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Soil nematodes are the most abundant soil metazoans, occupying multiple trophic levels in the soil food web and playing an important role in soil function. Research on the biogeographic distribution patterns of soil nematode communities and their drivers has received greater attention. However, the distribution characteristics of soil nematode communities along the elevational gradient in the arid and semi-arid regions of Northwest China remain unclear. In this study, four elevational gradients (1750–1900, 1900–2100, 2100–2350 and 2350–2560 m) were established on Luoshan Mountain, Ningxia, an arid and semi-arid region in Northwest China, and soil nematodes in the soil layers of 0–10, 10–20 and 20–40 cm were investigated using the improved Baermann funnel method. The results revealed a monotonically decreasing trend in the total number of soil nematodes along the elevational gradient and soil layer depth, decreasing by 63.32% to 79.94% and 73.59% to 86.90%, respectively, while the interactions were not obvious. A total of 1487 soil nematodes belonging to 27 families and 32 genera were identified across the elevational gradient, with Helicotylenchus as the dominant genus, accounting for 10.43% of the total number of nematodes, and bacterivore nematodes as the main trophic groups, accounting for 32.39% to 52.55% of the relative abundance at each elevation, which increased with increasing elevation. Soil nematode community diversity, richness and maturity indices were relatively low at high elevation and decreased by 44.62%, 48% and 54.74%, respectively, with increasing soil layer depth at high elevations. Compared to low elevations, high-elevation soils experienced greater disturbance, reduced structural complexity and nutrient enrichment of the soil food web, and a shift in soil organic matter decomposition from bacterial to fungal pathways as elevation increased. Finally, redundancy analysis showed that soil pH, bulk density, soil moisture, soil organic carbon, available nitrogen, available phosphorus and available potassium were the main soil factors affecting the composition of soil nematode communities, which well explained the differences in nematode communities at different elevations and soil depths. This study can be used as basic information for further research on soil biota in this mountainous region, expanding our further understanding of the spatial ecology of soil nematodes in the arid and semi-arid mountain ecosystems. [ABSTRACT FROM AUTHOR]

Soil nematodes are the most abundant soil metazoans, occupying multiple trophic levels in the soil food web and playing an important role in soil function. Research on the biogeographic distribution patterns of soil nematode communities and their drivers has received greater attention. However, the distribution characteristics of soil nematode communities along the elevational gradient in the arid and semi-arid regions of Northwest China remain unclear. In this study, four elevational gradients (1750-1900, 1900-2100, 2100-2350 and 2350-2560 m) were established on Luoshan Mountain, Ningxia, an arid and semi-arid region in Northwest China, and soil nematodes in the soil layers of 0-10, 10-20 and 20-40 cm were investigated using the improved Baermann funnel method. The results revealed a monotonically decreasing trend in the total number of soil nematodes along the elevational gradient and soil layer depth, decreasing by 63.32% to 79.94% and 73.59% to 86.90%, respectively, while the interactions were not obvious. A total of 1487 soil nematodes belonging to 27 families and 32 genera were identified across the elevational gradient, with Helicotylenchus as the dominant genus, accounting for 10.43% of the total number of nematodes, and bacterivore nematodes as the main trophic groups, accounting for 32.39% to 52.55% of the relative abundance at each elevation, which increased with increasing elevation. Soil nematode community diversity, richness and maturity indices were relatively low at high elevation and decreased by 44.62%, 48% and 54.74%, respectively, with increasing soil layer depth at high elevations. Compared to low elevations, high-elevation soils experienced greater disturbance, reduced structural complexity and nutrient enrichment of the soil food web, and a shift in soil organic matter decomposition from bacterial to fungal pathways as elevation increased. Finally, redundancy analysis showed that soil pH, bulk density, soil moisture, soil organic carbon, available nitrogen, available phosphorus and available potassium were the main soil factors affecting the composition of soil nematode communities, which well explained the differences in nematode communities at different elevations and soil depths. This study can be used as basic information for further research on soil biota in this mountainous region, expanding our further understanding of the spatial ecology of soil nematodes in the arid and semi-arid mountain ecosystems. [ABSTRACT FROM AUTHOR]

Purpose: The effects of trees on soil nematode communities are related to nutrient cycles in forest ecosystems. We conducted greenhouse pot experiments to determine the effects of a single tree species for each of coniferous and broad-leaved tree on soil nematodes. Methods: Soils were collected from a coniferous plantation and broad-leaved forests. Seedlings of a coniferous tree (Cryptomeria japonica) and a broad-leaved tree (Quercus serrata) were planted in soils derived from each species. After 11 months, seedling biomass, soil properties, and ectomycorrhizal fungal colonization of Q. serrata were measured. Soil nematodes were morphologically identified to the genus/family level and differentiated by community and trophic composition. Results: C. japonica root biomass was significantly higher than that of Q. serrata regardless of the soil and nematode community structures were significantly different between the species. The fungal: bacterial ratio and density of fungivorous nematodes were significantly higher in broad-leaved soils. Herbivorous nematodes increased significantly in C. japonica seedlings grown in broad-leaved soils. Structural equation modeling indicated that soil origin and tree species directly regulated nematode trophic compositions. Conclusion: Our findings suggest that tree species modify soil micro-food webs by affecting microbial abundance and nematode trophic composition. Specifically, C. japonica, with a larger root biomass, increased the number of herbivorous nematodes, whereas Q. serrata, with ectomycorrhizal fungal symbiosis, increased the number of fungivorous nematodes. Thus, tree species are tightly involved in shaping nematode communities in forest ecosystems through root traits and mycorrhizal types. [ABSTRACT FROM AUTHOR]

Aims: Tree logging in tropical tree plantations results in significant soil disturbances that negatively impact soil biodiversity and soil functioning. Here, we aimed to assess the effects of adding organic matter (OM) to soil after rubber tree logging on soil functioning over time. Methods: The experiment was conducted in two contrasting soil types in Ivory Coast. Four practices were replicated, including a control with no residues, the presence of legumes only, legumes and all tree parts excluding the trunk, and legumes and all the parts of the tree including the trunk. We monitored the response of soil nematode communities every six months for 24 months in each practice. Samples were collected from the topsoil layer (0–10 cm) in the interrow, and we also monitored soil carbon transformation by measuring in situ basal soil respiration, labile soil carbon and organic matter decay using the bait lamina method. Results: The results showed a sharp decrease in nematode abundance after tree logging, but OM restoration increased nematode abundance, the relative abundance of bacterivores, and resource availability to the soil food web. The resilience of the nematode communities depended on soil conditions and the amount and quality of logging residues. Total nematode abundance was positively and significantly related to soil functioning, measured through basal soil respiration, labile soil carbon, and organic matter decay rate. Conclusion: The results suggest that restoring logging residues can be an effective way to restore soil biodiversity and mitigate the negative impact of clear-cutting in tropical rubber plantations. [ABSTRACT FROM AUTHOR]

Faidherbia albida (Delile) A. Chev., hereafter F. albida is an important agroforestry tree species in the semi‐arid highlands of Tigray, northern Ethiopia. The paper analyses how different stand ages of the tree could influence nematodes' abundance, trophic composition and selected community index values. A total of 40 composite soil samples were collected from out‐canopies and under‐canopies of different tree stand age classes designated as young (15–20 years), medium age (35–40 years) and older (> 60 years). Nematodes were extracted following the Baermann funnel technique, identified and counted under an inverted Olympus microscope according to their trophic groups. The highest total count of nematodes and relative abundance of fungivores, omnivores and predatory nematode trophic groups were counted from soil samples influenced by older F. albida trees. The relative abundance of bacterivores and plant parasitic nematodes was low. The nematode channel ratio became lower in soils as influenced by older trees while the Wasilewska index was significantly high. The age difference of the trees influenced the abundance of the soil nematode feeding groups and their ecological index values. Moreover, the results have shown the enhancement of nematode trophic diversity. Redundancy analysis showed that tree age significantly influenced the relationships of nematode trophic groups with the studied soil bio‐physicochemical properties. Generally, the findings indicate that the soil food web becomes more complex and functional under the older trees. [ABSTRACT FROM AUTHOR]

Rising temperatures and higher atmospheric CO2 levels can potentially increase plant photosynthesis and boost forest productivity, thereby spurring litter inputs to soils on a global scale. Understanding the feedback loops between increased litter inputs and soil biota activity will allow for better prediction of organic matter and carbon (C) cycling in terrestrial ecosystems.Nematodes represent the full spectrum of trophic groups within the soil biota. Accordingly, we studied the link between nematode metabolic activities and plant litter input. For this, different litter input levels were manipulated in a temperate forest, including control zones without litter, natural litter input zones and zones with double, triple and quadruple amounts of natural litter input. Soil top layers (0–10 cm) were then collected to study the responses of nematode communities.Increased litter input positively influenced the abundance and diversity of nematodes, except for plant‐parasitic species. Higher litter input levels led to an enhancement in the ratio of bacterivores to the total of bacterivores and fungivores. More litter increased the K/r strategist ratio among bacterivores and the corresponding nematode metabolic footprints. More litter also stimulated nematode production and respiration components and improved the carbon use efficiency of bacterivores. Moreover, structural equation modelling revealed the crucial role of bacterivores in influencing soil organic C under increased litter input.In conclusion, our study shows that increased plant above‐ground litter input modifies the taxonomic and functional communities of soil nematodes, ultimately regulating carbon cycling in forest soils. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

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Introduction: 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. Methods: 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). Results and Discussion: 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 Fusariumstrains. 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. [ABSTRACT FROM AUTHOR]

This work evaluates the community of soil nematodes in agricultural and livestock environments with different intensity of land use in the southeast of the province of Buenos Aires. Nematodes were extracted from sites with different intensity of land use: corn (2 consecutive years of conventional tillage [LC]), potato (1 year of LC), soybean (direct seeding), and pastures (with grazing animals). 44 genera of nematodes belonging to 5 trophic groups were identified. The most abundant genera were Helicotylenchus, Pratylenchus and Cruznema. Significant differences were found in the structure of the nematode community between land uses. The total abundance and by trophic groups was higher in soybeans and pasture. Furthermore, in relation to the composition of the community of free-living nematodes (bacteriophages, frugivores, omnivores and predators), the sites with corn and soybeans presented a higher proportion of fungivores, while the sites with potatoes and grass showed a higher proportion of bacteriophages. In relation to phytophagous nematodes, the community associated with sites with greater agricultural disturbance (corn and potatoes) presented a different and less diverse assembly than those associated with sites with less disturbance (soybean and pasture). The nematological indices showed that the successional dynamics of the nematode communities were affected due to land use practices. This was confirmed through the analysis of the faunal profile, the majority of food chains, regardless of the type of land use, were affected by agronomic practices showing mature food webs. This work constitutes the first report on the composition of soil nematode communities in agricultural and livestock production fields in southeastern Buenos Aires, and contributes to understanding the ecology of soil nematode communities impacted by different anthropogenic practices. [ABSTRACT FROM AUTHOR]

Antarctica terrestrial ecosystems are facing the most threats from global climate change, which is altering plant composition greatly. These transformations may cause major reshuffling of soil community composition, including functional traits and diversity, and therefore affect ecosystem processes in Antarctica. We used high‐throughput sequencing analysis to investigate soil nematodes under 3 dominant plant functional groups (lichens, mosses, and vascular plants) and bare ground in the Antarctic region. We calculated functional diversity of nematodes based on their diet, life histories, and body mass with kernel density n‐dimensional hypervolumes. We also calculated taxonomic and functional beta diversity of the nematode communities based on Jaccard dissimilarity. The presence of plants had no significant effect on the taxonomic richness of nematodes but significantly increased nematode functional richness. The presence of plants also significantly decreased taxonomic beta diversity (homogenization). Only mosses and vascular plants decreased nematode functional beta diversity, which was mostly due to a decreased effect of the richness difference component. The presence of plants also increased the effect of deterministic processes potentially because environmental filtering created conditions favorable to nematodes at low trophic levels with short life histories and small body size. Increasing plant cover in the Antarctic due to climate change may lead to increased diversity of nematode species that can use the scarce resources and nematode taxonomic and functional homogenization. In a future under climate change, community restructuring in the region is possible. [ABSTRACT FROM AUTHOR]

Arthrobotrys oligospora is a nematode-trapping fungus belonging to the family Orbiliaceae and one of the main antagonists of nematodes in soil, including plant and animal parasitic nematodes and free-living nematodes. This species develops three-dimensional adhesive nets in which nematodes are trapped, destroyed and consumed by the fungus. It also possesses other strategies to immobilise, kill and degrade nematodes, i.e. nematode-attractant substances, cuticle adhesion polymers and a number of nematocidal metabolites. The objective of this study was to assess the in vitro nematocidal activity of a strain of A. oligospora through its predatory activity and its liquid culture filtrates (LCF) against the ruminant parasite Haemonchus contortus (HcL3) and to investigate the presence of myco-compounds with potential nematocidal activity. Predatory activity (PA) was assessed in agar plates; 200 HcL3 were placed on agar plates with the fungus and a control group and incubated for 10 days. The LCF confrontation with nematodes was performed in microtiter plates. Two media, Czapek-Dox Broth (Cz-DB) and potato dextrose broth, were assessed. Three concentrations (25, 50 and 100 mg/mL) were assessed at 48 and 72 h (n = 4, per concentration). The experiment was performed in triplicate. The results showed 73.6 ± 2.7% PA and the highest mortality (83%) with the LCF in Cz-DB after 72 h. Gas chromatography–mass spectrometry (GC–MS) analysis revealed that the A. oligospora ethyl acetate phase was composed of 1,2-benzenedicarboxylic acid, bis (2-methylpropyl) ester, (M) 1,4-benzenedicarboxylic acid, bis (2-methylpropyl) ester and (M) decanedioic acid (2-ethylexyl) ester. These compounds could be responsible for nematocidal activity. [ABSTRACT FROM AUTHOR]

This study is focused on soil nematode communities in undercrown areas of tree plants introduced to and cultivated for a long time in the botanical garden on Bolshoy Solovetsky Island (Arkhangelsk oblast, Russia). Soil nematode communities of natural forests (pine-, spruce-, and birch stands) are studied as the control. The study has demonstrated that the taxonomic diversity and abundance of nematodes, as well as the proportion of plant parasites in the trophic structure of nematode communities in the soil under introduced trees, are higher compared to natural forests. The ecological indices (structure index SI and enrichment index EI) change nonuniformly and so have poor performance as tools for evaluating the consequences of the plant introductions for the soil ecosystem. Correlation analysis reveals a significant positive relationship between the content of carbon and nitrogen in soil and the absolute and relative abundance and the taxonomic diversity of plant parasites, as well as significant negative relationships between C : N and fungal feeders, as well as between the soil pH and the taxonomic diversity of nematodes and the relative abundance of bacterial feeders and EI. The entomopathogenic nematode Steinernema affine Bovien revealed on the island has been reported for the first time in Russia. [ABSTRACT FROM AUTHOR]

Rio Grande do Sul State produces 70% of pecans in Brazil. There is a high density of phytopathogenic nematodes in orchards. This study characterises the populations of plant-parasitic nematodes and investigates their association with soil properties in pecan-cultivated areas. The genera Mesocriconema, Criconemoides, Discocriconemella, Xiphinema, Tylenchus, Pratylenchus, Helicotylenchus, and Aphelenchoides were all identified. Discocriconemella and Xiphinema were positively associated with soil organic matter, cation exchange capacity, clay content, copper, zinc, calcium, magnesium, and potassium. Conversely, Pratylenchus, Helicotylenchus, Tylenchus, Criconemoides, and Aphelenchoides were positively correlated with aluminium. Mesocriconema, the most commonly found nematode, negatively correlated with most soil chemical attributes. A significant correlation was observed between the genera Criconemoides, Mesocriconema, Aphelenchoides, and Tylenchus. Parasitic nematodes in pecan orchards have not previously been documented in this region of Brazil. [ABSTRACT FROM AUTHOR]

Nematodes serve as key indicators of soil health in ecological studies. Therefore, the current study examined the community structure and metabolic footprint of soil nematodes in alfalfa fields across varying levels of N supply in the semi-arid Loess Plateau. The findings offer theoretical guidance for the sustainable management of artificial alfalfa grasslands in this region. The research was based on alfalfa fields with different N application rates (0, 50, 100, 150 kg/ha2) as the research object, The shallow plate method was used to separate and extract soil nematodes, identify soil nematode groups, calculate ecological function index and metabolic footprint, and identify indicator species. A total of 6346 nematodes were isolated in this study, belonging to 27 genera and 19 families. Notably, the plant parasitic nematode Helicotylenchus was predominant. As N addition increased, the plant parasitic index (PPI) increased significantly. A N50 application significantly enhanced the soil nematode diversity index (H ) and the free-living index (MI). The findings showcased a noticeable decrease in disturbance within the N50 soil nematode community. This resulted in a mature and stable community structure primarily attributed to the heightened abundance of omnivorous/predatory nematodes. Across various N levels, soil nematode communities underwent significant alterations in the soil food web structure through shifts in their metabolic footprint. Future strategies should focus on refining N management practices and integrating sustainable approaches like crop rotation and pest management. These efforts will contribute to guidelines ensuring artificial alfalfa grasslands lasting health and productivity. [ABSTRACT FROM AUTHOR]

This paper mainly reveals the dhynamic occurrence rule of root-knot nematode in the vegetable soil of Chifeng protected area, and provides a theoretical basis for the control of southern root-knot nematode disease in this area. The dynamic change of root-knot nematode quantity in the soil of Chifeng protected land was monitored for 10 years. The dynamic change law of the lateral and vertical distribution of root-knot nematode in the soil from 2013 to 2014 was investigated. The dynamic occurrence law of the southern root-knot nematode under different years and agronomic measures was expounded. The results showed that the lateral distribution of southern root-knot nematodes in greenhouse soil was as follows: the northern and central nematodes were the most abundant, while the southern nematodes were the least abundant. The vertical distribution of nematodes was as follows; the southern root-knot nematodes distributed most in the 4-15 cm soil layer, and less in the 15-25 cm soil layer. During the 10 years of monitoring sites, the occurrence rule of southern root-knot nematodes was as follows: about 6 generations occurred every year in greenhouses of monitoring sites, and each crop occurred about 3 generations. In terms of quantity, the maximum number of root-knot nematodes appeared around May and November every year, and the number of overwinter stubble was greater than that of autumn stubble. The distribution and dynamic occurrence of southern root-knot nematode in soil were studied, which can provide theoretical guidance for the prevention and control of root-knot nematode disease in Chifeng area. [ABSTRACT FROM AUTHOR]

Nematodes adapt to variety of environments. Dynamics of a nematode community are highly associated with the soil condition, which can serve as an indicator for monitoring the impact of human activity on the soil ecosystem. However, a systematic study on nematode fauna is lacking in many regions across Taiwan. In this study, we provide morphological and molecular identification for the soil nematodes collected during the cultivation process of the first crop rice in Chiayi, Taiwan. Within the three-year survey, 26 morphospecies of 18 genera were identified in the soil from the rice paddy fields. Each morphospeices was initially identified based on morphology, and 11 were further examined using 18S rDNA sequences. Among these, nine predominant morphospeices represented over 90% of the abundance, while juveniles of the plant pathogenetic nematode, Meloidogyne, were the most abundant one. Bacterivore was the most diverse and abundant functional group in the nematode community. Eight morphospecies were supported by the molecular identification at the genus level, while three require further consideration due to inconsistencies between morphological and molecular analyses. [ABSTRACT FROM AUTHOR]

Animal body size exhibits rapid responses to environmental variations and displays considerable variability across ecological scales, significantly influencing ecological community assembly. However, our understanding of the extent of body size variation and its responses to environmental differences within soil fauna remains limited, impeding a comprehensive grasp of soil fauna's functional ecology. Here, we aim to investigate the magnitude of intrageneric body size variation and its implications for soil nematode community assembly along an altitudinal gradient. We examined soil nematode body size responses along an altitudinal gradient spanning from 3136 to 4128 m in an alpine mountain region of the eastern Tibetan Plateau. We assessed the contributions of intra‐ and intergeneric variations in body size, both within and among communities, using individual body size values. The implications of these variations for community assembly processes were determined through phenotypic variance ratios employing permutation tests. Our analyses did not reveal statistically significant correlations between altitude and the community‐weighted mean body mass, regardless of considering intrageneric trait variation (IGTV). Approximately 15% of the variation in body size among communities and a substantial 72% of the variation in body size within communities can be attributed to IGTV. Altitude did not significantly affect IGTV within or among communities. Furthermore, our results underscored the dominant role of internal filtering within the community in governing nematode community assembly, with external filtering outside the community playing a limited role within our altitudinal range. Our findings emphasize the dominant role of body size variation within communities rather than among communities, attributable to strong internal filtering processes. These findings advance our understanding of body size variation in soil nematodes across ecological scales and highlight the pivotal role of intrageneric variation in shaping the functional ecology of soil fauna. [ABSTRACT FROM AUTHOR]

Emerging knowledge of plant–soil biotic interactions and the role of soil organisms in shaping the world aboveground is advancing our understanding of ecosystem function. Nematodes are the most abundant animals on Earth. They are morphologically and functionally diverse, and play key roles in ecosystem function, making them ideal for developing a trait-based understanding of adaptation to the environment and for assessing their contributions to ecosystem function. Trait-based approaches allow us to capture the functional attributes of organisms beyond their taxonomic identity, provide insights on evolutionary fitness, and make global comparisons possible. We propose the nematode economics spectrum (NES), analogous to the plant economic spectrum, which describes the tradeoffs among growth, reproduction, and survival, potentially enabling us to predict the impacts of global change on nematode ecological strategies and the associated changes in ecosystem function. Trait-based approaches are being increasingly adopted to understand species' ecological strategies and how organisms influence ecosystem function. Trait-based research on soil organisms, however, remains poorly developed compared with that for plants. The abundant and diverse soil nematodes are prime candidates to advance trait-based approaches belowground, but a unified trait framework to describe nematode ecological strategies and assess their linkages with ecosystem function is lacking. We categorized nematode traits as morphological, physiological, life history, and community clusters, and proposed the nematode economics spectrum (NES) to better understand nematode ecological strategies and their association with ecosystem function. We argue that bridging the NES and the plant economics spectrum will facilitate a more holistic understanding of ecosystem carbon and nutrient cycling under global change. [ABSTRACT FROM AUTHOR]

The prevalence and abundance of plant-parasitic nematodes (PPNs) associated with corn (Zea mays; Poaceae) in the Anuradhapura district of Sri Lanka are poorly understood. This study investigated the occurrence and population densities of major PPN genera associated with corn. Over 92% of the corn fields were positive for PPNs in all the sampled fields. Major PPN genera identified were Pratylenchus spp. (71.4%), Helicotylenchus spp. (28.6%), Meloidogyne spp. (21.4%), Criconemella spp. (21.4%), and Hoplolaimus spp. (35.7%). The mean population density of Pratylenchus spp. was 2020 nematodes kg-1 of soil, in the Anuradhapura corn fields. During the cropping season from November (2021) to February (2022), all PPN genera except Meloidogyne spp. were observed. Pratylenchus spp. were detected at levels below 1000 nematodes kg-1 of soil at the seedling stage, except in Kelenikawewa where the initial population was 1865 nematodes kg-1. At the time of harvest, Pratylenchus spp. increased by 2 to 10 folds. These findings suggest a potential impact of Pratylenchus spp. on corn yield in Anuradhapura, highlighting the need for further research to assess damage levels and the overall effect of PPNs on corn production in Sri Lanka. [ABSTRACT FROM AUTHOR]

Apple replant disease (ARD) may cause significant losses both in commercial orchards and in fruit tree nurseries. The negative effects of ARD may be limited by using biofumigation. The aim of the study was to assess the influence of this treatment on the biological properties of replanted soil in a tree nursery. In two-year experiment, apple trees of the 'Golden Delicious' cultivar were used. The trees were planted into soil from two sites. The soil from one site had not been used in a nursery before (crop rotation soil). The other soil had been used for the production of apple trees (replanted soil). Three species of plants were used in the replanted soil as a forecrop: French marigold (Tagetes patula), white mustard (Sinapis alba), and oilseed radish (Raphanus sativus var. oleifera). The following parameters were assessed in the experiment: the enzyme and respiratory activity of the soil, the total count of bacteria, fungi, oomycetes and actinobacteria in the soil, as well as the count and species composition of soil nematodes. The vegetative growth parameters of the apple trees were also assessed. The biological properties of the replanted soil were worse than those of the crop rotation soil. In the replanted soil, the organic matter content, enzyme and respiratory activity as well as the count of soil microorganisms were lower. The biofumigants, used as a forecrop on the replanted soil, significantly increased its enzyme activity and respiratory activity. Dehydrogenase activity increased more than twofold. Growth parameters of the trees were significantly improved. The height of the trees increased by more than 50%, and the leaf area, weight and total length of side shoots were higher as well. The density of nematodes in the replanted soil after biofumigation was significantly reduced, with a larger reduction in the marigold fumigated soil. Eight of the eleven nematode species were completely reduced in the first year after biofumigation treatment. [ABSTRACT FROM AUTHOR]

The dataset presents comprehensive information on soil nematode genera distribution in ecosystems across Slovakia, Poland, Lithuania, and Russia. Data were collected from invaded plots by invasive plants and non-invaded plots from grasslands, deciduous forests, and coniferous forest ecosystems in diverse geographical regions. Invasive plant species included in this dataset are Asclepias syriaca, Fallopia japonica, Heracleum mantegazzianum, H. sosnowskyi, Impatiens parviflora and Solidago gigantea. The soil properties such as pH, moisture content, carbon, and nitrogen levels were recorded, providing comprehensive information on soil conditions. The data collection process involved standardized soil sampling techniques across all sites, ensuring consistency and comparability. The dataset offers valuable insights into soil nematode biodiversity dynamics in response to plant species invasions in European ecosystems. Nematode genera were classified according to feeding types and colonizer-persister class. Researchers interested in soil ecology, biodiversity conservation, and invasive species management can use this dataset for various purposes. Potential reuses include comparative analyses of nematode community composition, ecological modelling to predict invasive species impacts and assessments of ecosystem health and resilience.

Global changes in nitrogen deposition, precipitation patterns and land use could have an impact on soil biotas. Soil nematodes are important indicators of ecosystem function in degraded grasslands, and how global climate change affect soil nematode communities in degraded grasslands with poisonous weeds needs further study. This study conducted a control experiment on degraded grasslands with Sophora alopecuroides as a single dominant species. We set up a total of eight treatments, which are no nitrogen, no watering, no mowing (CK), nitrogen addition (N treatment), watering (W treatment), mowing (M treatment), nitrogen × watering (NW treatment), nitrogen × mowing (NM treatment), watering × mowing (WM treatment), nitrogen × watering × mowing (NWM treatment). We analyzed the patterns of change in nematode abundance, richness, ecological indices, and co-occurrence networks, as well as the relationships among nematode trophic taxa, soil salinity, and plants. Our results showed that: (1) Paratylenchus and Acrobeles were the main dominant genera. NW treatment significantly increased the relative abundance of plant parasites and significantly decreased the relative abundance of bacterivores. (2) N and NWM treatments increased nematode community network complexity. W, M, and WM treatments decreased nematode community network complexity. (3) Plant Parasites and Bacterivores nematodes community composition were significantly correlated with the structural characteristics of S. alopecuroides (biomass, height, coverage; biomass, height). Fungivores nematodes and Omnivores/Predators nematodes community composition were significantly correlated with soil salinity ions (Cl-, Mg2+; SO42-). (4) The average degree (characterizing the interaction intensity among nematodes genera and sparsity-density of the nematode ecological network) was significantly positively correlated with soil multifunctionality. In addition, the interaction of nitrogen and watering addition on the abundance of different feeding nematodes than nitrogen and watering addition alone. Mowing can alleviate the negative effects of nitrogen addition and watering on soil food webs. Our study suggested that there are complex interactions between soil nematodes and environmental factors in grassland ecosystems, and provided new insights for understanding the impact of global change on the formation and change of soil fauna diversity in poisonous weed type degraded grasslands.

Simple Summary: Entomopathogenic nematodes (EPNs) are beneficial soil fauna that participate in the food chain. Natural populations of these animals keep insect numbers at a certain level and provide food for other groups of invertebrates. EPNs are also used as biological pest control agents. The life and effectiveness of EPNs are affected by many biotic and abiotic factors of the soil environment. Our review describes characteristics and directions of the effects of various environmental factors on the biology of EPNs. Many organisms, including beneficial entomopathogenic nematodes (EPNs), are commonly found in the soil environment. EPNs are used as biopesticides for pest control. They have many positive characteristics and are able to survive at sites of application for a long time, producing new generations of individuals. The occurrence of populations depends on many environmental parameters, such as temperature, moisture, soil texture, and pH. Extreme temperatures result in a decrease in the survival rate and infectivity of EPNs. Both high humidity and acidic soil pH reduce populations and disrupt the biological activity of EPNs. Nematodes are also exposed to anthropogenic agents, such as heavy metals, oil, gasoline, and even essential oils. These limit their ability to move in the soil, thereby reducing their chances of successfully finding a host. Commonly used fertilizers and chemical pesticides are also a challenge. They reduce the pathogenicity of EPNs and negatively affect their reproduction, which reduces the population size. Biotic factors also influence nematode biology. Fungi and competition limit the reproduction and survival of EPNs in the soil. Host availability enables survival and affects infectivity. Knowledge of the influence of environmental factors on the biology of EPNs will allow more effective use of the insecticidal capacity of these organisms. [ABSTRACT FROM AUTHOR]

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Aphids (Hemiptera: Aphididae) are small, phloem-feeding insects that exhibit remarkable adaptability and resilience to various environmental conditions, including heat stress. Recent research has shed light on the role of bacterial symbionts in influencing the heat tolerance of aphids. Additionally, an intriguing avenue of investigation has explored how aphids can acquire bacterial symbionts through a unique mechanism involving soil nematodes. In this paper, we provide an in-depth overview of the interplay between heat stress, bacterial symbionts, and soil nematodes in the context of aphid biology. In reviewing the existing literature and collating available knowledge, we highlight the mechanisms by which bacterial symbionts contribute to aphid heat stress tolerance and examine the symbiont acquisition process facilitated by soil nematodes. Furthermore, we discuss the implications of these symbiotic associations in relation to the ecology, evolution, and agricultural management of a major globally expanding pest aphid, the corn leaf aphid, Rhopalosiphum maidis (Fitch). Overall, it may be concluded that both primary and secondary bacterial endosymbionts play a significant role in aphid biology with evolutionary consequences. These include adaptations through bacterial symbionts in terms of longevity and fecundity, heat shock tolerance, and resistance to fungal pathogens and primary hymenopterous wasp parasitoids. [ABSTRACT FROM AUTHOR]

The metacommunity theory enhances our understanding of how ecological processes regulate community structure. Yet, unraveling the complexities of soil nematode metacommunity structures across various spatial scales and determining the factors influencing these patterns remains challenging. Therefore, we conducted an investigation on soil nematode metacommunities spanning from north to south in the Northeastern China. Our aim was to test whether nematode metacommunities were structured by different drivers under three land covers (i.e., farmland, grassland and woodland) at the local and regional scales. The results revealed that the Clementsian, Gleasonian and their quasi‐structures of soil nematodes collectively accounted for 93% of the variation across the three land covers at the local and regional scales. These structures suggest that the soil nematode metacommunities in the Northeast China responded to fluctuations in environmental gradients. At the local scale, metacommunities were primarily shaped by biological interactions. At the regional scale, environmental heterogeneity, dispersal limitation and biological interactions all contributed to nematode metacommunities. Meanwhile, biological interactions under three land covers were represented within different trophic groups, with plant parasites predominant in farmlands and bacterivores in grasslands and woodlands. In conclusion, the metacommunity structures of soil nematodes remain stable at different spatial scales and land covers. Biological interactions are widespread among nematodes regardless of changes in spatial scales and land covers. This study reveals the importance of nematode sensitivity to the environment and biological interactions in shaping the nematode metacommunities, potentially enhancing our understanding of the spatial patterns of nematode metacommunities. [ABSTRACT FROM AUTHOR]

Aims: Plant functional group (PFG) removal experiments are recognized as an effective way to explore the role of plant diversity and species traits in ecosystem functioning. To minimize soil physical disturbance in plant removal experiments, aboveground parts of targeted plant species are usually cut off without removing their roots from the soil. However, the potential effects of their remaining roots (partially as root litter) on soil nematode communities are still unclear. Methods: We used a three-year PFG removal experiment in a Qinghai-Tibet alpine meadow and set up root-ingrowth mesh bags for one year where removal target plants' roots existed only outside the mesh bags. Results: We found that nematode communities outside the mesh bags had higher nematode channel ratio and lower channel index values, indicating that the root litter outside the mesh bags increased energy flux to bacterial-feeding nematodes over fungal-feeding nematodes. The relative abundance of plant-feeding nematodes was higher inside than outside the mesh bags, probably because of a higher ratio of living roots inside the mesh bags. Non-metric multidimensional scaling showed that the structure of nematode communities inside and outside of mesh bags was generally differentiated except for the no-removal control treatment. Conclusions: We conclude that the remaining roots outside mesh bags could modify the relative abundance ratio of different nematode guilds and soil nematode community structures, suggesting legacy effects of target plants' roots in PFG removal experiments. [ABSTRACT FROM AUTHOR]

Crop sequence and tillage can affect the yield of peanut (Arachis hypogaea L.) and other crops. Research was conducted from 2006 through 2022 to determine the response of peanut to previous crop sequences including corn (Zea mays L.) and cotton (Gossypium hirsutum L.) planted in continuous conventional tillage (e.g., disking, field cultivating, and bedding with in-row sub-soiling) or strip tillage (e.g., tilling a 45 cm section on rows spaced 91 cm apart using fluted coulters, rolling baskets, and in-row sub-soiling). In 2013, 2019, and 2022, the entire test area was planted with peanut. In 2019 and 2022, peanut was planted without or with fluopyram applied in the seed furrow at planting. Decreasing the number of years between peanut planting resulted in lower peanut yields compared with fewer years of peanut planting in the rotation sequence. Continuous conventional tillage and strip tillage resulted in similar peanut yields at one location, while the yield was lower at a second location when peanut was planted in continuous strip tillage. Fluopyram did not affect peanut yield regardless of previous crop rotation sequence, the number of years separating peanut plantings, or the tillage system. However, minor differences in the populations of plant-parasitic nematodes in soil were noted when comparing fluopyram treatment. The results from these experiments indicate that while fluopyram can reduce the populations of some plant-parasitic nematodes in soil, the magnitude of reduction does not translate into increases in peanut yield. [ABSTRACT FROM AUTHOR]

Globally, phytonematodes cause significant crop losses. Understanding the functions played by the plant rhizosphere soil microbiome during phytonematodes infection is crucial. This study examined the distribution of phytonematodes in the paddy fields of five provinces in Thailand, as well as determining the keystone microbial taxa in response to environmental factors that could be considered in the development of efficient biocontrol tactics in agriculture. The results demonstrated that Meloidogyne graminicola and Hirschmanniella spp. were the major and dominant phytonematodes distributed across the paddy fields of Thailand. Soil parameters (total P, Cu, Mg, and Zn) were the important factors affecting the abundance of both nematodes. Illumina next-generation sequencing demonstrated that the levels of bacterial diversity among all locations were not significantly different. The Acidobacteriota, Proteobacteria, Firmicutes, Actinobacteriota, Myxococcota, Chloroflexi, Verrucomicrobiota, Bacteroidota, Gemmatimonadota, and Desulfobacterota were the most abundant bacterial phyla observed at all sites. The number of classes of the Acidobacteriae, Clostridia, Bacilli, and Bacteroidia influenced the proportions of Hirschmanniella spp., Tylenchorhynchus spp., and free-living nematodes in the sampling dirt, whereas the number of classes of the Polyangia and Actinobacteria affected the amounts of Pratylenchus spp. in both roots and soils. Soil organic matter, N, andMnwere the main factors that influenced the structure of the bacterial community. Correlations among rhizosphere microbiota, soil nematodes, and soil properties will be informative data in considering phytonematode management in a rice production system. [ABSTRACT FROM AUTHOR]

Turfloop constitutes an area in Mankweng, situated in the Limpopo Province of South Africa, where several villages are home to smallholder farmers who specialize in vegetable farming. Among the most crucial crops cultivated in this region is tomato, a fruit that has gained significant commercial importance due to its high demand and versatility in various culinary applications. To determine the relationship of plant-parasitic nematodes and soil physicochemical properties, soil samples were collected from tomato fields. Overall, our results showed that seven nematode genera were in the tomato fields. There was a significant positive correlation between the number of Meloidogyne and potassium (r = 0.903) and a negative correlation with Na (r = −0.684). In contrast, there was no association between the number of Meloidogyne spp. and the pH and texture of the fields. The number of Criconema in the field was negatively correlated with pH (r = −0.732). Soil texture percentages, including clay (r = 0.744), sand (r = −0.744), and silt (r = 0.706), were only correlated with the number of Criconema. The number of dagger nematodes, Xiphinema, was only correlated negatively with NH4+ (r = −0.589) and positively with boron (B) (r = 0.779). None of the soil variables were correlated with the number of Pratylenchus. The principal component analysis (PCA) placed soil samples of tomatoes together, in which the number of Meloidogyne was not correlated to any soil sample site. In conclusion, plant-parasitic nematodes that were associated with tomatoes are of high economic importance as they can reduce the yield. Criconema was found to be sensitive to the soil's physicochemical properties. In addition, Helicotylenchus was found in all soil samples. Our results suggest that the plant-parasitic nematodes in tomatoes have high diversity with the potential to reduce crop production. [ABSTRACT FROM AUTHOR]

As the most diverse metazoan taxa, soil nematodes serve a diversity of functions in soil food webs and thus can regulate microbial community composition and affect organic matter decomposition and nutrient turnover rates. Because nematodes depend on water films to access food resources, drought can negatively affect nematode–microbial food webs, yet the impacts of drought on nematode diversity and abundance and how these changes may influence food web members and their functions are hardly explored. Here, we coupled research along a drought gradient in arid and semiarid grasslands with a detailed intact plant–soil microcosm experiment to explore the patterns and mechanisms of how drought impacts nematode abundance and carbon footprint, microbial phospholipid fatty acid (PLFA) and heterotrophic soil respiration. Overall, in the field and the microcosm experiments, we found that nematode abundance, carbon footprint and diversity, microbial PLFA and heterotrophic respiration were reduced under drier conditions. In addition, drought altered nematode and microbial community composition, through reducing the nematode channel ratio and increasing the relative fungivorous nematode abundance and the fungal to bacterial ratio. The soil decomposition channel shifted from a bacterial to a fungal pathway in response to drought, indicating decelerated heterotrophic respiration under drought. These results highlight the important contribution of soil nematodes and their associated microbial food web to soil carbon cycling. Our findings underscore the need to incorporate key soil fauna into terrestrial ecosystem model evaluation. [ABSTRACT FROM AUTHOR]

Abstract Animal body size exhibits rapid responses to environmental variations and displays considerable variability across ecological scales, significantly influencing ecological community assembly. However, our understanding of the extent of body size variation and its responses to environmental differences within soil fauna remains limited, impeding a comprehensive grasp of soil fauna's functional ecology. Here, we aim to investigate the magnitude of intrageneric body size variation and its implications for soil nematode community assembly along an altitudinal gradient. We examined soil nematode body size responses along an altitudinal gradient spanning from 3136 to 4128 m in an alpine mountain region of the eastern Tibetan Plateau. We assessed the contributions of intra‐ and intergeneric variations in body size, both within and among communities, using individual body size values. The implications of these variations for community assembly processes were determined through phenotypic variance ratios employing permutation tests. Our analyses did not reveal statistically significant correlations between altitude and the community‐weighted mean body mass, regardless of considering intrageneric trait variation (IGTV). Approximately 15% of the variation in body size among communities and a substantial 72% of the variation in body size within communities can be attributed to IGTV. Altitude did not significantly affect IGTV within or among communities. Furthermore, our results underscored the dominant role of internal filtering within the community in governing nematode community assembly, with external filtering outside the community playing a limited role within our altitudinal range. Our findings emphasize the dominant role of body size variation within communities rather than among communities, attributable to strong internal filtering processes. These findings advance our understanding of body size variation in soil nematodes across ecological scales and highlight the pivotal role of intrageneric variation in shaping the functional ecology of soil fauna.

The purpose of the research is to study the effect of insect compost obtained as a result of the vital activity of insects of the Coleoptera order Ulomoides dermestoides on the quantitative and qualitative composition of soil nematodes of various ecological and trophic groups, as well as on the morphological and physiological state of plants and infection of tomato plants with root-knot nematodes.Materials and methods. Under laboratory conditions, soil containing a diverse fauna of nematodes was treated with 1% dry and 0.5; 0.75 and 1% aqueous solutions of biocompost. Insect compost was obtained by keeping the U. dermestoides on a dry nutrient mixture. Then a mixture of lawn grasses was sown in the ground. After 30 days, the composition of nematodes was analyzed. The ability of insect compost to suppress parasitic nematode species was studied using the tomato-knot nematode model system. Tomatoes were infected with Meloidogyne incognita at a rate of 500 larvae (J2) per plant and simultaneously treated with a 0.5% aqueous biocompost solution.Results and discussion. The insect compost U. dermestoides has an effect on quantitative and qualitative indicators in the community of soil nematodes, increasing the number of predatory and saprobiotic nematodes and displacing parasitic ones. And due to the content of various biologically active compounds, it affects the development of rootknot nematodes in tomato roots. When tomatoes are treated with an aqueous solution of insect compost, the infection score and the number of nematodes that penetrate the roots are reduced. The introduction of compost when growing a mixture of lawn grasses and tomatoes can improve the condition of the plants.

Introduction: High-throughput sequencing (HTS) provides an efficient and cost-effective way to generate large amounts of sequence data, providing a very powerful tool to analyze biodiversity of soil organisms. However, marker-based methods and the resulting datasets come with a range of challenges and disputes, including incomplete reference databases, controversial sequence similarity thresholds for delimitating taxa, and downstream compositional data analysis. Methods: Here, we use HTS data from a soil nematode biodiversity experiment to explore standardized HTS data processing procedures. We compared the taxonomic assignment performance of two main rDNA reference databases (SILVA and PR2). We tested whether the same ecological patterns are detected with Amplicon Sequence Variants (ASV; 100% similarity) versus classical Operational Taxonomic Units (OTU; 97% similarity). Further, we tested how different HTS data normalization methods affect the recovery of beta diversity patterns and the identification of differentially abundant taxa. Results: At this time, the SILVA 138 eukaryotic database performed better than the PR2 4.12 database, assigning more reads to family level and providing higher phylogenetic resolution. ASV- and OTU-based alpha and beta diversity of nematodes correlated closely, indicating that OTU-based studies represent useful reference points. For downstream data analyses, our results indicate that loss of data during subsampling under rarefaction-based methods might reduce the sensitivity of the method, e.g. underestimate the differences between nematode communities under different treatments, while the clr-transformation-based methods may overestimate effects. The Analysis of Compositions of Microbiome with Bias Correction approach (ANCOM-BC) retains all data and accounts for uneven sampling fractions for each sample, suggesting that this is currently the optimal method to analyze compositional data. Discussion: Overall, our study highlights the importance of comparing and selecting taxonomic reference databases before data analyses, and provides solid evidence for the similarity and comparability between OTU- and ASV-based nematode studies. Further, the results highlight the potential weakness of rarefaction-based and clr-transformation-based methods. We recommend future studies use ASV and that both the taxonomic reference databases and normalization strategies are carefully tested and selected before analyzing the data. [ABSTRACT FROM AUTHOR]

To reduce plant-parasitic nematodes (PPNs), an alternative solution based on amendments from selected native shrub was used to favor mainly the increase of free-living nematodes (FLNs) that include high trophic (bacterivorous, fungivorous, omnivorous, and carnivorous) nematodes and influence soil microbial activities. The consequences of the subsequent reduce of PPNs of the soil were also determined. Experiments were performed in a shade house using six treatments consisting of shrub residues from Piliostigma reticulatum (Pil), Boscia senegalensis (Bos), and Crotalaria juncea (Cro); a Straw-based Compost (Cs); a Farmer practice (FP) using Nitrogen-Phosphorus-Potassium (NPK) fertilizer; and a control (C0, no amendments). Abundances of nematodes, trophic groups, and nematodes ecological indices were determined. Enzymatic activities (ß-glucosidase and acid phosphatase) and the fluorescein diacetate hydrolysis (FDA) were also determined. Soil amended by Bos and Cro increased the density of nematodes compared to control soil or amended with NPK fertilizer. Indices of taxonomic diversity (H') did not differ significantly between the treatments. However, soils amended with Bos and Cro had the highest enrichment index (EI), and the lowest Nematode Channel Ratio (NCR), indicating that these two shrub residues exhibited a higher food web in response to the available resources provided by the fungal decomposition pathway. Moreover, Bos favored omnivorous and increased enzymatic activities. Bos induce 'bottom-up' while Cro induce 'top-down' controls on nematode populations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Eutrophication, including nitrogen (N) enrichment, can affect soil microbial communities through changes in trophic interactions. However, a knowledge gap still exists about how plant resources ('bottom‐up effects') and microbial predators ('top‐down effects') regulate the impacts of N enrichment on microbial biomass at the global scale.To address this knowledge gap, we conducted a global meta‐analysis using 2885 paired observations from 217 publications to evaluate the regulatory effects of plant biomass and soil nematodes on soil microbial biomass under N enrichment across terrestrial ecosystems.We found that the effects of N enrichment on soil microbial biomass varied strongly across ecosystems. N enrichment decreased the soil microbial biomass of natural grasslands and forests due to soil acidification and the subsequent losses of predatory and microbivorous nematodes stimulating microbial growth. By contrast, N enrichment increased the microbial biomass of managed croplands mainly via increasing plant biomass production. Across diverse ecosystems, the short‐term N enrichment (experimental duration ≤5 years) could reduce microbial biomass via decreasing nematode abundance, whereas the long‐term N enrichment (experimental duration >5 years) mainly promoted microbial biomass via increasing plant biomass.These findings highlight the critical roles of microbial predators and plant input in shaping microbial responses to N enrichment, which are highly dependent on ecosystem type and the period of N enrichment. Earth system models that predict soil microbial biomass and their linkages to soil functioning should consider the variations in plant biomass and soil nematodes under future scenarios of N deposition. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

The role of arbuscular mycorrhizal fungi (AMF) and soil nematodes in primary production and plant nutrient uptake through plant-soil feedback in the Araucaria ecosystem remains poorly quantified. We aimed to understand the role of AMF and soil nematodes on Araucaria angustifolia using three phenological stages of this native plant species: adult/mature trees in field conditions (1st experiment), from germination to the seedling stage under in situ conditions (2nd experiment), and from the seedling to sapling stage under ex situ conditions (3rd experiment). In the field experiment, we determined soil biochemical properties and AMF and soil nematode community structure. Soil inoculum was collected in the 1st experiment. Throughout the 2nd experiment, we determined plant biomass production and plant P uptake. Finally, we determined root colonisation by AMF and root lesions by root-feeding nematodes and their relationship with plant biomass and plant P content in the 3rd experiment. At the high-quality site, there was significantly higher microbial respiration, microbial N and C biomass, soil pH, soil organic carbon, total nitrogen, and Olsen's P compared to the low-quality site. Both the in situ and ex situ stages were positively correlated with AMF diversity and negatively correlated with the abundance of root-feeding nematodes. Using structural equation modelling, we found evidence that root colonisation and root lesions were affected by AMF richness and soil nematodes. This study highlights the importance of considering the establishment of AMF and soil nematode communities, their correlation with soil quality, and Araucaria's phenological stages (germination, seedling, sapling, and adult trees), which can be influenced by soil inoculum. [ABSTRACT FROM AUTHOR]

During a survey of soil nematodes in South Africa, a species of predatory nematodes, namely Mylonchulus hawaiiensis was recovered from soil in the Magoebaskloof mountain of Limpopo Province, South Africa. The morphology of the material studied fit well with the previous populations of the same species. A molecular study of 18S rDNA region of M. hawaiiensis indicated a 100% similarity between the South African population and the Japanese population of M. hawaiiensis (AB361438; AB361439; AB361440; AB361442). In addition, phylogenetic analysis placed all M. hawaiiensis in a group with 0.97 posterior probability. Additionally, ITS rDNA of M. hawaiiensis amplified for the first time. However, Principal component analysis (PCA) showed a morphological variation among the different populations of M. hawaiiensis. In addition, haplotype analysis also revealed that the South African population is close to the Japanese population. In conclusion, 18S rDNA was a good marker for detecting M. hawaiiensis. Measurement, photographs, and phylogenetic position of South African M. hawaiinesis are given. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nematodes are the most abundant animals on earth and play essential roles in ecosystem functioning hence their abundance and diversity affect soil health. Nematodes have been reported in tea fields in some parts of Kenya and previous studies indicate that they may be a cause for the decline of tea population in some tea fields in Kenya. Nematodes of Moloidogyne spp have also been reported to be responsible for death of tea plants in nursery conditions. A survey was carried out in Weru and Kangaita tea factories catchment areas in Tharaka Nithi and Kirinyaga counties respectively. The survey aimed to determine the abundance and diversity of nematodes in small holder tea farms. Kangaita represented the high elevation site while Weru represented the low elevation site. Soil samples were collected from smallholder tea farms from which nematodes were extracted, identified based on their morphological characteristics, and classified according to their feeding habits then quantified using standard protocols. Nematodes from 23 genera were recovered in the two study sites representing all the five feeding groups: plant feeders, fungal feeders, bacterial feeders, omnivores, and predatory nematodes. Of the 23 genera, 11 were plant feeders, 6 bacterial feeders, 3 fungal feeders 2 omnivores and 1 predatory nematode. Kangaita, being a high elevation site reported higher population density in most genera reported than Weru which is a low elevation site. This is a departure from most studies that have reported higher nematode population densities in low altitudes. This can be attributed to differences in climatic and soil conditions in the two study sites in the same season. Kangaita was cooler with deep, well-ventilated, and loose soils while Weru was hotter with mostly compacted, shallow, and poorer soils in the tea farms. There is need for further research on the effect of elevation and farming practices on the distribution, abundance, and diversity of nematodes in tea fields. [ABSTRACT FROM AUTHOR]

Summary: Brazilian Caatinga is one of the most diverse, seasonally dry, tropical forests of the world and is threatened by strong land use pressure and poor protection. One way of understanding changes in the soil conditions caused by anthropogenic activities is using the nematode assemblages as potential bioindicators. This study analysed changes in nematode communities in three different types of land use (natural forest-CA, natural area with accumulation of salts-SS, and agricultural growing areas, such as cover crops-CC for cattle and fruit trees-IC) in the Caatinga, in the sub-median region of the São Francisco River Valley (SFRV), Pernambuco, northeastern Brazil. We recorded a total of 63 262 nematode individuals, representing 42 genera, belonging to 23 families. Nematode abundance, diversity and maturity indices were highest in the CC and lowest in the SS. Among the nematode trophic groups, bacterivores, omnivores + predators and plant parasites were significantly affected by type of land use. Different soil properties were related to the differences in taxonomic composition among the natural and agricultural areas, accounting for 26.6% of the total variation. In general, our results indicate that soil salinisation and desertification in the natural areas, as well as soils subjected to cover crops and fruit tree production, significantly influenced the composition of nematode communities in the São Francisco River Valley. [ABSTRACT FROM AUTHOR]

This article, published in the Russian Journal of Ecology, explores the influence of funnel material on the efficiency of nematode extraction using the Baermann method. The study found that the material of the funnel, whether glass or plastic, affects the extraction efficiency of nematodes. Plastic funnels resulted in a significantly higher number of extracted nematodes compared to glass funnels. Additionally, more nematodes were found to adhere to the walls of glass funnels compared to plastic funnels. The authors suggest that caution should be exercised when combining data from different studies if the funnel material is not specified, and recommend using funnels made of materials with hydrophobic properties to minimize losses. [Extracted from the article]

The intricate decomposition pathways within soil micro-food webs are vital for cycling soil organic carbon and nutrients, influencing the quality, productivity, and sustainability of soil systems. However, the impact of diverse phosphorus addition on these organic decomposition pathways still needs to be explored. In an 8-year experiment, phosphorus (P) fertilizer was added at varying levels (0 kg ha-1, CK; 60 kg ha-1, P60; 120 kg ha-1, P120; and 180 kg ha-1, P180), to investigate the response of the soil micro-food web. The results revealed a significant effect of phosphorus addition on soil microorganisms and nematodes, with P60 exerting a greater influence than other treatments. At P60, the Shannon index of nematodes and fungi surpassed other treatments, indicating higher diversity, while the Shannon index of bacteria was lower. The Chao1 index of bacteria and fungi at P60 was higher, contrasting with the lower index for nematodes. Metabolic footprints of bacterivores and omnivores-predators (BFMF and OPMF) were higher at P60, while metabolic footprints of fungivores and plant parasites (FFMF and PPMF) were lower, signifying altered energy flow. Functional metabolic footprints and energy flow analysis unveiled a stable soil micro-food web structure at P60, with enhanced energy conversion efficiency. Network analysis illustrated positive correlations between fungi, fungivorous nematodes (FF), and omnivorous-predatory nematodes (OP) at P60, while P120 and P180 showed positive correlations among bacteria, bacterivorous nematodes (BF), and OP. Path analysis underscored the higher contribution rate of BF-C, FF-C, and OP-C to soil organic carbon at P60 compared with P120 and P180. These findings suggest that nutrient interactions between fungi and nematodes regulate soil micro-food web decomposition under low phosphorus concentrations. In contrast, interactions between bacteria and nematodes dominate at high phosphorus concentrations. The study indicates that adding phosphorus has nuanced bottom-up effects, intricately shaping the structure and activity of the pathways and underscoring the need for a comprehensive understanding of nutrient dynamics in soil ecosystems. [ABSTRACT FROM AUTHOR]

The amount and timing of biochar application in scientific settings are currently the focal points of research aimed at enhancing and maintaining soil health. In this study, two groups of corn pot experiments（groups A and C）were designed. Group A was treated with a one-time application of biochar for 7 years, and group C was treated with a one-time application of biochar for 1 year. The application rates of each group were 0, 15.75, 31.50, 63.00 t·hm-2, and 126.00 t·hm-2, respectively. The effects of different amounts and timings of biochar application on the structural characteristics of nematode communities in sandy soil were studied. The results showed that the application of biochar could increase soil pH and nutrient content after 1 year. The effect of biomass charcoal on soil nutrient would decrease over time with aging. The dominant genus of soil nematodes was Acrobeloides, and bacterivores and predators / omnivores were the main trophic groups. Soil organic matter decomposition was dominated by bacterial decomposition. The increase in biochar application amount changed the soil nematode community structure, trophic group distribution, and nematode abundance after one year of biochar application. The increase in the amount of biochar applied substantially inhibited the number of soil nematodes. However, the number of soil nematodes recovered after 7 years of biochar application. With increasing years after application, biochar application led to a decrease in the abundance of soil bacterivores and an increase in the abundance of predators/omnivores and plant parasitic nematodes; however, it exerted little effect on the nematode diversity and richness indexes. A one-time application of 126.00 t·hm-2 biochar substantially reduced the number of soil nematodes after 7 years, whereas the application of 15.75 t·hm-2 biochar exerted a positive effect on the number and community structure of soil nematodes. [ABSTRACT FROM AUTHOR]

Bell pepper farming significantly contributes to economic development in Abua. However, phyto-parasitic nematodes are endemic in the area and affect quality of crop yield. Hence, this study was undertaken to investigate the dynamics of occurrence of nematodes in bell pepper roots and soil samples of the farms in Abua. Roots and soil from the root rhizosphere were simultaneously collected at 0-20 cm depth using an improvised soil auger and knife. Modified sieve plate technique was employed for nematode detection and a pictorial key was used for nematode identification at the genera level. An overall nematode abundance of 746 nematodes in the soil around the root region and 216 nematodes in the root tissues of the bell peppers were recorded. Gracilachus species (10.6 %) was more prevalent in the soil, and Meloidogyne species (35.2 %) exhibited the highest population in roots. The study found that Abua's cultivated soil is susceptible to nematode infestation, limiting crop performance. The nematodes showcased root burrowing which is an inherent pattern for survival. The result on root nematodes across the five bell farms surveyed was not significant (p > 0.05). The result opined that farmers in Abua, Rivers State, should understand the role of the soil nematodes and implement soil improvement strategies for improved crop performance and rural economic development. [ABSTRACT FROM AUTHOR]

The present investigation aimed to analyze the community structure and its relationship with selected soil parameters in the Gangetic plains. In total, 60 soil samples were collected from the fields of vegetable crops at different pH. Thirty-nine soil-inhabited nematodes were isolated and identified to the species level where possible. The most prevalent nematodes encountered were Hoplolaimus indicus followed by Helicotylenchus californicus and Pratylenchus thornei with 66.67, 53.33, and 40.00% frequency, respectively. Prominence Value of H. indicus (271.62), H. californicus (115.87), and P. thornei (31.62) was higher as compared to other PPN species. The result indicated that there is a significant correlation between the plant-parasitic species and pH (e.g., Rotylenchus reniformis; r = 0.991). On the other hand, EC showed a significant negative correlation with R. reniformis (r = –0.965). However, organic carbon and sand percentage significantly correlated with PPN. Organic carbon was highly correlated (r = 1.00) with R. reniformis. In contrast, organic carbon showed a significant positive correlation with Rhabditis and no correlation with Mesodorylaimus. In conclusion, the high-producing regions suggested a considerable range of plant-parasitic and free-living nematodes, with the highest diversity in Baghpat (H' = 0.604 ± 0.14). Therefore, further studies are required to evaluate the ecological and threshold level of damage by the PPN. Additionally, the current finding suggests that soil fertility in upper 'Gangetic plains' agricultural fields was reduced due to the high load of PPN infection. However, ecological indices could help assess the plant and soil health of all the regions in future investigations. [ABSTRACT FROM AUTHOR]

Summary: Accurate measurements of soil nematode communities are important for an in-depth understanding of the ecological functions of soil nematodes. High throughput sequencing (HTS) has been reported extensively, but the concordance between HTS and morphological identification results is still lacking. To compare two methods, we selected bare patches (BP), short-term recovery patches (SP), middle-term recovery patches (MP) and long-term recovery patches (LP) of different restoration succession stages in three sample sites to survey the nematode characteristics. In addition to nematode community structure and community ecological function, common nematode genera in BP, SP, MP and LP were compared by two methods: HTS and morphological identification. The results show that the number of species identified in the morphological analysis was lower than using HTS. The soil nematode diversity in different recovery patches was LP > MP > SP > BP. The indices of Shannon-Wiener, Pielou, Simpson and species number of different recovery patches based on HTS reflected the biodiversity of nematode communities, which was consistent with the results of morphological identification. Of the common nematode genera, Coslenchus , Aphelenchus and Leptonchus showed a significant correlation by the two methods. Although both methods have limitations, the HTS provides a more effective means of observing soil nematode biodiversity levels for rapid insight across recovery patches in degraded alpine meadows of the Yellow River source region in our results. [ABSTRACT FROM AUTHOR]