Soil Community Research Articles

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.

Effects of Vegetable Planting Ages on Community Structure of Ammonia-oxidizing Archaea and Ammonia-oxidizing Bacteria in Greenhouse Vegetable Fields

The ammonia oxidation process driven by microorganisms is a dominant source for nitrous oxide （N2O） emissions. Here, we examined the influence of greenhouse vegetable planting ages on soil ammonia-oxidizing archaea （AOA） and ammonia-oxidizing bacteria （AOB）, which is of great significance for assessing the soil quality status and greenhouse gas transformations. A field study was conducted at different times （1, 5, 10, and 20 a） in greenhouse vegetable soils of Gaoyi, Hebei Province. Chemical analysis and Illumina NovaSeq high-throughput sequencing were used to analyze the soil physicochemical properties and community structures and diversity of AOA and AOB. The variation in AOA and AOB communities and the driving factors in greenhouse soils at different ages were also investigated. The results showed that the contents of total nitrogen, organic matter, alkali-hydrolyzable nitrogen, available phosphorus, and available potassium first increased and then decreased with the prolongation of growth. The contents of nitrate nitrogen, ammonium nitrogen, and electrical conductivity first decreased and then increased with the prolongation of growth. The pH value of soils decreased with the prolongation of growth. The abundance and diversity index of AOA and AOB first decreased and then increased with the prolongation of growth. Nitrososphaeria, unclassified Thaumarchaeota, and Candidatus Nitrosocaldus were the dominant species of AOA, while Betaproteobacteria and Nitrosospira were the dominant species of AOB. The composition of the soil AOA community varied greatly compared to that of AOB with the prolongation of growth. Correlation analysis showed that the changes in soil nutrient factors had a significant correlation with AOA and AOB communities. Redundancy analysis indicated that ammonium nitrogen, alkali-hydrolyzable nitrogen, and nitrate nitrogen were key factors of AOA communities, while electrical conductivity, available potassium, and nitrate nitrogen were key factors for AOB. In summary, long-term planting of greenhouse vegetables significantly affected the abundance and composition of soil AOA and AOB communities. Our results provide a theoretical basis for further studies on the greenhouse gas transformation and microbial mechanisms of the nitrogen cycle in greenhouse soils.

EcoFAB 3.0: a sterile system for studying sorghum that replicates previous field and greenhouse observations.

Studying plant-microbe interactions is one of the key elements in understanding the path to sustainable agricultural practices. These interactions play a crucial role in ensuring survival of healthy plants, soil and microbial communities. Many platforms have been developed over the years to isolate these highly complex interactions however, these are designed for small model plants. This creates a need for complementary devices for larger plants, such as sorghum. This work introduces a novel platform, EcoFAB 3.0, which is designed to enable studying bioenergy plants such as sorghum for up to 4 weeks in a controlled sterile environment. Several other advantages of this platform such as dark root chambers and user-friendly assembly are also discussed in this work. EcoFAB 3.0 was found to replicate previous greenhouse and field observations when comparing an engineered sorghum line overproducing 4-hydroxybenzoic acid (4-HBA) and wildtype (variety BTx430). Consistent with greenhouse and field observations, it was found that the engineered line of sorghum grown in EcoFAB 3.0 had a higher 4-HBA content and a lower dry biomass.

Wild pigs influence tropical forest soil microbial communities in a forest-agriculture mosaic landscape

Edge effects, the altered abiotic and biotic conditions on the borders of natural areas, have rarely been linked to altered soil biota, which shape ecosystem processes including carbon storage, biogeochemical cycling, and plant performance. Here, we investigated if increased wildlife populations (their increase mediated by foraging in nearby oil palm plantations) affect soil biota when they move between plantations and natural habitats. We used a 22-year fenced exclusion experiment in a primary rain forest in Peninsular Malaysia. We found that the presence of wildlife (mainly native pigs; Sus scrofa) was associated with greater bacterial diversity, an altered bacterial community composition, and indications of a reduced abundance of symbiotic ectomycorrhizal fungi. There were only minor effects of pigs on soil chemistry or microclimate, so we suggest that changes in soil communities are driven by pigs’ leaf litter removal and alterations to plant composition. Our study highlights that indirect effects from agriculture can be induced by wildlife more than1 km into protected areas and this could have important repercussions for ecosystem processes and plant-soil feedbacks.

Community structure, diversity and function of endophytic and soil microorganisms in boreal forest.

Despite extensive studies on soil microbial community structure and functions, the significance of plant-associated microorganisms, especially endophytes, has been overlooked. To comprehensively anticipate future changes in forest ecosystem function under future climate change scenarios, it is imperative to gain a thorough understanding of the community structure, diversity, and function of both plant-associated microorganisms and soil microorganisms. In our study, we aimed to elucidate the structure, diversity, and function of leaf endophytes, root endophytes, rhizosphere, and soil microbial communities in boreal forest. The microbial structure and composition were determined by high-throughput sequencing. FAPROTAX and FUNGuild were used to analyze the microbial functional groups. Our findings revealed significant differences in the community structure and diversity of fungi and bacteria across leaves, roots, rhizosphere, and soil. Notably, we observed that the endophytic fungal or bacterial communities associated with plants comprised many species distinct from those found in the soil microbial communities, challenging the assumption that most of endophytic fungal or bacterial species in plants originate from the soil. Furthermore, our results indicated noteworthy differences in the composition functional groups of bacteria or fungi in leaf endophytes, root endophytes, rhizosphere, and soil, suggesting distinct roles played by microbial communities in plants and soil. These findings underscore the importance of recognizing the diverse functions performed by microbial communities in both plant and soil environments. In conclusion, our study emphasizes the necessity of a comprehensive understanding of the structure and function microbial communities in both plants and soil for assessing the functions of boreal forest ecosystems.

Assembly and co-occurrence pattern of microbial communities in bulk and rhizosphere soils of Pinus elliottii plantations on sandy lands in China

Assembly and co-occurrence pattern of microbial communities in bulk and rhizosphere soils of Pinus elliottii plantations on sandy lands in China

Positive plant diversity effects on soil detritivore feeding activity and stability increase with ecosystem age

Increasing species diversity frequently enhances ecosystem functioning - a pattern strengthened with ecosystem age. It has been suggested that strengthened responses over time may be due to community assembly processes and cumulative effects over the history of interactions between and among plant and soil communities. However, most soil studies are conducted with destructive one-time samplings, and little is known about how phenological patterns of soil activity change with biodiversity and ecosystem age. Here, we investigate phenology metrics related to soil detritivore feeding activity (i.e., duration, total magnitude, variability), measured via the bait-lamina method, in a long-term grassland biodiversity experiment that included an experimental removal of plant and soil history, resulting in older and younger assembled plant and soil communities. Detritivore feeding activity peaked in spring and/or early summer, with another short increase in fall. Increased plant species richness enhanced the total magnitude and variability (i.e., the coefficient of variation) of detritivore feeding activity. Plant and soil history enhanced the buffering effects of plant richness on variability, causing older plant and soil communities to have the strongest relationships between plant richness and stability. However, older plant and soil communities showed the shortest duration of detritivore feeding activity, and species richness was not important in changing activity duration. These findings underscore the importance of considering ecosystem age as a critical component that modifies plant diversity effects on ecosystem functioning, with important implications for promoting ecosystem stability and resilience under environmental change.

Forest types matter for the community and co-occurrence network patterns of soil bacteria, fungi, and nematodes.

Tree growth influences the biological, physical, and chemical properties of the soil through the input of different types of litter and various root exudates. However, our understanding of tree-mediated effects on the composition and diversity of soil biota remains limited. This study aimed to determine the effects of physically neighboring forest types (i.e., an artificial Japanese cedar (Cryptomeria japonica) plantation vs. a broadleaf (Quercus serrata) secondary forest) on individual bacterial, fungal, and nematode communities and the associations among these inter-kingdoms. Bacterial, fungal, and nematode aggregates were estimated using MiSeq high-throughput sequencing system. The amplicon sequence variant richness of fungi and nematodes was significantly greater in the cedar plantation than in the broadleaf forest, and the three soil biota community structures were significantly clustered among the forest types. Environmental factors such as soil pH, C, N, and C/N ratio significantly influenced the three soil biota community structures. The bacterial–fungal–nematode co-occurrence network of the broadleaf forest had more nodes and edges than that of the cedar plantation. Moreover, Ascomycota and Basidiomycota fungi mainly co-occurred with fungivorous nematodes in the cedar and broadleaf forests, respectively. Our results suggested that unique soil biota communities and characteristic co-occurrence network patterns were established among the tripartite inter-kingdom relationships between adjacent forest types.

Increased soil bacteria-fungus interactions promote soil nutrient availability, plant growth, and coexistence

Tree species and interkingdom relationships in the belowground metacommunity are key factors in determining soil microbial diversity and community composition. However, how bacterial-fungal interactions mediate soil nutrient and plant growth remains largely unexplored in the coniferous forests. Here, we selected three types of naturally growing coniferous forests on the Loess Plateau—pure stands of Platycladus orientalis, mixed stands of Platycladus orientalis and Pinus tabuliformis, and pure stands of Pinus tabuliformis—to compare the differences in soil properties, microbial diversity and community composition, soil enzymatic activity, and plant growth conditions across these stand types. We found that tree species mixing significantly alters soil microbial community diversity and composition, increasing the positive associations between bacteria and fungi. Compared to pure stands, mixed stands exhibit significantly higher bacterial diversity, whereas fungal diversity shows no significant difference. Additionally, available soil nutrients (ammonium nitrogen and available phosphorus) are significantly increased in mixed stands, along with their associated soil enzymatic activities. The partial least squares path model suggests that higher bacterial diversity enhances bacterial-fungal positive interactions, increasing the relative abundance of ectomycorrhizal fungi and the decomposition rate of organic matter in mixed stands, thereby boosting soil nutrient availability and plant growth. These results highlight the importance of positive bacterial-fungal associations for soil nutrient availability and plant growth, deepen the understanding of the role of soil microbial interactions in mediating plant species coexistence. Most importantly, our results implied a stable coexistence of the pioneer P. orientalis and the late successional species P. tabuliformis in the Loess Plateau region and provided a microbiological interpretation.

Modulation of fungal phosphate homeostasis by the plant hormone strigolactone

Inter-kingdom communication through small molecules is essential to the coexistence of organisms in an ecosystem. In soil communities, the plant root is a nexus of interactions for a remarkable number of fungi and is a source of small-molecule plant hormones that shape fungal compositions. Although hormone signaling pathways are established in plants, how fungi perceive and respond to molecules is unclear because many plant-associated fungi are recalcitrant to experimentation. Here, we develop an approach using the model fungus, Saccharomyces cerevisiae, to elucidate mechanisms of fungal response to plant hormones. Two plant hormones, strigolactone and methyl jasmonate, produce unique transcript profiles in yeast, affecting phosphate and sugar metabolism, respectively. Genetic analysis in combination with structural studies suggests that SLs require the high-affinity transporter Pho84 to modulate phosphate homeostasis. The ability to study small-molecule plant hormones in a tractable genetic system should have utility in understanding fungal-plant interactions.

A Dirt(y) World in a Changing Climate: Importance of Heat Stress in the Risk Assessment of Pesticides for Soil Arthropods.

The rise in global temperatures and increasing severity of heat waves pose significant threats to soil organisms, disrupting ecological balances in soil communities. Additionally, the implications of environmental pollution are exacerbated in a warmer world, as changes in temperature affect the uptake, transformation and elimination of toxicants, thereby increasing the vulnerability of organisms. Nevertheless, our understanding of such processes remains largely unexplored. The present study examines the impact of high temperatures on the uptake and effects of the fungicide fluazinam on the springtail Folsomia candida (Collembola, Isotomidae). Conducted under non-optimum but realistic high temperatures, the experiments revealed that increased temperature hampered detoxification processes in F. candida, enhancing the toxic effects of fluazinam. High temperatures and the fungicide exerted synergistic interactions, reducing F. candida's reproduction and increasing adult mortality beyond what would be predicted by simple addition of the heat and chemical effects. These findings highlight the need to reevaluate the current ecological risk assessment and the regulatory framework in response to climate changes. This research enhances our understanding of how global warming affects the toxicokinetics and toxicodynamics (TK-TD) of chemicals in terrestrial invertebrates. In conclusion, our results suggest that adjustments to regulatory threshold values are necessary to address the impact of a changing climate.

Host genotype and age shape the microbial community in the rhizosphere soils of Camellia forests.

Microbiota living in the rhizosphere influences plant growth and fitness, from the opposite perspective; whether host genotypes control its root microbiota is of great interest to forest breeders and microbiologists. To improve low-yield plantations and promote sustainable management of Camellia oleifera, high-throughput sequencing was used to study the chemical properties and microbiome in rhizosphere soil of Camellia forests under three genotypes (common C. oleifera, local C. gauchowensis, and C. chekiangoleosa) and three growth stages (sapling stage at 4-year-old, primary fruit stage at 7-year-old, and full fruiting stage at 11-year-old). The results showed that the rhizosphere soil organic matter (OM), nutrient concentrations, diversity, and community composition of the microbiome were significantly varied among different Camellia genotypes. The relative abundance of symbiotic and pathotrophic fungi in the rhizosphere soil of C. chekiangoleosa was significantly higher than that of C. gauchowensis. Concentrations of OM, available phosphorus (AP), and bacterial alpha diversity increased with tree age. Fungi of Saitozyma, Mortierella, and Glomeromycota and bacteria of Burkholderia-Caballeronia-Paraburkholderia and Vicinamibacterales had potential for fertilizer development for Camellia plantation. Camellia genotypes and growth stages were significantly correlated with the rhizosphere soil pH, OM, and available potassium (AK). Soil pH and OM were key factors that affected the microbiome in the Camellia rhizosphere soils. In conclusion, tree genotypes and growth stages shaped microbial communities in Camellia rhizosphere soils, and some plant growth-promoting rhizobacteria were identified as preliminary candidates for improving Camellia plantation growth.

Effects of volcanic environment on Setaria viridis rhizospheric soil microbial keystone taxa and ecosystem multifunctionality

Keystone taxa are significant within ecosystem multifunctionality, as certain species fulfil essential functions such as recycling soil nutrients, promoting plant growth, influencing biogeochemical processes, and contributing to human health maintenance. However, there are still gaps regarding the relationship between microbial communities in volcanic rhizospheric soil and ecosystem multifunctionality. As a result, in this research, we employed Illumina MiSeq high-throughput sequencing to analyse the microbial community composition of rhizospheric soil from volcanic S. viridis. Compared with non-volcanic areas, volcanic soils have higher fungal alpha diversity and the absolute abundance of bacteria (16S gene copies) showed significant variation between the two successions (P < 0.0001). The network analysis further demonstrated that the microbial diversity in non-volcanic regions surpassed that of the volcanic area. The volcanic fungi network has more nodes and edges, is more complex than non-volcanic areas (Nodes: 425 vs. 770; Edges: 21844 vs. 74532), and more rhizosphere growth-promoting bacteria are enriched. Regression analysis and correlation networks showed that fungal communities were more closely associated with ecosystem multifunctionality than bacteria. This study lays the groundwork for examining the microbial keystone taxa in the rhizosphere of volcanic plants and offers valuable insights into the multifaceted functions of plant rhizospheric soil ecosystems.

Development of root rot in Zanthoxylum bungeanum is closely linked to changes in soil microbial communities, enzyme activities, and physicochemical factors

Due to the emergence of root rot (RR), it can cause harm to the health of Zanthoxylum bungeanum (Z. bungeanum) plants. However, the reason for this is not clear, and further research is needed. We selected healthy and RR-affected 6-year-old Z. bungeanum trees (infected for 1 year), collected their rhizosphere and bulk soils, and analyzed soil microbial communities, enzyme activities, and physicochemical properties. When the plants were diseased, soil water content (SWC), available potassium (AK), organic matter (OM) contents, β-1,4-glucosidase (β-G) activity, and fungal Shannon index significantly decreased, while bacterial Shannon index significantly increased in the rhizosphere soil. Soil total nitrogen (TN), SWC, AK, OM contents, and β-G and N-acetyl-glucosamine (NAG) activity significantly reduced, while fungal Simpson index significantly increased in the bulk soil. There were significant differences in the bacterial communities of bulk and rhizosphere soil. However, there were no obvious differences in the fungal communities. Pearson's correlation analysis showed that changes in soil microbial communities were significantly correlated with changes in the contents of TN, AK, OM, and SWC, as well as the activities of β-G and NAG. In summary, changes in soil AK, OM, SWC, and TN resulted in changes in microbial community composition, as well as changes in β-G and NAG activities, and these alterations may lead to RR in Z. bungeanum.

Microbial production of methyl-uranium via the Wood-Ljungdahl pathway

The misuse of uranium is a major threat to human health and the environment. In microbial ecosystems, microbes deploy various strategies to cope with uranium-induced stress. However, the exact ecological strategies and mechanisms underlying uranium tolerance in microbes remain unclear. Therefore, this study aimed to investigate the survival strategies and tolerance mechanisms of microbial communities in uranium-contaminated soil and groundwater. Microbial co-occurrence networks and molecular biology techniques were used to analyze the properties of microbes in groundwater and soil samples from various depths of uranium-contaminated areas in Northwest China. Uranium pollution altered microbial ecological strategies. Uranium stress facilitated the formation of microbial community structures, leading to symbiosis. Furthermore, microbes primarily resisted uranium hazards by producing polysaccharides and phosphate groups that chelate uranium, releasing phosphate substances that precipitate uranium, and reducing U(VI) through sulfate- and iron-reducing processes. The relative abundance of metal-methylation genes in soil microorganisms positively correlated with uranium concentration, indicating that soil microorganisms can produce methyl uranium via the Wood-Ljungdahl pathway. Furthermore, soil and groundwater microorganisms demonstrated different responses to uranium stress. This study provides new insights into microbial responses to uranium stress and novel approaches for the bioremediation of uranium-contaminated sites.

The Marine-Origin Exopolysaccharide-Producing Bacteria Micrococcus Antarcticus HZ Inhibits Pb Uptake in Pakchoi (Brassica chinensis L.) and Affects Rhizosphere Microbial Communities.

Exopolysaccharides (EPSs) produced by microorganisms play an important role in biotolerance and reducing heavy metal (HM) contamination by limiting the migration of HMs into plants. However, research on the application of EPS-producing marine bacteria for soil heavy metal remediation remains limited, particularly regarding their mechanisms of HM immobilization in soil and impact on plant growth. In this study, the EPS-producing marine bacterium Micrococcus antarcticus HZ was investigated for its ability to immobilize Pb and produce EPSs in soil filtrate. The effects on the growth quality and biomass of pakchoi (Brassica chinensis L.), as well as bacterial communities in inter-root soil contaminated with Pb, were also investigated. The results indicated that HZ could reduce the Pb concentration in the soil filtrate, achieving a removal rate of 43.25-63.5%. The EPS content and pH levels increased in the presence of Pb. Pot experiments showed that adding HZ significantly increased the biomass of pakchoi (9.45-14.69%), vitamin C (Vc) (9.69-12.92%), and soluble protein content (22.58-49.7%). HZ reduced the Pb content in the roots (17.52-47.48%) and leaves (edible tissues) (43.82-52.83%) of pakchoi. HZ increased soil enzyme activities (alkaline phosphatase, dehydrogenase, and urease), and the contents of ammonium nitrogen and nitrate nitrogen. Additionally, HZ also increased the relative abundance of beneficial bacteria (e.g., Proteobacteria, Cyanobacteria, and Chlorobacteria) in the inter-root soil, which have prophylactic and heavy-metal fixation functions. In summary, HZ reduces effective Pb content in edible tissues, roots, and inter-root soil by regulating inter-root soil microbial community structure, increasing soil pH, nitrogen content, and soil enzyme activity, and altering dominant phylum abundance.

Genetic resistance to Fusarium wilt shapes rhizospheric beneficial microbiota in four banana cultivars

This study explores the dynamics of bacterial communities in the bulk soil, rhizosphere, and endosphere of banana plants, focusing on variations among cultivars with differing levels of genetic resistance to Fusarium wilt. We examined four banana cultivars: one resistant (P), one moderately susceptible (PT), and two susceptible (W and M). Using 16S rDNA sequencing, we analyzed the bacterial community structures in these habitats. The results showed significant differences in bacterial communities across the three habitats and among the cultivars, with the endosphere communities being the most distinct. The rhizosphere and bulk soil communities were more similar, likely due to the soil microbiome's influence on the rhizosphere. Resistant cultivars (PT and P) displayed unique bacterial communities, with notable taxa such as Burkholderia, Leifsonia, and Marmoricola in the rhizosphere, known for their antagonistic properties against Fusarium oxysporum. In contrast, susceptible cultivars (W and M) harbored different dominant genera, such as Reyranella and Mucilaginibacter, which did not play significant defensive roles against Fusarium wilt. Additionally, the endosphere of resistant cultivars featured beneficial genera like Amycolatopsis and Achromobacter, known for promoting plant growth and enhancing disease resistance. The findings underscore the importance of plant genotype in shaping the rhizosphere microbiome, with specific microbial taxa linked to resistance against Fusarium. These insights point to the potential for developing targeted microbial-based strategies to enhance disease resistance and overall plant health. The study identifies key microbial players that could be harnessed for biological control and improved management of Fusarium wilt in banana cultivation. This research advances our understanding of plant-microbe interactions and their implications for sustainable agriculture, particularly in combating soilborne pathogens.

Effects of Trichoderma harzianum Fertilizer on Growth and Rhizosphere Microbial Community of Continuous Cropping Lagenaria siceraria

This study analyzed the effects of Trichoderma harzianum fertilizer on the growth of continuous cropping Lagenaria siceraria and the physical and chemical properties of rhizosphere soil and microbial community structure, using Illumina Miseq (PE300) high-throughput sequencing technology along with physiological and biochemical detection. The results indicated that after applying T. harzianum fertilizer, the growth of L. siceraria was significantly promoted, with increases in plant height, fresh weight, and dry weight of 21.42%, 24.5%, and 4.5%, respectively. The pH of the rhizosphere soil decreased from 7.78 to 7.51, while the electrical conductivity (EC), the available phosphorus (AP), the available potassium (AK), and the total nitrogen (TN) were markedly higher compared to the CC group and increased by 13.95%, 22.54%, 21.37%, and 16.41%, respectively. The activities of catalase and sucrase in the rhizosphere increased by 18.33% and 61.47%, and the content of Soil Organic Carbon (SOC) elevated by 27.39%, which indicated that T. harzianum fertilizer could enhance soil enzyme activity and promotes the transformation of organic matter. Among them, the relative abundance of beneficial bacteria such as Pseudomonas increased, while the relative abundance of harmful fungi such as Fusarium and Podosphaera decreased significantly. This study clarified that T. harzianum fertilizer promoted the growth of continuously planted L. siceraria plants by improving soil physical and chemical properties and microbial community structure and was an effective microbial agent to alleviate the adverse effects of continuous cropping of L. siceraria.

Exploring the Effects of Trichoderma virens Biofungicide on Carrot Cavity Spot and Soil Fungal Community Dynamics

Carrot cavity spot (CCS) has conventionally been managed with fungicides. However, fungicide resistance, their potential risks to human health and the environment, and the increasing demand for organic produce necessitate the exploration of biofungicides as alternatives. In this study, we evaluated varying concentrations of SoilGard (Certis USA, Columbia, MD), a Trichoderma virens-based biofungicide, for efficacy against different CCS-causing Pythium species in vitro. Additionally, its effects on taxonomic and functional diversities of soil fungal communities were studied in vivo in the greenhouse. To our knowledge, this is the first study reporting SoilGard's effectiveness against CCS, with emphasis on its potential as an alternative for fungicide-resistant Pythium isolates. Our in vitro study revealed that SoilGard efficacy was significantly dose-dependent and isolate-specific, thus highlighting the importance of selecting its application rate and the target isolate. Analysis of soil fungal communities using Illumina MiSeq sequencing revealed that SoilGard exerted a significant, albeit temporary, effect on the fungal community structure. It negatively impacted co-occurrence network complexity and alpha diversity in carrot-cultivated soil, whereas bare soil communities remained largely unaffected, thus explaining why preplant applications may yield better results. Our study showed that carrot cultivation without SoilGard enhanced fungal diversity, which was more pronounced late in the season, possibly due to carrot root-associated exudates. Our study sheds light on how complex interactions within soil fungal communities can be impacted by the application of beneficial/pathogenic microbes.

Desertification indirectly affects soil fauna by reducing complexity of soil habitats and diversity of energy sources

Soil fauna is closely linked to ecological functions such as biogeochemical cycling, soil structure, ecosystem sustainability and trophic interactions. However, little consideration has been given to how desertification influences the abundance and diversity of soil fauna in arid areas. In this study, soil fauna was sampled in four desert habitats (gravel, sand, salt and mud desert) in northwest China. At the same time, the plant traits, geographic location and soil properties were investigated. We also measured contribution of environmental factors explained faunal community diversity and abundance, and by what pathways desertification controls soil fauna. The results showed that total abundance and diversity of soil fauna in the mud desert were significantly (P < 0.05) higher than salt, sand and gravel deserts. Soil fauna diversity, composition and community were more sensitive to desertification-induced changes in soil properties than to changes in plant traits and geographic locations (changes in soil properties explained 68.9 % and 73.7 % of the variation in diversity and abundance of soil fauna community, respectively). Among them, the available phosphorus, volumetric water content had a significant positive effect on community diversity and abundance, while pH had a significant negative effect (P < 0.01). The results of piecewise structural equation modeling imply that desertification may have mainly indirect impacts on soil fauna community, and that direct effects are almost zero. In summary, regardless of the type of desertification, it will affect the material cycle, energy flow and information transfer of ecosystems by destroying the soil habitats and vegetation conditions, and will affect the structure and diversity of soil fauna from the bottom up.