ABSTRACT Entomopathogenic fungi of the genera Metarhizium and Beauveria are important natural regulators of arthropod populations. To investigate their distribution and ecological drivers in real-world permanent grasslands, we did a survey analyzing fungal communities across 72 sites in Switzerland using ITS2 amplicon sequencing. We identified 10 Metarhizium and six Beauveria amplicon sequence variants (ASVs), with at least one ASV present at every site. Frequent ASVs included M. robertsii/M. pingshaense, M. brunneum, B. bassiana, and B. brongniartii. These ASVs showed distinct presence/absence and abundance patterns, indicating adaptation to climatic, soil physicochemical, and management-related factors. Factors such as soil pH, available phosphorus, temperature, bulk soil density, and management intensity significantly correlated with ASV distributions. For example, M. robertsii/M. pingshaense was widely distributed but strongly associated with soil pH, while B. brongniartii was restricted to subalpine regions, correlating with lower temperatures and nutrient levels. Plant communities, plant community-derived ecological indicator values (EIVs) reflecting environmental conditions, and indicator plant species analysis showed correlations with specific ASVs. On one hand, this suggests shared ecological niches and/or indicates possible direct plant–fungal interactions, consistent with the known endophytic or root-associated lifestyles of some entomopathogenic fungi. On the other hand, it suggests that plant-derived EIVs and individual indicator plant species may serve as effective indices for identifying habitats suitable for the presence and establishment of these entomopathogenic fungi. This approach may facilitate the evaluation of the suitability of particular environments for the application of Metarhizium and Beauveria strains as biological control agents.IMPORTANCEThe globally occurring fungal entomopathogens Metarhizium and Beauveria are key natural regulators of soil-dwelling arthropods and are widely used as biological control agents. Yet predicting their presence or potential to establish in particular habitats and provide their ecosystem function remains challenging. This survey study in real-world grasslands reveals distinct ecological niches characterized by climatic, soil physicochemical, and management parameters for different Metarhizium and Beauveria taxa. In addition, we demonstrate that plant community composition, plant-derived ecological indicator values, and individual indicator plant species are associated with Metarhizium and Beauveria presence and abundance. Our findings suggest that, within this regional context, vegetation data may serve as praxis-oriented proxies for efficient and non-invasive assessment of site suitability both for native fungal populations and biological control agents of selected Metarhizium and Beauveria taxa in grassland ecosystems.

Composting plays a key role in sustainable agriculture by converting organic waste into a valuable soil conditioner. The process is driven by complex microbial communities, whose characterization is essential for optimizing the composting process and compost quality. Molecular techniques such as amplicon sequencing are commonly used for this purpose. However, sampling procedures and DNA extraction methods, key steps in the sequencing workflow, often vary across studies, challenging comparability.We investigated two aspects of sample preparation that may influence compost microbial analyses. For DNA extraction, often fine fractions (<2 mm) are used. However, compost has a heterogeneous structure, including coarse particles. To assess the effect of particle size, we separately sequenced bacterial and fungal communities of the fine (0-2 mm) and coarse (2-10 mm) fractions of three composts. In addition, DNA was extracted using a carboxyl-affinity-based magnetic method and a silanol-affinity-based filter method to evaluate the impact of the extraction technique.We found that the coarse fraction had higher bacterial richness and distinct bacterial and fungal community structures compared to the fine fraction. DNA extraction method also influenced bacterial community profiles, with the magnetic bead method improving coverage, particularly for Bacillota. Although the effects of particle size and extraction method were small compared to the overall diversity among composts, we recommend including coarse particles in sequencing analyses and using standardized DNA extraction protocols, especially for studies aiming at high-resolution community analyses.

The Japanese beetle (Popillia japonica), native to Japan, is a major invasive species in North America and Europe. Its colonization of Europe began on the Azores (1970s), followed by Italy (2014) and southern Switzerland (2017). In 2023, the presence of the pest was reported in three areas of Switzerland: Kloten (Canton of Zürich, north-eastern Switzerland), Basel (Canton of Basel-Landschaft, northern Switzerland), and in eastern Canton of Valais (South Switzerland) near the Italian border. In 2024, P. japonica individuals were discovered in several other Swiss Cantons. To trace P. japonica spread and origins in Switzerland, we investigated 42 individuals from infested areas, comprising scattered findings across Switzerland. Phylogenetic and population structure analyses using whole-genome resequencing, including data of previously sequenced samples from Japan, North America, the Azores, Italy, and Southern Switzerland, revealed distinct P. japonica migration patterns. Populations in Basel, Valais, and central Switzerland likely originated from Ticino/Northern Italy via road or rail transport. Conversely, the population near Zürich Airport was identified as an independent introduction from North America, likely through unintentional air transport. These findings offer insights into P. japonica spread across Switzerland, highlighting the need for enhanced monitoring and identification of invasion pathways.

Soil biodegradable polyesters are designed to undergo to microbial utilization in aerobic soils, forming carbon dioxide and microbial biomass. These polyesters are thus viable substitutes for conventional, persistent polymers (e.g., polyethylene) in specific applications for which the transfer of some of the polymers into the soil is inevitable. While polymer biodegradability is often assessed in laboratory incubations using respirometric analysis of formed CO2, approaches to accurately quantify biodegradable polyesters in soils and to track their mass loss in field incubations over time remain missing. This study first introduces an analytical workflow combining Soxhlet extraction with proton nuclear magnetic resonance spectroscopy for the accurate, high-throughput, and chemically selective quantification of eight commercially important biodegradable polyesters (i.e., poly(butylene adipate-co-terephthalate), polylactic acid, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), poly(3-hydroxybutyrate-co-3-hydroxyvalerate), polycaprolactone, polybutylene adipate, polybutylene azelate, and polybutylene succinate), and the nonbiodegradable polymer polystyrene, in six soils spanning a range of types and physicochemical properties. This work introduces an effective sample deployment-retrieval approach that, combined with the analytical method, allows the biodegradation of poly(butylene adipate-co-terephthalate) and polylactic acid from a biodegradable mulch film in three agricultural soils to be monitored. In combination, the two parts of this work lay the foundation to accurately quantify and monitor biodegradable polymers in soils.

Compost is a valuable amendment for soil and potting substrate when it comes to suppressing soilborne pathogens. However, the effectiveness of different composts varies and cannot yet be predicted. Microbial communities in compost play a key role in disease suppression, and therefore their composition or specific taxa may serve as indicators of suppressive composts. In this study, we investigated 37 composts from 7 commercial compost producers to analyze the association of their bacterial and fungal communities with suppressive activity in three plant-pathogen systems: cress-Globisporangium ultimum, cucumber-G. ultimum, and cucumber-Rhizoctonia solani. Our results underscore that compost suppressiveness is primarily pathogen-specific and, to a lesser extent, host-plant-specific. Suppressiveness was not correlated with physicochemical properties, microbial activity, or the alpha- and beta-diversity of composts' bacterial and fungal communities. Instead, microbial composition was largely shaped by producer-specific composting conditions and maturation processes, which were not necessarily linked to suppressive activity. A more nuanced comparison between the most and least suppressive composts revealed bacterial and a few fungal taxa as potential indicators of suppressiveness for each plant-pathogen system. Notably, for G. ultimum-suppression, bacteria from the genera Luteimonas, Sphingopyxis, and Algoriphagus, and for R. solani, bacteria belonging to the phylum Actinomycetota emerged as promising candidates. IMPORTANCE:Soilborne diseases are a major yield-limiting factor in agricultural crop production worldwide, particularly in seedling cultivation. Their control remains a significant challenge and still largely relies on chemical fumigation of soils and steam sterilization of potting substrates. While chemical fumigants are increasingly criticized for their negative environmental impact, sterilization practices, in general, disrupt beneficial microbial communities, making substrates more susceptible to pathogen (re)-infestation. Amending soil or potting substrate with disease-suppressive compost offers a promising alternative. However, the targeted use of compost for plant protection is hindered by variable effectiveness and the lack of reliable tools to identify effective composts. This study provides a comprehensive abiotic and biotic characterization of compost, enabling a detailed analysis of the properties associated with suppressiveness. The identification of bacterial and fungal taxa indicative of disease-suppressive composts lays the groundwork for targeted isolation of microorganisms and functional studies, with the ultimate aim of predicting and optimizing compost-mediated disease suppression.

Popillia japonica is an invasive, polyphagous beetle feeding on more than 400 host plants and responsible for major crop damage in infested regions in North America, northern Italy and southern Switzerland. Currently, control of P. japonica largely relies on synthetic insecticides. Recently, Beauveria pseudobassiana has been described as the dominant pathogen on Melolontha melolontha adults, a native scarabaeoid relative of P. japonica. B. pseudobassiana has been detected on several insect species, in soil but also on plant leaves indicating its adaptation to environmental conditions above ground. We evaluated survival of P. japonica adults and larvae exposed to four strains of B. pseudobassiana (ART 2881, ART 2882, ART 2883, ART 2884) and a M. brunneum strain (Ma 43), registered as control agent against several Scarabaeidae species in Europe. All the fungal strains led to a significant three-to-five-fold reduction in the median survival of P. japonica adults, when dipped in conidia suspensions or exposed to fungus inoculated leaves, while ART 2884 was in both tests the most virulent strain. In contrast, none of the fungal isolates reduced larval survival, with mortality rates of 2-8 % after 70 days. From field-collected beetles, we obtained natural Beauveria isolates, some of which were identified as B. pseudobassiana, indicating a possible role of the fungus in natural infection scenarios. The high in vitro virulence of B. pseudobassiana together with its competence for above ground conditions and occurrence on P. japonica in the field indicates potential of this fungus as biological control agent (BCA) against adult P. japonica.

Soilborne diseases pose a significant threat to crop production and their control remains a major challenge. Compost is a valuable soil amendment when it comes to suppressing soilborne pathogens, but the effectiveness of different composts varies and cannot yet be predicted. Microbial communities in compost play a key role in disease suppression, and therefore microbial taxa may serve as indicators for suppressive composts. In this study, we investigated 37 composts from seven commercial compost producers to analyze the association of their bacterial and fungal communities with disease-suppressive activity across three plant-pathogen systems: cress- Globisporangium ultimum , cucumber- G. ultimum and cucumber- Rhizoctonia solani . Our results underscore that compost suppressiveness is primarily pathogen-specific and, to a smaller extent, host-plant-specific. Suppressiveness was not found to be correlated to physicochemical properties or microbial activity, alpha- and beta-diversity of the composts. However, specific bacterial and a few fungal taxa were identified as potential indicators of suppression for each plant-pathogen system. Notably, for G. ultimum -suppression, bacteria from the genera Luteimonas , Sphingopyxis , and Algoriphagus emerged as promising candidates. These findings provide a foundation for targeted microbial isolation, aiming to elucidate the role of microorganisms in compost-mediated disease suppression, and to predict and optimize suppressive activity. ### Competing Interest Statement The authors have declared no competing interest.

Beauveria brongniartii specifically infects the insect pest Melolontha melolontha and is commonly isolated from soil and larvae. Since 1990, it has been used commercially as a biological control agent (BCA) against the larvae. Recent research revealed that B. pseudobassiana was the most frequently isolated pathogen from adult beetles collected aboveground across 35 alpine sites. This led us to hypothesize that B. pseudobassiana primarily infects adults aboveground, while B. brongniartii mainly targets larvae in soil. To test these hypotheses, we investigated the occurrence and distribution of both species at two M. melolontha-infested sites in Switzerland using a combination of phylogenetic analyses and microsatellite markers. Species-specific microsatellite markers were developed for B. pseudobassiana, and existing markers were applied to B. brongniartii. From 399 Beauveria spp. isolates collected from adult beetles, soil, grassland plants, and tree leaves, 362 were identified as B. brongniartii, which was present in all sources except tree leaves, and 37 as B. pseudobassiana, found in all sources including tree leaves, except soil. The most common B. brongniartii multilocus genotypes (MLGs) were those of the BCAs BIPESCO 2 and BIPESCO 4, perhaps reflecting previous BCA applications at these locations. One B. pseudobassiana microsatellite-based MLG was isolated from both tree leaves and M. melolontha in the tree canopy. Additionally, B. pseudobassiana isolated from the phylloplane exhibited pathogenicity toward M. melolontha adults, suggesting the possibility of acquiring infections aboveground. To detail B. pseudobassiana intraspecific diversity, a sequence dataset was constructed including 13 unique haplotypes of the nuclear intergenic region Bloc sequenced in this study, 58 Bloc sequences downloaded from GenBank, and sphyngomyelin phosphodiesterase, glycosyl hydrolase, and AAA-ATPase midasin I sequences from 18 isolates illustrative of B. pseudobassiana genome diversity accessioned in GenBank. Phylogenetic analysis of this data reveals the species to comprise a cryptic complex with distinct genetic clusters that group isolates independently of their geographic origin and isolation substrate. Overall, this study shows B. brongniartii predominates in soil, while B. pseudobassiana occurs in the phylloplane, suggesting its potential as a complementary biological control for adult beetles aboveground.

Agricultural grassland management intensity strongly influences soil microbial community structure in Europe, though the influence of individual practices, such as fertilization and cutting frequency, requires further investigation. Using a 46 year old field experiment in the Swiss Jura region, we examined how both fertilizer input and cutting frequency influence both soil microbial community structure and functional potential. For community structures of soil bacteria and fungi (determined via genetic metabarcoding) and plants (determined via plant species releves) the effect of fertilization had a stronger effect than that of cutting frequency. The fatty acid biomarker for arbuscular mycorrhizal fungi (AMF, 16:1 omega 5), however, responded more to cutting frequency (relative effect size = 87.71 %) than fertilization (relative effect size = -7.90 %). Among bacteria with genes linked to soil phosphorous (P) and nitrogen (N) mobilization, only the abundance of the gcd gene (inorganic P solubilisation) displayed a significant fertilization effect. These findings suggest that long-term mineral fertilizer application is a key driver of differences in microbial community structure in grasslands of contrasting management type, and may influence bacterial P solubilisation capacity. Some microbial groups, such as AMF, appear more sensitive to cutting frequency, possibly due to additional plant re-growth. This study highlights the importance of disentangling agricultural management practices to better predict grassland plant and soil microbial responses to intensification.

Understanding co-occurrences of different taxa is of both fundamental and applied relevance, for example, to understand ecosystem processes and to design monitoring programs for above- and belowground biodiversity. Plants and microorganisms form complex, interdependent relationships, which are exposed to and may be compromised by agricultural management. Here we assessed the effect of grassland management intensities on bacterial, fungal and plant communities and their associations. We further analyzed the potential of inferring information from taxa of one community on structural changes of the other communities with the aim of potentially enhancing the efficiency of biodiversity assessments by finding common indicator taxa. For that, bacterial, fungal and plant communities as well as environmental factors were assessed in 89 grassland sites of either extensive type (no fertilization, late and infrequent cuttings) or intensive type (fertilization, early and frequent cuttings) of management in the Swiss lowlands. Bacterial, fungal and plant community structures as well as plant indicator values for soil nutrients and moisture differed between management types. Also, community homogeneity was significantly higher for all communities in the intensively managed grassland. For bacterial community structures, this was likely related to a smaller soil pH range in intensively managed grassland, while a lower fungal and plant richness may have caused more homogenous fungal and plant community structures in intensively managed grassland. Further, correlation strength among community structures dropped by 25-66 % from extensively to intensively managed grassland. Finally, indicator analysis suggested that future monitoring programs may use plant taxa to estimate expected effects on fungal communities and vice versa, but bacterial communities require additional assessment. Our results revealed a multifaceted and profound effect of management on bacterial, fungal and plant communities, which reinforces the conservation value of extensively managed grassland.

Earthworms and enchytraeids play an important role in biogeochemical cycles and are good indicators of soil fertility. However, assessing their assemblages is difficult, mainly because the methods to identify them require expert knowledge, which becomes a technical challenge when surveying large areas. Soil DNA metabarcoding is a promising method that enables the identification of individual species directly from a bulk composite sample in large field experiments. Here, we investigated in parallel both earthworm (family Lumbricidae) and enchytraeid (family Enchytraeidae) assemblages in three land-use types (arable land, grassland, forest) across 29 Swiss Soil Monitoring Network (NABO) sites, using high-throughput amplicon sequencing of marker genes. For both earthworms and enchytraeids, alpha-diversity was higher in grasslands than in arable land and forests, and it was significantly affected by soil physico-chemical, climate and biological properties, especially pH and climate properties. In addition, we found negative correlations between earthworms alpha-diversity and soil total carbon (TC) content and the soil carbon to nitrogen ratio. Using the DNA metabarcoding, we observed sequences of Aporrectodea nocturna in soils with low pH, while other Aporrectodea species occurred in soils with high pH. We identified Bimastos rubidus in soils with low pH but higher TC, total nitrogen, organic C, and low silt content, while the enchytraeids Cognettia sphagnetorum and Cernosvitoviella atrata occurred in forest soils with high water and organic matter contents. We identified some indicator taxa for the different land-use types, for grassland: Aporrectodea icterica, Lumbricus rubellus, Marionina communis, Fridericia bisetosa and Fridericia connata; arable land: Allolobophora chlorotica, Enchytraeus dichaetus, Achaeta iberica, Prodtodrilus antipae and Fridericia tuberosa; and for forest: Octolasion cyaneum, Octolasion lacteum and Cognettia chlorophila. Although these indicator taxa are unlikely to provide information about the effect of land-use change on soil biodiversity at large spatial scales, these species do drive assemblage differences between land-use types. Soil DNA metabarcoding could therefore assist land managers in monitoring soil biodiversity and quality.

Seed health tests are performed to prevent sowing untreated seeds with problematic pathogen levels. The detection of internal seedborne pathogens like Ustilago nuda, causing loose smut in barley (Hordeum vulgare), is challenging because symptoms only appear when teliospores replace barley inflorescences and smutted ears develop. Currently, U. nuda seed infection levels are determined from the visual inspections of extracted embryos or fields of plants used for seed production, both of which are laborious and can be unreliable. To improve U. nuda detection, we developed a multiplex qPCR method targeting U. nuda and H. vulgare DNA. Naturally infected seed lots were tested using this qPCR method and the visual analysis of embryos. We grew the same seed lots in the field over two seasons and used the observed smutted ears as the reference infection level. The qPCR results, U. nuda DNA normalized to H. vulgare DNA, better correlated with observed field infections than the number of infected embryos. Our qPCR method more accurately distinguished seed lots with infections above and below the field tolerance threshold. It offers a reliable alternative to the visual analysis of extracted embryos. The integration of our qPCR method with field observations can enhance U. nuda management and reduce unnecessary prophylactic seed treatments, thereby bolstering integrated pest management strategies.

Beauveria brongniartii is a fungal pathogen that infects the beetle Melolontha melolontha, a significant agricultural pest in Europe. While research has primarily focused on the use of B. brongniartii for controlling M. melolontha, the genomic structure of the B. brongniartii population remains unknown. This includes whether its structure is influenced by its interaction with M. melolontha, the timing of beetle-swarming flights, geographical factors, or reproductive mode. To address this, we analysed genome-wide SNPs to infer the population genomics of Beauveria spp., which were isolated from infected M. melolontha adults in an Alpine region. Surprisingly, only one-third of the isolates were identified as B. brongniartii, while two-thirds were distributed among cryptic taxa within B. pseudobassiana, a fungal species not previously recognized as a pathogen of M. melolontha. Given the prevalence of B. pseudobassiana, we conducted analyses on both species. We found no spatial or temporal genomic patterns within either species and no correlation with the population structure of M. melolontha, suggesting that the dispersal of the fungi is independent of the beetle. Both species exhibited clonal population structures, with B. brongniartii fixed for one mating type and B. pseudobassiana displaying both mating types. This implies that factors other than mating compatibility limit sexual reproduction. We conclude that the population genomic structure of Beauveria spp. is primarily influenced by predominant asexual reproduction and dispersal.

Dietary tannins can affect rumen microbiota and enteric fermentation to mitigate methane emissions, although such effects have not yet been fully elucidated. We tested two subunits of hydrolyzable tannins named gallic acid (GA) and ellagic acid (EA), alone (75 mg/g DM each) or combined (150 mg/g DM in total), using the Rusitec system. EA and EA+GA treatments decreased methane production, volatile fatty acids, nutrient degradation, relative abundance of Butyrivibrio fibrisolvens, Fibrobacter succinogenes, Ruminococcus flavefaciens but increased Selenomonas ruminantium. EA and EA+GA increased urolithins A and B. Also, EA and EA+GA reduced bacterial richness, with limited effects on archaeal richness. For bacteria, Megasphaera elsdenii was more abundant after EA and EA+GA, while Methanomethylophilaceae dominated archaea in all treatments. EA was more effective than GA in altering rumen microbiota and fermentation but GA did not reduce VFA and nutrient degradation. Thus, dietary supplementation of EA-plant extracts for ruminants may be considered to mitigate enteric methane, although a suitable dosage must be ensured to minimize the negative effects on fermentation.

Genetically engineered gene drives (geGD) are potentially powerful tools for suppressing or even eradicating populations of pest insects. Before living geGD insects can be released into the environment, they must pass an environmental risk assessment to ensure that their release will not cause unacceptable harm to non-targeted entities of the environment. A key research question concerns the likelihood that nontarget species will acquire the functional GD elements; such acquisition could lead to reduced abundance or loss of those species and to a disruption of the ecosystem services they provide. The main route for gene flow is through hybridization between the geGD insect strain and closely related species that co-occur in the area of release and its expected dispersal. Using the invasive spotted-wing drosophila, Drosophila suzukii, as a case study, we provide a generally applicable strategy on how a combination of interspecific hybridization experiments, behavioral observations, and molecular genetic analyses can be used to assess the potential for hybridization.

Abstract The European cockchafer Melolontha melolontha is an agricultural pest in many European countries. Populations have a synchronized 3 or 4 years life cycle, leading to temporally isolated populations. Despite the economic importance and availability of comprehensive historical as well as current records on cockchafer occurrence, population genomic analyses of M. melolontha are missing. For example, the effects of geographic separation caused by the mountainous terrain of the Alps and of temporal isolation on the genomic structure of M. melolontha still remain unknown. To address this gap, we genotyped 475 M. melolontha adults collected during 3 years from 35 sites in a central Alpine region. Subsequent population structure analyses discriminated two main genetic clusters, i.e., the South Tyrol cluster including collections located southeast of the Alpine mountain range, and a northwestern alpine cluster with all the other collections, reflecting distinct evolutionary history and geographic barriers. The “passo di Resia” linking South and North Tyrol represented a regional contact zone of the two genetic clusters, highlighting genomic differentiation between the collections from the northern and southern regions. Although the collections from northwestern Italy were assigned to the northwestern alpine genetic cluster, they displayed evidence of admixture with the South Tyrolean genetic cluster, suggesting shared ancestry. A linear mixed model confirmed that both geographic distance and, to a lower extent, also temporal isolation had a significant effect on the genetic distance among M. melolontha populations. These effects may be attributed to limited dispersal capacity and reproductive isolation resulting from synchronized and non‐synchronized swarming flights, respectively. This study contributes to the understanding of the phylogeography of an organism that is recognized as an agricultural problem and provides significant information on the population genomics of insect species with prolonged temporally shifted and locally synchronized life cycles.

&lt;p&gt;Non-biodegradable polyethylene mulch films are widely used in agriculture to allow for an extended growing season and to increase crop yields. These mulch films are, however, difficult to completely recollect from the field after use, particularly when they are thin (&lt; 25 &amp;#181;m). Residual mulch film pieces can accumulate in soils over time, thereby negatively impacting soil productivity and possibly turning agricultural soils into sources of plastics to surrounding environments. Mulch films certified as biodegradable in soils promise to be a solution to these problems. While such mulch films are already commercially available, a thorough assessment of the biodegradation dynamics of biodegradable mulch film products in soils in the field is lacking. So far, certification relies exclusively on laboratory soil incubations coupled to respirometric analysis of CO&lt;sub&gt;2&lt;/sub&gt; formed from the mulch films during biodegradation. Respirometric analyses are, however, very challenging to implement in field incubation studies. Past studies determining concentrations of biodegradable mulch films in field soils and attempts to follow their biodegradation dynamics in the field have relied on approximate quantification approaches, such as determining the decrease in surface area or gravimetric mass of film pieces recollected by hand. To advance a more robust and quantitative analytical approach for residual mulch film quantification in soils, we present a methodology to solvent extract and quantify the main synthetic polymeric components of commercial biodegradable mulch films, poly(butylene adipate-co-terephthalate) (PBAT) and polylactic acid (PLA), from soil. The methodology is based on exhaustive Soxhlet extraction using chloroform/methanol coupled to quantitative &lt;sup&gt;1&lt;/sup&gt;H-NMR of the extracted residual PBAT and PLA. We show full recovery of these polymers added to soils in spike-recovery experiments. Here, we use this approach to assess the biodegradation of two commercial biodegradable mulch films in three Swiss agricultural soils in a multiyear incubation study. These incubations are conducted at three experimental incubation scales: flasks in the laboratory, mesocosms in a greenhouse and the actual field. We statistically compare biodegradation rates and extents between three soils, two tested films across the three incubation scales, as well as differences in the relative rates of biodegradation between PBAT and PLA. Thereby, we assess the transferability of biodegradation results from laboratory incubations to field incubations. Our results highlight variations in biodegradation between soils and polyesters and indicate that laboratory soil incubations show faster biodegradation than measured in the same soil in the field.&lt;/p&gt;

Soil microbial community structure is determined by environmental conditions and influenced by other factors, such as the intensity of the land use management. Studies addressing the effect of environmental factors and management on grassland soil microbial communities at the continental scale are missing, and the wide range of ecosystem services provided by these ecosystems are thus also wanting. To address this knowledge gap, this study presents data on grassland soil microbial communities along a pan-European agro-ecological gradient. The transect included five geographical locations (Sweden, Germany, Switzerland, Portugal mainland, Portugal Azores). At each location, soils were collected in two regions characterized by favourable and less favourable conditions for plant growth. In each of these ten regions, grasslands along a gradient of management intensity were selected, i.e. grassland under intensive, less intensive and extensive management. Phospholipid fatty acid analysis (PLFA) was used to characterize the microbial community structure (PLFA pattern) in relation to climatic and soil properties. Over the whole geographical range, the environmental properties determined the soil microbial community structure. In Sweden and Switzerland, the regional growth conditions had the strongest influence on the soil microbial communities, while in Germany, Portugal mainland and Azores the management intensity was more important. Splitting up this whole community response into individual groups reveals that, in general, saprotrophic fungal biomarkers were highest in extensively managed grasslands while bacterial biomarkers differed mainly between the regions. We conclude that at the transect level, climate and soil properties were the most important factors influencing soil bacterial community structure, while soil fungal groups were more responsive to grassland management intensity. Overall agricultural sustainability could benefit from informed soil health promoting management practices, and this study contributes to such knowledge, showing the importance of management for the soil microbial biomass and community structure.

Many studies in soil microbial ecology are undertaken with a single sampling event, with the influence of temporal progression rarely being considered. Under field conditions, soil samples were taken from different agricultural systems; a sown grassland to maize rotation (MC), an intensively managed permanent grassland (INT), as well as extensively managed permanent grasslands with high (EXT_HP), low to sufficient (EXT_LP) and deficient available P (EXT_DP), six times throughout the 2017 growing season. Thus, this study aimed to determine if any differences in soil microbiome structures between both sharply contrasting (MC - INT - EXT), slightly differing (EXT_HP - EXT_DP) and quite similar (EXT_HP - EXT_LP and EXT_LP - EXT_DP) agricultural systems persist through changing growth conditions within the growing season. For both fungal and bacterial community structure, the influence of agricultural system (CV = 0.256, P < 0.001 and CV = 0.145, P < 0.01, respectively) was much greater than that of temporal progression (√CV = 0.065 and 0.042, respectively, both P < 0.001). Importantly, nearly all agricultural systems persistently harbored significantly distinct fungal community structures across each of the six sampling events (all at least P < 0.05). There were not as many pairwise differences in bacterial community structure between the agricultural systems, but some did persist (MC and EXT_HP ∼ EXT_DP, all P < 0.001). Additionally, persistent indicator fungal OTUs (IndVal >0.7, P ≤ 0.05) associated to each agricultural system (except EXT_LP) were found in each of the six sampling events. These results highlight the temporal stability of pairwise differences in soil microbiome structures between established agricultural systems through changing plant growth conditions, even between those with a comparable management regime. This is a highly relevant finding in informing the sampling strategy of studies in soil microbial ecology as well as for designing efficient soil biodiversity monitoring systems.

Boden ist ein Habitat, das eine grosse Vielfalt an Mikroorganismen, d. h. Bakterien, Archaeen, Pilzen und Protisten, beherbergt. Wir wissen, dass diese Kleinstlebewesen für eine Vielzahl spezifischer Bodenfunktionen verantwortlich sind. Im Rahmen des Biodiversitätsmonitorings der Schweiz haben wir an 255 Standorten die Diversität der Bodenbakterien und -pilze untersucht. Insgesamt wurden 109 693 Bakterien- und 28 085 Pilztaxa gefunden, wobei etwa 2/3 der Bakterien- und 1/3 der Pilztaxa einer Gattung und der Rest nur einer höheren taxonomischen Klasse zugeordnet werden konnte. Die verschiedenen Landnutzungstypen unterschieden sich signifikant in Vielfalt und Struktur ihrer Bakterien- und Pilzgemeinschaften. Innerhalb des Waldes waren z. B. Pilzgemeinschaften signifikant vom Waldtyp und Bakteriengemeinschaften am stärksten vom pH des Bodens bestimmt. Unsere erste systematische Erhebung von Bakterien und Pilzen in Schweizer Böden zeigte eine immense und dem Lebensraum angepasste mikrobielle Diversität, deren umfassende funktionelle Bedeutung wir erst beginnen zu verstehen.