172 research outputs found

    Die Baumart beeinflusst die Menge und Stöchiometrie der organischen Bodensubstanz sowie die mikrobielle Biomasse in Streuauflagen und Mineralböden von Waldböden

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    Die Menge und QualitĂ€t der organischen Bodensubstanz (OBS) ist von entscheidender Bedeutung fĂŒr die ökosystemaren Leistungen, Resistenz und Resilienz von Waldböden. Ziel der Arbeit ist, die VorrĂ€te und Zusammensetzung der OBS von Waldböden, welche unter dem Einfluss unterschiedlicher Baumarten stehen, zu charakterisieren. Verglichen wurden die VorrĂ€te an organischem Kohlenstoff (Corg), Stickstoff (N), Schwefel (S), Wasserstoff (H) und Sauerstoff (O) in den Streuauflagen und den verschiedenen Tiefenstufen des Mineralbodens (0-5 cm, 5-10 cm, 10-30 cm) unter fĂŒnf verbreiteten Baumarten der gemĂ€ĂŸigten Zone: Douglasie (Pseudotsuga menziesii), Gemeine Fichte (Picea abies), Rotbuche (Fagus sylvatica), Roteiche (Quercus rubra) und Schwarzkiefer (Pinus nigra). ZusĂ€tzlich wurden C-Gehalt der mikrobiellen Biomasse (MBC) und der Ergosterolgehalt als Indikator fĂŒr die pilzliche Biomasse bestimmt. Die Studie wurde auf einer seit 1980 rekultivierten Abraumhalde im rheinischen Braunkohlerevier durchgefĂŒhrt. Durch die Standortwahl sind abiotische Faktoren wie Klima, Ausgangssubstrat, Relief usw. unter den BaumbestĂ€nden gleich, sodass angenommen werden kann, dass Unterschiede in den Bodeneigenschaften auf den Einfluss der verschiedenen Baumarten zurĂŒckzufĂŒhren sind. Bereits in der jungen 35-jĂ€hrigen Bodenentwicklung seit der Rekultivierung wurden Auflagen sowie mineralische Bodenhorizonte mit unterschiedlichen Corg-VorrĂ€ten und unterschiedlichen C:N:S:H:O-VerhĂ€ltnissen unter dem Einfluss der fĂŒnf Baumarten herausgebildet. So steigen die Corg-VorrĂ€te in den Auflagen in folgender Reihenfolge an: Douglasie < Rotbuche = Roteiche < Schwarzkiefer < Fichte. Im Mineralboden werden mit zunehmender Tiefe die Unterschiede zwischen den Baumarten signifikant kleiner, wobei unter Rotbuche die kleinsten und unter Fichte sowie Roteiche die grĂ¶ĂŸten Corg-VorrĂ€te bestimmt wurden. Die C/N-VerhĂ€ltnisse der Auflagenhorizonte unter Koniferenbestand sind signifikant weiter verglichen zu den Laubbaumarten, was auf Unterschiede in der Humifizierung hindeutet. Die H/C- und O/C-VerhĂ€ltnisse sind in den Auflagenhorizonten unter der Schwarzkiefer am kleinsten und unter Douglasie (HC) bzw. Fichte (OC) am grĂ¶ĂŸten. Die mit der Tiefe kleiner werdenden mikrobiellen Parameter korrelieren mit den stöchiometrischen VerhĂ€ltnissen und unterscheiden sich signifikant zwischen den Baumarten. Die untersuchten Bodenparameter bilden eine Grundlage zur Bewertung des Potenzials Kohlenstoff in Waldböden zu sequestrieren

    Short-term soil response under plastic mulching in strawberry cultivation

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    Plastic mulches (PM) are known for increasing soil temperature and retaining soil moisture, suppressing weeds and avoiding ground contact of on-soil growing products. Thus, the use of PM in agriculture has been significantly increased in the last years, with important economic benefits for the farmers. Most studies dealing with PM emphasize the positive effects of this management, yet recent reports have shown that the use of PM is linked to a decrease of SOM content, soil erosion, soil contamination with plastic residues and in some cases to a high mycotoxin production by soil fungi. This questions the sustainability of the intensive use of PM in agriculture. The aim of this study was to assess the short-term modification of soil physicochemical and microbial parameters under PM, compared to no-mulch (NM). The experiment was conducted in a 2016-planted strawberry field. For each management (PM vs. NM) five plots were selected. Cultivation of strawberry in both PM and NM was done in a ridge-furrow system with subsurface irrigation. Samples were collected prior to the planting (T0) and successively at two (T1) and four months (T2) after planting. Different depths were sampled in the ridges (0-10, 10-30 and 30-60 cm) and in the furrows (0-10 and 10-40 cm). The analysis of the quantity and quality of soil organic matter is ongoing and comprised soil physicochemical analysis: pH, electrical conductivity, water content, bulk density and stability, organic C and N and density fractionation. Moreover, soil microbiology was studied via soil microbial carbon and mycotoxin occurrence as indicator of fungal stress. Additionally, temperature, humidity and pH of soil were daily recorded using an in-field installed measuring station. The continuously recorded environmental data showed differences in the temperature patterns between PM and NM, with highest average temperature under plastic. As well, pH and humidity data indicated differences between the treatments

    Transport von Dieselruß durch Wasser in gestörten und ungestörten Böden - Resultierende, kleinskalige Verteilung und Nachweismethoden

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    Durch den Diesel-Kfz-Verkehr gelangen jĂ€hrlich ca. 1,8 g Ruß/km in straßennahe Böden. Ruß enthĂ€lt hohe Gehalte an PAK und ist aufgrund seiner Sorptionseigenschaften gleichzeitig Senke fĂŒr weitere hydrophobe Schadstoffe. Es ist daher zu vermuten, dass derartige Schadstoffe prioritĂ€r mit dem Ruß transportiert werden. Zur Verlagerung bzw. Retention von Ruß in Böden liegen jedoch kaum Informationen vor. Ziel dieser Arbeit war es daher, den Transport von Ruß in aggregierten bzw. homogenisierten Böden unterschiedlichen Stoffbestandes mit Hilfe von SĂ€ulenperkolationsexperimenten zu bestimmen. Zur Ermittlung des Durchbruchs bzw. der Retention des Rußes wurden DOC und DON im Perkolat sowie PAK-Gehalte in unterschiedlichen Bodentiefen bestimmt. Die resultierende rĂ€umliche Verteilung des Rußes in den BodensĂ€ulen und PorenrĂ€umen wurde mittels bildgebender Verfahren untersucht. Dies erfolgte zum einem unter Verwendung einer Hyperspektralkamera (Neo HySpex VNIR-1600) und Maximum Likelihood Classification (MLC) sowie autoPartial Least Squares Regression (aPLSR) als Auswertungsmethoden. Die Identifizierung des Rußes erfolgte durch konfokale Raman-Imaging Mikroskopie. Die Ergebnisse zeigen, dass Ruß vorrangig an der BodenoberflĂ€che ausgefiltert wird, wo er potentiell einem Abtrag durch runoff, Auswehung, etc. unterliegt. Eine Tiefenverlagerung erfolgt ĂŒber MakroporenrĂ€ume als prĂ€ferentielle Fließwege

    Langzeitbelastung von Weinbergsböden mit Cu beeinflusst die Stressresistenz der mikrobiellen Gemeinschaft

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    Eine lang andauernde Bodenbelastung fĂŒhrt hĂ€ufig zur Akklimatisierung bzw. Adaptation von Mikroorganismen, weshalb negative Wirkungen der Belastung durch ĂŒbliche ToxizitĂ€tstests mit Bodenorganismen nicht angezeigt werden. Dies kann selbst bei sehr hohen Schadstoffgehalten auftreten, die bei Experimenten mit frisch zugegebenem Schadstoff eindeutig zu negativen Effekten fĂŒhren. Langzeitkontaminationen durch Cu treten in Weinbergsböden verbreitet auf; seit dem spĂ€ten 19. Jahrhundert und mit Applikationsmaxima in den 1920er bis 1930er Jahren sowie in den 1950er Jahren werden Cu-haltige Fungizide dort angewendet. In der Folge haben Weinbergsböden hohe Gehalte an Cu akkumuliert; Cu-Gehalte liegen in Weinbergsböden der Moselregion im Mittel bei 170 mg kg-1 Boden. Die mikrobielle Abundanz und AktivitĂ€t in Böden mit Langzeitkontamination steht jedoch meist in keinem eindeutigen Zusammenhang zu der Höhe der Belastung. Grundlage dieser Studie war die Hypothese, dass die Vorbelastung der Böden mit Cu zu einer erhöhten Empfindlichkeit gegenĂŒber zusĂ€tzlichem Stress fĂŒhrt, was sich in einer verminderten Resistenz und Resilienz der mikrobiellen Gemeinschaft ausdrĂŒckt. Um dies zu untersuchen, wurden zehn Weinbergsböden des Weinbaugebietes Mosel mit Cu-Gesamtgehalten zwischen 20 und 440 mg kg‑1 ausgewĂ€hlt. Die Stressresistenz der mikrobiellen Gemeinschaft in diesen Böden wurde mithilfe des relativen BodenstabilitĂ€ts-Index (relative soil stability index - RSSI) ermittelt. Dazu wurden die Böden in Laborexperimenten einer kurzzeitigen Hitzebehandlung als zusĂ€tzlichem, zweitem Stress ausgesetzt und nachfolgend EnzymaktivitĂ€ten der Dehydrogenase und alkalischen Phosphatase als Endo- und Exoenzyme ĂŒber 15 Tage gemessen. Die Ergebnisse bestĂ€tigen, dass die vorhandene, mikrobielle AktivitĂ€t in den Böden in keinem Zusammenhang zu den Gehalten an Gesamt-Cu wie auch mobilem Cu steht. ZusĂ€tzlicher Stress bewirkte weitere Verminderungen der EnzymaktivitĂ€ten, die ĂŒber den beobachteten Zeitraum in unterschiedlichem Maß wieder kompensiert wurden. Diese Parameter stehen zumindest teilweise in Zusammenhang mit der Cu-Belastung. Überraschenderweise waren die Resistenz, Resilienz und der RSSI positiv mit der Cu-Belastung korreliert; eine höhere Cu-Belastung induziert eine höhere Resistenz gegen zusĂ€tzlichen Stress. Es wird vermutet, dass die Langzeit-Kontamination zur Selektion einer stressresistenteren mikrobiellen Gemeinschaft gefĂŒhrt hat. Dies wird durch weitere Parameter ĂŒberprĂŒft

    Shift of microbial communities and reduced enzymatic activity in soil under plastic mulching system in strawberry cultivation

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    The use of plastic mulching (PM) in agriculture has strongly increased in the last years. Improved water saving and higher soil temperature are some advantages of this management. Yet, an intensive use of PM has been recently linked to negative effects on soil quality. The aim of this study is thus to assess the effects of long-term plastic mulching (PM) on soil microbial indicators. PM was compared with the use of wheat straw mulching (SM), an also widely used mulch material. Samples were collected at two depths (0-5 and 5-10 cm) from strawberry fields, after 4-year management. Cultivation in PM and SM was done in a ridge-furrow system with subsurface irrigation. Soil characterization comprised soil texture and aggregate stability, soil organic carbon, pH and water content. Soil microbial analysis included: Soil microbial biomass (Cmic), a fraction of soil cultivable fungi (CFU values), soil bacteria (16S rRNA), denitrifying community (nirK, nirS, narG, napA genes), soil enzyme activity (C-Chitinase, P-Phosphatase and N Leucine-aminopeptidase), deoxynivalenol (DON) content and Cmic:Corg ratio. Positive effects on soil physicochemical properties were observed under PM as compared to SM, reflected by a higher soil carbon content and better aggregate stability (p>0.05). Yet, soil microbial analysis revealed some differences between managements. Cmic values were comparable in both systems, showing no differences in soil microbial biomass. In the same way, the analysis of functional genes of the N cycle and the activity of the enzymes P-Phosphatase and N Leucine-aminopeptidase was not affected by the mulching treatment. But, the abundance of bacteria (18%) and a fraction of soil cultivable fungi were reduced by respectively 18 and 62% under PM. Since the Cmic values remained similar between treatments, this accounts for a shift of microbial communities under PM. Additionally, C-Chitinase activity declined under PM. Interestingly, this enzyme correlated positively with CFU values (r=0.781, p=0.001), suggesting that a reduction of the activity is a consequence of the reduction of the fungal biomass. Additionally, a higher deoxynivalenol concentration (2.2 ± 2.4 ”g kg-1) and a reduced Cmic:Corg ratio (1.3±0.3%) were observed under PM, indicative of less appropriate soil conditions after long-term PM management

    Sorption and Photodegradation Processes Govern Distribution and Fate of Sulfamethazine in Freshwater−Sediment Microcosms

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    The antibiotic sulfamethazine can be transported from manured fields to surface water bodies. We investigated the degradation and fate of sulfamethazine in pond water using 14C-phenyl-sulfamethazine in small pond water microcosms containing intact sediment and pond water. We found a 2.7-day half-life in pond water and 4.2-day half-life when sulfamethazine was added to the water (5 mg L–1 initial concentration) with swine manure diluted to simulate runoff. Sulfamethazine dissipated exponentially from the water column, with the majority of loss occurring via movement into the sediment phase. Extractable sulfamethazine in sediment accounted for 1.9–6.1% of the applied antibiotic within 14 days and then declined thereafter. Sulfamethazine was transformed mainly into nonextractable sediment-bound residue (40–60% of applied radioactivity) and smaller amounts of photoproducts. Biodegradation, as indicated by metabolite formation and 14CO2 evolution, was less significant than photodegradation. Two photoproducts accounted for 15–30% of radioactivity in the water column at the end of the 63-day study; the photoproducts were the major degradates in the aqueous and sediment phases. Other unidentified metabolites individually accounted for \u3c7% of radioactivity in the water or sediment. Less than 3% of applied radioactivity was mineralized to 14CO2. Manure input significantly increased sorption and binding of sulfamethazine residues to the sediment. These results show concurrent processes of photodegradation and sorption to sediment control aqueous concentrations and establish that sediment is a sink for sulfamethazine and sulfamethazine-related residues. Accumulation of the photoproducts and sulfamethazine in sediment may have important implications for benthic organisms

    The MRN complex is transcriptionally regulated by MYCN during neural cell proliferation to control replication stress

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    The MRE11/RAD50/NBS1 (MRN) complex is a major sensor of DNA double strand breaks, whose role in controlling faithful DNA replication and preventing replication stress is also emerging. Inactivation of the MRN complex invariably leads to developmental and/or degenerative neuronal defects, the pathogenesis of which still remains poorly understood. In particular, NBS1 gene mutations are associated with microcephaly and strongly impaired cerebellar development, both in humans and in the mouse model. These phenotypes strikingly overlap those induced by inactivation of MYCN, an essential promoter of the expansion of neuronal stem and progenitor cells, suggesting that MYCN and the MRN complex might be connected on a unique pathway essential for the safe expansion of neuronal cells. Here, we show that MYCN transcriptionally controls the expression of each component of the MRN complex. By genetic and pharmacological inhibition of the MRN complex in a MYCN overexpression model and in the more physiological context of the Hedgehog-dependent expansion of primary cerebellar granule progenitor cells, we also show that the MRN complex is required for MYCN-dependent proliferation. Indeed, its inhibition resulted in DNA damage, activation of a DNA damage response, and cell death in a MYCN- and replication-dependent manner. Our data indicate the MRN complex is essential to restrain MYCN-induced replication stress during neural cell proliferation and support the hypothesis that replication-born DNA damage is responsible for the neuronal defects associated with MRN dysfunctions.Cell Death and Differentiation advance online publication, 12 June 2015; doi:10.1038/cdd.2015.81

    Soil-derived Nature's Contributions to People and their contribution to the un Sustainable Development Goals

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    This special issue provides an assessment of the contribution of soils to Nature's Contributions to People (NCP). Here, we combine this assessment and previously published relationships between NCP and delivery on the UN Sustainable Development Goals (SDGs) to infer contributions of soils to the SDGs. We show that in addition to contributing positively to the delivery of all NCP, soils also have a role in underpinning all SDGs. While highlighting the great potential of soils to contribute to sustainable development, it is recognized that poorly managed, degraded or polluted soils may contribute negatively to both NCP and SDGs. The positive contribution, however, cannot be taken for granted, and soils must be managed carefully to keep them healthy and capable of playing this vital role. A priority for soil management must include: (i) for healthy soils in natural ecosystems, protect them from conversion and degradation; (ii) for managed soils, manage in a way to protect and enhance soil biodiversity, health and sustainability and to prevent degradation; and (iii) for degraded soils, restore to full soil health. We have enough knowledge now to move forward with the implementation of best management practices to maintain and improve soil health. This analysis shows that this is not just desirable, it is essential if we are to meet the SDG targets by 2030 and achieve sustainable development more broadly in the decades to come. This article is part of the theme issue 'The role of soils in delivering Nature's Contributions to People'. © 2021 The Author(s)

    Selection of Resistant Bacteria at Very Low Antibiotic Concentrations

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    The widespread use of antibiotics is selecting for a variety of resistance mechanisms that seriously challenge our ability to treat bacterial infections. Resistant bacteria can be selected at the high concentrations of antibiotics used therapeutically, but what role the much lower antibiotic concentrations present in many environments plays in selection remains largely unclear. Here we show using highly sensitive competition experiments that selection of resistant bacteria occurs at extremely low antibiotic concentrations. Thus, for three clinically important antibiotics, drug concentrations up to several hundred-fold below the minimal inhibitory concentration of susceptible bacteria could enrich for resistant bacteria, even when present at a very low initial fraction. We also show that de novo mutants can be selected at sub-MIC concentrations of antibiotics, and we provide a mathematical model predicting how rapidly such mutants would take over in a susceptible population. These results add another dimension to the evolution of resistance and suggest that the low antibiotic concentrations found in many natural environments are important for enrichment and maintenance of resistance in bacterial populations
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