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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]

Soil viral ecology is a growing research field; however, the state of knowledge still lags behind that of aquatic systems. Therefore, to facilitate progress, the first Soil Viral Workshop was held to encourage international scientific discussion and collaboration, suggest guidelines for future research, and establish soil viral research as a concrete research area. The workshop took place at Søminestationen, Denmark, between 15 and 17th of June 2022. The meeting was primarily held in person, but the sessions were also streamed online. The workshop was attended by 23 researchers from ten different countries and from a wide range of subfields and career stages. Eleven talks were presented, followed by discussions revolving around three major topics: viral genomics, virus-host interactions, and viruses in the soil food web. The main take-home messages and suggestions from the discussions are summarized in this report.

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]

Neonicotinoid insecticides are widely used to control early-season and foliar-feeding pests. Some studies have revealed their nontarget impacts on pollinators and other invertebrates but few investigated their effects on soil microbiota. Given the crucial role of soil prokaryotic and eukaryotic microbial communities in agroecosystem regulation and their contribution to soil fertility, it is critical to understand their structure and changes in response to disturbances such as pesticide application. Among these communities, free-living nematodes have the potential to indicate the ecological changes in soil caused by environmental stress and have a key role in forming and modulating soil microbial composition and function by feeding on other soil microorganisms or interacting with them. Here, we used 18S ribosomal RNA gene amplicon sequencing to characterize the effects of neonicotinoids on soil nematode communities in a 3-year soybean-corn crop rotation in Quebec, Canada. We also quantified the changes in nematode-bacteria cooccurrence networks in soil exposed to neonicotinoids. We found that neonicotinoid seed treatment significantly explained variation in nematode community composition and affected the relative abundance of some nematode families, such as a decrease in the omnivorous family Dorylaimidae in neonicotinoid-treated samples. Moreover, neonicotinoids altered the patterns of nematode-bacteria cooccurrence, including the structure and taxonomic composition of the networks. However, it is unclear whether neonicotinoids affected bacterial cooccurrence networks directly, or indirectly by affecting nematodes that feed on bacteria. Further research is needed to understand how neonicotinoids affect nematodes and the role of nematodes in microbial network variation in soil exposed to neonicotinoids.

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.

Molecular gut content analysis via diagnostic PCR or high-throughput sequencing (metabarcoding) of consumers allows unravelling of feeding interactions in a wide range of animals. This is of particular advantage for analyzing the diet of small invertebrates living in opaque habitats such as the soil. Due to their small body size, which complicates dissection, microarthropods are subjected to whole-body DNA extraction-step before their gut content is screened for DNA of their food. This poses the problem that body surface contaminants, such as fungal spores may be incorrectly identified as ingested food particles for fungivorous species. We investigated the effectiveness of ten methods for body surface decontamination in litter-dwelling oribatid mites using Steganacarus magnus as model species. Furthermore, we tested for potential adverse effects of the decontamination techniques on the molecular detection of ingested prey organisms. Prior to decontamination, oribatid mites were fed with an oversupply of nematodes (Plectus sp.) and postmortem contaminated with fungal spores (Chaetomium globosum). We used diagnostic PCR with primers specific for C. globosum and Plectus sp. to detect contaminants and prey, respectively. The results suggest that chlorine bleach (sodium hypochloride, NaClO, 5%) is most efficient in removing fungal surface contamination without significantly affecting the detection of prey DNA in the gut. Based on these results, we provide a standard protocol for efficient body surface decontamination allowing to trace the prey spectrum of microarthropods using molecular gut content analysis. [ABSTRACT FROM AUTHOR]

Nitrogen deposition can promote belowground soil carbon pools, and precipitation reduction can eliminate this positive effect. Soil fauna play crucial roles in regulating the dynamics of organic matter and maintaining biodiversity in ecosystems. However, it is not clear whether belowground soil fauna have similar responses to changes after long-term nitrogen deposition and drought. We simulated nitrogen deposition by applying fertilizer, and simulated drought by excluding 30% of the ambient precipitation in a temperate forest from 2009. Our results showed that experimental precipitation reduction alone significantly changed the composition and decreased the abundance of the soil faunal community. Precipitation reduction could also promote the soil food web in a fungal-dominated pathway by decreasing trophic groups of Isotomidae abundance. In contrast, although nitrogen addition treatment increased soil available nitrogen content, it had a neutral effect on the soil faunal community. Soil faunal community showed strong temporal variations in response to both nitrogen deposition and precipitation reduction treatments. Notably, interactions between precipitation reduction, nitrogen addition, and sampling time were significant for specific trophic groups, including saprozoites and omnivores. Shannon-Weiner diversity was not sensitive to these global change factors. Our results suggest that soil water content and plant richness may, directly and indirectly, regulate the soil faunal community. [ABSTRACT FROM AUTHOR]

Stable isotope technique is important for understanding the structure and function of soil food web, which is considered as a belowground black box. We reviewed typical application cases of stable isotope techniques in the research of soil food webs, including to determine food sources and feeding preferences of soil fauna by using isotopes, and to analyze the trophic structure of soil food webs through isotope fractionation effects during the process of feeding and nutrient sequestration by soil fauna. Additionally, stable isotope techniques could reveal the role of soil biota at different trophic levels within soil food web in ecosystem matter and energy flow, which favored to carry out accurate and efficient research on the contribution of soil food webs to soil carbon and nitrogen cycling process and the corresponding influence mechanism. We further put forward the limitations of current stable isotope techniques and the future development directions. [ABSTRACT FROM AUTHOR]

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Selecting the appropriate indicators and measuring time point numbers is important for accurately examining the shift in soil gross decomposition channel structure. Through a selected case study on a natural forest vs. rainfed arable system over a two-month-long experiment, the utility of three commonly employed indicators (fungi to bacteria ratio (F:B), fungivore to bacterivore ratio (FF:BF), and glucosamine to muramic acid ratio (GlcN:MurN)) were compared to reflect the shift in soil gross decomposition channel structure. The requirement of measuring the time point numbers for the three indicators was also assessed, and we suggest a potential methodology. Our results revealed that the GlcN:MurN ratio was more reliable for assessing the shifts in gross decomposition channel structure for long-term land use changes, while it was less sensitive to short-term drought compared with the other two indicators. The F:B ratio was more applicable than the FF:BF ratio for reflecting both long- and short-term changes. Furthermore, the reliability of the GlcN:MurN ratio was the least dependent on measuring time point numbers. We suggest the use of multiple indicators and the adoption of multiple measuring time points for the overall methodology. [ABSTRACT FROM AUTHOR]

Summary: Soil nematode communities are one of the most used bioindicators for assessing soil health and soil conditions. However, they are dependent on the presence of plants, some of which, known as 'invasive', affect local biodiversity when established. This study aimed to compare the communities of soil nematodes in riverbanks non-invaded and invaded by Fallopia japonica at three sites characterised by different environmental conditions. Our findings indicated that the ecosystem had a larger impact on the nematode communities than did the environmental variability at the study sites. Soil properties, such as pH, moisture content and organic-carbon content, differed significantly amongst the sites, but the nematode communities remained similar. Organic-carbon content was lower, and soil pH was higher, in the ecosystem with invasive F. japonica. Total nematode abundance, the abundances of fungivores, herbivores, omnivores and predators, and the maturity indices were significantly lower with invasive F. japonica. Fungivorous nematodes are essential for breaking down organic matter and releasing nutrients. Herbivorous nematodes respond to changes in the vegetation, and omnivorous and predatory nematodes contribute to the overall biodiversity and ecological balance in the soil ecosystem, so their lower abundance suggests a disturbance in the soil food web. The lower maturity indices suggested a disturbance or degradation of the soil ecosystem, which could have secondary negative effects on plant growth, nutrient availability and ecosystem resilience. These findings indicate that invasion both decreased the abundance of important soil organisms and disrupted the cycling of nutrients, potentially leading to long-term negative consequences for the invaded ecosystems. Understanding and managing the effects of invasive plants such as F. japonica are crucial for preserving soil health and promoting sustainable ecosystem functioning. [ABSTRACT FROM AUTHOR]

Upland rainfed rice cropping in the highlands of Madagascar is strongly limited by poor Ferralsol mineral fertility. There is an urgent need to identify efficient and sustainable fertilization practices that improve soil fertility without inducing pest proliferation. For that purpose, using a field trial for 2 successive years, we tested the effect of 16 fertilization practices on the abundance and taxonomic diversity of soil active nematodes, which are known to be biological indicators of soil fertility. We tested both fertilization practices traditionally used by farmers and innovative ones based on the assemblage of organic, mineral and biological (earthworms and mycorrhiza) fertilizers. We identified eight types of practices: (1) no fertilization; (2) fertilization with NPK and urea; (3) low input rates (3 t dry matter ha−1) of organic fertilizers without NPK; (4) low input rates of organic fertilizers with NPK; (5) high input rates (6 t dry matter ha−1) of organic fertilizers; (6) high input rates of organic fertilizers with mineral fertilizers; (7) high input rates of a mixture of organic fertilizers and (8) high input rates of a mixture of organic fertilizer with mineral fertilizers. After 2 years, we identified 41 soil nematode taxa. The taxonomic composition of the nematode communities revealed that Ferralsols are a stressful environment for the soil biota. The low abundance of opportunistic bacterivores indicated that the different fertilization practices did not significantly and deeply increase the amount of plant-available nutrients, and thus soil fertility. However, organic fertilizers significantly increased the abundance of omni-predators, indicating a moderately mature food web. Some practices induced worrying increases in the endoparasitic Meloidogyne and Pratylenchus, which requires monitoring of root symptoms to avoid the establishment of their populations. Monitor soil nematode communities in upland rice growing on Ferralsols could be used as agronomic indicators to promote sustainable rice production systems in Madagascar. [ABSTRACT FROM AUTHOR]

Soil nematode communities can offer valuable indicators for monitoring the status of soil ecosystems. However, their potential for assessing soil restoration under revegetation has been neglected in temperate arid and semiarid areas. This study examined the characteristics of soil nematode communities and their relationships with soil physicochemical properties under five typical revegetation approaches in the semiarid Loess Plateau of China. The results showed that planting an artificial Caragana korshinskii forest led to the recovery of the soil food web, which significantly increased soil nematode abundance (138.10 ± 11.60 inds./100 g dry soil) and community diversity (Shannon-Wiener diversity: 2.48 ± 0.13; trophic diversity: 3.08 ± 0.02), associated with the high contents of SOC and NH4+-N. However, establishing an artificial Prunus sibirica forest improved neither soil properties nor nematode community characteristics, reflecting poor soil ecosystem restoration. After establishing an artificial Prunus davidiana forest (PD) and an artificial Medicago sativa grassland (MS), substantial increases in herbivorous and fungivorous nematodes were observed, respectively, likely due to the accumulation of particular genera that fed on roots (e.g., Pratylenchus) or their symbiotic fungi (e.g., Tylencholaimus), which might result in the deterioration (in MS) or restoration (in PD) of the soil food webs. Natural grassland restoration greatly improved soil properties (i.e., SOC, NH4+-N, microbial biomass carbon) but did not change the nematode community obviously, probably due to top-down predation in natural habitats. In conclusion, the characteristics of nematode communities can effectively indicate the restoration of soil food webs and identify their possible driving forces under revegetation, which have important implications for vegetation restoration in arid and semiarid regions. [ABSTRACT FROM AUTHOR]

Molecular gut content analysis via diagnostic PCR or high-throughput sequencing (metabarcoding) of consumers allows unravelling of feeding interactions in a wide range of animals. This is of particular advantage for analyzing the diet of small invertebrates living in opaque habitats such as the soil. Due to their small body size, which complicates dissection, microarthropods are subjected to whole-body DNA extraction-step before their gut content is screened for DNA of their food. This poses the problem that body surface contaminants, such as fungal spores may be incorrectly identified as ingested food particles for fungivorous species. We investigated the effectiveness of ten methods for body surface decontamination in litter-dwelling oribatid mites using Steganacarus magnus as model species. Furthermore, we tested for potential adverse effects of the decontamination techniques on the molecular detection of ingested prey organisms. Prior to decontamination, oribatid mites were fed with an oversupply of nematodes (Plectus sp.) and postmortem contaminated with fungal spores (Chaetomium globosum). We used diagnostic PCR with primers specific for C. globosum and Plectus sp. to detect contaminants and prey, respectively. The results suggest that chlorine bleach (sodium hypochloride, NaClO, 5%) is most efficient in removing fungal surface contamination without significantly affecting the detection of prey DNA in the gut. Based on these results, we provide a standard protocol for efficient body surface decontamination allowing to trace the prey spectrum of microarthropods using molecular gut content analysis.

Long-term vegetation cover can affect soil organic carbon content and carbon flow within the soil food web. Nematode trophic structure and soil properties were evaluated in pear rows (intra) maintained without weeds applying herbicide and in the inter-rows (between rows) covered with: Medicago+grasses (MG), fescue or spontaneous vegetation. Soil samples were taken at 0-20 and 20-40 cm depths from 2012 to 2014. Nematode assemblage was different in each inter-row and row, mainly in the topsoil. The inter-rows were reservoirs of omnivores-predators. The MG inter-row promoted the highest accumulation of organic carbon, total N and exchangeable K in the soil. The enrichment index was related to the quantity of dry matter produced by cover crops with the highest index observed in MG. Nematode biomass showed a positive correlation with intra and inter-rows soil organic carbon. Carbon flow through bacterivores prevailed in intra-rows, while bacterivores or herbivores canalized the inter-rows. Highlights: • Each cover crop (Medicago+grasses, spontaneous vegetation and fescue) was associated with a different nematode assemblage, mainly in the topsoil. • Omnivores-predators were higher in the inter-row than its associated row. • Nematode Biomass showed a positive correlation with the content of SOC in the row and in the inter-row. • Soil energy channels revealed higher carbon flow within the soil food web under Medicago+grasses and spontaneous vegetation than under fescue.

Exogenous carbon turnover within soil food web is important in determining the trade‐offs between soil organic carbon (SOC) storage and carbon emission. However, it remains largely unknown how soil food web influences carbon sequestration through mediating the dual roles of microbes as decomposers and contributors, hindering our ability to develop policies for soil carbon management. Here, we conducted a 13C‐labeled straw experiment to demonstrate how soil food web regulated the residing microbes to influence the soil carbon transformation and stabilization process after 11 years of no‐tillage. Our work demonstrated that soil fauna, as a "temporary storage container," indirectly influenced the SOC transformation processes and mediated the SOC sequestration through feeding on soil microbes. Soil biota communities acted as both drivers of and contributors to SOC cycling, with 32.0% of exogenous carbon being stabilizing in the form of microbial necromass as "new" carbon. Additionally, the proportion of mineral‐associated organic carbon and particulate organic carbon showed that the "renewal effect" driven by the soil food web promoted the SOC to be more stable. Our study clearly illustrated that soil food web regulated the turnover of exogenous carbon inputs by and mediated soil carbon sequestration through microbial necromass accumulation. [ABSTRACT FROM AUTHOR]

Multi-factor experiments suggest that interactions among environmental changes commonly influence biodiversity and community composition. However, most field experiments manipulate only single factors. Soil food webs are critical to ecosystem health and may be particularly sensitive to interactions among environmental changes that include soil warming, eutrophication, and altered precipitation. Here, we asked how environmental changes interacted to alter soil nematode communities in a northern Chihuahuan Desert grassland. Factorial manipulations of nitrogen, winter rainfall, and nighttime warming matched predictions for regional environmental change. Warming reduced nematode diversity by 25% and genus-level richness by 32%, but declines dissipated with additional winter rain, suggesting that warming effects occurred via drying. Interactions between precipitation and nitrogen also altered nematode community composition, but only weakly affected total nematode abundance, indicating that most change involved reordering of species abundances. Specifically, under ambient precipitation, nitrogen fertilizer reduced bacterivores by 68% and herbivores by 73%, but did not affect fungivores. In contrast, under winter rain addition, nitrogen fertilization increased bacterivores by 95%, did not affect herbivores, and doubled fungivore abundance. Rain can reduce soil nitrogen availability and increase turnover in the microbial loop, potentially promoting the recovery of nematode populations overwhelmed by nitrogen eutrophication. Nematode communities were not tightly coupled to plant community composition and may instead track microbes, including biocrusts or decomposers. Our results highlight the importance of interactions among environmental change stressors for shaping the composition and function of soil food webs in drylands. [ABSTRACT FROM AUTHOR]

Long-term vegetation cover can affect soil organic carbon content and carbon flow within the soil food web. Nematode trophic structure and soil properties were evaluated in pear rows (intra) maintained without weeds applying herbicide and in the inter-rows (between rows) covered with: Medicago+grasses (MG), fescue or spontaneous vegetation. Soil samples were taken at 0-20 and 20-40 cm depths from 2012 to 2014. Nematode assemblage was different in each inter-row and row, mainly in the topsoil. The inter-rows were reservoirs of omnivores-predators. The MG inter-row promoted the highest accumulation of organic carbon, total N and exchangeable K in the soil. The enrichment index was related to the quantity of dry matter produced by cover crops with the highest index observed in MG. Nematode biomass showed a positive correlation with intra and inter-rows soil organic carbon. Carbon flow through bacterivores prevailed in intra-rows, while bacterivores or herbivores canalized the inter-rows. [ABSTRACT FROM AUTHOR]

We aimed to explore how the invasion of the alien plant Solanum elaeagnifolium affects soil microbial and nematode communities in Mediterranean pines (Pinus brutia) and maquis (Quercus coccifera). In each habitat, we studied soil communities from the undisturbed core of both formations and from their disturbed peripheral areas that were either invaded or not by S. elaeagnifolium. Most studied variables were affected by habitat type, while the effect of S. elaeagnifolium was different in each habitat. Compared to maquis, the soil in pines had higher silt content and lower sand content and higher water content and organic content, supporting a much larger microbial biomass (PLFA) and an abundance of microbivorous nematodes. The invasion of S. elaeagnifolium in pines had a negative effect on organic content and microbial biomass, which was reflected in most bacterivorous and fungivorous nematode genera. Herbivores were not affected. In contrast, in maquis, organic content and microbial biomass responded positively to invasion, raising the few genera of enrichment opportunists and the Enrichment Index. Most microbivores were not affected, while herbivores, mostly Paratylenchus, increased. The plants colonizing the peripheral areas in maquis probably offered a qualitative food source to microbes and root herbivores, which in pines was not sufficient to affect the much larger microbial biomass. [ABSTRACT FROM AUTHOR]

● Matching nitrification inhibitors with soil properties and nitrifiers is vital to achieve a higher NUE. ● Enhancing BNF, DNRA and microbial N immobilization processes via soil amendments can greatly contribute to less chemical N fertilizer input. ● Plant-associated microbiomes are critical for plant nutrient uptake, growth and fitness. ● Coevolutionary trophic relationships among soil biota need to be considered for improving crop NUE. Soil microbiomes drive the biogeochemical cycling of nitrogen and regulate soil N supply and loss, thus, pivotal nitrogen use efficiency (NUE). Meanwhile, there is an increasing awareness that plant associated microbiomes and soil food web interactions is vital for modulating crop productivity and N uptake. The rapid advances in modern omics-based techniques and biotechnologies make it possible to manipulate soil-plant microbiomes for improving NUE and reducing N environmental impacts. This paper summarizes current progress in research on regulating soil microbial N cycle processes for NUE improvement, plant-microbe interactions benefiting plant N uptake, and the importance of soil microbiomes in promoting soil health and crop productivity. We also proposes a potential holistic (rhizosphere-root-phyllosphere) microbe-based approach to improve NUE and reduce dependence on mineral N fertilizer in agroecosystems, toward nature-based solution for nutrient management in intensive cropping systems.

Belowground life relies on plant litter, while its linkage to living roots had long been understudied, and remains unknown in the tropics. Here, we analysed the response of 30 soil animal groups to root trenching and litter removal in rainforest and plantations in Sumatra, and found that roots are similarly important to soil fauna as litter. Trenching effects were stronger in soil than in litter, with an overall decrease in animal abundance in rainforest by 42% and in plantations by 30%. Litter removal little affected animals in soil, but decreased the total abundance by 60% in rainforest and rubber plantations but not in oil palm plantations. Litter and root effects on animal group abundances were explained by body size or vertical distribution. Our study quantifies principle carbon pathways in soil food webs under tropical land use, providing the basis for mechanistic modelling and ecosystem‐friendly management of tropical soils. [ABSTRACT FROM AUTHOR]

Nitrogen (N) fertilization and warming are two crucial global change factors affecting the soil nematode communities. The effects of N fertilization and warming, however, on nematode communities in soils are inconsistent across ecosystems and maybe be even opposite.One key reason is that the commonly used taxonomic diversity is less sensitive to environmental changes than the seldom‐used trait‐based indicators. To verify this, we performed an 8‐year field experiment with four N fertilization levels with and without soil warming and collected an extensive dataset consisting of (i) six traits related to the nematode performance, that is, body size, maximum body length, maximum body width, stylet length, oesophagus length and intestinal length; (ii) the taxonomic alpha (richness and abundance) and beta diversity (Bray–Curtis dissimilarities) of the whole nematode community and each nematode functional group, (iii) soil food web resources (the total taxonomic richness and abundance of plant, bacterial and fungal communities) and (iv) soil properties (pH, total, ammonium and nitrate N, microbial N and C, total and available P and soil water content).We found that N fertilization altered plant diversity and soil nitrate levels, which in turn decreased taxonomic alpha diversity of two nematode functional groups (phytophagous nematodes and predators), but taxonomic diversity for the whole nematode community remained stable. The decreased taxonomic alpha diversity of phytophagous nematodes resulted in increased maximum body width, but decreased stylet length and oesophageal length. Mild warming (~ 0.7°C) had no effects on soil properties and soil food web resources, and the taxonomic diversity or nematode traits remained unchanged.Our results reveal that nematode functional traits show strong responses to N fertilization as individual nematode groups adapted quickly to changed soil properties and food web resources. Taxonomic diversity indices, however, were more stable under these changes showing that the functional composition of nematode communities may respond in the short term despite little effects on species diversity. Thus, the trait‐based indicators not only reveal how nematodes respond to N fertilization, but also how nematodes mediate the effects of N fertilization on ecosystem functioning (i.e. soil nutrient cycling). Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Managing olive mill wastewater (OMW) is a major environmental problem. We followed two methods for OMW bioremediation: one with the white-rot fungus Pleurotus ostreatus alone and one with the fungus plus the microalga Chlorella vulgaris. To evaluate the potential use of both final products as soil amendments, in a pot experiment, we applied treated OMW to soil cultivated with Lactuca sativa, and we studied their short-term effects on the soil nematode community in terms of trophic and functional structure, metabolic footprint, genera composition, and interaction networks. We also applied non-treated OMW and simply water (control). The addition of non-treated OMW significantly reduced the abundance of all nematodes, and the network of interactions was the most fragmented and the least robust against future disturbance. The effect on trophic group abundances was similar but less pronounced when OMW was previously detoxified either by the fungus alone or by its combination with the alga. In the latter case, the phytoparasites were suppressed but the bacterivorous nematodes were not affected. However, the most cohesive and robust nematode network was formed in the soil that received the fungal-treated OMW. None of our OMW applications significantly changed community composition, none improved the already degraded status of the soil food web—which is attributed to the sandy texture of our soil—and none affected the growth of lettuce plants, perhaps because of the short duration of the experiment (30 days). Thus, our future research will aim to estimate the long-term impact of OMW. [ABSTRACT FROM AUTHOR]

The response of soil biotas to climate change has the potential to regulate multiple ecosystem functions. However, it is still challenging to accurately predict how multiple climate change factors will affect multiple ecosystem functions. Here, we assessed the short‐term responses of agroecosystem multifunctionality to a factorial combination of elevated CO2 (+200 ppm) and O3 (+40 ppb) and identified the key soil biotas (i.e., bacteria, fungi, protists, and nematodes) concerning the changes in the multiple ecosystem functions for two rice varieties (Japonica, Nanjing 5055 vs. Wuyujing 3). We provided strong evidence that combined treatment rather than individual treatments of short‐term elevated CO2 and O3 significantly increased the agroecosystem multifunctionality index by 32.3% in the Wuyujing 3 variety, but not in the Nanjing 5055 variety. Soil biotas exhibited an important role in regulating multifunctionality under short‐term elevated CO2 and O3, with soil nematode abundances better explaining the changes in ecosystem multifunctionality than soil biota diversity. Furthermore, the higher trophic groups of nematodes, omnivores‐predators served as the principal predictor of agroecosystem multifunctionality. These results provide unprecedented new evidence that short‐term elevated CO2 and O3 can potentially affect agroecosystem multifunctionality through soil nematode abundances, especially omnivores‐predators. Our study demonstrates that high trophic groups were specifically beneficial for regulating multiple ecosystem functions and highlights the importance of soil nematode communities for the maintenance of agroecosystem functions and health under climate change in the future. [ABSTRACT FROM AUTHOR]

The response of soil biotas to climate change has the potential to regulate multiple ecosystem functions. However, it is still challenging to accurately predict how multiple climate change factors will affect multiple ecosystem functions. Here, we assessed the short‐term responses of agroecosystem multifunctionality to a factorial combination of elevated CO2 (+200 ppm) and O3 (+40 ppb) and identified the key soil biotas (i.e., bacteria, fungi, protists, and nematodes) concerning the changes in the multiple ecosystem functions for two rice varieties (Japonica, Nanjing 5055 vs. Wuyujing 3). We provided strong evidence that combined treatment rather than individual treatments of short‐term elevated CO2 and O3 significantly increased the agroecosystem multifunctionality index by 32.3% in the Wuyujing 3 variety, but not in the Nanjing 5055 variety. Soil biotas exhibited an important role in regulating multifunctionality under short‐term elevated CO2 and O3, with soil nematode abundances better explaining the changes in ecosystem multifunctionality than soil biota diversity. Furthermore, the higher trophic groups of nematodes, omnivores‐predators served as the principal predictor of agroecosystem multifunctionality. These results provide unprecedented new evidence that short‐term elevated CO2 and O3 can potentially affect agroecosystem multifunctionality through soil nematode abundances, especially omnivores‐predators. Our study demonstrates that high trophic groups were specifically beneficial for regulating multiple ecosystem functions and highlights the importance of soil nematode communities for the maintenance of agroecosystem functions and health under climate change in the future. [ABSTRACT FROM AUTHOR]