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Arbuscular mycorrhizal fungi (AMF) transport substantial plant carbon (C) that serves as a substrate for soil organisms, a precursor of soil organic matter (SOM), and a driver of soil microbial dynamics. Using two-chamber microcosms where an air gap isolated AMF from roots, we 13CO2-labeled Avena barbata for 6 wk and measured the C Rhizophagus intraradices transferred to SOM and hyphosphere microorganisms. NanoSIMS imaging revealed hyphae and roots had similar 13C enrichment. SOM density fractionation, 13C NMR, and IRMS showed AMF transferred 0.77 mg C g-1 of soil (increasing total C by 2% relative to non-mycorrhizal controls); 33% was found in occluded or mineral-associated pools. In the AMF hyphosphere, there was no overall change in community diversity but 36 bacterial ASVs significantly changed in relative abundance. With stable isotope probing (SIP)-enabled shotgun sequencing, we found taxa from the Solibacterales, Sphingobacteriales, Myxococcales, and Nitrososphaerales (ammonium oxidizing archaea) were highly enriched in AMF-imported 13C (> 20 atom%). Mapping sequences from 13C-SIP metagenomes to total ASVs showed at least 92 bacteria and archaea were significantly 13C-enriched. Our results illustrate the quantitative and ecological impact of hyphal C transport on the formation of potentially protective SOM pools and microbial roles in the AMF hyphosphere soil food web.

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. [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]

Summary: Solidago gigantea is one of the most problematic species of invasive plants in Europe, where its rapid spread threatens the stability of ecosystems. The effect of invasion by S. gigantea on soil ecosystems and food webs can be evaluated using nematode communities as suitable and useful soil bioindicators. We compared the effect of S. gigantea on nematode communities in plots invaded with S. gigantea and non-invaded grasslands across three sites with varying soil and climatic conditions. Our findings indicated that invasion by S. gigantea did not strongly affect nematode taxonomic diversity but negatively affected functional diversity. This effect was evident in the increased abundance of bacterivore and fungivore nematodes and decrease in values of ecological and functional indices. The evaluation of the soil food web using nematode communities confirmed that soil in plots with S. gigantea were less mature and more disturbed with a degraded or depleted food web indicated by lower values of maturity, enrichment and structure indices, compared with non-invaded grasslands. On the other hand, taxonomic diversity, abundance, biomass and the functional indices differed between three study sites, but site had little or no effect on the values of the maturity indices. The interaction between site and invasion status confirmed the effect of invasion on nematode biomass, with the abundance of bacterivore and fungivore nematodes and the functional indices more prominent at sites characterised by cold and humid climates. These findings underscore the importance of considering both taxonomic and functional diversity and the characteristics of the plants and sites when evaluating the impact of plant invasion on soil biota. [ABSTRACT FROM AUTHOR]

Land uses may shift soil biota community composition, and soil chemical traits. Our aims were to assess if the land uses may influence the soil biota community composition and soil chemical traits; if there are differences into soil biota biomass as influenced by land uses; and what are the plant-soil feedback among the land uses, soil biota, and soil chemical traits. We have collected soil samples and extracted soil biota individuals from four different land uses (e.g., natural ecosystem, conventional farming system, agroecological farming system, and fruticulture). Our results have revealed that land uses have influenced soil biota abundance (from 59.0 to 210.12 ind. trap− 1 in the natural ecosystem and fruticulture system, respectively), richness (from 6.5 to 10.5 in the fruticulture system, and natural ecosystem, respectively), diversity (from 1.01 to 1.75 in the conventional farming system, and natural ecosystem, respectively), dominance (from 0.52 to 0.71 in the natural ecosystem, and conventional farming system, respectively), and its biomass. The studied land uses have decreased the soil organic carbon when compared with the natural ecosystem (5.75 g kg− 1). SOC, soil pH, Olsen's available P, Mg2+, K+, and Na+ were the main factors contributing to the variance of the samples accounting for 78% of the data variance. The results of our study highlight the importance of considering land uses as key factors influencing soil biota community and soil chemical traits. Thus, long-term experiments considering land uses (e.g., conventional farming system, fruticulture, and agroecological farming system) may exploit negative effects of land uses on soil biota abundance on the one hand, while positive effects on soil chemical traits on the other hand. [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]

We assessed the impact of increasing olive mill waste (OMW) concentrations (10%, 35%, 70%, and 100% v/v) on soil free-living nematode communities and Lactuca sativa (lettuce) growth, 10 and 45 days after application (DAA). L. sativa plants showed a survival threshold at OMW10%, with higher concentrations proving fatal. Contrary to expectations, nematode abundance increased with OMW concentration. OMW10% induced a rapid surge in nematode abundance, stabilizing at 45 DAA, resembling control values. OMW35%, OMW70%, and OMW100% plots exhibited persistent, gradual increases, surpassing control values at 45 DAA. All treatments favored fungal feeders, resulting in the overdominance of the genus Aphelenchus both at 10 and 45 DAA. Even though OMW did not exert a toxic effect on nematode populations, this shift in the community structure towards the dominance of a single genus could suggest an imbalance in the soil community, which could have negative implications for soil health and ecosystem functioning. Overall, our study provides insights into the complex interactions between OMW, soil nematode communities, and plant growth, emphasizing the importance of understanding soil ecology for sustainable agricultural management. [ABSTRACT FROM AUTHOR]

Tree pathogens threaten the survival of many forest foundation tree species worldwide. However, there is limited knowledge of how dieback of foundation tree species may threaten other components of forest ecosystems, such as soil biodiversity and associated ecosystem functions. Kauri (Agathis australis), threatened by the root-borne pathogen Phytophthora agathidicida, are culturally and ecologically significant tree species that exert great influence on soil properties. We aimed to characterise soil mesofauna community structure and energy fluxes in kauri forests and assess the potential threat that tree pathogens such as P. agathidicida pose to belowground ecosystems. We sampled soil mesofauna communities and identified specimens to functional feeding groups at 24 pairs of kauri and adjacent broadleaf trees in sites across the Waitakere Ranges Regional Park, Aotearoa -- New Zealand. We attributed kauri canopy health scores, measured tree diameter, slope, forest floor depth, and soil carbon dioxide efflux. We also analysed soil samples for P. agathidicida presence, total carbon, and total nitrogen. We constructed soil mesofauna food webs associated with kauri and broadleaf trees, and assessed the uniqueness of food webs associated with kauri and the impacts of P. agathidicida on density, biomass, mean body mass, and energy fluxes of mesofauna taxonomic and trophic groups. We found omnivores with larger body mass at kauri where P. agathidicida was detected (i.e., P. agathidicida-positive soils). Compared to broadleaf trees, mesofauna density and biomass were lower in soils under kauri, and body masses of Symphyla and omnivores were smaller in soils under kauri. Differences in mesofauna community response variables between tree types were mainly modulated by the soil C:N ratio, which had positive effects under broadleaf and neutral to negative effects under kauri. Energy fluxes to detritivores and fungivores were greater under larger trees, regardless of tree type or P. agathidicida detection status. Our findings suggest that kauri support soil mesofauna food webs that are distinctly different from those found under broadleaf trees in the same habitat. A decreased presence of this foundation species may be linked to future impacts on soil mesofauna in this forest ecosystem with increasingly advanced stages of kauri dieback. [ABSTRACT FROM AUTHOR]

In this review, an overview was given of the mutual interactions between nematodes and fungi of the genus Trichoderma sp. due to the potential of these fungi to protect plant roots from plant-parasitic nematodes on the one hand and the influence of nematodes (fungivores) on the efficacy of the fungus on the other. In addition, an overview of the advantages of Trichoderma sp. for agricultural production was given. The basis of sustainable agricultural production is the healthy functioning of the soil ecosystem. The diversity of organisms—bacteria, protozoa, algae, metazoans (nematodes) and fungi—improves the quality and performance of the soil by maintaining biological productivity. Root exudates in the rhizosphere support microbial communities that play a key role in regulating the dynamics of organic matter decomposition and the availability of plant nutrients. The microbial activity of organisms in the soil is interconnected and interacts to form a soil food web that reflects the condition, function and health of the soil. The energy in food webs flows through trophic chains of consumers, which are divided into energy channels. Root, bacterial and fungal channels increase soil biomass, carbon (C) and energy flow through the soil food web. The structure of the nematode community is an effective tool for the biological assessment of soil quality. This is due to a number of characteristics that nematodes have, including the following: a great diversity of species, the possibility of subdivision according to different criteria such as trophic groups and c-p groups, the duration of reproduction, the ease of sampling, the identification of genera and preservation, etc. Nematodes are involved in various ecological functions in the soil, of which the interaction between them and fungi is based on antagonism or mutualism, which is the basis for a better understanding of their impact on the ecosystem. Fungi of the genus Trichoderma sp. are successful colonizers of all habitats, secondary opportunists and fast growing. [ABSTRACT FROM AUTHOR]

Climate change will likely increase habitat loss of endemic tree species and drives forest conversion in mountainous forests. Elevation gradients provide the opportunity to predict possible consequences of such changes. While species compositions of various taxa have been investigated along elevation gradients, data on trophic changes in soil-dwelling organisms are scarce. Here, we investigated trophic changes of the Collembola communities along the northern slope of Changbai Mountain, China. We sampled Collembola in primary forests at seven elevations (800–1700 m asl). We measured individual body lengths and bulk stable isotopes on species level. We further categorized Collembola species into life forms. The community-weighted means of Δ15N and Δ13C values as well as minimum Δ15N values and isotopic uniqueness of Collembola communities increased with increasing elevation, while the range of Δ15N values decreased. Maximum and minimum of Δ13C values differed between elevations but showed no linear trend. Further, Δ15N values of Collembola species occurring across all elevations increased with elevation. Changes in Δ15N values with elevation were most pronounced in hemiedaphic species, while Δ13C values increased strongest with elevation in euedaphic species. Δ15N values increased with decreasing body size in hemiedaphic and euedaphic species. Overall, the results suggest that Collembola species functioning as primary decomposers at lower elevations shift towards functioning as secondary decomposers or even predators or scavengers at higher elevation forests. The results further indicate that access to alternative food resources depends on Collembola life form as well as body size and varies between ecosystems. [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]

A study was conducted in the mountains of Magoebaskloof, Limpopo Province, where oak trees grow along the banks of the Broederstroom River. This study revealed that 22 nematode genera were associated with oak trees (Quercus robur). The most frequently occurring nematodes were Aphelenchus sp. (100%) and Plectus sp. (100%), followed by Helicotylenchus sp. (90%). This study examined the relationship between nematodes and the physicochemical properties of the soil using Pearson correlation. It uncovered that the organic matter content (OMC) had a negative correlation with the number of Panagrolaimus sp. (r = −0.770) and Hemicycliophora sp. (r = −0.674). Conversely, the sand percentage positively correlated (r = 0.695) with the number of Hemicycliophora sp. The clay content of the soil showed a positive correlation (r = 0.617) with the number of Ditylenchus. Soil pH demonstrated a significant negative correlation with Acrobeloides sp. (r = −0.877). The canonical correspondence analysis (CCA) explained 63.3% of the relationship between nematodes and soil physicochemical properties. The CCA results indicated that Ditylenchus exhibited a positive correlation with OMC, while the Panagrolaimus and Hemicycliophora species showed a negative correlation with OMC. The results indicated that none of the soil sample sites were under stress. The soil food web analysis revealed that most soil samples were nutrient-enriched with a low C/N ratio. In conclusion, this study revealed that oak trees harbor a high diversity of plant-parasitic and free-living nematodes. The results suggest that soil nematodes, particularly free-living bacterivores, such as Panagrolaimus, can indicate organic matter content in the soil.

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.

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

Intensive agriculture has led to widespread losses of native grasslands. Restoration projects are trying to reestablish native communities. However, the poor quality and altered food webs of former agricultural soils act as barriers to establishing diverse plant communities. Soil amendments such as biochar have been used to improve soil quality and increase crop yield, but little research has been on biochar in restoration settings. Eastern Washington University is attempting to restore a former wheat field to native Palouse prairie vegetation. In this study, we compared (1) soil abiotic properties and food webs between Palouse prairie remnants and Eastern Washington University's (EWU) restoration site and (2) tested whether biochar can move soil conditions at EWU's restoration site closer to those of remnant sites. We compared soils from three Palouse prairie remnants and EWU's restoration site, and compared soils at the restoration site that were treated with different levels of biochar. Soil nematodes were extracted and sorted to functional groups as an assay of the structure and functional diversity of the soil food web. The soil at EWU's restoration site had significantly lower nematode abundance, pH, and organic matter compared to prairie remnants. In addition, nematode abundance and pH increased significantly at the EWU site with the addition of biochar, both increasing to conditions similar to what is found at the prairie remnant sites. These results suggest biochar can improve some soil conditions in former agricultural lands even prior to native plant restoration. [ABSTRACT FROM AUTHOR]

Mountain forests are at risk as the consequences of climate change will likely lead to altered tree species boundaries. Characterizing food webs along elevation gradients in primary forests may help to predict the potential consequences of such changes, for example with regard to the decomposition of dead organic matter. Here, for the first time, we studied trophic variations in two species‐rich microarthropod taxa, Collembola and Oribatida, along an elevation gradient of primary forest at Changbai Mountain, China. Samples were taken at seven elevations of 150‐m elevational difference between 800 and 1700 m. At each elevation, Collembola and Oribatida were extracted from litter samples of eight subplots. We applied three state‐of‐the‐art methods to elucidate trophic positions and basal resource use at community level: Bulk stable isotope analysis of nitrogen (Δ15Nbulk) and carbon (Δ13Cbulk), compound‐specific stable isotope analysis of amino acids (CSIA‐AA), and dietary routing of neutral lipid fatty acids (NLFAs). Trophic positions calculated using Δ15Nbulk and CSIA‐AA (TPCSIA) in both taxa increased similarly with elevation by about half and one third of a trophic position, respectively. Stable isotope mixing models and linear discriminant analysis bootstrapping using δ13C of essential amino acids indicated fungi as the most important resource at all elevations for both taxa. Also, proportions of marker NLFAs changed little across elevations in both taxa; overall high proportions of linoleic acid indicated high fungal contributions, but in Collembola the contribution of bacterial markers was generally higher than in Oribatida. Δ13Cbulk did not respond linearly to the elevation gradient; however, changes in elevation differed between Collembola and Oribatida. A strong linear relationship between δ15N of phenylalanine and δ15N of litter indicated litter as the basis of energy channels in both taxa. Overall, food web functioning likely changes with changing forest types along elevation gradients, with microarthropods switching from feeding closer to the base of the food web at lower elevations to feeding at higher trophic levels at higher elevations, potentially compromising their role in litter decomposition and nutrient cycling. [ABSTRACT FROM AUTHOR]

The Antarctic continent hosts life forms specially adapted to the extreme climatic challenges. Among these organisms are nematodes, key organisms in the cycling of nutrients in soil food webs. These organisms are bioindicators of environmental disturbances, making their study essential for assessing the impact of human activity in this unique ecosystem. The Carlini Station and the Antarctic Specially Protected Area 132 on the 25 de Mayo/King George Island, Antarctica, has seen limited investigation of free-living soil nematodes. This study aimed to analyze free-living nematode communities in pristine soils and anthropic-intervened soils in the Carlini Station area. Nematodes were extracted from soil samples and morphologically identified at the genus and family levels to calculated ecological indices to assess nematode community structure. Ecological indices (abundance, maturity, enrichment, and soil food structure) were calculated and their values were compared between anthropic and pristine sites using the ANOSIM, SIMPER, and ANOVA statistical tests. Additionally, using molecular analysis, a phylogenetic study was conducted. The study identified four nematode genera, including Plectus spp., Calcaridorylaimus spp., Eudorylaimus spp., and Coomansus spp., with Plectus spp. being the most abundant and widely distributed. Anthropic sites had lower maturity and higher enrichment values, indicative of disturbance, while pristine sites exhibited higher maturity and structure values, suggesting a healthier soil food web. These results suggest that anthropic intervention disrupts nematode communities and represent a significant contribution to the understanding of free-living nematode communities in Antarctica. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (RKNs) pose a serious threat to crop production. Flooding soil with biogas slurry, combined with soil heating before crop planting, has the potential for RKN disease suppression. However, the actual effect of this method has not been verified under field conditions. Here, we present the results of a two-year field experiment in a greenhouse demonstrating the control effect on RKN disease and plant growth using this method, as well as its influence on the soil nematode community. Four treatments were set: untreated control (CK), local control method for RKN (CC), soil flooded with 70 % biogas slurry (BS70), and soil flooded with undiluted biogas slurry (BS100). In the first year, all three RKN control treatments significantly reduced the root-knot index (p 0.05), indicating that biogas slurry application did not increase the soil food web complex. Principal component analysis showed that the application of biogas slurry changed the nematode community, especially under BS70, which presented a more lasting influence. The high-level input of biogas slurry also caused soil NH4+-N and heavy-metal and arsenic accumulation in the first year, but these soil-pollution risks disappeared in the second year.

Tree pathogens threaten the survival of many forest foundation tree species worldwide. However, there is limited knowledge of how dieback of foundation tree species may threaten other components of forest ecosystems, such as soil biodiversity and associated ecosystem functions. Kauri (Agathis australis), threatened by the root-borne pathogen Phytophthora agathidicida, are culturally and ecologically significant tree species that exert great influence on soil properties. We aimed to characterise soil mesofauna community structure and energy fluxes in kauri forests and assess the potential threat that tree pathogens such as P. agathidicida pose to belowground ecosystems. We sampled soil mesofauna communities and identified specimens to functional feeding groups at 24 pairs of kauri and adjacent broadleaf trees in sites across the Waitākere Ranges Regional Park, Aotearoa – New Zealand. We attributed kauri canopy health scores, measured tree diameter, slope, forest floor depth, and soil carbon dioxide efflux. We also analysed soil samples for P. agathidicida presence, total carbon, and total nitrogen. We constructed soil mesofauna food webs associated with kauri and broadleaf trees, and assessed the uniqueness of food webs associated with kauri and the impacts of P. agathidicida on density, biomass, mean body mass, and energy fluxes of mesofauna taxonomic and trophic groups. We found omnivores with larger body mass at kauri where P. agathidicida was detected (i.e., P. agathidicida-positive soils). Compared to broadleaf trees, mesofauna density and biomass were lower in soils under kauri, and body masses of Symphyla and omnivores were smaller in soils under kauri. Differences in mesofauna community response variables between tree types were mainly modulated by the soil C:N ratio, which had positive effects under broadleaf and neutral to negative effects under kauri. Energy fluxes to detritivores and fungivores were greater under larger trees, regardless of tree type or P. agathidicida detection status. Our findings suggest that kauri support soil mesofauna food webs that are distinctly different from those found under broadleaf trees in the same habitat. A decreased presence of this foundation species may be linked to future impacts on soil mesofauna in this forest ecosystem with increasingly advanced stages of kauri dieback.

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

Anthropogenic activities have resulted in rising atmospheric concentrations of carbon dioxide (CO 2) and ozone (O 3), exerting substantial direct and indirect impacts on soil biodiversity within agroecosystems. Despite the considerable attention given to the individual impacts of elevated CO 2 and O 3 levels, the combined effects on soil nematode communities have not been extensively explored. In this study, we investigated the interactive effects of elevated CO 2 (+200 ppm, eCO 2) and O 3 (+40 ppb, eO 3) levels on the abundance, diversity, and trophic composition of soil nematode communities associated with two rice cultivars (Nanjing 5055, NJ5055 and Wuyujing 3, WYJ3). Our findings revealed that soil nematodes had greater abundances under eO 3 , whereas eCO 2 had no significant impacts. Conversely, both eCO 2 and eO 3 , and their combination led to significant reductions in nematode generic richness, accompanied by a decline in the diversity particularly associated with the WYJ3 cultivar. Moreover, eCO 2 and eO 3 influenced nematode community composition and environmental factors, particularly for the WYJ3 cultivar. Both eCO 2 and eO 3 significantly increased soil nitrate levels. The changes in nematode community composition were related to soil nitrate levels, as well as nitrogen and carbon concentrations in rice plant roots. Furthermore, interactions between eCO 2 and eO 3 significantly impacted soil nematode abundance and trophic composition, revealing intricate consequences for soil nematode communities that transcend predictions based on single-factor experiments. This study unveils the potential impacts posed by eCO 2 and eO 3 on soil biodiversity mediated by rice cultivars, plant functional characteristics and soil feedback mechanisms, thereby underscoring the complex and interactive outcomes arising from concurrent drivers of climate change within the soil food web. • This study factorially assessed the impacts of elevated CO 2 and O 3 on soil nematodes. • Elevated O 3 had stronger effects than CO 2 on the abundance of soil nematodes. • Elevated CO 2 and O 3 jointly decreased the diversity of soil nematodes. • Crop cultivar altered the effects of climate change on soil nematodes. [ABSTRACT FROM AUTHOR]

Soil micro-food webs play an important role in ecosystem functions through energy flow; they are strongly influenced by land use types. Previous studies have typically utilized the space-for-time substitution or single-time sampling method to reflect the land-use change effects by comparing differences among existing land-use types. These methods would increase random error. Research on how synchronized land-use change (starting at the same time and place) influences soil ecological processes and functions is urgently needed. Based on a controlled field experiment and seven years of observations, this study explored the effects of land-use change from natural shrubland to cropland (maize), forage land (tall-grass forage), and economic forest land (walnut plantation) on the community structure and energy dynamics of the soil micro-food webs. Cropland simplified the complexity of the soil food webs compared to the other three land-uses. Forage grassland maintained the highest biomasses of soil total microbes, fungi, and arbuscular mycorrhizal fungi. In addition, economic forest land improved the flow uniformity of the micro-food web by increasing energy transfer from resources to bacterivores, fungivores, and herbivores while decreasing herbivore energy flow to omnivores-predators. Omnivore abundance and nematode diversity were important predictors of total energy flux and flow uniformity of the soil micro-food webs, respectively. In addition, omnivores maintained the complexity of soil micro-food webs by promoting interactions among trophic groups through top-down control. Soil organisms are sensitive to the response of agricultural management and planting time, and it may take several years or more to reach a dynamic equilibrium. Different types and levels of ecosystem disturbance (e.g., tillage and no-tillage, fertilizer rates, aboveground biomass removal intensity) may be the major drivers of soil community during land use change. Our findings highlight the importance of conservation agriculture in maintaining soil food web structure and energy flow for future sustainable land uses, and that promoting omnivore abundance is essential for food web complexity and stability. • High level of disturbance in maize cropland suppressed the soil biota and food web energy flow. • Omnivores enhance the soil micro-food web complexity by strengthening the interactions between trophic groups. • Omnivore abundance is good predictor of total energy flux through soil food webs. • Nematode diversity is good indicator of flow uniformity of soil food webs. • Conservation agriculture maintains soil biota and food web energy flow and is a sustainable land use type. [ABSTRACT FROM AUTHOR]

Enchytraeids, also known as pot worms, represent one of the least studied groups of soil mesofauna. These organisms can be found throughout the globe from coasts to deserts reaching high densities and biomass, but their specific roles within the soil food web remain a stark knowledge gap. Enchytraeid species are involved in belowground trophic interactions, which could be distinguished by their morphological characteristics and ecological traits. To quantify this, we analyzed stable isotopes δ13C and δ15N in 16 enchytraeid species across various biomes and habitats in European Russia. Their isotopic niches were compared with different potential food sources and other soil invertebrates. We found that the total δ13C and δ15N range by across single enchytraeid samples reached 8 and 11‰, and isotopic niche of species depends on soil stratification and is reflected in the chaeta number per bundle, and, to a lesser extent, on the size or genera identity. These findings enabled us to split enchytraeids into three guilds within the functional group of secondary decomposers: (i) epigeic – that include litter-dwelling species that predominantly feed on plant material but also can ingest microorganisms; (ii) epi-endogeic – inhabiting upper humified soil and F-litter horizons, and feed primarily on various saprotrophic microorganisms; (iii) endogeic – consuming old processed humified and dissolved organic matter in lower H-horizon and even mineral A-horizons beneath. Our results are an important step forward in integrating enchytraeids into the next-generation food web models, not as a single black box, but as multiple blocks delivering different functions. • Despite prevalence, enchytraeids pose a knowledge gap in the soil food web. • We assessed the trophic niches of 16 common terrestrial enchytraeid species. • Enchytraeids act as secondary decomposers with three trophic guilds. • Soil stratification, chaeta number, and size affect enchytraeids' isotopic niches. • Advancing food web models, our study reveals diverse enchytraeid ecological functions. [ABSTRACT FROM AUTHOR]

Monocropping is commonly practiced by small-scale banana farmers for ease of management; however, concerns arise regarding its long-term effects on soil health and ecosystem stability. In order to ascertain the fact, this study investigated the impact of different durations of monocropping Lakatan banana on soil health as reflected by nematode community structure. For the extraction of nematodes, soil and root samples were collected from various banana farms practicing monocropping for 2-4, 5-9 and 10-15 years. Farms with prolonged monocropping showed an increased population of plant-parasitic nematodes compared to free-living nematodes. Nematode family Hoplolaimidae was recorded as the most dominant (59.59%-80.49%) across all monocropping durations. Shannon and Simpson's diversity indices were lowest at 10-15 years of continuous monocropping period, as compared to 2-4 years and 5-9-years. Maturity index (MI, 2.26) was highest at 5-9 years of continuous cultivation while structure index (SI, 68.93), and enrichment index (EI, 73.74) were highest in banana farms with monocropping periods of 2-4 years, and lower in banana farms with longer monocropping periods. Higher plant parasite index (PPI, 2.89-2.93) and PPI/MI (1.37) ratios were observed in monocropping periods of 10-15 years. Analysis of the c-p data indicated that soil conditions approach stress levels when farms are cultivated under 10-15 years of monoculture. Soil food web analysis revealed disturbances in the soil ecosystem, particularly in banana monocropping farms used for 5-15 years. Continuous monocropping for 5-15 years could disrupt the soil conditions, as evidenced by changes in the nematode community structure. These findings highlight that nematode communities can serve as sensitive indicators of soil quality and have the potential to elucidate the impact of farming management on soil health. [ABSTRACT FROM AUTHOR]

Protists are important key players in the microbial loop and influence their environment by grazing, which leads to the return of nutrients into the soil and reduces pathogen pressure on plants. Specifically, protists on and around plant roots are important for plants' development and growth. For this study, the fourth most important crop in the world, Hordeum vulgare , was selected. Seeds of H. vulgare were inoculated with Acanthamoeba castellanii alone or with additional soil bacteria at the beginning and during the experiment. The germination of the seeds and the growth of the plants in pouches were monitored over 3 weeks. No differences were found in leaf growth, root growth, root and leaf nitrogen content or ammonia content of the liquid from the pouches. In contrast, the relative increase in root and leaf dry weight showed a small difference compared to the controls. The results of this experiment demonstrated that seed inoculation with A. castellanii alone or with additional unidentified soil bacteria did not have a major effect on the growth and development of barley. Nevertheless, small changes in plant development were detected, indicating that A. castellanii should be considered for further investigation of co-inoculations with plant growth-promoting bacteria and additional nutrients., Competing Interests: The authors declare that there are no conflicts of interest., (Copyright © 2024 The Authors.)

Biodiversity can enhance soil multifunctionality through strengthening biotic interactions in soil food webs, but largely unknown in agroecosystems. We therefore predicted that vermicompost, serving as an organic amendment and soil health conditioner, could enhance trophic interactions among bacteria, fungi and nematodes and mediate synergies and trade-offs among soil functions, especially when substituting synthetic fertilizer was applied to soils. Soil multifunctionality was assessed from plant growth and product quality, carbon and nutrient cycling, water and climate regulation in an intensive cropping system. Pepper, tomato and spinach were cultivated in rotation annually, with substituting vermicompost as a nutrient replacement for synthetic fertilizer for 5 years. Results showed that substituting a moderate dose of vermicompost for synthetic fertilizer offered the highest soil multifunctionality by enhancing synergies among multiple functions. The vermicompost-stimulated multifunctionality was primarily attributed to the cascading effects of the complex food web structure induced by omnivorous nematode. These effects were regulated by the physicochemical environment of the vermicompost-amended soil. Notably, the multifunctional benefits degraded when higher rates of vermicompost were applied, suggesting that over-use of vermicompost combined with an inadequate amount of synthetic fertilizer could simplify soil food web structure and decrease soil functions, mainly due to the nutrient limitation and increasing harmful substances as indicated by C:N stoichiometry, heavy metals and antibiotic resistance genes. In intensive agricultural systems, finding an optimal balance of organic amendments and synthetic fertilizer that supports complex soil food web interactions is therefore crucial for promoting multiple soil functions and particularly sustaining the production of high-quality food crops. • The highest soil multifunctionality was observed in moderate vermicompost substitution. • Moderate vermicompost addition enhanced synergies among multiple functions. • Soil food web structure coordinated by omnivores was associated with multifunctionality. • Vermicompost supported multifunctionality of ecologically intensive agriculture. [ABSTRACT FROM AUTHOR]

Soil nematode biomass is of growing importance in elucidating soil food web structure, ecosystem functioning, and global biogeographical cycling. However, a significant challenge exists in quickly obtaining body mass data for a large number of nematode specimens without compromising measurement quality. Recently, a simplified method has been proposed, utilizing only the maximum diameter of nematodes to evaluate their fresh weight (W) as a substitute for Andrássy's formula. This approach is based on strong linear correlations between nematode body length (L) and maximum diameter (D). Despite its effectiveness, further testing is needed in extensive regions with numerous specimens. For this purpose, we conducted a study comprising 24,465 nematode specimens obtained from 222 soil samples in five types of grasslands across China. Our findings provided a robust support for the wide use of this simplified method. Furthermore, we proposed new weight formulas for total nematodes, morphological groups, and trophic groups, which were all well fitted to power models as W = a D b / (1.6 × 106), with various values of a for different aggregations and approximately constant b ≈ 3. Based on additional comparative analyses of the formulas used to assess the mean weight of functional groups, community-weighted mean body size, and community metabolic functional footprints, we firstly recommend using trophic group-specific formulas to minimize weight deviations from Andrássy's formula. Our new simplified power-law formulas enable reliable estimates of nematode body mass and are therefore promising for future applications. Moreover, our findings suggest that the classical Euclidean scaling theory significantly contributes to precisely estimating the body mass of small-sized soil fauna using only maximum diameter. In a global approach with a large number of individuals, for functional biogeography studies for instance, measuring the maximum diameter of animals to calculate their biomass is intriguing and compelling to motivate scientists to embrace functional approaches. • Andrássy's formula for calculating nematode weight can be simplified to a single parameter: the greatest body diameter. • Trophic group-specific simplified formulas minimize weight deviations. • Measuring animals' maximum width to calculate their biomass shall motivate scientists to embrace functional methodologies. [ABSTRACT FROM AUTHOR]

Root-knot nematodes (RKNs) pose a serious threat to crop production. Flooding soil with biogas slurry, combined with soil heating before crop planting, has the potential for RKN disease suppression. However, the actual effect of this method has not been verified under field conditions. Here, we present the results of a two-year field experiment in a greenhouse demonstrating the control effect on RKN disease and plant growth using this method, as well as its influence on the soil nematode community. Four treatments were set: untreated control (CK), local control method for RKN (CC), soil flooded with 70 % biogas slurry (BS70), and soil flooded with undiluted biogas slurry (BS100). In the first year, all three RKN control treatments significantly reduced the root-knot index ( p <  0.05). In the next year, only BS70 and BS100 still presented significantly suppressed effects ( p <  0.05), and it was more obvious under BS70 with a relative control effect of 74.6 %. In the first year, BS70 and BS100 significantly inhibited the plant height of watermelon ( p <  0.05). In the next year, however, all three RKN control treatments promoted the growth of watermelon, and their stem diameter was significantly greater than that of CK. The application of biogas slurry (BS70 and BS100) significantly increased nematode richness and the Shannon index in the second year ( p  < 0.05). However, the structure index showed no significant difference among treatments (p > 0.05), indicating that biogas slurry application did not increase the soil food web complex. Principal component analysis showed that the application of biogas slurry changed the nematode community, especially under BS70, which presented a more lasting influence. The high-level input of biogas slurry also caused soil NH 4 + -N and heavy-metal and arsenic accumulation in the first year, but these soil-pollution risks disappeared in the second year., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier Ltd.)

While it is acknowledged that alpine soil bacterial communities are primarily driven by season and elevation, there is no consensus on the factors influencing fungi and protists. Here we used a holistic approach of the microbiome to investigate the seasonal dynamics in alpine grasslands, focusing on soil food web interactions. We collected 158 soil samples along elevation transects from three mountains in the Alps, in spring during snowmelt and in the following summer. Using metatranscriptomics, we simultaneously assessed prokaryotic and eukaryotic communities, further classified into trophic guilds. Our findings reveal that the consumers' pressure increases from spring to summer, leading to more diverse and evenly distributed prey communities. Consequently, consumers effectively maintain the diverse soil bacterial and fungal communities essential for ecosystem functioning. Our research highlights the significance of biotic interactions in understanding the distribution and dynamics of alpine microbial communities., Competing Interests: The authors declare that they do not have any competing interests in relation to the work described., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)