Soil Food Web Research Articles

Ground beetle trophic interactions alter available nitrogen in forest soil

It is generally held that microbes exert primary control over nitrogen availability in temperate forests. Yet the role of soil and litter‐dwelling invertebrates to provide additional control via the breakdown of organic matter is an area of current exploration. Through trophic interactions within soil food webs, predators may indirectly affect prey with cascading effects on litter breakdown and nitrogen availability. The importance of these interactions, however, may be context‐dependent, varying with the stage of forest development and associated decomposer species composition given that young and old forests have vast differences in nitrogen availability, vegetation litter, soil properties and invertebrate functional groups. We examined ground beetle control over soil nitrogen and soil properties using a 68‐day mesocosm experiment that manipulated trophic structure (omnivore + predator beetles, predator beetles, and no beetles) in a young and old forest stand in the northeastern United States. In the young forest, net nitrogen mineralization decreased under predator + omnivore and the bulk soil C:N ratio in the old forest. However, we found no response in either forest context to the predator only treatment. Our study demonstrates the potential for ground beetles to strongly impact nitrogen availability and soil properties in forest ecosystems. Therefore, animal trophic interactions and their contexts must be included in our paradigm of nutrient cycles in temperate forests.

The Impact of Winter Cover Crops on Soil Nematode Communities and Food Web Stability in Corn and Soybean Cultivation.

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

Impact of Transition from Natural Grasslands Steppe to Monoculture Artificial Grasslands on Soil Food Webs in the Qinghai–Tibet Plateau

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.

Continuous cropping obstacles: Insights from the community composition and the imbalance carbon fluxes within soil nematode food web

Long-term continuouscroppingcan lead to the deterioration of soil environment and the decrease of soil productivity. However, the biological mechanism on the negative effects of long-term continuous cropping has not been extensively explored. Soil nematode food web with multiple trophic levels play critical roles in nutrient cycling and energy flowing in the agroecosystem. Quantifying the carbon flux through different trophic channels within the nematode food web can indicate how continuous cropping influences carbon cycling in the agroecosystem by altering soil biota communities. Therefore, the effects of continuous peanut cropping with different years (1, 5, 20, and 30 years) on soil properties, soil nematode community composition, carbon flux within nematode food web and crop yields were investigated. Results showed that soil pH significantly decreased with increasing continuous cropping years. Differently, soil organic carbon and total nitrogen were the highest in 20-year, and decreased in 30-year of continuous cropping. As continuous cropping years increased, the relative abundance of microbivorous nematodes decreased and that of plant parasites reached as high as 76.11 % and 68.22 % in 20- and 30-year, respectively. Pearson correlation analysis revealed the nematode diversity, the carbon flux uniformity and peanut yield had a significant negative correlation with continuous cropping years. The random forest model indicated that the soil pH and the relative abundance of plant parasites were the key influence factor of the carbon flux uniformity within soil nematode food web. Outbreaks of plant parasites lead to the disruption of carbon flux uniformity within soil nematode food web, which can increase the risk of peanut yield decline after long-term continuous cropping. In conclusion, continuous peanut cropping changed soil properties, reduced soil nematode diversity, and disturbed the multitrophic carbon flux complementarity and uniformity in soil nematode food web, ultimately limiting the crop productivity. This study enhances our understanding of the importance of the resource transfers among soil food web in maintaining sustainable agroecosystem productivity.

Global perspective of ecological risk of plastic pollution on soil microbial communities.

The impacts of plastic pollution on soil ecosystems have emerged as a significant global environmental concern. The progress in understanding how plastic pollution affects soil microbial communities and ecological functions is essential for addressing this issue effectively. A bibliometric analysis was conducted on the literature from the Web of Science Core Collection database to offer valuable insights into the dynamics and trends in this field. To date, the effects of plastic residues on soil enzymatic activities, microbial biomass, respiration rate, community diversity and functions have been examined, whereas the effects of plastic pollution on soil microbes are still controversial. To include a comprehensive examination of the combined effects of plastic residue properties (Type, element composition, size and age), soil properties (soil texture, pH) at environmentally relevant concentrations with various exposure durations under field conditions in future studies is crucial for a holistic understanding of the impact of plastic pollution on soil ecosystems. Risk assessment of plastic pollution, particularly for nanoplasctics, from the perspective of soil food web and ecosystem multifunctioning is also needed. By addressing critical knowledge gaps, scholars can play a pivotal role in developing strategies to mitigate the ecological risks posed by plastic pollution on soil microorganisms.

Elevated O3 has stronger effects than CO2 on soil nematode abundances but jointly inhibits their diversity in paddy soils

Anthropogenic activities have resulted in rising atmospheric concentrations of carbon dioxide (CO2) and ozone (O3), exerting substantial direct and indirect impacts on soil biodiversity within agroecosystems. Despite the considerable attention given to the individual impacts of elevated CO2 and O3 levels, the combined effects on soil nematode communities have not been extensively explored. In this study, we investigated the interactive effects of elevated CO2 (+200 ppm, eCO2) and O3 (+40 ppb, eO3) 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 eO3, whereas eCO2 had no significant impacts. Conversely, both eCO2 and eO3, 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, eCO2 and eO3 influenced nematode community composition and environmental factors, particularly for the WYJ3 cultivar. Both eCO2 and eO3 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 eCO2 and eO3 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 eCO2 and eO3 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.

Changes in Arenosol Nematode Abundance and Trophic Composition as Influenced by Different Faidherbia albida (Delile) A. Chev. Tree Stand Ages in Northern Ethiopia

ABSTRACTFaidherbia 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.

Microbial communities and high trophic level nematodes in protected argan soil show strong suppressive effect against Meloidogyne spp.

In many agroecosystems, soil suppressiveness to root knot nematodes (RKN) is of great interest in defining the biological agents controlling population density, especially with growing concerns about the environmental and human health impacts of chemicals. In this study, we evaluated the suppressiveness to Meloidogyne spp. in two land use soils: a protected argan soil from the Souss Massa National Park (SMNP), Morocco, and a conventional soil from an adjacent non-protected area. Using next-generation sequencing (NGS) technology, we characterized the fungal and bacterial communities in these soils for the first time. Nematodes belonging to different trophic guilds were also analyzed to further understand ecological factors that enable suppressive organisms to function and persist in the soil. The experiment was conducted in a greenhouse with tomato plants grown in untreated and autoclaved soils, each inoculated with 800 Meloidogyne infective juveniles (J2). We found that omnivore-predator nematode abundance, structure, and maturity indices were higher in the protected soil indicating the presence of a well-structured soil food web and a stable ecosystem. After sixty-seven days, RKN population density and gall index were reduced by 79.6 % and 81.5 % in the protected soil, respectively. 50 % autoclaved protected soil was also suppressive, but not 75 % and totally autoclaved soil. In contrast, conventional soil amplified the RKN population by 1319 %. More than 6770 bacterial and 558 fungal taxa were detected in this study, with Firmicutes, Actinobacteria, Mortierellales, Orbiliales, Agaricales, Diversisporales, and Pleosporales being consistently associated with RKN suppression. We found that fungal diversity was higher in SMNP-protected soil. In conclusion, soil protection enhances soil ecosystem resilience and that protected argan soils can serve as a valuable source of biological agents for the sustainable management of phytoparasitic nematodes.

Fate of chlordecone in soil food webs in a banana agroecosystem in Martinique

Large quantities of chlordecone-based insecticides were produced and used throughout the world. One of its most important uses was to control the damage caused by Cosmopolites sordidus in banana-growing regions. In the islands of Martinique and Guadeloupe, 18,000 ha of farmland are potentially contaminated. Despite the key role played by soil macrofauna in agroecosystems, there are currently no data on their contamination. The aim of this study was to explore the fate of chlordecone (CLD) and its transfer to different organisms of the soil food web.Seven species of invertebrates representing different taxonomic groups and trophic levels of the soil communities of Martinique were targeted and collected in six experimental banana fields, with a level of contamination within a range of values classically observed. Soil samples and macrofauna from the study sites were analysed for CLD and chlordecol (CLDOH) its main transformation product. The contamination of the soil fauna were related to δ15N (trophic level), proportion of soil ingestion (diet) and types of epidermis (mucus or exoskeleton) in order to study the different mechanisms of macrofauna contamination.Presence of CLD and CLDOH could be quantified in all the soil organisms from contaminated fields. Results showed a significant relationship between the CLD contamination of detritivorous and the ash content of their faeces, suggesting that soil ingestion was the main contamination pathway. In contrast, the exoskeleton-bearing diplopod Trigoniulus coralinus and the soft-bodied earthworm Eudrilus eugeniae, both detritivores with a comparable diet, had similar contamination levels, suggesting that the type of tegument has little influence on bioaccumulation. At the scale of the entire trophic network, a significant relationship was uncovered between δ15N values and CLD contamination of the fauna, therefore providing some in situ evidence for a bioamplification process along the soil food chain.

Colonization of mudflat substrate by microarthropods: the role of distance, inundation frequency and body size

Salt marshes represent a unique ecosystem at the marine-terrestrial boundary of shallow protected coastlines. Microarthropods form an essential component of soil food webs, but how they colonize new intertidal habitats is little understood. By establishing two experimental systems without animals, we investigated microarthropod colonization (1) at the seashore from the pioneer zone to the lower and upper salt marsh and (2) at the same tidal height on artificial islands 500 m from the seashore. Potential source populations of microarthropods in the respective zones were also investigated. Colonization of microarthropods after 5 years was consistently faster on the seashore than on the artificial islands. Collembola and Mesostigmata colonized all the zones both on the seashore and on the artificial islands, with colonization being faster in the upper salt marsh and in the pioneer zone than in the lower salt marsh. Oribatida colonized the new habitats on the seashore, but only little on the artificial islands. Variations in species composition were more pronounced between salt marsh zones than between experimental systems, indicating that local environmental conditions (i.e., inundation frequency) are more important for the assembly of microarthropod communities than the distance from source populations (i.e., dispersal processes). Variations in community body size of Oribatida and Mesostigmata indicated environmental filtering of traits, with smaller species suffering from frequent inundations. Notably, Mesostigmata most successfully colonized the new habitats across salt marsh zones on both systems. Overall, the results document major mechanisms of colonization of intertidal habitats by microarthropods with different life histories and feeding strategies.

Resource omnivory in soil food webs and meta-ecosystem connections

Soil food webs were long considered an ecosystem sink for primary production and a black box of reticulated interactions. Quantification of multiple and changing interactions among consumers and resources within and beyond soil food webs stands up as a major challenge. In this mini-review/opinion paper, I present development of ideas on soil food-web structure focusing on resource omnivory – a central characteristic that is linked to food-web structure and stability. There is plenty of empirical evidence for trophic differentiation among soil invertebrates along different food-web dimensions (food resources, trophic levels, microhabitats, time). This comes along with the pervasive idea of widespread omnivory in soil food webs. I argue that we need to quantitatively assess multiple-resource feeding by soil consumers and related drivers across various taxa and different ecosystem types to come closer to predictions of soil food-web structure and dynamics. At the meta-ecosystem level, cross-ecosystem omnivory (i.e. feeding across energy fluxes from different ecosystems) plays an important role in connecting soil with aboveground and aquatic food webs. Aboveground-belowground studies have been focusing on the interfaces such as the rhizosphere and litter surface. Broader cascading impacts of the energy and organismic fluxes across these interfaces within the recipient ecosystem are, however, less understood. Of particular interest here are connections of vertebrate communities to soil food webs and the central role of soil-borne insects in cross-ecosystem energy exchange. Interactions between soil and aquatic food webs span for dozens to hundreds of meters from the terrestrial-aquatic interface, transferring significant amount of energy and matter between these ecosystems. Consequent changes of the structure and functioning in the recipient ecosystem requires more attention, especially how biodiversity-ecosystem functioning relationships manifest across ecosystems. Continuously developing methods, such as compound-specific isotopic analyses, can facilitate quantification of cross-ecosystem omnivory, helping to understand effects of food-web changes across the ecosystem borders. Overall, I present soil food webs as an open and dynamic pool with multiple cross-ecosystem connections and call for quantitative studies in this direction.

Linking soil health and carbon dynamics to conservation measures: Evidence from nematode communities in Souss-Massa National Park, Morocco

Global environmental policies have effectively designated 17 % of the Earth's surface as protected areas and implemented robust measures to address climate change. However, the importance of soils as critical reservoirs of biodiversity and carbon is often overlooked in global policy making. In the present study, we used nematodes as indicators to assess the impact of conservation strategies on soil food web connectance. We explored nematode metabolic footprints and their carbon budget, and evaluated soil health by identifying factors that influence nematode functional diversity. We collected 180 soil samples from three zones in the Souss Massa National Park in Morocco: transitional zone (organic cropping and grazing activities), buffer zone (grazing activity), core zone (strictly protected area), and a nearby intensively farmed non-protected area. We noted a consistent decline in diversity within all trophic groups from the core zone (56 taxa) to the non-protected zone (18 taxa). A notable increase in total nematode abundance and herbivore diversity was observed in the organic soils of the transitional zone. In contrast, nematode abundance and diversity were lower in non-protected zones. Meloidogyne, a sedentary endoparasite, was prevalent in conventional crops outside the park but was not reported within the park. Nitrogen, phosphorus, and potassium were the major soil parameters affecting nematode food webs. The functional metabolic footprints of nematodes were enhanced by nature conservation, highlighting the crucial role of nematodes in generating carbon influxes in protected areas. Our results show that 3.11× 1012 nematodes (with a total biomass of 330.47 tonnes) inhabit surface soils across the park, which is 14.38 times greater than the same area in the non-protected zone. Daily production and storage of biomass and carbon budget were 43.85 and 48.93 % higher in the park top soils than in the non-protected zone, respectively. This knowledge is significant for decision makers when formulating nature conservation programs, planning sustainable land use strategies, and addressing the challenges of rising CO2 emissions.

The effect of substrate concentration on the methane-driven interaction network

Methane, the primary substrate for aerobic methanotrophs, regulates the rate of methanotrophic activity and shapes the composition of the methane-oxidizing community. Given that methane-derived carbon may fuel the food web in the soil, methane availability can potentially be a key determinant, structuring the network of the interacting methane-oxidizing community. Here, we determined the response of the methane-driven interaction network to different methane concentrations (∼1.5 %v/v, 3 %v/v, and 7 %v/v), indicative of different levels of energy flow through the soil food web, using a stable isotope probing approach with 13C-methane coupled to a co-occurrence network analysis in a microcosm study. The accumulated 13C-atom fraction in the total carbon content increased from 1.08 % (background level) to an average of 7.2 % in the incubation under 7 %v/v methane, indicating that the carbon-flow via the methanotrophs can significantly contribute to the total carbon in the rice paddy soil. The 13C-enriched 16 S rRNA gene sequencing analysis revealed the predominance of gammaproteobacterial methanotrophs and Methylocystis. The composition of the actively growing (13C-labelled) bacterial community was dissimilar in the incubation under ∼3 %v/v than under 1.5 %v/v and 7 %v/v methane. This was also reflected in the co-occurrence network analysis, where the topological properties indicated a more complex and connected network in the incubation under 3 %v/v methane. It thus appears that moderate methane concentrations fostered closer associations among members of the methane-oxidizing community. Overall, our research findings showed that the methanotrophs can contribute to the total soil carbon, and methane concentrations not only shifted the bacterial community, including the methanotrophic composition, but also affected bacterial interactions.

Molecular characters of free-living nematode Panagrolaimus (Nematoda: Rhabditida) using 28S rDNA from South Africa

Bacterivorous nematodes are a type of nematodes that live in the soil. Free-living bacterivores are crucial for the soil food web, biological control, and ecological studies. Within the free-living bacterivorous nematodes, Panagrolaimus is a species that feeds on pathogenic bacteria, making it important in the transmission of plant-pathogenic bacteria. Additionally, Panagrolaimus plays a role in the nitrification of minerals in the soil. In 2023, a molecular study was conducted at the University of Limpopo to identify bacterivorous nematodes in South Africa's soils using the 28S rDNA marker. The nematode was extracted using the tray method, and its DNA was extracted using the Chelex method. It was then identified as Panagrolaimus. To further identify the nematode, 18S rDNA was amplified using specific primers. The Nblast analysis based on the small subunit ribosomal DNA showed that South African Panagrolaimus has a 95% similarity (EU543176) with the Belgian population. Based on a phylogenetic analysis using maximum likelihood, this species has been placed within the same clade as other species identified as Panagrolaimus, with highly supported (100) bootstrap values. Therefore, this species has been properly identified using 18S rDNA. However, to gain a better understanding of the phylogeny of Panagrolaimus, it is recommended to use other DNA markers as well.

Plasticine models confirm high predator pressure on surfaced earthworms in different ecosystems

Aboveground communities may strongly depend on the detrital subsidy, i.e. the release of energy and nutrients from the soil food webs. Earthworms predated by aboveground animals are seemingly among the most important links connecting belowground and aboveground food webs. Here, we conducted an experiment with plasticine models in alpine tundra, temperate, and monsoon tropical forests to estimate predator pressure on surfaced earthworms compared to aboveground prey (caterpillars). Earthworm models on the ground were attacked several times more often than caterpillar models on the plants. The attack rate was highest in the tropical forest; the most common types of attacks on earthworms were arthropod bites in both forests and mammal bites in tundra.

Benefit and risk: Keystone biomes in maize rhizosphere associated with crop yield under different fertilizations

The highly diverse beneficial and deleterious microbes in the rhizosphere influence plant growth and crop production in agricultural ecosystems. However, our understanding of the relationships between beneficial and risky phylotypes in the rhizosphere, and plant growth, in addition to their potentially varied response to different fertilization treatments in black soils, remains poor. Here, we investigated variations in multitrophic (e.g., bacteria, fungi, invertebrates, and protists) community composition and diversity under different five-year fertilization treatments, and identified the potential beneficial and potential risky keystone multitrophic biota in maize rhizosphere and bulk soils based on ecological networks and soil food web structure. Bacteria and protist community compositions exhibited greater variations under different fertilization regimes when compared with those of fungi and invertebrates. In addition, two keystone phylotype groups associated with crop yield and soil function were detected, and the potential beneficial keystone phylotypes exhibited higher relative abundances in C-fixation, N-fixation, and P-mineralization genes; conversely, the potential risky keystone phylotypes were associated with denitrification and nitrate reduction genes, and included more potential fungal pathogens. Furthermore, structural equation modeling results indicated that organic amendments, particularly cow manure, could improve crop yield by enriching beneficial keystone phylotypes and suppressing risky keystone phylotypes. Altogether, the results of the present study highlight the critical roles of rhizosphere biota in food production, and identify keystone phylotypes that are beneficial or harmful to crop production and soil function, which could facilitate the conservation of beneficial biota and the early detection of potential pathogens, as well as the exploitation of beneficial biota to increase crop yield.

Integrating viruses into soil food web biogeochemistry.

The soil microbiome is recognized as an essential component of healthy soils. Viruses are also diverse and abundant in soils, but their roles in soil systems remain unclear. Here we argue for the consideration of viruses in soil microbial food webs and describe the impact of viruses on soil biogeochemistry. The soil food web is an intricate series of trophic levels that span from autotrophic microorganisms to plants and animals. Each soil system encompasses contrasting and dynamic physicochemical conditions, with labyrinthine habitats composed of particles. Conditions are prone to shifts in space and time, and this variability can obstruct or facilitate interactions of microorganisms and viruses. Because viruses can infect all domains of life, they must be considered as key regulators of soil food web dynamics and biogeochemical cycling. We highlight future research avenues that will enable a more robust understanding of the roles of viruses in soil function and health.

Response of soil nematode community structure and metabolic footprint to nitrogen addition in alfalfa fields on the Loess Plateau

Nematodes serve as key indicators of soil health in ecological studies. Therefore, the current study examined the community structure and metabolic footprint of soil nematodes in alfalfa fields across varying levels of N supply in the semi-arid Loess Plateau. The findings offer theoretical guidance for the sustainable management of artificial alfalfa grasslands in this region. The research was based on alfalfa fields with different N application rates (0, 50, 100, 150 kg/ha2) as the research object, The shallow plate method was used to separate and extract soil nematodes, identify soil nematode groups, calculate ecological function index and metabolic footprint, and identify indicator species. A total of 6346 nematodes were isolated in this study, belonging to 27 genera and 19 families. Notably, the plant parasitic nematode Helicotylenchus was predominant. As N addition increased, the plant parasitic index (PPI) increased significantly. A N50 application significantly enhanced the soil nematode diversity index (H\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{H}$$\\end{document}) and the free-living index (MI). The findings showcased a noticeable decrease in disturbance within the N50 soil nematode community. This resulted in a mature and stable community structure primarily attributed to the heightened abundance of omnivorous/predatory nematodes. Across various N levels, soil nematode communities underwent significant alterations in the soil food web structure through shifts in their metabolic footprint. Future strategies should focus on refining N management practices and integrating sustainable approaches like crop rotation and pest management. These efforts will contribute to guidelines ensuring artificial alfalfa grasslands lasting health and productivity.

Impacts of sand and dust storms on food production

Abstract Sand and dust storms (SDS) are common in the world’s drylands, regions that are also critically important for global food production. Agriculture is the most prevalent land use resulting in anthropogenic SDS sources, resulting in impacts on cropland and rangeland, but food production is also affected by impacts from natural SDS sources. This review assesses our knowledge of SDS impacts on all the major types of food production in terrestrial and oceanic environments, impacts that occur in all three phases of the wind erosion system: during particle entrainment, during transport, and on deposition. These effects are short term and long term, direct and indirect. Wind erosion is a major cause of land degradation and there is good evidence to indicate that the deleterious effects of SDS can reduce food production via substantially diminished yields of crops, pastures and livestock. However, it is also clear that soil dust plays an important role in major biogeochemical cycles—especially phosphorus, nitrogen and iron—with implications for the valuable environmental services provided by numerous ecosystems, both terrestrial and marine. Ultimately, these nutrients have particular significance for soil formation, ecosystem productivity and food webs on land and at sea, and hence the provision of food for human societies. Efforts to mitigate the negative impacts of SDS on the sustainability of agriculture should be balanced with an appreciation of the significance of soil dust to the Earth system.

Incorporation of the 15N-labeled simulated arthropod rain in the soil food web.

Direct trophic links between aboveground and belowground animal communities are rarely considered in food web models. Most invertebrate animals inhabiting aboveground space eventually become prey of soil predators and scavengers forming a gravity-driven spatial subsidy to detrital food webs, but its importance remains unquantified. We used laboratory-grown 15N-labeled Collembola to trace the incorporation of arthropod rain into soil food webs. Live or euthanized Collembola were supplemented once to field mesocosms in the amount equivalent to the mean daily input of the arthropod rain (19mg d.w. m-2). After the addition of live Collembola, the isotopic label was found most often in predatory Trombidiformes (83% of samples) and Mesostigmata mites (85%), followed by Araneae (58%), Chilopoda (45%), and Coleoptera (29%). Among non-predatory groups, the isotopic label was recorded in Thysanoptera (27%), Collembola (24%), and Oribatida (18%). The 15N-label was also detected in Symphyla, Formicidae, Diplura, Diplopoda, Opiliones, Diptera, Hemiptera, Oligochaeta, and Nematoda. There was a positive correlation between natural 15N abundance and the frequency of the isotopic label among predators, but not among decomposers. In the non-replicated treatment, in which dead collembolans were added, the label was found in predators and decomposers in approximately equal proportions (21-25%). Unlike other forms of the aboveground subsidy (such as leaflitter, frass, or honeydew) that are primarily processed by microorganisms, arthropod rain is assimilated directly by the animals. The high frequency of consumption of the aboveground subsidy suggests that it plays a significant role in maintaining the abundance of soil predators.