 | 45.0 | – | – | 8.4 | 7.2 | 5.0 | 5.5 | 0.6 | 1.3 | 0.6 | 1.3 |
|
Bthy | 2 | – | – | – | – | 19.2 | 15.6 | – | – | – | – | – | – |
|
Ccos | 2 | 5.0 | 11.0 | – | – | 1.8 | 2.7 | – | – | – | – | – | – |
|
Fmis | 2 | 70.2 | 79.0 | – | – | – | – | – | – | 14.2 | 28.0 | 1.4 | 1.9 |
|
Fvul | 2 | 23.0 | 29.0 | 7.2 | 2.9 | 20.8 | 9.1 | 11.2 | 12.1 | 10.0 | 14.2 | 6.4 | 12.7 |
|
Mexi | 2 | 7.6 | 7.1 | – | – | 5.4 | 2.7 | 0.6 | 1.3 | – | – | 0.6 | 1.3 |
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Saff | 1 | 3.0 | 3.0 | – | – | 0.4 | 0.9 | 0.2 | 0.4 | – | – | – | – |
Total number of species | 36 | 31 | 49 | 37 | 35 | 34 | ||||||||
Total number of genera | 30 | 27 | 39 | 32 | 31 | 31 |
F-values from two-way ANOVAd or main effect ANOVA with factors ‘Ecosystem’ (forest, grassland, wetland) and ‘Invasion’ (invaded, uninvaded).
Ecosystem | Invasion | ||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Ecosystem | Invasion | Ecosystem×Invasion | Forest | Grassland | Wetland | Uninvaded | Invaded | ||||||||||||||
Indices | F(1,26) |
|
F(2,26) |
|
|
Mean | SD | Mean | SD | Mean | SD | Mean | SD | Mean | SD | ||||||
Abundanced | 0.87 | ns | 25.86 | *** | 5.08 | * | 305.80 | 247.48 | 324.40 | 117.03 | 324.50 | 229.34 | 436.60 | 199.02 | 199.87 | 111.92 | |||||
Species diversity index | 3.94 | * | 3.95 | ns | 2.09 | 0.42 | a | 2.52 | 0.34 | b | 2.33 | 0.31 | ab | 2.43 | 0.43 | 2.19 | 0.31 | ||||
Bacterivoresd | 0.32 | ns | 5.78 | * | 4.98 | * | 92.70 | 59.04 | 96.80 | 45.01 | 136.50 | 115.95 | 138.87 | 95.54 | 78.47 | 44.05 | |||||
Fungivores | 16.58 | *** | 0.80 | ns | 0.90 | 0.88 | a | 17.10 | 12.01 | b | 19.10 | 27.19 | b | 17.33 | 24.05 | 7.40 | 8.93 | ||||
Omnivores | 4.34 | * | 22.87 | *** | 14.30 | 12.27 | a | 25.80 | 21.46 | ab | 33.70 | 27.36 | b | 37.07 | 23.29 | A | 12.13 | 11.58 | B | ||
Predators | 2.64 | ns | 0.27 | ns | 18.30 | 12.54 | 7.90 | 9.26 | 4.80 | 3.94 | 10.80 | 11.10 | 9.87 | 10.68 | |||||||
Plant parasites | 1.30 | ns | 11.06 | ** | 110.30 | 129.87 | 140.60 | 82.53 | 113.50 | 57.80 | 161.93 | 88.30 | A | 81.00 | 80.37 | B | |||||
Root-fungal feeders | 4.25 | * | 9.65 | ** | 69.30 | 107.53 | a | 36.20 | 26.56 | a | 16.90 | 31.04 | b | 70.60 | 86.71 | A | 11.00 | 9.38 | B | ||
Maturity Index | 0.90 | ns | 7.05 | * | 2.22 | 0.37 | 2.20 | 0.32 | 2.05 | 0.34 | 2.31 | 0.32 | A | 2.01 | 0.30 | B | |||||
Plant-Parasitic Index | 2.00 | ns | 0.15 | ns | 2.57 | 0.32 | 2.58 | 0.20 | 2.77 | 0.19 | 2.62 | 0.28 | 2.66 | 0.23 | |||||||
Channel Index | 1.18 | ns | 5.32 | * | 22.16 | 29.72 | 12.44 | 8.81 | 8.36 | 9.38 | 21.35 | 24.04 | A | 7.29 | 7.91 | B | |||||
Basal Index | 0.65 | ns | 2.67 | ns | 10.39 | 8.76 | 11.06 | 5.36 | 11.22 | 5.38 | 12.92 | 7.23 | 8.86 | 5.06 | |||||||
Enrichment Index | 0.09 | ns | 6.45 | * | 80.54 | 16.57 | 80.95 | 11.08 | 83.01 | 7.97 | 76.10 | 13.48 | A | 86.88 | 7.42 | B | |||||
Structure Index | 1.27 | ns | 0.00 | ns | 78.73 | 15.51 | 76.59 | 11.14 | 72.35 | 12.72 | 76.58 | 10.65 | 75.20 | 15.45 |
Note: dThere was an interaction between ‘ecosystem’ and ‘invasion status’; df’s are (1, 24), (2, 24) and significant differences among plots from post hoc Fisher LSD test are reported only in text. If significant effect of factor is confirmed by ANOVA, small letters (a, b, c) within ‘ecosystem’ and capital letters A, B within ‘invasion status’ indicate significant differences between sites with p less than 0.05. Means and standard errors (SD) of the nematode community indices and nematode total abundance in the trophic groups in different ecosystems: forest, grassland, wetland; uninvaded and invaded. *,**,***Significant at 0.05, 0.01 and 0.001 levels, respectively.
The ordination analysis identified two explanatory variables (pH and SMR) that accounted for 53.5% of the total variation of nematode species abundance (Fig. 1). Monte Carlo permutation tests identified statistical significance of all axes for this relation (pseudo
RDA ordination diagram of nematode communities and Soil pH and Soil Microbial Respiration (Resp) as constrained variables in different ecosystems: forest F; forest with
The NMS analysis compared nematode composition based on species diversity. The best three-dimensional solution for the NMS ordination had a final stress of 10.40 (
NMS analysis of samples characterized by nematode species abundance, the grouping factor is presence/absence of
A total of 62 nematode species were identified: 18 of which were bacterial feeders (29.0%), 15 were plant parasites (24.2%), 9 were omnivores (14.5%), 7 were predators (11.3%), 6 were fungivores and root-fungal feeders (both 9.7%), and 1 was an insect parasite (1.6%).
Plant parasites were the most abundant trophic group in F and G (Table 3). The abundance of plant parasites was significantly higher in the uninvaded rather than the invaded plots (
Maturity and Channel indices were significantly higher in the uninvaded compared to the invaded plots (
The recent exhaustive literature review on Japanese knotweed indicated that invasion may or may not alter chemical properties of the soil, suggesting that impacts depend on the native plant species that the knotweed replace (Lavoie, 2017). Native flora, as well as actual weather conditions, soil and ecosystem type, date of soil sampling, etc., are probably responsible for the variable impacts of invasion on soil acidity and moisture among studies. Dassonville et al. (2011) in Belgium and France and Suseela et al. (2016) in USA found that invasion of
Most previous studies detected a higher abundance, biomass and/or species richness of fungi, and a lower bacterial abundance or biomass in
To the best of our knowledge, nematode communities have never been studied in natural habitats invaded by
According to Bongers (1990), the Maturity index (MI) represents the degree of environmental disturbance, with lower values being indicative of a more disturbed and enriched environment, and higher values being characteristic of a less disturbed and stable environment. We observed lower MI only in the invaded compared to the uninvaded plots, thus conforming with results presented by Renčo and Baležentiené (2011) in sites invaded by
In conclusion, our study demonstrated that the invasive plant species