Hidden miners - The role of microorganisms under cover crops for phosphorus management

Phosphorus (P) is a limiting and non-renewable nutrient for which improper management is becoming a threat to food security and an environmental hazard for aquatic ecosystems. Phosphorus is particularly difficult to manage as complex physicochemical processes in the soil leave most P unavailable for crop uptake. Cover crops are a promising tool of agronomic management, which may increase P availability for the following crops through various mechanisms, such as an overall extended root system, greater P mobilization via exudation of organic anions, enhanced P mineralization by phosphatase excretion and microbial interactions. Better understanding of plant-microbial interactions offer the possibility to unravel the potential of cover crops for P management. In the frame of the EU Horizon2020 Project SoilCare we present the results of two studies in SW Germany about P dynamics under cover crops. The first field experiment investigated the effects of cover crop mixtures and no-tillage in a field experiment in the research station Tachenhausen of Nuertingen-Geislingen University, the second one studied the effects of single cover crop species in a low-P field near Rottenburg. The samples were analyzed for PLFA/NLFA content, enzymatic activities (acid and alkaline phospho-monoesterases and phosphodiesterase) and microbial P. The results reveal significant effects of cover crop mixtures on soil microbes, increasing their abundance and activity, as well as shifts in the microbial community structure. The effects were more pronounced near the soil surface and were still detectable more than one year after cover cropping in winter wheat. The microbial abundance, including Pmic and the activity of several enzymes of the P cycle were strongly increased in the rhizosphere of the cover crops. The results indicate that, under optimized agronomic management, the use of cover crops and minimum tillage can have measurable positive effects on the cycling of P in temperate agroecosystems

Microbial growth response to substrate complexity under different temperature regimes

Soil microbial communities mediate soil feedbacks to climate change and a thorough understanding of their response to increasing temperatures is central for predicting climate-induced changes in carbon fluxes. However, it is still unclear how microbial communities will change their structure and functions in response to temperature change and availability of organic carbon of varying complexity. Here, we present results from a lab-based study where soil microbial communities were exposed to different temperatures and organic C of different stability. Soil samples were collected from vegetated and bare fallow plots located in two regions in southwest Germany varying in climatic and edaphic conditions. Soils amended with cellobiose (CB), xylan or coniferyl alcohol (CA, lignin precursor) were incubated at 5, 15 and 25 °C. We generally found highest cumulative respiration (CO2-C) at 25 °C in all substrate treatments even though total microbial growth (measured as total extracted DNA) was higher at 15 °C. Fungal biomass (measured from ergosterol content and fungal PLFAs) responded significantly to added substrate and incubation temperature, with higher fungal biomass at 5 or 15 °C than 25 °C in all substrate amendments. Xylan addition resulted in significantly higher ergosterol contents than for CB and CA. Within region, land-use significantly affected fungal biomass response to added substrate; however, the temperature response was similar between fallow and vegetated plots. Bacterial community response was also significantly affected by substrate quality. In contrast to fungi, the growth response of Gram+ and Gram- bacteria declined in the order CB > xylan > CA. Currently, we are analyzing the qPCR data understand the response of different bacterial taxa to temperature and substrate complexity. Our results demonstrate the importance of the interaction between soil temperature and substrate quality for soil microbial community functions and growth strategies

Entwicklungslinien und Grundsätze im Werk von Anna Lülja Praun

Da zu Beginn meiner Arbeit keinerlei inhaltliche Aufarbeitung von Leben und Werk Anna Lülja Prauns vorhanden war und nur sehr wenige Materialien und konkrete Angaben zu den Ausbildungs- und ersten Berufsjahren der Architektin erhalten bzw. von ihr selbst dokumentiert waren, wurde besonderes Augenmerk auf das Zusammentragen aller wesentlichen Daten durch Recherchen und zahlreiche persönliche Gespräche sowie auf die Darstellung des jeweiligen Umfelds gelegt, die die Basis des ersten Teils der vorliegenden Dokumentation Entwicklungslinien und Grundsätze im Werk Anna Lülja Prauns bildet. Unter dem Titel Anna Lülja Praun – Lebensdaten, Ausbildung, erste Tätigkeiten widmet sich dieser Teil der Arbeit der Biografie der als Tochter einer russischen Ärztin und des bulgarischen Verlegers Boris Simidoff 1906 in St. Peterburg, im noch zaristischen Russland geborenen, vor allem in Bulgarien aufgewachsenen Architektin, die ein interessantes und bewegtes Leben führte. Ihrem Studium an der Technischen Hochschule in Graz als einzige Frau unter männlichen Studenten, ihrer Mitarbeit im Atelier Herbert Eichholzers, der zu den wichtigsten Vertretern der Avantgarde in der Steiermark gehörte, der Mitarbeit im Atelier Clemens Holzmeisters in Wien, beides noch während des Studiums sowie ihre nach Studienende 1939 aufgenommene Tätigkeit in Bulgarien, wo sie bis März 1942 blieb um wieder nach Wien zurückzukehren und den Architekten Richard Praun zu heiraten, wird hier entsprechender Raum geboten um letztlich so Einflüsse und Auswirkungen auf ihr Werk untersuchen zu können. Der zweite Teil der Arbeit gilt der Darstellung und Untersuchung des Werks Anna Lülja Prauns, das im Rahmen ihrer Tätigkeit als selbständige Architektin entstanden ist, einem Oeuvre, das sich im Laufe ihres jahrzehntelangen Schaffens unterschiedlichsten Aufgaben widmete; die Spannbreite ihrer Planungen reichte von Einzelmöbeln, über Geschäfts- und Wohnungseinrichtungen bis hin zu Häusern und Segelyachten. Beginnend mit ihrer Tätigkeit als selbständige Architektin, die nach der Trennung von Richard Praun begann, über ihre von 1954 bis 1958 andauernde Mitarbeit in dem von Josef Frank und Oskar Wlach gegründeten Einrichtungshaus Haus & Garten , einem Geschäft, das von seinen Anfängen Mitte der zwanziger Jahre bis zum Ende seines Bestehens wesentlich dazu beitrug, einen Wiener Möbel- bzw. Wohnstil auszubilden, der weit über Österreichs Grenzen hinaus bekannt war und wirkte, wird in den Kapiteln des zweiten Teils Anna Lülja Prauns herausragender Einzelbeitrag zur Wiener Einrichtungs- und Wohnkultur sowie zum individuellen nutzerbezogenen Einzelmöbel ausführlich dargestellt, das durchwegs Qualitäten des legendären Wiener Möbels aufweist, dessen Tradition sie eigenständig und bereichert durch Elemente der Wiener Raumkunst der Jahrhundertwende, der Wiener Moderne, des Art Déco, aber auch der internationalen Moderne fortsetzte. Durch unterschiedlichste Einflüsse und Architekturauffassungen der Ausbildungs- und ersten Berufsjahre geprägt, entwickelte Anna Lülja Praun in der Folge ihren ganz eigenen und unverkennbaren Stil, deren gemeinsamer Nenner über alle Jahre, bis zu ihrem Tod 2004, die intensive Kommunikation mit dem Auftraggeber und der damit einhergehenden Beschäftigung mit dessen Bedürfnissen bildet. Neben der Definition des einzelnen Möbels im Raum sowie Prauns hohem Anspruch an Funktionalität bei allen Gestaltungsaufgaben und ihrer differenzierten Auseinandersetzung mit den jeweils gewählten, meist kostbaren und dauerhaften Materialien, wie edlen Hölzern, Halbedelsteinen und Ammoniten, Metall oder Leder, galt ein ganz spezifisches Merkmal ihrer Entwürfe der allerhöchsten handwerklichen Qualität und Präzision der Ausführungen, die durch die befruchtende Zusammenarbeit mit Handwerkern und ihren tradierten Fertigungsmethoden ermöglicht wurde. Betrachtet man ihr Gesamtwerk, so sind Konstanten der Formensprache, wie Transparenz von Raumfolgen, geometrische bzw. symmetrische Gliederungen von Räumen, Wandflächen und Einzelmöbeln, sowie gerüsthafter Möbelaufbau und der häufige Einsatz von Farbe als Gestaltungselement auffallend, denen in dieser Untersuchung reichlich Platz gegeben wird

Flooding forested groundwater recharge areas modifies microbial communities from top soil to groundwater table

Subsurface microorganisms are crucial for contaminant degradation and maintenance of groundwater quality. This study investigates the microbial biomass and community composition [by phospholipid fatty acids (PLFAs)], as well as physical and chemical soil characteristics at woodland flooding sites of an artificial groundwater recharge system used for drinking water production. Vertical soil profiles to c. 4 m at two watered and one nonwatered site were analyzed. The microbial biomass was equal in watered and nonwatered sites, and considerable fractions (25-42%) were located in 40-340 cm depth. The microbial community structure differed significantly between watered and nonwatered sites, predominantly below 100 cm depth. Proportions of the bacterial PLFAs 16:1ω5, 16:1ω7, cy17:0 and 18:1ω9t, and the long-chained PLFAs 22:1ω9 and 24:1ω9 were more prominent at the watered sites, whereas branched, saturated PLFAs (iso/anteiso) dominated at the nonwatered site. PLFA community indices indicated stress response (trans/cis ratio), higher nutrient availability (unsaturation index) and changes in membrane fluidity (iso/anteiso ratio) due to flooding. In conclusion, water recharge processes led to nutrient input and altered environmental conditions, which resulted in a highly active and adapted microbial community residing in the vadose zone that effectively degraded organic compound

Auto- und Heterotrophic Respiration in the Hohenheim Climate Change Experiment - The Importance of Temperature Change and Vegetation Period

Current Climate change (CC) research in soil science mainly focusses on natural ecosystems, without considering the potential of agro-ecosystems for feedback mechanisms to CC and CC mitigation through Carbon(C)-sequestration. We expect that CC induces increasing water limitation under elevated temperature, lowers the intensity of soil respiration and changes the ratio between the amount of root-dependent and basal soil respiration. Such changes might be due to differences in the intrinsic temperature and moisture sensitivity of microbial and root respiration and due to altered root exudation. In this project, we focus on CC-induced effects on plant-dependent and basal soil respiration to improve the estimation of long-term soil organic matter stabilization. Within the Hohenheim Climate Change (HoCC) experiment (established in 2008), barley plants were pulse-labelled with 20-atom% 13CO2 for 4 h using ventilated transparent chambers on warmed and control plots in an agricultural field. The labeling was done during three different stages (advanced tillering, booting and grain-filling) of the vegetation period, at which C-sink strength of shoot and root differs according to plant development. CO2-fluxes and isotopic composition were measured in real time in the field for the first 50h (post labeling) using a 13CO2 isotope analyzer. Results from tracing 13C-fluxes will clarify how soil moisture and long-term elevated temperature affect the overall C-balance in agricultural soils in dependence of the vegetation period. This will allow estimations of direction and strength of feedback mechanisms of terrestrial C-cycling under CC. Overall, insights obtained in this project will provide better understanding of the CC impact on and of temperate agricultural production systems

Functional microbial community response to nutrient pulses by artificial groundwater recharge practice in surface soils and subsoils

Subsurface microorganisms are essential constituents of the soil purification processes associated with groundwater quality. In particular, soil enzyme activity determines the biodegradation of organic compounds passing through the soil profile. Transects from surface soil to a depth of 3.5 m were investigated for microbial and chemical soil characteristics at two groundwater recharge sites and one control site. The functional diversity of the microbial community was analyzed via the activity of eight enzymes. Acid phosphomonoesterase was dominant across sites and depths, followed by l-leucine aminopeptidase and β-glucosidase. Structural [e.g. phospholipid fatty acid (PLFA) pattern] and functional microbial diversities were linked to each other at the nonwatered site, whereas amendment with nutrients (DOC, NO3−) by flooding uncoupled this relationship. Microbial biomass did not differ between sites, whereas microbial respiration was the highest at the watered sites. Hence, excess nutrients available due to artificial groundwater recharge could not compensate for the limitation by others (e.g. phosphorus as assigned by acid phosphomonoesterase activity). Instead, at a similar microbial biomass, waste respiration via overflow metabolism occurred. In summary, ample supply of carbon by flooding led to a separation of decomposition and microbial growth, which may play an important role in regulating purification processes during groundwater recharg

Microbial carbon turnover in the detritusphere

Microbial decomposition processes at the soil-litter interface involves a complex food web including fungi, bacteria, and archaea that compete for the organic matter. During the decomposition, the nutrient quantity and quality changes as well as the microbial community composition. It is still a challenge to identify and quantify active microbial species in concurrency with their absolute contribution to the carbon (C) turnover. In the frame of the DFG-Project (FOR 918) “Carbon flow in belowground food webs assessed by isotope tracers“ we determined the C flow and turnover of differently aged maize litter in bacteria and fungi of an arable soil. A microcosm experiment was set up with C-13-labeled and unlabeled maize litter on top of soil cores. A reciprocal transplantation of the labeled litter on soil cores with unlabeled litter allowed us to follow the C flow into different microbial groups at the early (0-4d), intermediate (4-12d) and late stage (28-36d) of litter decomposition. We analyzed microbial CO2 respiration, microbial biomass and PLFA pattern in the top 3 mm of the soil cores. To identify and quantify microbial species feeding on the substrate and to assess their degree of C-13 assimilation, DNA stable isotope probing followed by gene-targeted sequencing of bacteria and fungi are currently performed on the soil metagenome. We expected specific microbial communities (copio- and oligotrophic) involved in maize litter decomposition at the different stages of litter decay. During the initial days of the experiment, up to 17% of the CO2-C was maize-derived C. The C-13 content in the CO2 decreased with continuous decomposition of the litter. The highest absolute amount of maize-derived C was found in gram-positive bacteria in the early stage of litter decomposition. For fungi, the highest maize C incorporation was in the intermediate stage of litter decomposition. We calculated a faster C turnover in the fungal biomass than in the bacterial biomass for all three decomposition stages. But during the later stage of litter decomposition, maize-derived C was less utilized by both bacteria and fungi. These results will be concluded by the quantitative DNA-SIP method to provide a species-resolved contribution to the C turnover in the microbial food web at different decomposition stages in the detritusphere

Unraveling spatiotemporal variability of arbuscular mycorrhizal fungi in a temperate grassland plot

© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Goldmann, K., Boeddinghaus, R. S., Klemmer, S., Regan, K. M., Heintz-Buschart, A., Fischer, M., Prati, D., Piepho, H., Berner, D., Marhan, S., Kandeler, E., Buscot, F., & Wubet, T. Unraveling spatiotemporal variability of arbuscular mycorrhizal fungi in a temperate grassland plot. Environmental Microbiology, 22(3),(2020): 873-888, doi:10.1111/1462-2920.14653.Soils provide a heterogeneous environment varying in space and time; consequently, the biodiversity of soil microorganisms also differs spatially and temporally. For soil microbes tightly associated with plant roots, such as arbuscular mycorrhizal fungi (AMF), the diversity of plant partners and seasonal variability in trophic exchanges between the symbionts introduce additional heterogeneity. To clarify the impact of such heterogeneity, we investigated spatiotemporal variation in AMF diversity on a plot scale (10 × 10 m) in a grassland managed at low intensity in southwest Germany. AMF diversity was determined using 18S rDNA pyrosequencing analysis of 360 soil samples taken at six time points within a year. We observed high AMF alpha‐ and beta‐diversity across the plot and at all investigated time points. Relationships were detected between spatiotemporal variation in AMF OTU richness and plant species richness, root biomass, minimal changes in soil texture and pH. The plot was characterized by high AMF turnover rates with a positive spatiotemporal relationship for AMF beta‐diversity. However, environmental variables explained only ≈20% of the variation in AMF communities. This indicates that the observed spatiotemporal richness and community variability of AMF was largely independent of the abiotic environment, but related to plant properties and the cooccurring microbiome.We thank the managers of the three Exploratories, Kirsten Reichel‐Jung, Swen Renner, Katrin Hartwich, Sonja Gockel, Kerstin Wiesner, and Martin Gorke for their work in maintaining the plot and project infrastructure; Christiane Fischer and Simone Pfeiffer for giving support through the central office, Michael Owonibi and Andreas Ostrowski for managing the central data base, and Eduard Linsenmair, Dominik Hessenmöller, Jens Nieschulze, Ernst‐Detlef Schulze, Wolfgang W. Weisser and the late Elisabeth Kalko for their role in setting up the Biodiversity Exploratories project. The work has been funded by the DFG Priority Program 1374 ‘Infrastructure‐Biodiversity‐Exploratories’ (BU 941/22‐1, BU 941/22‐3, KA 1590/8‐2, KA 1590/8‐3). Field work permits were issued by the responsible state environmental office of Baden‐Württemberg (according to § 72 BbgNatSchG). Likewise, we kindly thank Beatrix Schnabel, Melanie Günther and Sigrid Härtling for 454 sequencing in Halle. AHB gratefully acknowledges the support of the German Centre for Integrative Biodiversity Research (iDiv) Halle‐Jena‐Leipzig funded by the German Research Foundation (FZT 118). Authors declare no conflict of interests

Effects of soil warming and altered precipitation patterns on photosynthesis, biomass production and yield of barley

Crop productivity and plant physiology are affected by rising temperatures and altered precipitation patterns due to climate change. We studied the impacts of an increase in soil temperature of 2.5 °C, a decrease in summer precipitation amount of 25%, a reduction in summer precipitation frequency of 50%, and their interactions on photosynthesis, biomass production, and yield of spring barley (Hordeum vulgare L. cv. RGT Planet) in a temperate agricultural ecosystem near Stuttgart (Germany). Leaf gas exchange of barley appeared to be affected mainly by drought in the form of reduced precipitation frequency or by a combination of changes in soil temperature and precipitation patterns. In contrast, biomass production and yield parameters were more affected under soil warming alone. In addition, biomass of roots increased under soil warming at stem elongation. Stable grain yield was observed under reduced precipitation amount and also under increased evaporation through soil warming. These findings provide additional evidence that barley is relatively drought tolerant, which should be taken into consideration in the context of appropriate crop selection under climate change