Soil Nematode Community Composition Research Articles

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

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

Cover crop functional types alter soil nematode community composition and structure in dryland crop-fallow rotations

Increasing dryland cropping intensity by integrating cover crops into crop-fallow rotations can add diversity and alter soil ecosystem functions, including improvements in soil nutrient and water retention and cycling, and suppression of soil-borne pests. However, the use of cover crops can also carry the risk of increasing the abundance of plant-parasitic nematodes that could undermine system productivity. Here, we examined how the integration of diverse cover crops of different functional groups: Poaceae [forage oat (Avena sativa L.)]; Brassicaceae [forage rape (Brassica napus L.)]; and Fabaceae [common vetch (Vicia sativa subsp. sativa L. and fababean (Vicia faba L.) in monocultures and mixtures into a dryland crop-fallow rotation altered soil nematode community composition and structure relative to conventional fallows. We found that cover crop mixtures had greater diversity and complexity of free-living nematodes, indicating enhanced cycling of energy and nutrients (enrichment index >50 %) compared to monocultures. Furthermore, using a structural equation modelling approach, we showed the abundance of free-living nematodes is driven primarily by cover crop residue quality (C:N ratio, and cellulose content) and marginally by cover crop quantity (biomass). The grass-legume mixture had the highest abundance of plant-parasitic nematodes (Pratylenchus neglectus and Merlinius brevidens) but also fostered robust soil food webs with complex soil nematode trophic interactions, indicating promotion of soil ecosystem functions related to N and C cycling and overall improvement in soil health. The results indicate bottom-up effects of cover crops on soil nematode communities are modulated by cover crop functional type and mixture composition. Consequently, cover crops with appropriate traits must be selected if soil health is to be improved via suppression of plant-parasitic nematodes, promotion of free-living nematodes, and enhancement of soil food web complexity.

Effect of land use on soil nematode community composition and co-occurrence network relationship

Effect of land use on soil nematode community composition and co-occurrence network relationship

The effects of Eisenia fetida and Metaphire guillelmi on the soil micro-food web in a microcosm experiment.

Numerous studies have shown that the function of earthworms may depend on their ecotype and density, which affects how they impact soil microbial and nematode communities. However, it is unclear how different earthworm species and densities alter the composition of soil microbial and nematode communities and how these modifications impact the soil micro-food web. The structural equation model (SEM) is a more accurate tool for identifying the intricate relationships between various trophic levels in the soil micro-food webs than the widely used bivariate data analysis. In order to ascertain the effects of earthworm species, including epigeic earthworm Eisenia fetida and anecic earthworm Metaphire guillelmi, as well as varying densities on the composition of main microbial groups, soil nematodes and their relationships, a microcosm experiment was conducted in a greenhouse. After nine weeks of observation, compared with the control treatments, Eisenia fetida increased the biomasses of total microorganism and bacteria, whereas Metaphire guillelmi decreased the biomasses of total microorganism, bacteria, and gram-positive bacteria, but showed an increase in AMF biomass. Additionally, both two earthworm species decreased the abundance of total soil nematode, bacterivores, and omnivore-predators, which is in contrast with the control treatments. The SEM results indicated that the addition of Eisenia fetida at different densities had indirect negative effects on the abundance of omnivore-predators, as it significantly increased the content of soil organic carbon, ammonium nitrogen, and nitrate nitrogen. The bottom-up effects were found to be the dominant forces, which promoted bacterial-dominated decomposition channels. The addition of Metaphire guillelmi with different density had direct negative impact on bacterivores and fungivores. Moreover, it had indirect negative effects on omnivore-predators by altering the soil properties. The dominant forces were still the bottom-up effects. Our study suggests that different earthworm species have distinct mechanisms that affect the soil micro-food web in different ways.

Unraveling the interaction effects of soil temperature and moisture on soil nematode community: A laboratory study

Soil nematode communities and their functions are simultaneously influenced by abiotic factors such as temperature and soil moisture. However, the complex interaction effects of these factors have not been clearly demonstrated, limiting our understanding of soil biodiversity and functions under different climate scenarios. Here, we conducted a short-term microcosm experiment, implementing three temperature treatments (20 °C, 25 °C, and 30 °C) combined with two soil moisture treatments (50% and 80% water-holding capacity). We comprehensively assessed the changes in abundance, diversity, composition, and functions (carbon footprints) of soil nematode communities under these different treatments. Our findings revealed that temperature and moisture did not have significant effects on the richness or Shannon diversity of nematodes, while they did have significant impacts on other properties. We found that the interaction effect between temperature and moisture had a greater influence on total abundance compared to their independent effects. Moisture emerged as the primary driver of nematode community composition, followed by the interaction term, while temperature exhibited the least influence. Contrary to expectations, increasing temperature did not cause a shift in the community towards small-bodied genera when considering intraspecific variability in body mass. However, elevating moisture level led to an increase in community-weighted mean body mass, irrespective of intraspecific variability. Consequently, the body-mass-related footprints varied among treatments when considering intraspecific variability, with the dominant influence arising from the interaction effect. Overall, our study highlights the dominant interaction effect of temperature and soil moisture on multiple ecological properties of nematode communities. Additionally, we underscore the importance of incorporating intraspecific trait variability when assessing the responses and functions of nematodes under distinct environmental conditions.

Responses of soil nematode abundance and food web to cover crops in a kiwifruit orchard.

Soil biodiversity plays an important role in both agricultural productivity and ecosystem functions. Cover crop species influence the primary productivity of the ecosystem and basal resources. However, it remains poorly understood how different cover crop treatments influence the community of soil nematodes in an orchard ecosystem. In this study, field experiments were conducted to investigate the effects of cover crop treatments with different species numbers, i.e., no cover crop (CK), two cover crop species (C2), four cover crop species (C4), and eight cover crop species (C8), on weed biomass, together with composition, abundance, and metabolic footprint of soil nematode community in a kiwifruit orchard. As compared to the CK group, the groups of cover crop treatments had lower weed biomass, which decreased with the increase of the cover crop diversity. Moreover, for the abundance of total nematodes, fungivores exhibited higher levels in C4 and C8 treatments than that in CK, bacterivores had a higher abundance in C4 treatment, and plant parasites had a higher abundance in C2 and C8 treatments. Cover crop treatments also changed the structure of nematode community and enhanced the nematode interactions and complexity of nematode community network. In addition, C4 increased the Wasilewska index but decreased the plant-parasite index. The metabolic footprints of fungivores were higher in cover crop treatments compared with CK, and C4 and C8 also increased the functional metabolic footprint of nematode. Soil nematode faunal analysis based on nematode metabolic footprints showed that C8 improved the soil nutrient status and food wed stability. Mantel test and redundancy analysis showed that soil microbial biomass nitrogen and carbon, organic carbon, nitrate nitrogen, moisture content, pH, and cover crop biomass were the main factors that affect soil nematode community. In conclusion, cover crop treatments with four or eight plant species displayed a positive role in weed control, improvement of soil health, and promotion of energy flow in the soil food web through the increase in the metabolic footprints of nematodes in kiwifruit orchard.

Dominant plants mediate effects of grazing on soil nematode traits in a wet meadow grassland

Grazing is an integral disturbance in grassland ecosystems, however, its effects on belowground ecosystems are poorly understood. As the extent and quality of grasslands continue to decline around the world, metrics are required to monitor the effects of grazing on the function of rangeland soils. Soil nematodes are an important group of soil biota used to understand soil function. However, traditional approaches that rely on indices based on life-history information of soil nematodes have been supplemented in recent literature with trait-based analyses. Here, we test how changes in the structure and composition of soil nematode communities relate to grazing. We collected and measured morphological and reproductive traits of dominant genera of soil nematodes in a wet meadow grassland in Manitoba, Canada, to test how grazing alters trait profiles of nematode communities. For ten genera of soil nematodes, representing 80 % of community abundance, we measured morphometric traits, including body length and mass and used published literature to collect data describing reproductive traits. Communities of free-living nematodes were dominated by bacteriovore and root feeding genera and grazing intensity decreased the richness, diversity, and evenness of soil nematode communities. However, we observed no significant differences in the feeding structure of nematode communities based on the timing or intensity of grazing and no effect of grazing on mean trait values of the most abundant genera of soil nematodes. In contrast, changes in the community weighted means of nematode traits were strongly related to the abundance of dominant vegetation. We discuss the potential effects of changes in soil nematode communities on the function of wet grassland soils. Results from our research indicate that sustainable management and restoration of wet meadow rangelands must consider the impacts of grazing intensity on soil function and that plants play a key role in structuring the soil nematode communities belowground.

Composition of Soil Bacterial and Nematode Communities within Soil Aggregates in a Kiwifruit Orchard under Cover Crop Treatment

Soil, which exhibits difference in nutrient contents and aggregate sizes, provides spatially distinct habitats for biota. Cover crops influence the compositions of soil organism communities, playing an indispensable role in regulation of underground food webs and ecosystem functions. However, the effect of cover crops on soil microbes and nematodes distribution within different aggregate sizes remains unknown. Thus, a field experiment in a kiwifruit orchard with cover crops was conducted to estimate the distribution of soil nematodes and bacteria with different soil aggregate sizes (mega-aggregate (>2 mm, LMA), macro-aggregate (0.25–2 mm, SMA), and micro-aggregate (<0.25 mm, MA)) and cover crop treatments (four cover crop species (CC) and no cover crop as control (CK)). The results showed that bacterial compositions varied with both aggregate sizes and cover crop treatments. The composition of bacterial community was significantly different between mega-aggregate and micro-aggregate, and bacterial community diversity was significantly higher in micro-aggregate compared with mega-aggregate. Moreover, cover crop treatment dramatically changed the compositions of bacterial communities. However, the nematode communities were mainly impacted by soil aggregate sizes. Larger aggregates (mega- and macro-aggregates) contained higher abundance of omnivores/predators and lower abundance of fungivores. In contrast to bacterial community, the richness of nematode community was lower in micro-aggregates compared with larger aggregates (mega- and macro-aggregates). Redundancy analysis (RDA) and structural equation model (SEM) showed soil organic carbon (SOC) was the main soil factor that directly and indirectly affected both bacterial and nematode communities. The investigations of both bacterial and nematode communities could provide a better understanding on carbon and nutrient cycling across aggregate size fractions.

Climate and edaphic factors drive soil nematode diversity and community composition in urban ecosystems

Rapid urbanization profoundly affects global biodiversity. How urbanization modifies soil biodiversity and perturbs nematodes remains limited. Here, we investigated soil nematodes in four land-use types: Parks, residential areas, natural forests, and maize fields across 12 cities in China. Urban parks and surrounding forests had similar nematode richness exceeding that in urban residential areas and surrounding farmlands. Nematode communities in parks and residential areas were, however, more homogenous than in forests and farmlands. Variations in nematode assemblages in both core urban and urban surroundings were mainly due to taxa replacement, indicating that nematodes were spatially isolated in cities. Urban residential areas were colonized by the lowest number of specialists (i.e., with narrow niche width) and smaller body sizes. Urban parks, conversely, served as hotspots for soil nematodes in cities. Together, our results indicate that urbanization processes reduce nematode diversity, with e.g., 30% loss in residential areas compared to forests, and homogenize soil nematode communities.

Change in land-use from natural forest impacts functional composition and metabolic footprint of soil nematode community in Western Himalayas

Change in aboveground land-use confer many alterations in belowground soil ecology, which is a growing concern for the loss of biodiversity and the functioning of terrestrial ecosystems. Here, we studied nematodes - a key component and bioindicators of soil biodiversity in native temperate forests and its derived land-use (scrubland; SL, grassland; GL, cropland; CL) in western Himalayas. Five composite soil samples as replicates were collected from each land-use for analysis of soil properties and nematodes. Land-use change reduced the total nematode abundance. Contrary to our expectations, higher level of diversity was found in soils of SL while GL and CL had an overall lower level of diversity. Sigma maturity index and soil faunal profile suggested that replacement of natural forest with GL and CL was accompanied by disturbance, with lesser food web complexity and stability in the belowground soil food web. Metabolic footprint contributed through the structural component of nematode community decreased in GL and CL. Functional and trophic shifts in nematode metabolic footprint were recorded. Overall, we demonstrated that conversion lowered soil nematode abundance, altered soil nematode community structure, changed their stability and function and lowered their diversity. Moreover, this study have advantages for the sustainable management and restoration of native temperate forests in the region for the conservation of belowground biodiversity.

Changes in diversity patterns and assembly processes of soil nematode communities during forest secondary succession on the Loess Plateau

The secondary succession of plant communities involves considerable changes in belowground communities of microbes and animals. Nematodes are the most abundant animals in soil and play a vital role in maintaining soil biodiversity and functions. Exploring the ecological processes that drive soil nematode diversity and community assembly during secondary succession can help to gain a predictive and mechanistic understanding of soil biodiversity maintenance and ecosystem recovery. In this study, based on the investigation of soil nematode community composition and structure, we examined the changes in nematode α- and β-diversity along forest secondary succession and disentangled the contributions of different community assembly processes (deterministic and stochastic processes) in each successional stage on the Loess Plateau, a key region of ecological restoration in China. The results showed that: (1) Abundances of plant-parasitic and bacterial-feeding nematodes were lower in the pioneer and climax forest stages than in the grassland and shrub stages. Meanwhile, nematode community composition considerably changed, with the dominant trophic group changing from plant-parasitic (grassland stage: 35.48%) and bacterial-feeding (shrub stage: 35.63%) to fungal-feeding (pioneer and climax forest stages: 30.65–36.44%). These changes might be associated with higher carbon-to-nitrogen ratios of fine roots and litters, as well as higher litter phosphorus content (LTP), in pioneer and climax forests; (2) Nematode α-diversity and β-diversity peaked in the shrub stage and decreased substantially in the climax forest stage, but β-diversity differed more significantly between successional stages than α-diversity. Fine root biomass, root carbon to nitrogen ratio, and litter phosphorus content were the main predictors of nematode α- and β-diversity, while geographic distance positively affected nematode β-diversity; (3) In the grassland and climax forest stages, deterministic processes dominated nematode community assembly, probably due to the strong influence of environmental factors such as the quantity or quality of plant resources. Especially, in the climax forest stage, the low quality of plant resources might be responsible for the low nematode diversity and network complexity. In the shrub and pioneer forest stages, the contribution of stochastic processes gradually increased, and nematode networks became more complex. Taken together, our results emphasize the importance of litter and root quality in regulating nematode diversity and community assembly, especially in the late successional stage, which provides insights into forest restoration and sustainable management in the Loess Plateau and other similar arid and semiarid regions.

Plant diversity effects on herbivory are related to soil biodiversity and plant chemistry

Abstract Insect herbivory is a key process in ecosystem functioning. While theory predicts that plant diversity modulates herbivory, the mechanistic links remain unclear. We postulated that the plant metabolome mechanistically links plant diversity and herbivory. In late summer and in spring, we assessed individual plant above‐ground herbivory rates and metabolomes of seven plant species in experimental plant communities varying in plant species diversity and resource acquisition strategies. In the same communities, we also measured plant individual biomass as well as soil microbial and nematode community composition. Herbivory rates decreased with increasing plant species richness. Path modelling revealed that plant species richness and community resource acquisition strategy correlated with soil community composition. In particular, changes in nematode community composition were related to plant metabolome composition and thereby herbivory rates. Synthesis. These results suggest that soil community composition plays an important role in reducing herbivory rates with increasing plant diversity by changing plant metabolomes.

Unveiling the drivers of nematode community structure and function across rice agroecosystems

Rice agroecosystems has drawn global attention due to its unique transition of flooding to wetland to a terrestrial ecosystem with high biodiversity throughout its growing period. While biodiversity of the aboveground organisms in the rice ecosystem is well studied, understanding the diversity and functions of soil biota, particularly the nematofauna, are often neglected. In the present study, variations in soil nematode community composition in response to edaphic and climatic variables were assessed (n = 501 samples) across three agro-ecological zones of Jharkhand, India. Functional diversity measures were used to estimate the biological soil health of different rice growing areas across the agroecological zones. Relative contribution of edaphic, climatic and spatial structure in shaping nematode community composition was measured using variation partitioning. Among the identified nematode genera (n = 58), Meloidogyne spp. was the most abundant and dominant taxon. Taxonomic diversity measures varied significantly across agro-ecological zones, with highest diversity reported in the central and north-eastern plateau, followed by the south-eastern plateau and western plateau. Average annual temperature, annual precipitation, available nitrogen and organic carbon had significant relationships with taxonomic diversity measures. The spatial variation map of the nematode community composition depicted spatial heterogeneity across agro-ecological zones. Climatic predictors also strongly influenced both the community composition and richness of nematodes, while edaphic factors showed a strong influence on beta diversity, but not on variation partitioning. A moderate level of spatial structure pattern suggested limited dispersal of nematodes. Functional diversity measures based on nematode community composition depicted better soil biological health in the central and north-eastern plateau than rest two zones. This study demonstrates how climatic predictors have a greater influence on nematode community composition than edaphic parameters, presumably as a result of intensively managed rice agroecosystems.

Effect of Habitat Disturbance on the Composition of Soil Nematode Functional Groups Associated with a Tropical Herb: Heliconia collinsiana

Habitat loss affects the nature of biotic interactions in all ecosystems and at all levels of the food web. Nevertheless, little attention has been given to soil nematodes in tropical habitats despite their important role in ecosystem functioning worldwide. Here, we analyzed the influence of anthropogenic habitat disturbance on the absolute and relative density and composition (i.e., trophic guilds) of soil nematode communities associated with the rhizosphere of the tropical herb Heliconia collinsiana in continuous mature forests and human-induced secondary forests. We compared nematode densities based on the following feeding guilds: bacterivores, fungivores, herbivores and predators. Thereafter, we classified herbivorous nematodes into genera and described soil properties in both habitat types including pH, electrical conductivity, and organic matter content. Herbivores were significantly the most abundant feeding guild for both habitats represented by Criconemella spp., Helicotylenchus spp., and Meloidogyne spp., which showed no significant differences in density between habitats. Relative but not absolute nematode density differed between habitats, with fungivore nematodes being significantly lower in secondary forests. No significant differences in soil properties were detected. Overall, our results suggest that forest disturbance affects the nematode community associated with the rhizosphere of H. collinsiana which may affect forest succession and the dynamics of the soil biota. Our study contributes to the understanding of biotic interactions in conserved and disturbed tropical habitats.

The global impact of management on soil nematode abundances.

Research Highlight: Li, X., Liu, T., Li, H., Geisen, S., Hu, F., & Liu, M. (2022). Management effects on soil nematode abundance differ among functional groups and land-use types at a global scale. Journal of Animal Ecology, https://doi.org/10.1111/1365-2656.13744. Despite the well-documented decline of aboveground species abundances as a result of land-use intensification, there has been little attention on the effects of human activities on belowground species abundances. Li et al. analyse nematode data, the most abundant animal on the planet, from across the globe to determine whether their abundances vary between managed and unmanaged habitats. The authors show that, unlike aboveground biodiversity, nematode abundance is higher in managed than unmanaged primary and secondary habitats. Furthermore, responses to land management vary between trophic groups and they do not appear to follow the general hypothesis that higher trophic levels are more vulnerable to human activity than those further down the food chain, except in urban habitats. Finally, Li et al. show that the relationships between environmental predictors and species abundance were weakened (and sometimes reversed) in managed habitats. Together, their results reveal how land-use management is impacting the trophic composition of soil nematode communities and their relationships with the environment, which has implications for ecosystem functioning.

Increasing Levels of Physical Disturbance Affect Soil Nematode Community Composition in a Previously Undisturbed Ecosystem.

Soil is essential for the sustenance of life. Diverse soil organisms support several biological processes such as organic matter decomposition, mineralization, nutrient cycling, and controlling pests and diseases. Among multicellular soil organisms, nematodes are ubiquitous, functionally diverse, and abundant. Notably, agricultural practices have diverse impacts on plants, soils, and soil organisms. Tillage affects nematodes directly by altering pore size and disrupting the continuity of water films and indirectly by affecting the lower trophic groups such as bacteria and fungi. The primary goal of this study was to examine the effect of increasing levels of physical disturbance on nematode communities in an undisturbed forest ecosystem. The experiment included four treatments: control with no disturbance, surface litter removed with no litter and no vegetation, tilling the soil with a rototiller every 2 mon, and every 2 wk. Tillage significantly reduced the overall abundance and overall richness of nematode communities over time. Among nematode trophic groups, tillage significantly reduced the abundance and richness of bacterial feeders, predators, and omnivores over time. The abundance and richness of c-p 2, c-p 4, and c-p 5 class nematodes were significantly decreased by tillage. Unlike tillage, minimal disturbance such as removal of surface litter resulted in a significant decrease in the abundance of only three genera: Acrobeles, Aporcelaimellus, and Boleodorus. Nonmetric multidimensional scaling analysis revealed that nematodes of higher c-p classes such as Dorylaimida, Aporcelaimellus, Alaimus, Clarkus, and Tripyla were sensitive to physical disturbances. Bacterial feeders belonging to the c-p 2 class such as Tylocephalus, Acrobeles, Ceratoplectus, Plectus, and Pseudacrobeles were significantly reduced by tillage. Moreover, tillage significantly reduced the functional metabolic footprint of nematodes, which indicates decreased metabolic activity, reduced C inflow, and poorly structured soil food webs. Previous studies conducted in agricultural ecosystems determined that Clarkus, Filenchus, and Plectus were tolerant to tillage; however, they were found sensitive to tillage in our study. Overall, our study suggests that increasing levels of physical disturbance are detrimental to nematode community abundance and diversity that could affect soil ecosystem stability and sustainability.

Adaptation of soil micro-food web to elemental limitation: evidence from the forest-steppe ecotone

Stoichiometric imbalance between resources and their decomposers can alter the activity and structure of soil microbial communities and play an important role in regulating nutrient and carbon cycling in terrestrial ecosystems. However, whether and how ecological networks of soil micro-food web change to cope with the stoichiometric imbalance has never been assessed so far. In this study, we tested how the soil micro-food web responded to elemental limitations along a forest-steppe ecotone. We measured several adaptation mechanisms including soil microbial stoichiometry, enzyme activities and the composition of soil microbial and nematode communities. The microbial investment in resource acquisition shifted from nutrient-to C-acquiring enzymes with decreasing soil C:N:P ratios along the forest-steppe ecotone. The shifts in element use efficiencies could be a compensatory way besides enzyme allocation, implemented by microbial communities to cope with stoichiometric imbalance in their substrates. The community structure of soil micro-food web also changed with a decrease in saprotrophic fungi and fungivorous nematodes from the steppe plots towards the forest plots. The co-occurrence networks were less complex and stable with decreasing soil C:N:P ratios, suggesting that trophic interactions were less diverse and C-limitation plays an important role in structuring ecological interactions in soil food webs. Our findings provide insights into how stoichiometric constraints may induce shifts in ecological networks and have important implications for integrating shifts in individual physiological metabolism as well as changes in community composition of soil biota and to better understand and predict soil biogeochemical cycling in terrestrial ecosystems.

Changes in the soil nematode community among climate zones do not keep pace with changes in plant communities

Revealing the distribution patterns of soil nematode communities among climate zones helps uncover the spatial distribution patterns of belowground biodiversity. The aims of this study were to reveal the spatial distribution patterns of the taxonomic composition, diversity and trophic structure of soil nematode communities among continuous climate zones. Investigations were conducted for five altitudinal vegetation types, i.e., subtropical evergreen broad-leaved forest (SEB), subtropical evergreen and deciduous broad-leaved mixed forest (SEDB), warm temperate deciduous broad-leaved forest (WTDB), mid-temperate coniferous and broad-leaved mixed forest (MTC) and cold temperate coniferous forest (CTC), on the eastern slope of Gongga Mountain from 2014 to 2017. The taxonomic compositions of the soil nematode communities in the SEDB, WTDB, MTC and CTC were similar but differed markedly from that in the SED, with patterns varying among sampling years. Abundances and diversity showed unimodal distribution patterns, with maximum values occurring in the WTDB. The abundances of the four trophic groups varied significantly among the vegetation types. Relative abundances stabilized for bacterivores and plant parasites but declined for fungivores and increased for omnivores-predators from the SEB to the CTC. The ratio of fungivores to bacterivores in the SEB was significantly higher than those in the other vegetation types, implying that the trophic structure and material cycling channels differed among forest types. The spatial distribution of the soil nematode communities was mainly influenced by pH, total K, total P and soil temperature. These findings suggested that the taxonomic composition, abundance, diversity and trophic structure of soil nematode communities vary among climate zones, but the changes in the soil nematode communities among climate zones did not keep pace with those in aboveground plant communities.

Straw Return and Nitrogen Fertilization to Maize Regulate Soil Properties, Microbial Community, and Enzyme Activities Under a Dual Cropping System.

Soil sustainability is based on soil microbial communities’ abundance and composition. Straw returning (SR) and nitrogen (N) fertilization influence soil fertility, enzyme activities, and the soil microbial community and structure. However, it remains unclear due to heterogeneous composition and varying decomposition rates of added straw. Therefore, the current study aimed to determine the effect of SR and N fertilizer application on soil organic carbon (SOC), total nitrogen (TN), urease (S-UE) activity, sucrase (S-SC) activity, cellulose (S-CL) activity, and bacterial, fungal, and nematode community composition from March to December 2020 at Guangxi University, China. Treatments included two planting patterns, that is, SR and traditional planting (TP) and six N fertilizer with 0, 100, 150, 200, 250, and 300 kg N ha–1. Straw returning significantly increased soil fertility, enzymatic activities, community diversity, and composition of bacterial and fungal communities compared to TP. Nitrogen fertilizer application increased soil fertility and enzymes and decreased the richness of bacterial and fungal communities. In SR added plots, the dominated bacterial phyla were Proteobacteria, Acidobacterioia, Nitrospirae, Chloroflexi, and Actinobacteriota; whereas fungal phyla were Ascomycota and Mortierellomycota and nematode genera were Pratylenchus and Acrobeloides. Co-occurrence network and redundancy analysis (RDA) showed that TN, SOC, and S-SC were closely correlated with bacterial community composition. It was concluded that the continuous SR and N fertilizer improved soil fertility and improved soil bacterial, fungal, and nematode community composition.

Seasonal variation in cropland soil nematode community composition in the lower reaches of Liaohe Plain

Seasonal variation in cropland soil nematode community composition in the lower reaches of Liaohe Plain