Biology subjects

Rillig, M. C.

Publications and source records attributed to Rillig, M. C..

35 records · Page 2Linked to original sources

bioRxiv2021

Time-dependent toxicity of tire particles on soil nematodes

Tire-wear particles (TWPs) are being released into the environment by wearing down during car driving, and are considered an important microplastic pollution source. The chemical additive leaching from these polymer-based materials and its potential effects are likely temporally dynamic, since larger amounts of potentially toxic compounds can gradually increase with contact time of plastic particles with surrounding media. In the present study, we conducted soil toxicity tests using the soil nematode Caenorhabditis elegans with different soil pre-incubation (30 and 75 days) and exposure (short-term exposure, 2 days; lifetime exposure, 10 days) times. Soil pre-incubation increased toxicity of TWPs, and the effective concentrations after the pre-incubation were much lower than environmentally relevant concentrations. The lifetime of C. elegans was reduced faster in the TWP treatment groups, and the effective concentration for lifetime exposure tests were 100- to 1,000-fold lower than those of short-term exposure tests. Water-extractable metal concentrations (Cr, Cu, Ni, Pb, and Zn) in the TWP-soils showed no correlation with nominal TWP concentrations or pre-incubation times, and the incorporated metals in the TWPs may be not the main reason of toxicity in this study. Our results show that toxic effects of TWPs can be time-dependent, both in terms of the microplastic particles themselves and their interactions in the soil matrix, but also because of susceptibility of target organisms depending on developmental stage. It is vital that future work consider these aspects, since otherwise effects of microplastics and TWPs could be underestimated. Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

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bioRxiv2021

Tire abrasion particles negatively affect plant growth even at low concentrations and alter soil biogeochemical cycling

Tire particles (TPs) are a major source of microplastic on land, and considering their chemical composition, they represent a potential hazard for the terrestrial environment. We studied the effects of TPs at environmentally relevant concentrations along a wide concentration gradient (0 - 160 mg g-1) and tested the effects on plant growth, soil pH and the key ecosystem process of litter decomposition and soil respiration. The addition of TPs negatively affected shoot and root growth already at low concentrations. Tea litter decomposition slightly increased with lower additions of TPs but decreased later on. Soil pH increased until a TP concentration of 80 mg kg-1 and leveled off afterwards. Soil respiration clearly increased with increasing concentration of added TPs. Plant growth was likely reduced with starting contamination and stopped when contamination reached a certain level in the soil. The presence of TPs altered a number of biogeochemical soil parameters that can have further effects on plant performance. Considering the quantities of yearly produced TPs, their persistence, and toxic potential, we assume that these particles will eventually have a significant impact on terrestrial ecosystems.

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bioRxiv2020

Microplastic fibers affect dynamics and intensity of CO2 and N2O fluxes from soil differently

Microplastics may affect soil ecosystem functioning in critical ways, with previously documented effects including changes in soil structure and water dynamics; this suggests that microbial populations and the processes they mediate could also be affected. Given the importance for global carbon and nitrogen cycle and greenhouse warming potential, we here experimentally examined potential effects of plastic microfiber additions on CO2 and N2O greenhouse gas fluxes. We carried out a fully factorial laboratory experiment with the factors presence of microplastic fibers (0.4% w/w) and addition of urea fertilizer (100 mg N kg-1). The conditions in an intensively N-fertilized arable soil were simulated by adding biogas digestate at the beginning of the incubation to all samples. We continuously monitored CO2 and N2O emissions from soil before and after urea application using a custom-built flow-through steady-state system, and we assessed soil properties, including soil structure. Microplastics affected soil properties, notably increasing soil aggregate water-stability and pneumatic conductivity, and caused changes in the dynamics and overall level of emission of both gases, but in opposite directions: overall fluxes of CO2 were increased by microplastic presence, whereas N2O emission were decreased, a pattern that was intensified following urea addition. This divergent response is explained by effects of microplastic on soil structure, with the increased air permeability likely improving O2 supply: this will have stimulated CO2 production, since mineralization benefits from better aeration. Increased O2 would at the same time have inhibited denitrification, a process contributing to N2O emissions, thus likely explaining the decrease in the latter. Our results clearly suggest that microplastic consequences for greenhouse gas emissions should become an integral part of future impact assessments, and that to understand such responses, soil structure should be assessed.

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bioRxiv2020

Microplastic shape, concentration and polymer type affect soil properties and plant biomass

Microplastics are an increasing concern in terrestrial systems. These particles can be incorporated into the soil in a wide range of shapes and polymers, reflecting the fact that manufacturers produce plastics in a variety of physical and chemical properties matching their intended use.Despite of this, little is known about the effects that the addition into the soil of microplastics of different shapes, polymer type and concentration levels may have on soil properties and plant performance. To fill this gap, we selected four microplastic shapes: fibers, films, foams and fragments; and for each shape we selected three microplastics made of one of the following polymers: polyester, polyamide, polypropylene, polyethylene, polyethylenterephthalat, polyurethane, polystyrene and polycarbonate. In a glasshouse experiment, each microplastic was added to a soil from a dry grassland at a concentration of 0.1%, 0.2%, 0.3% and 0,4%. A carrot (Daucus carota) plant grew in each pot during four weeks. At harvest, shoot and root mass, soil aggregation and microbial activity were measured. Our results showed that all microplastic shapes increased shoot and root masses. As concentration increased, microfibers increased plant biomass probably as fibers may hold water in the soil for longer. In contrast, microfilms decreased biomass with concentration, likely because they can create channels in the soil that promote water evaporation affecting plant performance. All microplastic shapes decreased soil aggregation, probably since microplastics may introduce fracture points in the aggregates affecting their stability and also due to potential negative effects on soil biota. The latter may also explain the decrease in microbial activity with, for example, polyethylene films. Similar to plant biomass, microfilms decreased soil aggregation with increasing concentration. Our study tested the microplastic shape mediation and dissimilarity hypotheses, highlighting the importance of microplastic shape, polymer type and concentration when studying the effects of microplastics on terrestrial systems.

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bioRxiv2020

Effects Of Microplastics And Drought On Ecosystem Functions And Multifunctionality

O_LIMicroplastics in soils have become an important threat for terrestrial systems, which can be exacerbated by drought as microplastics may affect soil water content. Thus, the interaction between these two factors may alter ecosystem functions such as litter decomposition, stability of soil aggregates, as well as functions related to nutrient cycling. Despite this potential interaction, we know relatively little about how microplastics, under different soil water conditions, affect ecosystem functions and ecosystem multifunctionality. C_LIO_LITo address this gap, we carried out a controlled-environment study using grassland plant communities. We applied the two factors microplastic fibers (absent, present) and soil water conditions (well-watered, drought), in all possible combinations in a factorial experiment. At harvest, we measured multiple ecosystem functions linked to nutrient cycling, litter decomposition, and soil aggregation and as terrestrial systems provide these functions simultaneously, we also assessed ecosystem multifunctionality. C_LIO_LIOur results showed that the interaction between microplastic fibers and drought affected ecosystem functions and multifunctionality. Overall, drought had negatively affected nutrient cycling by decreasing potential enzymatic activities and increasing nutrient leaching, while microplastic fibers had a positive impact on soil aggregation and nutrient retention by diminishing nutrient leaching. Microplastic fibers also impacted enzymatic activities, soil respiration and ecosystem multifunctionality, but importantly, the direction of these effects depended on soil water status (i.e., they decreased under well watered conditions, but tended to increase or had similar effects under drought conditions). Litter decomposition had a contrary pattern. C_LIO_LISynthesis and applications. As soil water content is affected by climate change, our results suggest that areas with sufficiency of water would be negatively affected in their ecosystem functioning as microplastics increase in the soil; however, in areas subjected to drought, microplastics would have a neutral or slightly positive effect on ecosystem functioning. C_LI

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bioRxiv2020

Microplastics have shape- and polymer-dependent effects on soil processes

Microplastics are a diverse and ubiquitous contaminant, a global change driver with potential to alter ecosystem properties and processes. Microplastic-induced effects in soils are manifold as microplastics differ in a variety of properties among which the shape is of special interest. Microplastic shapes can resemble natural forms or be dissimilar from natural objects. Our knowledge is limited regarding the impact of various microplastic shapes on soil processes. Therefore, we conducted this two-part research comprising a meta-analysis on published literature and a lab experiment focusing on microplastic shapes- and polymer-induced effects on soil aggregation and organic matter decomposition. We here focus on fibers, films, foams and fragments as microplastic shapes. In the meta-analysis, we revealed a strong research focus on fibrous and particulate microplastic materials, with films and foams neglected. Our experiment showed that microplastic shapes are important modulators of responses in soil aggregation and organic matter decomposition. Fibers, irrespective of their chemistry, negatively affected the formation of aggregates. This supported the shape dissimilarity hypothesis. However, for other shapes like foams and fragments, the polymer identity is clearly an important factor co-modulating the soil responses. Further research is needed to generate a data-driven foundation to build on our developing mechanistic understanding of the importance and consequences of microplastic shapes added to our soils.

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bioRxiv2020

Stress priming affects fungal competition - evidence from a combined experimental and modeling study

Priming, an inducible stress defense strategy that prepares an organism for an impending stress event, is common in microbes and has been studied mostly in isolated organisms or populations. How the benefits of priming change in the microbial community context and, vice versa, whether priming influences competition between organisms, remains largely unknown. In this combined experimental and modeling study, we developed a cellular automaton model based on dedicated data of different isolates of soil fungi in isolation and pairwise competition experiments. With the model, we simulated growth of the ascomycete Chaetomium elatum competing against other fungi to understand which species traits influence the benefit of priming and the effect of priming on competition. We showed that competition changes the priming benefit compared to isolated growth, and that it depends not only on the primeable species itself, but also on the competitors traits such as growth rate, primeability and stress susceptibility. In addition, we showed that priming benefits were not always reflected in the competitive outcome. With this study, we transferred insights on priming from studies in isolation to the community context. This is an important step towards understanding the role of inducible defenses in microbial community assembly and composition.

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bioRxiv2020

The fungal collaboration gradient dominates the root economics space in plants

Plant economics run on carbon and nutrients instead of money. Leaf strategies aboveground span an economic spectrum from live fast and die young to slow and steady, but the economy defined by root strategies belowground remains unclear. Here we take a holistic view of the belowground economy, and show that root-mycorrhizal collaboration can short circuit a one-dimensional economic spectrum, providing an entire space of economic possibilities. Root trait data from 1,781 species across the globe confirm a classical fast-slow conservation gradient but show that most variation is explained by an orthogonal collaboration gradient, ranging from do-it-yourself resource uptake to outsourcing of resource uptake to mycorrhizal fungi. This broadened root economics space provides a solid foundation for predictive understanding of belowground responses to changing environmental conditions. One Sentence SummaryCollaboration broadens the root economics space ranging from do-it-yourself resource acquisition to outsourcing to mycorrhizal partners.

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bioRxiv2019

The effects of arbuscular mycorrhizal fungi (AMF) and Rhizophagus irregularis in soil microorganisms accessed by metatranscriptomics and metaproteomics

Arbuscular mycorrhizal fungi (AMF) form symbioses with approximately 80% of plant species and potentially benefit their hosts (e.g. nutrient acquisition) and the soil environment (e.g. soil aggregation). AMF also affect soil microbiota and soil multifunctionality. We manipulated AMF presence (via inoculation of non-sterile soil with Rhizophagus irregularis and using a hyphal compartment design) and used RNA-seq and metaproteomics to assess AMF roles in soil. The results indicated that AMF drove an active soil microbial community expressing transcripts and proteins related to nine metabolic functions, including the metabolism of C and N. We suggest two possible mechanisms: 1) the AMF hyphae produce exudates that select a beneficial community, or, 2) the hyphae compete with other soil microbes for available nutrients and consequently induce the community to mineralize nutrients from soil organic matter. We also identified candidate proteins that are potentially related to soil aggregation, such as Lpt and HSP60. Our results bridge microbial ecology and ecosystem functioning. We show that the AMF hyphosphere contains an active community related to soil respiration and nutrient cycling, thus potentially improving nutrient mineralization from soil organic matter and nutrient supply to the plants.

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bioRxiv2019

Root trait responses to drought depend on plant functional group

O_LIDrought can strongly modify plant diversity and ecosystem processes. As droughts are expected to intensify in the future, it is important to better understand plant responses to drought. We expect that roots traits constitute an overlooked but powerful predictor of plant responses as roots are in direct contact with the soil environment, taking up nutrients and water.\nC_LIO_LIHere, we determine which root traits are sensitive to drought, the magnitude of that response, whether their predictive power and relationships with shoot biomass are affected by drought and whether all these responses depend on plant functional group. To do so, we conducted a glasshouse experiment with 24 plant species grown in pots (10 replicates per species), which represent three different functional groups: grasses, herbs and legumes. All replicates were well watered during the first month and then half of the replicates were kept under drought (30 % water holding capacity (WHC)) with the other half serving as control (kept at 70% WHC). After two months of the treatment, leaf and root traits were measured.\nC_LIO_LILeaf traits had a strong but more uniform response to drought compared to root traits. Root trait response was variable and differed by plant functional group. Most grasses had increased root diameter, specific root surface area (SRSA) while decreased root tissue density (RTD) with drought. Production of thicker roots with a low tissue density could allow grasses to achieve greater nutrient and water acquisition through mycotrophy and would be linked to an increase in the reserve of non-structural carbohydrates needed for osmoregulation. Herbs had decreased SRSA and specific root length (SRL) while increase root carbon allocation. Reduction of root elongation or sacrifice of fine roots would be compensated by an increase in root carbon allocation, which allow herbs to improve water uptake. Legumes did not alter root morphological traits but promote an early flowering in order to scape drought.\nC_LIO_LIOur results identify changes in root morphological traits as mechanisms to likely face drought, a response that is species-specific and differed among functional groups.\nC_LI

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bioRxiv2019

Diversity of responses of soil saprobic fungi to recurring heat events

As a consequence of ongoing climate change, the frequency of extreme heat events is expected to increase. Recurring heat pulses may disrupt functions supported by soil microorganisms, thus affecting the entire ecosystem. However, most perturbation experiments only test effects of single heat events, and therefore it remains largely unknown how soil microorganisms react to repeated pulse events. Here we present data from a lab experiment exposing 32 filamentous fungi, originally isolated from the same soil, to sequential heat perturbations. Soil saprobic fungi isolates were exposed to one or two heat pulses: mild (35{degrees}C/2h), strong (45{degrees}C/1h), or both in sequence (35{degrees}C/2h+45{degrees}C/1h), and we assessed growth rate. Out of the 32 isolates 13 isolates showed an antagonistic response, 3 isolates a synergistic response and 16 isolates responded in an additive manner. These differences in species responses to the thermal environment may contribute to species coexistence, and such dissimilarities in thermal perturbation responses may be a key aspect influencing ecosystem services that soil saprobic fungi support.

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bioRxiv2019

Fungal traits important for soil aggregation

Soil health and sustainability is essential for ecosystem functioning and human well-being. Soil structure, the complex arrangement of soil into aggregates and pore spaces, is a key feature of soils under the influence of soil life. Soil biota, and among them filamentous saprobic fungi, have well-documented effects on soil aggregation. However, it is unclear what fungal properties, or traits, contribute to the overall positive effect on soil aggregation. So far, we lack a systematic investigation of a broad suite of fungal species for their trait expression and the relation of these traits to their soil aggregation capability.\n\nHere, we apply a trait-based approach to a set of 15 traits measured under standardized conditions on 31 fungal strains including Ascomycota, Basidiomycota and Mucoromycota, all isolated from the same soil.\n\nWe found a spectrum of soil aggregate formation capability ranging from neutral to positive and large differences in trait expression among strains. We identified biomass density (positive effects), leucine aminopeptidase activity (negative effects) and phylogeny as important modulators of fungal aggregate formation capability. Our results point to a typical suite of traits characterizing fungi that are good soil aggregators; this could inform screening for fungi to be used in biotechnological applications, and illustrates the power of employing a trait-based approach to unravel biological mechanisms of soil aggregation, which could now be extended to other organism groups.

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bioRxiv2019

Global distribution of earthworm diversity

Soil organisms provide crucial ecosystem services that support human life. However, little is known about their diversity, distribution, and the threats affecting them. Here, we compiled a global dataset of sampled earthworm communities from over 7000 sites in 56 countries to predict patterns in earthworm diversity, abundance, and biomass. We identify the environmental drivers shaping these patterns. Local species richness and abundance typically peaked at higher latitudes, while biomass peaked in the tropics, patterns opposite to those observed in aboveground organisms. Similar to many aboveground taxa, climate variables were more important in shaping earthworm communities than soil properties or habitat cover. These findings highlight that, while the environmental drivers are similar, conservation strategies to conserve aboveground biodiversity might not be appropriate for earthworm diversity, especially in a changing climate.\n\nOne sentence summaryGlobal patterns of earthworm diversity, abundance and biomass are driven by climate but patterns differ from many aboveground taxa.

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bioRxiv2018

How to build a mycelium: tradeoffs in fungal architectural traits

The fungal mycelium represents the essence of the fungal lifestyle, and understanding how a mycelium is constructed is of fundamental importance in fungal biology and ecology. Previous studies have examined initial developmental patterns or focused on a few strains, often mutants of model species, and frequently grown under non-harmonized growth conditions; these factors currently collectively hamper systematic insights into rules of mycelium architecture. To address this, we here use a broader suite of fungi (31 species including members of the Ascomycota, Basidiomycota and Mucoromycotina), all isolated from the same soil, and test for ten architectural traits under standardized laboratory conditions.\n\nWe find great variability in traits among the saprobic fungal species, and detect several clear tradeoffs in mycelial architecture, for example between internodal length and hyphal diameter. Within the constraints so identified, we document otherwise great versatility in mycelium architecture in this set of fungi, and there was no evidence of trait syndromes as might be expected.\n\nOur results point to an important dimension of fungal properties with likely consequences for coexistence within local communities, as well as for functional complementarity (e.g. decomposition, soil aggregation).

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bioRxiv2018

Growth rate trades off with enzymatic investment in soil filamentous fungi

Saprobic soil fungi drive many important ecosystem processes, including decomposition, and many of their effects are related to growth rate and enzymatic ability. In mycology, there has long been the implicit assumption of trade-off between growth and enzymatic investment, which we here test. Using a set of 31 filamentous fungi isolated from the same ecosystem, we measured growth rate (as colony radial extension) and enzymatic repertoire (activities of four enzymes: laccase, cellobiohydrolase, leucine aminopeptidase and acid phosphatase). Our results support the existence of a trade-off, however only for the enzymes representing a larger metabolic cost (laccase and cellobiohydrolase). Our study offers new insights into functional complementarity within the soil fungal community in a number of ecosystem processes, and experimentally supports an enzymatic investment/ growth rate tradeoff in explaining phenomena including substrate succession.

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bioRxiv2018

Evidence for subsoil specialization in arbuscular mycorrhizal fungi

Arbuscular mycorrhizal (AM) fungal communities are now known to vary with depth in arable land. Here we use two previously published high-throughput Illumina sequencing data sets, and compare a 52 year long chronosequence of recultivated agriculture fields after a topsoil and subsoil mixing event, with a set of undisturbed topsoil and subsoil samples from a similar field. We show that AM taxa identified as subsoil indicators are exclusively present in early stages of the chronosequence, whereas topsoil indicator taxa can be found across the chronosequence, and that similarities from the chronosequence fields to the subsoil communities decrease with time. Our results provide evidence on the ecological specialization of certain AM fungal taxa to deep soil layers.

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bioRxiv2017

Subsoil arbuscular mycorrhizal fungal communities in arable soil differ from those in topsoil

Arbuscular mycorrhizal fungi are recognized as important drivers of plant health and productivity in agriculture but very often existing knowledge is limited to the topsoil. With growing interest in the role of subsoil in sustainable agriculture, we used high-throughput Illumina sequencing on a set of samples encompassing drilosphere, rhizosphere and bulk soil, in both top- and subsoil. Our results show subsoil AMF communities harbor unique Operational Taxonomic Units (OTUs) and that both soil depths differ in community structure both at the OTU and family level. Our results emphasize the distinctness of subsoil AMF communities and the potential role of subsoil as a biodiversity reservoir.

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