Stability of methane oxidation capacity to variations in methane and nutrient concentrations

Uptake rate constants for atmospheric methane consumption by the 4-6 cm depth interval of a forest soil did not change during 4 months incubation in vitro, even though atmospheric methane concentrations were significantly higher than in situ concentrations. Uptake rate constants were also unaffected by continous incubation at a constant methane concentration of 17 ppm for 2 weeks and 170 ppm for 3 weeks. Uptake rates during incubation with 1000 ppm methane increased 176-fold when assayed with 1000 ppm methane and 5.5-fold when assayed with 1.7 ppm methane. These enhancements were lost after subsequent incubation with atmospheric methane. The ratio of methane oxidized to carbon dioxide produced varied from 49-53% at methane concentrations up to 170 ppm. Incorporation of 14C-methane into phospholipids was 0.35% and 0.22% at atmospheric and 170 ppm methane concentrations, respectively, suggesting that patterns of assimilation were independent of methane concentrations. Addition of several carbon substrates (glucose, starch, yeast extract, methanol, ethanol, formate, acetate, malate, or lactate) to soils incubated at 1.7 or 100 ppm methane did not stimulate methane oxidation. Addition of copper, nitrate or a mineral medium also did not affect methane oxidation. However, incubations with 0.2 or 2% oxygen resulted in lower activity than with ambient air. The methane-consuming capacity of soil decreased exponentially with time when starved for methane by continuous incubation with air containing \u3c 0.03 ppm methane. After 6.3 days of starvation, the soil lost 50% of its original activity; activity was not recoverable after further incubation with atmospheric methane. Methane uptake by soil was rapidly inhibited by the addition of antibacterial antibiotics (streptomycin, chloro-tetracycline, chloramphenicol, ampicillin) as well as by the eukaryotic antibiotic, cycloheximide. Culture suspensions of Methylosinus trichosporium OB3b showed a similar sensitivity to both types of antibiotics. Cell suspensions of Methylosinus trichosporium OB3b and Methylobacter albus consumed atmospheric methane, but consumption rates decreased continuously over a period of 15 days. In contrast, methane consuuption by soil incubated under the same conditions was temporally stable. However, cell suspensions of both cultures showed higher consumption rates for atmospheric methane when sprayed on sand relative to incubations in liquid media. © 1995

Einfluss fermentierter organischer Dünger auf Spurengasemissionen im Ökologischen Pflanzenbau

Agriculture belongs to the major sources of the trace gases nitrous oxide (N2O) and methane (CH4). However, little is known about the contribution of the increasing area of organically managed arable soils in organic farming systems to the greenhouse gas emissions. The objective of our study was the quantification of the in-situ N2O- and CH4- emissions in common organic crop cultivation without livestock. In comparison to this control variant, we focused on the manuring effect of fermented herbal organic matter on the emissions (biogas variant). The straw of the crops and the growth of the intercrops were harvested, fermented in a biogas reactor and applied as fertilizer on the field when the nutrient demand of the crops occurred. The results obtained in 2003/2004 in winter wheat generally revealed a low level of N2O emissions and indicated reduced losses (458 g N ha-1 yr-1) of the soil in the biogas variant compared to the control variant (770 g N ha-1 yr-1). Measurements of the CH4 fluxes showed a slightly decreased CH4 uptake rate in the biogas variant (484 g C ha-1 yr-1) in comparison to the control variant (591 g C ha-1 yr-1)

Domestication Impacts the Wheat-Associated Microbiota and the Rhizosphere Colonization by Seed- and Soil-Originated Microbiomes, Across Different Fields

The seed-transmitted microorganisms and the microbiome of the soil in which the plant grows are major drivers of the rhizosphere microbiome, a crucial component of the plant holobiont. The seed-borne microbiome can be even coevolved with the host plant as a result of adaptation and vertical transmission over generations. The reduced genome diversity and crossing events during domestication might have influenced plant traits that are important for root colonization by seed-borne microbes and also rhizosphere recruitment of microbes from the bulk soil. However, the impact of the breeding on seed-transmitted microbiome composition and the plant ability of microbiome selection from the soil remain unknown. Here, we analyzed both endorhiza and rhizosphere microbiome of two couples of genetically related wild and cultivated wheat species (Aegilops tauschii/Triticum aestivum and T. dicoccoides/T. durum) grown in three locations, using 16S rRNA gene and ITS2 metabarcoding, to assess the relative contribution of seed-borne and soil-derived microbes to the assemblage of the rhizosphere microbiome. We found that more bacterial and fungal ASVs are transmitted from seed to the endosphere of all species compared with the rhizosphere, and these transmitted ASVs were species-specific regardless of location. Only in one location, more microbial seed transmission occurred also in the rhizosphere of A. tauschii compared with other species. Concerning soil-derived microbiome, the most distinct microbial genera occurred in the rhizosphere of A. tauschii compared with other species in all locations. The rhizosphere of genetically connected wheat species was enriched with similar taxa, differently between locations. Our results demonstrate that host plant criteria for soil bank’s and seed-originated microbiome recruitment depend on both plants’ genotype and availability of microorganisms in a particular environment. This study also provides indications of coevolution between the host plant and its associated microbiome resulting from the vertical transmission of seed-originated taxa

Auswirkung der Fermentation biogener Rückstände in Biogasanlagen auf Flächenproduktivität und Umweltverträglichkeit im Ökologischen Landbau – Pflanzenbauliche, ökonomische und ökologische Gesamtbewertung im Rahmen typischer Fruchtfolgen viehhaltender und viehloser ökologisch wirtschaftender Betriebe

Die Effekte der Vergärung von Gülle und Nebenernteprodukten wurden auf der Ebene des gesamten landwirtschaftlichen Systems für einen viehhaltenden Gemischtbetrieb und einen viehlosen Marktfruchtbetrieb untersucht. Dabei wurden die Wirkungen der Vergärung von Gülle und Kleegras auf die Flächenproduktivität, auf die innerbetrieblichen Nährstoffflüsse, auf die Nitratauswaschungsgefahr sowie auf die Gefahr von bodenbürtigen Spurengasemissionen untersucht. Ferner wurde eine ökologische Bilanzierung der Biogasvergärung im ökologischen Landbau mittels Öko-Bilanzierung durchgeführt

Elevated Atmospheric {CO}2 Modifies Mostly the Metabolic Active Rhizosphere Soil Microbiome in the Giessen {FACE} Experiment

Elevated levels of atmospheric CO2 lead to the increase of plant photosynthetic rates, carbon inputs into soil and root exudation. In this work, the effects of rising atmospheric CO2 levels on the metabolic active soil microbiome have been investigated at the Giessen free-air CO2 enrichment (Gi-FACE) experiment on a permanent grassland site near Giessen, Germany. The aim was to assess the effects of increased C supply into the soil, due to elevated CO2, on the active soil microbiome composition. RNA extraction and 16S rRNA (cDNA) metabarcoding sequencing were performed from bulk and rhizosphere soils, and the obtained data were processed for a compositional data analysis calculating diversity indices and differential abundance analyses. The structure of the metabolic active microbiome in the rhizospheric soil showed a clear separation between elevated and ambient CO2 (p = 0.002); increased atmospheric CO2 concentration exerted a significant influence on the microbiomes differentiation (p = 0.01). In contrast, elevated CO2 had no major influence on the structure of the bulk soil microbiome (p = 0.097). Differential abundance results demonstrated that 42 bacterial genera were stimulated under elevated CO2. The RNA-based metabarcoding approach used in this research showed that the ongoing atmospheric CO2 increase of climate change will significantly shift the microbiome structure in the rhizosphere

The transcriptionally active bacterial communities of grapevine rhizosphere in dependence on rootstock and scion variety

The rhizosphere is where crucial processes for the productivity of viticultural systems occur. The composition of the bacterial communities associated with the rhizosphere of grapevines is known to depend on plant genotype. However, the genotype of grafted grapevines differs between scion and rootstock; the role of each genotype is unclear. To untangle the effect of scion and rootstock, the rRNA (V4–V5 region of 16S rRNA) extracted from the rhizosphere of the grape varieties Riesling and Mueller-Thurgau ungrafted vs grafted on different rootstocks was sequenced. The bioinformatic analysis with tools designed to be robust for compositional data showed that the investigated rootstocks or scions or combinations, respectively, recruited bacterial communities with distinguishable traits. Statistical differences were revealed between ungrafted Riesling vs Mueller-Thurgau, between grafted Riesling vs ungrafted Riesling, and between ungrafted Mueller-Thurgau vs grafted Mueller-Thurgau. Thus, confirming the role of scion and rootstock genotype as a driver of the structure and composition of bacterial communities in the rhizosphere of grapevines

Einfluss von Cd-, Cu- und Zn-Kontaminationen auf die mikrobielle Population und Respiration in bewässerten Kastanozems in SE-Georgien

Das Untersuchungsgebiet befindet sich etwa 80 km südlich der Hauptstadt Tiflis im Mashavera-Tal in SE-Georgien. Aufgrund kontinentaler Klimabedingungen (504 mm) werden die intensiv landwirtschaftlich genutzten Böden mit Wasser aus dem Mashavera-Fluss bewässert. Der Fluss ist stark mit spurenmetallhaltigen (Cd, Cu, Zn) Schwebstoffen belastet, die aus Erosionsprozessen von Abraumhalden und Abwassereinleitungen der Flotationsanlagen einer NE-Metallmine stammen. Hierdurch werden die bewässerten Böden im Mashavera-Tal großflächig mit Cd, Cu und Zn belastet. Im Rahmen der Untersuchungen wurden die Auswirkungen der Spurenmetallbelastung auf die Lebensraumfunktion der Böden geprüft. Die im Mashavera-Tal anthropogen verursachte Cd-, Cu- und Zn-Kontamination der landwirtschaftlich genutzten Böden wirkt sich negativ auf die untersuchten mikrobiellen Parameter aus. Auf stark belasteten Flächen ist ein deutlicher Rückgang der mikrobiellen Respiration zu verzeichen. Zudem zeigt sich eine geringere Diversität in der bakteriellen Populationsstruktur in stark belasteten Bodenproben

Auswirkungen des Buntemetallbergbaus im Mashavera-Tal (Georgien) auf Bodenfunktionen und Möglichkeiten der in-situ Sanierung

Bie Böden des Mashavera-Tals (SE-Georgien) werden seit Jahrzehnten mit durch Buntmetallbergbau belastetet Wassser des Flusses Mashavera bewässert. Die daraus resultierenden hohen Cd, Cu und Zn Gehalte der Oberböden stellen ein erhebliches Belastungspotenzial für die Nahrungskette dar. Im Gefäßversuch gelang es durch Zugabe von Divergan® (ein Polyvinylpyrrolidon)die Spurenmetalle in schwer mobilisierbare Fraktionen zu überführen und dadurch die Pflanzenaufnahme zu reduzieren. Ob das Verfahren auch als Sanierungsstrategie im Mashavera-Tal anwendbar ist, muss aber zunächst noch im Feldversuch getestet werden