Nematode Community Research Articles

Effect of Application Rates of N and P Fertilizers on Soil Nematode Community Structure in Mollisols

Long-term application of chemical fertilizer poses an environmental threat to belowground ecosystems. However, the impact of nitrogen (N) or phosphorus (P) fertilizers on soil biodiversity and the conditions of soil food web remains largely unknown. Soil nematodes are the most abundant multicellular soil animals and serve as excellent bioindicators of soil. Here, we investigated soil nematode communities and food web structure in a long-term experiment with different application rates of N and P fertilizers in northeast China. The application of N and P fertilizers increased the abundance of bacterivores but suppressed the abundance of omnivores and predators. The abundance of bacterivores exhibited an increasing trend, while that of omnivores and predators showed a decreasing trend with increasing rates of N and P fertilizers. Plant parasites displayed a decreasing trend in response to N fertilizer, but not to P fertilizer. N and P fertilizers also altered nematode functional guild composition, with N fertilizer increasing the abundance of Ba1, and P fertilizer increasing the abundance of Fu2 and Ba3. Nonmetric multidimensional scaling (NMDS) analysis revealed apparent successions of nematode communities from no fertilizer soils to high rates of N or P fertilizer soils at both the genus and functional guild levels. Furthermore, N and P fertilizers resulted in different nematode communities. In terms of nematode food web indices, N fertilizer increased the enrichment index (EI) but reduced the channel index (CI) and structure index (SI), whereas P fertilizer only reduced the SI value. High rates of N and P fertilizers increased the respired carbon of bacterivores but reduced the respired carbon of predators. Mantel tests revealed significant correlations between soil properties and the community composition of both fungivores and omnivores. Among all soil properties, available phosphorus (AP) had the greatest influence on the community structure of soil nematodes. Our findings indicate that N fertilizer has a powerful effect on nematode food web structure, while P fertilizer exerts a stronger effect on soil nematode community composition.

A combined amplicon approach to nematode polyparasitism occurring in captive wild animals in southern China

BackgroundGastrointestinal tract (GIT) nematodes prefer to live in the intestines of wild animals, causing damage and even death, and posing a zoonotic risk. The polyparasitism of GIT nematodes results in the complex dynamics of the nematode communities that occur naturally in wild animals. However, the nematode community in captive wild animals is poorly understood.MethodsWe combined microscopic examination and amplicon sequencing for community diversity.ResultsWe characterized GIT nematode assemblages to one order, one family, four genera, and ten species, in 512 fecal samples of 121 species from captive wild animals in southern China. The positive rate of GIT nematodes was 20.7% (106/512), including 42.3% (11/26) in reptiles, 26.5% (39/147) in herbivores, 25.0% (25/100) in non-human primates, 20.0% (5/25) in omnivores, 12.2% (9/74) in carnivores, and 12.1% (17/140) in avians. The dominant nematodes were Haemonchus contortus in herbivores and Trichuris species in primates. The nematode communities of arboreal primates differed from their terrestrial counterparts, reflecting both host phylogeny and ecological constraints. Soil-transmitted Strongyloides species were widespread throughout the herbivore, primate, avian, and carnivore communities, and tended to infect omnivorous primates and terrestrial herbivores. In addition, new Trichuris and Heterakis species were found in the nematode communities of captive porcupines and peafowls.ConclusionThis study highlights the variation in the composition of the GIT nematode community and strengthens the attention to the harms induced by zoonotic nematodes and co-infective nematodes with low species richness.Graphical

Metabarcoding study to reveal the structural community of strongylid nematodes in domesticated horses in Thailand

BackgroundMixed strongylid infections significantly impact equine health and performance. Traditional microscopy-based methods exhibit limitations in accurately identifying strongylid species. Nemabiome deep amplicon sequencing approach previously succeeded in describing the strongylid communities in livestock including equids. However, there are no available studies that describe the structural communities of strongylid parasites in horses in Thailand. Therefore, this study was undertaken encompassing the ITS-2 rDNA metabarcoding assay to characterize strongylid species within horse fecal samples collected from a cohort of yearlings at the largest domesticated stud farm in Thailand. In addition, to investigate the capability of ITS-2 rDNA in assessing the phylogenetic relationships among the identified strongylid species.ResultsThe study identified 14 strongylid species in the examined equine populations, each with varying prevalence. Notably, Cylicocyclus nassatus and Cylicostephanus longibursatus were identified as the predominant species, with Strongylus spp. conspicuously absent. The phylogenetic analysis of 207 amplicon sequence variants (ASVs) displayed a complex relationship among the investigated cyathostomin species, with some species are positioned across multiple clades, demonstrating close associations with various species and genera.ConclusionThe ITS-2 nemabiome sequencing technique provided a detailed picture of horse strongylid parasite species in the studied population. This establishes a foundation for future investigations into the resistance status of these parasites and enables efforts to mitigate their impact.

An Earthworm Peptide Alters Soil Nematode, Microbial, and Nutrient Dynamics: A Novel Mechanism of Soil Food Web Feedbacks

Earthworms are soil macrofauna that control soil ecosystems by strongly influencing soil nematodes, microorganisms, and nutrient cycling, as well as soil environmental factors. We have discovered an earthworm cyclic peptide that disrupts nematode DNA, affecting its lifespan, reproduction, and feeding preferences. To investigate the effects of this peptide on soil, it was added to soil, and changes in soil nematode, bacterial and fungal communities, soil nutrient contents, and basal respiration were measured on days 5 and 21. The results showed that the peptide reduced soil basal respiration on day 5 and soil NO3-N on day 21, decreased soil fungivores nematodes on day 5 and soil nematode abundance on day 21, and increased soil fungal community richness and diversity. It also altered the soil bacterial community structure between day 5 and the soil fungal community structure on days 5 and 21. The peptide regulates the soil environment by influencing the structure of soil bacterial and fungal communities through the soil nematode community, as demonstrated by partial least squares path modelling (PLS-PM) analyses. Earthworm cyclic peptides mediates tri-trophic interactions between earthworms, nematodes, microbes, and environmental factors, providing new insights into soil biota interactions and feedback in dynamic soil food webs.

Effects of drought-induced stress on nematode communities in aquatic and terrestrial habitats of the Nebraska Sandhills

IntroductionGlobal change events (e.g., worsening drought) are increasing environmental stress in a variety of terrestrial and aquatic habitats. The degree to which communities in soils and sediments are driven by temporal environmental changes across multiple habitat types from the same region is not clear.MethodsWe used nematodes, a common bioindicator of soil and sediment health, to determine how community diversity and composition are altered by rising alkalinity across lakes, shorelines, and prairies in the western Nebraska Sandhills. We sampled these three habitats from five lake basins spanning an alkalinity gradient (pH 7–11) across three years (2019, 2020, 2021). During our sampling, the Sandhills experienced a range of drought intensities, with 2019 being a wet year, followed by severe drought in 2020, and abnormally dry/moderate drought in 2021. To determine if diversity and composition of nematodes responded to increased alkalinity and drought-induced stress we used different modelling approaches, including Random Forest and pairwise comparisons.Results and discussionOverall, nematode diversity in lakes was most affected by increasing alkalinity over time, whereas in shorelines and prairies diversity was most reliant on bacterial diversity and potential nematode-nematode interactions. In comparison to shorelines and prairies, community composition in lakes was the least variable and consistently driven by pH and lake water levels. In contrast, compositions in the shorelines and prairies were more variable and explained at varying degrees by pH, year, lake basin, and climate-associated variables. In addition, relative abundance and compositional nature of select copious taxa were highly unpredictable, indicating potential instability in these habitats. Future research is necessary to address the ecologic stability of the Sandhills and determine where conservation efforts are most needed.

Influence of Eisenia fetida on the Nematode Populations during Vermicomposting Process

Vermicomposting stands as a sustainable and environmentally friendly waste management practice, leveraging the metabolic prowess of earthworms to facilitate the decomposition of organic matter into nutrient-rich compost. The aim of this experiment was to study the influence of Eisenia fetida on the density and the tropic structure of a nematode community during the vermicomposting process over a period of 3 months. Sewage sludge and green waste served as composting substrates. Overall, six compost variants were prepared consisting of three variants incorporating E. fetida and three control variants lacking E. fetida. Throughout the investigation, samples were gathered on a monthly basis, with each variant undergoing three repetitions. The aim was to isolate nematodes, determine the population density of the five trophic groups, and identify the dominant community. The anaysis was conducted employing both microscopic examination and molecular metabarcoding (NGS). It was shown that the bacterial-feeding community maintained dominance. The introduction of E. fetida into the compost led to a significant rise in the abundance of Diplogasteridae. In the variant without E. fetida, the amount of Diplodasteridae exceeded 0.1% only after the 30th (C3) or the 60th (C1, C2) day of composting, while in the compost with E. fetida, they were present in large amounts (ranging from 11.0% to 28.0%) already on the 30th day of composting. The introduction of Eisenia fetida also led to a notable reduction in H. gingivalis with significant implications for mitigating the risk of halicephalobiosis. The introduction of E. fetida resulted in reducing H. gingivalis to levels below 0.1% in all compost variants.

Nematode production in artificial ponds: a long-term perspective

Summary Nematodes are the most abundant multicellular animals on Earth and play an important role as intermediaries in energy fluxes. However, estimations of nematode biomass turnover and secondary production have been poorly defined for decades and it is difficult to reach a consensus about the importance of nematodes for ecosystem functioning. Here we monitored monthly the nematode species composition, abundance and biomass over 3-10 years in a set of artificial urban ponds, and we used different allometric models to estimate biomass turnover and secondary production. During the first 3 years of colonisation of the pond bottom, the nematode community was rather species-poor and mostly composed of small bacterivorous species (Monhysterids); however, the community quickly reached impressive numbers (up to 21 million individuals m−2) achieving a maximum annual production of 3.8-11.6 gC m−2 year−1 depending on the allometric model used for estimation. However, over the long-term (3-10 years), abundance and community structure eventually became dramatically altered by anoxic events occurring in one pond, dampening nematode production to low levels (0.3-0.6 gC m−2 year−1) without clear resilience. The comparison of models helped us to formulate general recommendations in order to popularise the use of nematode secondary production as a useful ecosystem diagnostic tool. Overall, results indicated that under good conditions of oxygenation nematodes are a highly productive component of the zoobenthos of ponds. We also discussed the consequences of this finding for sustainable pond aquaculture, as nematodes constitute an important local and nutritive resource for juveniles of economically important fish, such as carp and tilapia.

Glyphosate-based restoration of a degraded grassland threatens soil health and the diversity of nematode communities

Invasive species have become a dominant component of native grasslands, leading to a reduction in biodiversity and ecosystem functioning. Grasslands hold the potential to sequester more carbon than forests, yet few large-scale intact grasslands remain on Earth. Consequently, the restoration of degraded grasslands is critical to resurrect the ecological and economic services they once provided. Although glyphosate-based herbicide restoration projects are among the most effective strategies to remove invasive plants and allow native species to reestablish, their off-target effects on belowground diversity are unclear. Nematodes are the most abundant and diverse animals on Earth and have been recognized as indicators of soil health due to their positioning at all trophic levels and ability to respond to environmental change such as pollution, disturbance, and climate change. The goal of this study was to examine the response of nematode communities to a glyphosate-based grassland restoration project. We applied different frequencies of Roundup ProMax® to field plots in the first year of the project and characterized the impact on nematode communities over the following four years using morphological counts and 18S rRNA metabarcoding. To test the effects of the herbicide on nematode community diversity, composition, and structure, we utilized a modelling approach with general linear models, PERMANOVAs, distance-based redundancy and co-occurrence network analyses. We show persistent negative effects on nematode diversity across all four years. In addition, compositional shifts and changes in nematode-specific functional indices indicated less healthy soils in herbicide-treated plots. Co-occurrence networks further confirmed less structured and more disturbed communities. No recovery of nematode communities in glyphosate treated plots was observed after four years, demonstrating the longevity of effects. In conclusion, this study reports negative off-target effects of glyphosate herbicide restoration projects on belowground diversity and the need to consider these factors in evaluating the long-term success of herbicide-based grassland restoration.

Soil nematode communities vary among populations of the iconic desert plant, Welwitschia mirabilis

Scattered throughout the Namib Desert of Namibia are populations of Welwitschia mirabilis, a unique, low-lying, and slow-growing gymnosperm plant. We studied soils under Welwitschia plants and in adjacent interplant areas along a 400-km range to examine the potential of these plants as resource islands supporting nematode communities. We found significant differences in nematode density and community structure among the sites that were correlated to differences in climate, edaphic factors, and plant size and density. Soils from the Torra Conservancy site, which receives the most precipitation and had the highest density of Welwitschia plants, contained the highest organic matter and the most diverse nematode communities, with the broadest representation of nematode trophic groups. The largest and likely oldest Welwitschia plants occurred in the Messum Crater, the site with the least rainfall, which hosted the densest nematode communities (mean = 14,683 kg−1 soil). These communities consisted almost entirely of the bacterial-feeding nematode Panagrolaimus sp. Two other sites, Welwitschia Plain, a well-known tourist destination, and Hope Mine, the southernmost known population, contained the fewest nematodes with moderate levels of diversity. Differences in nematode abundance between Welwitschia soils and interplant soils were not discernable at three of the four field sites, suggesting the resource island effect is not very strong. Interplant spaces also support diverse and abundant nematode communities, perhaps due to the growth of cryptobiotic crusts or ephemeral rainfall-induced vegetation.

Body size induced changes in metabolic carbon of soil nematodes under N deposition and precipitation regime change in a temperate grassland

Abstract Background Global climate change has resulted in precipitation regimes exhibiting an increasing trend in rainfall intensity but a reduction in its frequency. Nitrogen (N) deposition is a crucial component of the global N cycling. Nematode body size is a trait that responds to climate change and is used as a standard trait-based indicator in soil community analysis. Variations in body size influence metabolic carbon (C). We examined the ways by which body size and metabolic C of nematodes respond to changing precipitation regimes and how N deposition regulates these responses by an 8-year manipulative experiment. Methods Nematode body size was indicated by the community-weighted mean (CWM) mass. We quantified C metabolism components of soil nematodes including production C, respiration C, and corresponding C use efficiency (CUE) under different precipitation intensities and N addition in a semi-arid steppe on the Mongolian Plateau. The Mantel test was used to determine the correlations between CWM, CUE and environmental factors. The partial least squares path modeling (PLS-PM) was conducted to quantify direct or indirect contributions among latent variables. Results We found that heavy precipitation intensity increased the CWM mass of total nematodes and omnivores-predators without N addition. N addition decreased CWM mass of bacterivores across all the precipitation intensity treatments. Stronger precipitation intensities might be favorable for nematode production and respiration C. Variations in the nematode CWM mass drove the CUE to change with N addition. Conclusions Our findings provide new insights into the mechanisms underlying nematode body size and C metabolism, and highlight that explorative studies, such as manipulative experiments, are needed to identify traits underlying size-related effects and to investigate how they affect CUE of nematodes. These efforts may increase our understanding of how changes in precipitation regimes and N deposition may alter soil nematode communities in grassland ecosystems.

Community assembly of organisms regulates soil microbial functional potential through dual mechanisms.

Unraveling the influence of community assembly processes on soil ecosystem functioning presents a major challenge in the field of theoretical ecology, as it has received limited attention. Here, we used a series of long-term experiments spanning over 25 years to explore the assembly processes of bacterial, fungal, protist, and nematode communities using high-throughput sequencing. We characterized the soil microbial functional potential by the abundance of microbial genes associated with carbon, nitrogen, phosphorus, and sulfur cycling using GeoChip-based functional gene profiling, and determined how the assembly processes of organism groups regulate soil microbial functional potential through community diversity and network stability. Our results indicated that balanced fertilization (NPK) treatment improved the stochastic assembly of bacterial, fungal, and protist communities compared to phosphorus-deficient fertilization (NK) treatment. However, there was a nonsignificant increase in the normalized stochasticity ratio of the nematode community in response to fertilization across sites. Our findings emphasized that soil environmental factors influenced the assembly processes of the biotic community, which regulated soil microbial functional potential through dual mechanisms. One mechanism indicated that the high phosphorus levels and low soil nutrient stoichiometry may increase the stochasticity of bacterial, fungal, and protist communities and the determinism of the nematode community under NPK treatment, ultimately enhancing soil microbial functional potential by reinforcing the network stability of the biotic community. The other mechanism indicated that the low phosphorus levels and high soil nutrient stoichiometry may increase the stochastic process of the bacterial community and the determinism of the fungal, protist, and nematode communities under NK treatment, thereby enhancing soil microbial functional potential by improving the β-diversity of the biotic community. Taken together, these results provide valuable insights into the mechanisms underlying the assembly processes of the biotic community that regulate ecosystem functioning.

Long-term fertilization and cultivation impacts on nematode abundance and community structure in tall fescue turfgrass.

Impacts of long-term fertilization and cultivation were evaluated on nematode communities associated with tall fescue turfgrass following 11 years of treatment applications. Fertilizer treatments of biosolid, synthetic, and plant-based fertilizers and cultivation treatments of 0×, 1×, and 2× aerification passes were applied to randomized and replicated tall fescue plots at the University of Maryland Paint Branch Turfgrass facility in College Park, Maryland. Free-living and plant-parasitic nematodes were identified, enumerated, and categorized into functional groups. Nematode count data were compared using generalized linear mixed modeling with negative binomial distribution and two-way ANOVA was used to compare nematode ecological indices. Biosolid treatments resulted in lower omnivore-predator densities than plant-based fertilizer treatments (p ≤ .001) and significantly greater Hoplolaimus densities than plant-based fertilizer plots (p ≤ .05). Synthetic fertilizer applications resulted in the greatest Eucephalobus (p ≤ .05) and total bacterivore densities (p ≤ .001) of all fertilizer treatments. Plant-based fertilizer-treated plots had the largest Maturity Index cp 2-5 and Structure Index (p ≤ .05). Cultivation of 1× resulted in fewer total bacterivore densities than 2× (p ≤ .01) while omnivore-predator densities were greater in 1× than 0× (p ≤ .001). Plant health, as measured by NDVI, was lowest in biosolid-treated turfgrass (p ≤ .05). These findings suggest that long-term turfgrass management practices can have variable impacts on nematode abundance and community structure in tall fescue and provide insights into ecological impacts of turfgrass management practices.

Increased N2O emissions by the soil nematode community cannot be fully explained by enhanced mineral N availability

Soil nematodes are the most abundant soil fauna, with a potential great impact on soil N mineralization via interaction with soil microorganisms. As a consequence, nematodes likely also influence soil N2O production and emission but the very few studies on this matter were carried out in simplified setups with single nematode species and in (highly) disturbed soil conditions. Here we measured soil N2O emissions in a 74-day incubation experiment in the presence or absence of the entire soil nematode community with minimal disturbance of the soil microbial community and soil nutrients. This was e.g. evidenced by readily recovery of nitrifiers after the mild and selective sterilization and soil powder inoculation. N2O emissions increased in the presence of nematodes, varying between soils +747.7 % in a loamy sand, +55.8 % in a loam, and +51.9 % in a silt loam cropland topsoil, in line with nematode abundance in these soils. In particular, the loamy sand soil showed an atypical N2O emission peak at the time of high nematode abundance. Soil nematodes also increased net N mineralization by +8.4, +6.8 and +4.75 %, in these respective soils and to a smaller extent C mineralization as well. The extra soil nitrate buildup and the overall net stimulation of N mineralization by nematodes could not or just slightly explain the observed increased N2O emission. This research revealed the important role of soil nematodes in regulating N2O emission, and further stresses the need to consider the change in community composition and activity of denitrifiers, and connectivity of soil pores, rather than the stimulation of N mineralization as potential explanations for this role of nematodes.

The significance of nematode communities in South African citrus decline orchards

The significance of nematode communities in South African citrus decline orchards

Assessing the diversity of nematodes in the Store Mosse National Park (Sweden) using metabarcoding

The Store Mosse National Park in the south of Sweden was surveyed for nematode diversity and distribution using DNA metabarcoding. Fifty samples were collected from five vegetation types in the park across a range of habitats (e.g. soil, litter, lichens, sphagnum and roots). The other habitats, aside from soil and litter, were sampled in order to capture the diversity of nematodes that may be uniquely associated with them. Nematodes were characterised using the V7-V8 variable domain (~ 350 bp) of the 18S ribosomal RNA gene. We identified 46 families, 76 genera (21 new to Swedish fauna) and 60 species (31 new to Swedish fauna). Some nematodes showed strong associations with their habitats, especially at the species level. Although soil and litter supported the most diverse nematode communities, our results support a strong justification for sampling across different media types to quantify nematode diversity accurately. Soil and litter communities showed high levels of stability with balanced distribution of all the various trophic and coloniser-persister groups.

Changes in Soil Bacterial and Nematode Communities during Long-term Continuous Cotton Cropping in an Arid Region.

larifying the effects of continuous cotton cropping (CC) on soil biological communities is essential for maintaining agricultural productivity. In this study, high-throughput sequencing was used to study the effects of different CC durations (0-yr, 5-yr, 10-yr, 15-yr, 20-yr, and 25-yr CC treatments) on soil microbial and nematode communities. The results showed that the dominant bacterial phyla were Actinobacteria and Proteobacteria, and the dominant nematode genus was Helicotylenchus in all CC treatments. The richness indexes (ACE and Chao1 index) and diversity index (Shannon index) of bacterial and nematode communities were the highest in the 15-yr and 10-yr CC treatments, respectively. Bacterial community was significantly correlated with soil pH and available potassium (AK), and nematode abundance was significantly correlated with microbial biomass carbon (MBC). Soil bacterial PICRUSt analysis results showed that carbon metabolism and amino acid metabolism were the main metabolic functions of bacteria in the CC treatments. The composition and diversity of soil nematode communities were significantly related to the structure of soil bacterial communities, and the niche breadth of soil bacteria was negatively correlated with that of nematodes. Panagrolaimus and Acrobeles were the main genera of bacterialfeeding nematodes affecting bacterial communities, and their relative abundances were significantly positively correlated with the relative abundance of bacterial communities. Overall, long-term (10-15 years) continuous cotton cropping negatively impacts soil biota and the microecological environment of cotton fields in arid regions.

Assessing performance of simplified bioassays for soil-borne pathogens in smallholder systems of western Kenya.

Soil-borne pathogens cause considerable crop losses and food insecurity in smallholder systems of sub-Saharan Africa. Soil and crop testing is critical for estimating pathogen inoculum levels and potential for disease development, understanding pathogen interactions with soil nutrient and water limitations, as well as for developing informed soil health and disease management decisions. However, formal laboratory analyses and diagnostic services for pathogens are often out of reach for smallholder farmers due to the high cost of testing and a lack of local laboratories. To address this challenge, we assessed the performance of a suite of simplified soil bioassays to screen for plant parasitic nematodes (e.g., Meloidogyne, Pratylenchus) and other key soil-borne pathogens (Pythium and Fusarium). We sampled soils from on-farm trials in western Kenya examining the impact of distinct nutrient inputs (organic vs. synthetic) on bean production. Key soil health parameters and common soil-borne pathogens were evaluated using both simple bioassays and formal laboratory methods across eleven farms, each with three nutrient input treatments (66 samples in total). The soil bioassays, which involved counting galls on lettuce roots and lesions on soybean were well correlated with the abundance of gall forming (Meloidogyne) and root lesion nematodes (e.g., Pratylenchus) recovered in standard laboratory-based extractions. Effectiveness of a Fusarium bioassay, involving the counting of lesions on buried bean stems, was verified via sequencing and a pathogenicity test of cultured Fusarium strains. Finally, a Pythium soil bioassay using selective media clearly distinguished pathogen infestation of soils and infected seeds. When examining management impact on nematode communities, soils amended with manure had fewer plant parasites and considerably more bacterivore and fungivore nematodes compared to soils amended with synthetic N and P. Similarly, Pythium presence was 35% lower in soils amended with manure, while the Fusarium assays indicated 23% higher Fusarium infection in plots with amended manure. Our findings suggest that relatively simple bioassays can be used to help farmers assess soil-borne pathogens in a timely manner, with minimal costs, thus enabling them to make informed decisions on soil health and pathogen management.

Use of PCR-DGGE-Based Molecular Methods to Analyze Nematode Community Diversity.

DGGE (denaturing gradient gel electrophoresis) is a nucleic acid separation technique applied to the evaluation of microbial biodiversity. This technique is quite rapid and cheap compared to other types of analysis. Here we describe the comparison of nematode communities inhabiting different ecosystems. After an ecologically representative sampling collection and the nematode extraction from soil, nematodes are centrifuged in Eppendorf tubes to facilitate DNA extraction. DNA from the whole community of each type of soil is extracted, amplified with primers for 18 S rDNA and used in DGGE analysis. The profiles of DGGE can be analyzed with appropriate software, and biodiversity indices can be estimated.

Dynamic changes of soil nematodes between bulk and rhizosphere soils in the maize (Zea mays L.)/alfalfa (Medicago sativa L.) intercropping system

The importance of habitat spatial variability as a key driver of soil biota patterning (e.g., soil nematodes) has lately gained a lot of attention. It is generally accepted that rhizosphere soil has a distinct faunal assemblage than bulk soil, but less is known about the patterning of soil nematodes and the causes of these changes in maize-alfalfa agroecosystems. As a result, the purpose of this study was to assess the dynamic changes in soil nematodes across bulk and rhizosphere soils when maize and alfalfa were grown separately and in a combination at varying levels of nitrogen fertilizer. The results of a field experiment in a 2 × 3 factorial completely randomized block design revealed that total nematode and omnivore-predator abundance, as well as nematode generic diversity and richness, maturity, and structure indices, were significantly increased in the rhizosphere of monoculture alfalfa and alfalfa grown in a mixture with maize when compared to the bulk soil. Furthermore, we discovered elevated levels of total sugars and organic acids in rhizosphere soils. Plant- and fungal-feeding nematodes increased in both bulk and rhizosphere soils, whereas omnivores and predators decreased in soils treated with monoculture and nitrogen fertilizer. Furthermore, we discovered a significant positive relationship between total nematode and omnivore-predator abundance and soil organic carbon and total nitrogen, soil moisture content, and microbial biomass C and N, implying that changes in these soil properties and rhizodeposition may shape the nematode community assemblage between the bulk and rhizosphere soils. Our findings suggest that crop mixes containing alfalfa would improve soil characteristics and rhizodeposition, resulting in increased nematode number and variety and contributing to sustainable agriculture.

Taxonomic Composition Change after Environmental Levels Addition of Polyethylene Microplastic (PE-MPs) to Mediterranean Sediment: Case Study of Bizerte Lagoon Nematodes Communities

Taxonomic Composition Change after Environmental Levels Addition of Polyethylene Microplastic (PE-MPs) to Mediterranean Sediment: Case Study of Bizerte Lagoon Nematodes Communities