Search Results (73)

Soil nematodes are essential components of the soil food web and are widely recognised as key bioindicators of soil health because of their sensitivity to environmental factors and disturbance. In agriculture, many studies have documented the effects of fertilisation on nematode communities and explored their role in nutrient cycling. Despite this, a key gap in knowledge still exists regarding how fertilisation-induced changes in nematode communities modify their role in nutrient cycling. We reviewed the literature on the mechanisms by which nematodes contribute to nutrient cycling and on how organic, inorganic, and recycling-derived fertilisers (RDFs) impact nematode communities. The literature revealed that the type of organic matter and its C:N ratio are key factors shaping nematode communities in organically fertilised soils. In contrast, soil acidification and ammonium suppression have a greater influence in inorganically fertilised soils. The key sources of variability across studies include differences in the amount of fertiliser applied, the duration of the fertiliser use, management practices, and context-specific factors, all of which led to differences in how nematode communities respond to both fertilisation regimes. The influence of RDFs on nematode communities is largely determined by the fertiliser’s origin and its chemical composition. While fertilisation-induced changes in nematode communities affect their role in nutrient cycling, oversimplifying experiments makes it difficult to understand nematodes’ functions in these processes. The challenges and knowledge gaps for further research to understand the effects of fertilisation on soil nematodes and their impact on nutrient cycling have been highlighted in this review to inform sustainable agricultural practices. Full article

This study investigates the impact of golden moles (Amblysomus sp.) on the abundance, diversity, and community structure of nematodes in kweek grass (Cynodon dactylon) within the Sovenga Hills of Limpopo Province, South Africa. Eight sites were sampled: four with active moles (sites: M1–M4), and four without (sites: T1–T4). Eighty soil samples were collected, and nematodes were extracted. A total of 23 nematode genera were identified, including 3 plant-parasitic and 20 free-living genera. The frequency of occurrence (FO) data showed that Aphelenchus sp. and Acrobeles sp. were the most prevalent nematodes, each occurring in 87.5% of the samples. In contrast, Eucephalobus sp., Tripylina sp., Discolaimus sp., and Tylenchus sp. had the lowest FO, appearing in only 12.5% of samples. The diversity indices (the Shannon index, the maturity index, and the plant-parasitic index) showed significant differences between the two environments. The Shannon index (H′) and maturity index were the most effective indicators of ecosystem disturbance. The lowest H′ was found at T4 (1.7 ± 0.2), compared with a higher value at M1 (2.4 ± 0.1). The principal component analysis (PCA) results revealed a positive correlation between Ditylenchus and the clay in the soil. In addition, Cervidellus was associated with soil pH. Network analysis revealed increased complexity in the nematode community structure at mole-affected sites. These findings suggest that mole activity alters soil properties and indirectly affects nematode diversity and trophic structure. Full article

Polymer application combined with nitrogen (N) fertilization can increase soil N transformation efficiency. However, the mechanism of polymer influencing soil biocommunity characteristics and nitrogen transformation is still unclear. In this field experiment, a self-developed water-soluble polymer material (PPM, a mixture of anionic polyacrylamide, polyvinyl alcohol, and manganese sulfate) was combined with N fertilization N100 (300 kg/hm² of N), PN100 (PPM + 300 kg/hm² of N), and PN80 (PPM + 240 kg/hm² of N) to investigate soil biodiversity, enzyme activities, and metabolomics. The results showed that under the application of PPM, the contents of soil total nitrogen (TN), alkali hydrolyzable nitrogen (ANS), nitrate nitrogen, organic carbon (SOC), and microbial biomass nitrogen (MBN) increased with a decrease in the N application rate, while soil bulk density, pH, and EC (electrical conductivity) decreased. The Chao 1 index of soil bacterial and nematode communities of the PN80 treatment was 30.6% and 10.7% higher than that of the N100 treatment, respectively, and the Shannon index was 2.72% and 2.64% higher than that of the N100 treatment, respectively. In the short term, the application of PPM affected the structure and composition of soil bacterial and nematode communities. In particular, the relative abundances of omnivorous (Aporcelaimellus) and bacterivorous (Prismatolaimus) nematodes were significantly higher than those of the N100 treatment. These changes further regulated the soil metabolites, promoting soil nitrogen transformation. This study will provide a scientific basis for nitrogen reduction in drip-irrigated wheat planting in arid regions. Full article

To clarify the response mechanisms of soil nematodes as bioindicators of ecosystem health to precipitation variations in loess hilly forests, this study investigated soil nematodes in pure Populus hopeiensis forests across different precipitation gradients in Wuqi County. Through soil physicochemical analysis and high-throughput sequencing of soil nematodes, we analyzed the characteristics of soil nematode communities and their responses to precipitation variation. The results demonstrated the following: (1) Dominant genera and trophic groups of soil nematodes were significantly influenced by precipitation, with Acrobeloides prevailing across all gradients while Paratylenchus reached maximum abundance (26.8%) in moderate precipitation zones. (2) Bacterivorous nematodes prevailed in both low- and high-precipitation zones, while herbivorous nematodes constituted the highest proportion in moderate precipitation zones. The abundances of herbivorous and fungivorous nematodes exhibited an initial increase followed by a decrease with rising precipitation, whereas predatory–omnivorous nematodes displayed the opposite trend. (3) The Chao1 and Shannon indices of soil nematodes initially increased and then decreased with increasing precipitation, reaching a peak in the Jinfoping site. Moreover, there were significant differences in nematode community structure among different precipitation gradients. (4) Redundancy analysis and PLS-PM modeling identified soil water content (SWC), total nitrogen (TN), and capillary water holding capacity (CWHC) as key drivers of nematode communities. Precipitation indirectly regulated nematode functionality by modifying soil physicochemical properties and microbial activity. (5) Ecological function analysis revealed bacterial-dominated organic matter decomposition (Nematode Channel Ratio, NCR > 0.75) in the Changcheng and Baibao sites, contrasting with fungal channel predominance (NCR < 0.75) in Jinfoping. This research elucidates the mechanism whereby precipitation drives nematode community divergence through regulating soil physicochemical properties and microbial activity. The findings provide scientific basis for soil biodiversity conservation and ecological restoration benefit assessment in regional ecological restoration projects, and soil health management and sustainable land use in agricultural ecosystems. Full article

Invasive plants can significantly alter the composition and functioning of soil ecosystems, which in turn affects soil fauna such as microorganisms; mesofauna including mites, springtails, nematodes, and insects; and other invertebrates. We used clusters of three different tree species to investigate how they affect the composition of belowground soil nematode communities. The clusters included Acer negundo (L.) (an invasive, non-native species), Fraxinus excelsior (L.), and Alnus glutinosa (Gaertn.) (both as native representatives) in floodplain forest habitats of the Morava River. We investigated the families, genera, trophic groups, and functional guilds of soil nematodes in each tree cluster to assess the usefulness of nematodes as indicators of the impact of alien tree species on native communities. The study was complemented by measuring basic soil physico-chemical properties. The data show that nematode communities were not sensitive to A. negundo invasion, as clusters of invasive trees had similar nematode abundance, genus richness, diversity, family and genus composition, and trophic structure compared to species-specific clusters of two native tree species. A cumulative total of 96 nematode genera, belonging to 52 families, were recorded in the investigated floodplain forest sites. The most abundant families across all clusters were Alaimidae, Cephalobidae, Hoplolaimidae, and Rhabditidae for all tree clusters. Among the genera, Helicotylenchus, Pratylenchus, Paratylenchus (as obligate plant parasites), Filenchus, and Malenchus (as facultative plant parasites), as well as Acrobeloides, Eucephalobus, Plectus, and Rhabditis (as bacterivores), were the most dominant taxa. The measured soil properties did not differ significantly among tree species (p < 0.05). Nevertheless, redundancy analysis identified a significant correlation between soil moisture content and abundance of several nematode genera, nematode trophic groups, and functional guilds. The results indicate that the presence of invasive ash-leaved maple trees in the studied floodplain forests had no adverse effect on the diversity and functional structure of soil nematode communities. This study offers initial insights into nematode communities in Acer negundo invaded habitats, but further studies are needed to verify these findings. Full article

Arbuscular mycorrhizal fungi (AMF) and Trichoderma spp. (T) are known as plant-beneficial fungi effective against root-knot nematodes, but their interactions in the rhizosphere are not well understood. This study examined how Meloidogyne javanica influences AMF colonization and community diversity at the root-soil interface of tomato plants. A 60-day growth chamber experiment was conducted with tomato plants grown in non-sterile agricultural soil, either infected or not with M. javanica, that received a single inoculation with AMF or Trichoderma (strains T363 or TJ15), combined AMF + T inoculations, or no inoculation (Control). Both single and combined inoculations significantly reduced root galls, eggs, and soil nematode larvae. An AMF community analysis via single-strand conformation polymorphism of the D1 region of 28S rDNA gene (Glomeraceae family) revealed that M. javanica decreased AMF diversity and altered community structure, in plants single-inoculated with AMF. However, a combined inoculation with Trichoderma appears to prevent this reduction and maintain AMF diversity. While M. javanica reduced root mycorrhizal colonization, it did not affect Trichoderma abundance. These results suggest that Trichoderma may be more resilient to nematode infection, helping stabilize AMF communities and enhance biocontrol. Thus, combining AMF and Trichoderma inoculations could better preserve root health and improve biological control effectiveness against M. javanica. Full article

Soil microorganisms provide multifaceted benefits, including maintaining soil nutrient dynamics, improving soil structure, and instituting decomposition, all of which are important to soil health. Unpredictable weather events, including flooding from heavy rainfall, flash floods, and seawater intrusion, profoundly impact soil ecology, which is primarily challenged by flooding stress, and imbalances these microbial communities and their functions. This disturbance impairs the symbiotic exchanges between microbes and plants by limiting root exudates and habitats for microbes, as well as nutrient acquisition efficiency for plants. Therefore, this review comprehensively examines the changes in soil microbial communities that occur under flooding conditions. Flooding reduces soil oxygen (O₂) levels, limiting aerobic microbes but promoting anaerobic ones, including potential pathogens. In flooded soil, O₂ deficiency indirectly depends on the size of the soil particles and water turbidity during flooding. O₂ depletion is critical in shaping microbial community adaptation, which is linked to variations in soil pH, nutrient concentrations, and redox status, and fresh and saline water vary differently in terms of the adaptation of microorganisms. Wet soil alters soil enzyme activity, which influences microbial community composition. Notably, three-month post-flooding conditions allow microbial communities to adapt and stabilize more effectively than once-weekly flooding frequency. Based on the presence of aboveground species, fungi are found to reduce under flooding conditions, while nematode numbers, surprisingly, increase. Direct and indirect impacts between soil microbes and physio-chemical properties indicate positive or negative feedback loops that influence the soil ecosystem. Over the years, beneficial microorganisms such as plant-growth-promoting microbes (PGPMs) have been identified as important in regulating soil nutrients and microbial communities in wetland environments, thereby enhancing soil health and promoting better plant growth and development. Overall, understanding the mechanisms of belowground ecosystems under flooding conditions is essential for optimizing agricultural practices and ensuring sustainable crop production in flood-prone areas. Full article

Citrus greening disease (CGD), also known as Huanglongbing in China, is caused by the endophytic bacterium ‘Candidatus Liberibacter asiaticus’ and poses a severe threat to the global citrus industry. The disease affects microbial communities in leaves, stems, roots, and soil. Soil nematodes, which occupy multiple trophic levels, play crucial roles in nutrient cycling, pest regulation, and plant-soil interactions. However, the impact of CGD on soil nematode community structure and energy flow remains unclear. This study examined the effects of different levels of CGD infection on soil nematode communities and energy dynamics. Three infection levels were selected: control (healthy plants with no yellowing symptoms), mild infection (≤50% leaf yellowing), and severe infection (entire canopy affected). The results showed that increasing CGD severity significantly reduced the nematode abundance, community structure index, and total energy flux by 94.2%, 86.7%, and 93.5%, respectively, in the severely infected group. Both mild and severe infections resulted in a higher proportion of bacterivorous nematodes compared to the control. Moreover, herbivorous energy flux was significantly reduced by 99.2% in the severe infection group, suggesting that herbivorous endophytic nematodes are particularly sensitive to CGD. The total energy flux through nematode food web, the energy flux through fungal or herbivorous channels, and the energy flow uniformity were positively correlated with the nematode structure index but negatively correlated with the nematode richness and evenness indices. Furthermore, the reduction in soil resource input (especially total nitrogen and total carbon) caused by CGD was the primary driver of the changes in nematode communities and energy flows. These findings highlight the destructive effects of CGD on soil ecosystems through bottom-up control. The CGD-induced obstruction of photosynthate transport primarily impacts phytophagous organisms and could also influence other trophic levels. To mitigate these effects and ensure healthy citrus production, future research should focus on early detection and effective CGD management strategies. Full article

Tillage, cover crops (CC) and nutrient amendments are regenerative agricultural practices (RAPs) which enhance desirable ecosystem services (DESs), including the beneficial nematode community structure (BNCS), soil organic matter (SOM), pH, and available nitrogen, and the Ferris et al. soil food web (SFW) model relates changes in the BNCS to biophysicochemical conditions generating DESs. However, the SFW model’s power to identify soil health conditions influencing DESs’ outcomes has been limited. We tested how tillage, winter rye CC, and 0, 112, or 224 kg N/ha from inorganic and compost sources affected the DESs after four years of corn production. The SOM and NO₃ was much greater in the no-till than the tilled soil, and the SOM in the 224 kg organic source, compared with the rest of the N rates, was significantly increased. The N recovery was not proportional to what was applied. The variable effects of the RAPs on the DESs suggest either changing or continuing treatments until suitable outcomes are achieved, all without knowing the source(s) of variability. The SFW model revealed primarily resource-limited and structured (Quadrant C) conditions, suggesting that (1) nutrient cycling needs biological activities and (2) the presence of a process-limiting factor may have contributed to the variable results. The impacts of the SFW model as a diagnostic tool are outlined. Full article

The forest swamp ecosystem, as a special wetland ecosystem, is a key link in the material cycle and an important carbon sink in the carbon cycle. The global carbon cycle is of great significance, but the impact of forest swamp succession and soil depth on soil active organic matter and nematode community structure and diversity is unclear. This study used the “space instead of time” method to investigate the succession process of forest swamps from grasslands (WC) and shrubs (WG) to forests (WS) in national nature reserves. The results showed that during the forest succession process, the dominant nematode communities in the WC and WG stages were dominated by the genera Apis and Labroidei, while the dominant genera increased in the WS stage. The total abundance of nematodes increased, and the number of groups was ordered WG > WC > WS. The diversity in soil nematode communities according to Shannon–Wiener (H′), Pielou (J), and Trophic diversity (TD) was WS > WG > WC, which is related to vegetation, soil physical and chemical properties, and microbial community structure. The maturity index (MI) was WG > WS > WC. The soil food web was dominated by bacterial channels and had characteristics in forest metabolic activity and regulation ability. At different soil depths, there were significant differences in the community, with species such as the spiny cushioned blade genus being key. The number and group size of nematodes varied from 0–10 cm > 10–20 cm > 20–30 cm. The relative abundance of feeding nematodes changed with depth, while diversity indices such as H′, J, and TD decreased with depth. Ecological function indices such as MI and PPI showed depth variation patterns, while basic indices (BI) and channel indices (CI) showed significant differences. In terms of soil variables, during the forest succession stage, soil organic carbon (SOC), soluble organic nitrogen (DON), easily oxidizable organic carbon (ROC), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) showed a gradually increasing trend with WC-WG-WS, while total nitrogen (TN), soluble organic carbon (DOC), soil temperature (ST), and soil moisture (SM) showed opposite changes. There were significant differences in soil ST, SM, and DON values with succession (p < 0.05). At different soil depths, except for DON and ROC, which increased first and then decrease with depth, the values of other physical and chemical factors and active carbon and nitrogen components at depths of 0–10 cm were higher than those at other depths and decreased with depth. An analysis of variance showed significant differences in MBC and MBN values at different soil depths (p < 0.05), which is of great significance for a deeper understanding of the mechanism of soil nematode community construction and its relationship with the environment. Full article

Nitrogen deposition has a significant impact on biodiversity and ecosystem functions. However, various mechanisms by which nitrogen deposition affects soil nematode communities in nitrogen-limited temperate forests remain unclear. We conducted long-term nitrogen deposition simulation experiments (including two treatments, control and 50 kg N ha⁻¹ yr⁻¹) in the Lesser Khingan Range, Greater Khingan Range, and Changbai Mountain, applying nitrogen fertilizer solutions to investigate the effects of long-term nitrogen addition on soil nematode communities in northeastern Chinese forests. Nitrogen addition significantly decreased the total abundance of soil nematodes in the Lesser Khingan Range, Greater Khingan Range, and Changbai Mountain by 20%, 23%, and 18%, respectively. Furthermore, nitrogen addition reduced the α-diversity of soil nematodes and altered the β-diversity indices. The nematode channel ratio increased significantly, while the relative abundance of bacterivores, such as Euteratocephalus, also rose. In contrast, the structure index of the soil nematode community decreased, whereas the basal index increased. These results suggest that nitrogen addition simplifies the soil nematode community structure, which may be an important factor contributing to the decline in ecosystem function. Therefore, we selected soil nematodes as the research subject to provide a scientific basis for the effective protection, sustainable management, and resource utilization of major forest ecosystems in northeastern China under the context of nitrogen deposition. Full article

Soil biodiversity plays a critical role in supporting multiple ecosystem functions. As some of the most diverse and abundant metazoans on the Earth, soil nematode communities exhibit changes along environmental gradients, but the ways in which the abundance and diversity of nematode communities vary along elevational gradients remain poorly understood. Taking advantage of an investigation on Huangshan Mountain, Southeast China, with elevation ranging from 500 to 1200 m, we assessed the abundance and diversity of soil nematodes, as well as the soil physicochemical properties, across subtropical forest ecosystems. Nematode communities were analyzed at the genus level, and the α-diversity was calculated as the genus richness, while the β-diversity was based on the Bray–Curtis dissimilarity. The results showed that, among the top 20 nematode genera ranked by absolute abundance, most genera, such as Eucephalobus, Prismatolaimus, Filenchus, and Rotylenchulus, reached their peak abundance at the highest elevation (1000 m). Additionally, the abundances of Oriverutus, Tylenchus, Criconema, and Tripyla exhibited a positive correlation with the elevation. Moreover, the abundance and α-diversity of the total nematodes and each trophic group of nematodes increased linearly with the elevation, likely due to increased soil moisture at higher elevation. In contrast, the β-diversity of the total nematodes, bacterivores, and herbivores decreased with increasing elevation, indicating the importance of stochastic processes in shaping community assembly at high altitudes. This pattern suggests that as the elevation increases, the nematode communities become more homogeneous in structure. Taken together, our study’s findings demonstrate the divergent responses of nematodes’ α- and β-diversity to an elevation gradient, highlighting the importance of the soil nematode diversity in maintaining ecosystem functions such as nutrient cycling and food web stability in mountainous regions. These results emphasize the need to incorporate the below-ground biodiversity into conservation strategies, particularly in the face of environmental changes driven by climate and human activities. Full article

The Loess Plateau is one of the most vulnerable areas in the world. Numerous studies have been conducted to investigate alfalfa fields with different planting years. Soil microorganisms and nematodes are vital in ecosystem functionality and nutrient cycling. Therefore, comprehending their response to alfalfa fields with varying years of planting is essential for predicting the direction and trajectory of degradation. Alfalfa fields with different planting years (2 years, 9 years, and 18 years) were used as the research object, and farmland was used as the control (CK). High-throughput sequencing and morphological methods determined the community composition of microorganisms and nematodes. Carbon metabolic footprints, correlation networks, and structural equations were used to study soil microorganisms and nematode interactions. Principal component analysis (PCA) results showed that alfalfa fields with different planting years significantly impacted soil microorganisms and nematode community structures. Planting alfalfa significantly increased the nematode channel ratio (NCR) and Wasilewska index (WI), but significantly reduced the soil nematode PPI/MI and dominance (λ). The correlation network results indicated that, for the 2-year and 18-year treatments, the total number of links and positive links are higher than other treatments. Conversely, the 9-year treatment had fewer positive links and more negative links compared to other treatments. Additionally, the keystone species within each network varied based on the treatment years. Structural equation results show that alfalfa planting years directly impact soil fungal community structure and plant-parasitic nematodes’ carbon metabolism omnivorous-predatory nematodes. Furthermore, the carbon metabolism of omnivorous-predatory nematodes directly influences soil organic carbon fixation. Moreover, as the duration of alfalfa planting increases, the metabolic footprint of plant-parasitic nematodes decreases while that of omnivorous-predatory nematodes rises. Among treatments varying in alfalfa planting durations, the 9-year treatment exhibited the most incredible energy conversion and utilization efficiency within the soil food web, demonstrating the most stable structure. This study reveals optimal alfalfa planting duration for soil ecosystem stability in the Loess Plateau. Future research should explore sustainable crop rotations and alfalfa–soil–climate interactions for improved agricultural management. Full article

There is increasing adoption of winter cover crops (WCCs) in corn and soybean production in Canada, primarily to reduce erosion and increase soil organic matter content. WCCs have the potential to influence nematode communities by increasing free-living nematodes and decreasing plant-parasitic nematodes or vice versa. However, the mechanism by which WCCs change nematode community assemblages still remains a key question in soil food web ecology. We tested the hypothesis that the long-term use of rye (Secale cereale), barley (Hordeum vulgare) and oat (Avena sativa) as monocultures or mixtures promotes nematode communities and improves overall soil health conditions compared to winter fallow. The results from this study revealed that the use of WCCs generally promoted a higher abundance and diversity of nematode communities, whereas plant parasitic nematodes were the most abundant in winter fallow. Moreover, the mixtures of WCCs had more similar nematode communities compared to rye alone and winter fallow. The structure and enrichment indices were higher with WCCs, indicating higher nutrient cycling and soil suppressiveness, which are signs of healthy soil conditions. Furthermore, WCCs significantly reduced the populations of root lesion nematode Pratylenchus, although their numbers recovered and increased during the main crop stages. Additionally, mixtures of WCCs promoted the highest abundance of the stunt nematode Tylenchorhynchus, whereas winter fallow had a higher abundance of the spiral nematode Helicotylenchus during the fallow period and the main crop stages. The results show that the long-term use of cover crops can have a positive impact on nematode communities and the soil food web, but these changes depend on the type of WCCs and how they are used. Full article

Addressing the imbalance of the livestock–forage–environment system on the Qinghai–Tibet Plateau (QTP), the extensive replacement of natural grasslands with artificial grasslands has been pursued to enhance forage yield and quality. Recognizing their pivotal role in soil ecology, soil nematodes serve as sensitive indicators of the soil ecosystem structure and function. In this context, we embarked on a field investigation aimed at discerning the impact of varying artificial grasslands on soil nematode communities and food webs, with the intent of identifying an optimal forage species through the lens of soil nematode dynamics in the temperate steppe of the QTP. Our findings indicate that artificial grasslands, on the whole, tend to augment the soil nematode diversity—as reflected in the increased Margalef richness—and modify the community structure. Notable enhancements were observed in the abundance of bacterivores and omnivores, the fungivore and omnivore biomass carbon, and the connectance within fungal and bacterial channels. Specific insights reveal that grasslands established with Elymus nutans and Elymus sinosubmuticus notably boost the Margalef richness, omnivore biomass carbon, and both functional and structural metabolic footprints, with E. sinosubmuticus grasslands uniquely elevating the fungal channel connectivity. Elymus sibiricus grasslands, in particular, were associated with increased fungivore biomass carbon and metabolic footprints, as well as increased connectance in fungal and omnivore–predator channels. In summation, E. sibiricus, E. nutans, and E. sinosubmuticus emerge as superior choices for artificial grassland cultivation on the QTP, as suggested by soil nematode indicators. The adoption of mixed-species sowing incorporating these three candidates potentially offers enhanced benefits to the soil food web, although this hypothesis warrants further investigation. Full article