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  1. Article: Himalayan treeline soil and foliar C:N:P stoichiometry indicate nutrient shortage with elevation

    Müller, Michael / Jürgen Böhner / Thomas Scholten / Udo Schickhoff / Yvonne Oelmann

    Geoderma. 2017 Apr. 01, v. 291

    2017  

    Abstract: Only a few studies have addressed the soil and foliar carbon:nitrogen:phosphorus (C:N:P) stoichiometry in alpine treeline ecotones. Moreover, information on the soil nutrient availability (primarily N, P) in such ecosystems is rare. To fill these gaps, ... ...

    Abstract Only a few studies have addressed the soil and foliar carbon:nitrogen:phosphorus (C:N:P) stoichiometry in alpine treeline ecotones. Moreover, information on the soil nutrient availability (primarily N, P) in such ecosystems is rare. To fill these gaps, we performed a multiple data sampling in a near-natural alpine treeline ecotone in Rolwaling Himal, Nepal.Our results show strongly varying soil C:N:P ratios and nutrient availability with soil depth. Caused by high monsoon precipitation and coarse-grained soils with low water-holding capacities, a vertical transport of nutrients and potentially mineralizable soil organic matter (SOM) in soils occurs, which is a general problem in the study area impeding growing conditions for trees. Soil N and P availability, and soil C:P and N:P ratios decrease significantly as elevation increases, especially at the transition from krummholz (dominated by Rhododendron campanulatum) to the alpine tundra (dwarf scrub heath). Soil C:N ratios increase significantly with elevation, most notably from the subalpine forest to krummholz and the alpine tundra. These altitudinal trends indicate increasing nutrient (N, P) shortage especially in the alpine tundra. Low N and P availability in alpine tundra soils are likely caused by a lower litter input from dwarf shrub vegetation, and a decline in litter mineralization in this altitudinal zone resulting in small accumulation of SOM. Nutrient availability in the entire study area is generally limited by low soil pH (from 2.5 to 4). In total six investigated tree species show diverse relationships between foliar and soil stoichiometric ratios, and soil nutrient availability. Significantly increasing foliar C:N and C:P ratios with elevation due to significantly decreasing foliar N and P concentrations suggest a limitation in N and P. Foliar N:P ratios indicate N rather than P limitation. Contrary to previous studies from different alpine treeline ecotones, we do not consider the Rolwaling treeline ecotone as an area of nutrient accumulation. We conclude that altitudinal variations in stand structures themselves govern nutrient cycling through the input of C, N, and P into soils by differences in leaf fall.
    Keywords alpine tundra ; biogeochemical cycles ; carbon nitrogen ratio ; coarse-textured soils ; ecosystems ; ecotones ; krummholz ; leaves ; mineralization ; monsoon season ; nutrient availability ; nutrients ; Rhododendron ; shrublands ; shrubs ; soil depth ; soil nutrients ; soil organic matter ; soil pH ; stoichiometry ; treeline ; trees ; tundra soils ; water holding capacity
    Language English
    Dates of publication 2017-0401
    Size p. 21-32.
    Publishing place Elsevier B.V.
    Document type Article
    ZDB-ID 281080-3
    ISSN 1872-6259 ; 0016-7061
    ISSN (online) 1872-6259
    ISSN 0016-7061
    DOI 10.1016/j.geoderma.2016.12.015
    Database NAL-Catalogue (AGRICOLA)

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  2. Article: Soil Temperature and Soil Moisture Patterns in a Himalayan Alpine Treeline Ecotone

    Müller, Michael / Böhner Jürgen / Schickhoff Udo / Scholten Thomas / Schwab Niels

    Arctic, Antarctic, and Alpine Research. 2016 Aug., v. 48, no. 3

    2016  

    Abstract: Soil properties in alpine treeline ecotones are insufficiently explored. In particular, an extensive monitoring of soil moisture conditions over a longer period of time is rare, and the effects of soil moisture variability on alpine treelines have not ... ...

    Abstract Soil properties in alpine treeline ecotones are insufficiently explored. In particular, an extensive monitoring of soil moisture conditions over a longer period of time is rare, and the effects of soil moisture variability on alpine treelines have not received adequate attention yet. Soil temperature patterns are generally well documented, and soil temperature is considered a key factor in limiting tree growth at both global and local scales. We performed a 2½-year monitoring in a near-natural treeline ecotone in Rolwaling Himal, Nepal. In this paper, we present new findings on spatiotemporal soil temperature and moisture variability in relation to topographical features and vegetation patterns (variations in stand structures and tree physiognomy). Our results show a growing season mean soil temperature of 7.5 ± 0.6 °C at 10 cm depth at the Rolwaling treeline. Multivariate statistical analyses yield a significant relation between soil temperatures and the variability in tree height, crown length, crown width, and leaf area index (LAI). In turn, soil temperature variability is controlled by the tree physiognomy itself. Soil moisture conditions (available water capacity, 0–10 cm) appear to be less substantial for current stand structures and tree physiognomy. In turn, tree physiognomy patterns control soil moisture, which additionally is affected by snow cover. In Rolwaling, shallow and coarse-grained soils cause low water-holding capacities, and thus a remarkable amount of water percolates from topsoils to subsoils. In the alpine tundra with missing forest canopy, year-round lowest available water capacities are additionally caused by high solar radiation, wind, and thus high evaporation. We assume low soil moisture availability causing largely prevented tree regeneration especially in the alpine tundra.We conclude that soil temperature and moisture patterns reflect tree physiognomy patterns. The latter cause disparities in soil temperature and moisture conditions inside and outside of the closed forest by shading effects and differences in leaf fall.
    Keywords alpine tundra ; available water capacity ; coarse-textured soils ; ecotones ; evaporation ; forest canopy ; forests ; growing season ; leaf area index ; leaves ; monitoring ; multivariate analysis ; shade ; snowpack ; soil temperature ; soil water ; solar radiation ; topsoil ; tree growth ; treeline ; trees ; water holding capacity ; wind ; Nepal
    Language English
    Dates of publication 2016-08
    Size p. 501-521.
    Publishing place Institute of Arctic and Alpine Research (INSTAAR), University of Colorado
    Document type Article
    ZDB-ID 2045941-5
    ISSN 1938-4246 ; 1523-0430
    ISSN (online) 1938-4246
    ISSN 1523-0430
    DOI 10.1657%2FAAAR0016-004
    Database NAL-Catalogue (AGRICOLA)

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  3. Article: The susceptibility of European tree species to invasive Asian pathogens: a literature based analysis

    Müller, Michael M / Jarkko Hantula / Leena Hamberg

    Biological invasions. 2016 Oct., v. 18, no. 10

    2016  

    Abstract: Alien invasive pathogens have caused numerous disastrous epidemics around the globe during the last two centuries. The frequency of these catastrophes has increased in parallel with the increase of international plant trade. Effective control of the ... ...

    Abstract Alien invasive pathogens have caused numerous disastrous epidemics around the globe during the last two centuries. The frequency of these catastrophes has increased in parallel with the increase of international plant trade. Effective control of the risks requires understanding of factors governing vulnerability of indigenous plants. We tested whether the threat caused by alien pathogens of Asian origin is random among various tree species in Europe or whether it relates to their distribution range. A database including distribution ranges of 75 European tree species and literature-derived information on their susceptibility to invasive forest pathogens (IFPs) of Asian origin was compiled. Analysis on this database indicated that the susceptibility to Asian pathogens is significantly more common among tree species that occur only within Europe than among species with distributional ranges from Europe to Siberia (disease susceptibility percentage, DSP, 52 and 19 %, respectively). Notably, all severely attacked tree species are strictly European while tree species with distribution ranges extending from Europe to Siberia show at most only mild or moderate symptoms of Asian IFPs. Furthermore, the proportion of European broadleaf tree species susceptible to Asian IFPs is significantly higher than that of conifer species. Our results suggest that in Europe, Asian pathogens cause a higher risk to temperate and Mediterranean forests, largely composed of broadleaved species with distributional ranges restricted to Europe, than to boreal forests dominated by conifers distributed to Siberia.
    Keywords biogeography ; boreal forests ; conifers ; databases ; disease outbreaks ; disease resistance ; ecological invasion ; invasive species ; pathogens ; risk ; trade ; trees ; Siberia
    Language English
    Dates of publication 2016-10
    Size p. 2841-2851.
    Publishing place Springer International Publishing
    Document type Article
    ZDB-ID 1438729-3
    ISSN 1573-1464 ; 1387-3547
    ISSN (online) 1573-1464
    ISSN 1387-3547
    DOI 10.1007/s10530-016-1174-6
    Database NAL-Catalogue (AGRICOLA)

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  4. Article: Henckelia wijesundarae (Gesneriaceae), a new endemic species from Sri Lanka, and lectotypification of Chirita walkerae and C. walkerae var. parviflora

    Ranasinghe, Subhani / Jayasekara Rohana / Möller Michael / Milne Richard / Rubasinghe Sumudu

    Willdenowia. 2016 Aug., v. 46, no. 2

    2016  

    Abstract: A new species, Henckelia wijesundarae, endemic to Hiniduma, Galle, Sri Lanka, is described and illustrated. Diagnostic features of the new species are discussed and compared to the closely allied species H. walkerae. Based on fieldwork studies, we ... ...

    Abstract A new species, Henckelia wijesundarae, endemic to Hiniduma, Galle, Sri Lanka, is described and illustrated. Diagnostic features of the new species are discussed and compared to the closely allied species H. walkerae. Based on fieldwork studies, we propose an IUCN conservation status of Critically Endangered (CR) for H. wijesundarae. At the same time we lectotypify the names Chirita walkerae (the basionym of H. walkerae) and C. walkerae var. parviflora (treated here in the synonymy of H. wijesundarae).Citation: Ranasinghe S., Milne R., Jayasekara R. Rubasinghe S. & Möller M. 2016: Henckelia wijesundarae (Gesneriaceae), a new endemic species from Sri Lanka, and lectotypification of Chirita walkerae and C. walkerae var. parviflora. — Willdenowia 46: 213–224. doi: http://dx.doi.org/10.3372/wi.46.46202Version of record first published online on 28 July 2016 ahead of inclusion in August 2016 issue.
    Keywords conservation status ; Gesneriaceae ; indigenous species ; lectotypes ; new species ; scientific illustration ; taxon descriptions ; Sri Lanka
    Language English
    Dates of publication 2016-08
    Size p. 213-224.
    Publishing place Botanic Garden and Botanical Museum Berlin-Dahlem (BGBM)
    Document type Article
    ZDB-ID 2177080-3
    ISSN 1868-6397 ; 0511-9618 ; 0374-8960
    ISSN (online) 1868-6397
    ISSN 0511-9618 ; 0374-8960
    DOI 10.3372%2Fwi.46.46202
    Database NAL-Catalogue (AGRICOLA)

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  5. Article: Identifying the missing steps of the autotrophic 3-hydroxypropionate CO₂ fixation cycle in Chloroflexus aurantiacus

    Zarzycki, Jan / Brecht, Volker / Müller, Michael / Fuchs, Georg

    Proceedings of the National Academy of Sciences of the United States of America. 2009 Dec. 15, v. 106, no. 50

    2009  

    Abstract: The phototrophic bacterium Chloroflexus aurantiacus uses a yet unsolved 3-hydroxypropionate cycle for autotrophic CO₂ fixation. It starts from acetyl-CoA, with acetyl-CoA and propionyl-CoA carboxylases acting as carboxylating enzymes. In a first cycle, ...

    Abstract The phototrophic bacterium Chloroflexus aurantiacus uses a yet unsolved 3-hydroxypropionate cycle for autotrophic CO₂ fixation. It starts from acetyl-CoA, with acetyl-CoA and propionyl-CoA carboxylases acting as carboxylating enzymes. In a first cycle, (S)-malyl-CoA is formed from acetyl-CoA and 2 molecules of bicarbonate. (S)-Malyl-CoA cleavage releases the CO₂ fixation product glyoxylate and regenerates the starting molecule acetyl-CoA. Here we complete the missing steps devoted to glyoxylate assimilation. In a second cycle, glyoxylate is combined with propionyl-CoA, an intermediate of the first cycle, to form β-methylmalyl-CoA. This condensation is followed by dehydration to mesaconyl-C1-CoA. An unprecedented CoA transferase catalyzes the intramolecular transfer of the CoA moiety to the C4 carboxyl group of mesaconate. Mesaconyl-C4-CoA then is hydrated by an enoyl-CoA hydratase to (S)-citramalyl-CoA. (S)-Citramalyl-CoA is cleaved into acetyl-CoA and pyruvate by a tri-functional lyase, which previously cleaved (S)-malyl-CoA and formed β-methylmalyl-CoA. Thus, the enigmatic disproportionation of glyoxylate and propionyl-CoA into acetyl-CoA and pyruvate is solved in an elegant and economic way requiring only 3 additional enzymes. The whole bicyclic pathway results in pyruvate formation from 3 molecules of bicarbonate and involves 19 steps but only 13 enzymes. Elements of the 3-hydroxypropionate cycle may be used for the assimilation of small organic molecules. The 3-hydroxypropionate cycle is compared with the Calvin-Benson-Bassham cycle and other autotrophic pathways.
    Keywords Chloroflexus aurantiacus ; acetyl coenzyme A ; bicarbonates ; carbon dioxide ; enzymes ; photosynthetic bacteria ; pyruvic acid
    Language English
    Dates of publication 2009-1215
    Size p. 21317-21322.
    Publishing place National Academy of Sciences
    Document type Article
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.0908356106
    Database NAL-Catalogue (AGRICOLA)

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  6. Article: Carboxylation mechanism and stereochemistry of crotonyl-CoA carboxylase/reductase, a carboxylating enoyl-thioester reductase

    Erb, Tobias J / Brecht, Volker / Fuchs, Georg / Müller, Michael / Alber, Birgit E

    Proceedings of the National Academy of Sciences of the United States of America. 2009 June 2, v. 106, no. 22

    2009  

    Abstract: Chemo- and stereoselective reductions are important reactions in chemistry and biology, and reductases from biological sources are increasingly applied in organic synthesis. In contrast, carboxylases are used only sporadically. We recently described ... ...

    Abstract Chemo- and stereoselective reductions are important reactions in chemistry and biology, and reductases from biological sources are increasingly applied in organic synthesis. In contrast, carboxylases are used only sporadically. We recently described crotonyl-CoA carboxylase/reductase, which catalyzes the reduction of (E)-crotonyl-CoA to butyryl-CoA but also the reductive carboxylation of (E)-crotonyl-CoA to ethylmalonyl-CoA. In this study, the complete stereochemical course of both reactions was investigated in detail. The pro-(4R) hydrogen of NADPH is transferred in both reactions to the re face of the C3 position of crotonyl-CoA. In the course of the carboxylation reaction, carbon dioxide is incorporated in anti fashion at the C2 atom of crotonyl-CoA. For the reduction reaction that yields butyryl-CoA, a solvent proton is added in anti fashion instead of the CO₂. Amino acid sequence analysis showed that crotonyl-CoA carboxylase/reductase is a member of the medium-chain dehydrogenase/reductase superfamily and shares the same phylogenetic origin. The stereospecificity of the hydride transfer from NAD(P)H within this superfamily is highly conserved, although the substrates and reduction reactions catalyzed by its individual representatives differ quite considerably. Our findings led to a reassessment of the stereospecificity of enoyl(-thioester) reductases and related enzymes with respect to their amino acid sequence, revealing a general pattern of stereospecificity that allows the prediction of the stereochemistry of the hydride transfer for enoyl reductases of unknown specificity. Further considerations on the reaction mechanism indicated that crotonyl-CoA carboxylase/reductase may have evolved from enoyl-CoA reductases. This may be useful for protein engineering of enoyl reductases and their application in biocatalysis.
    Keywords NADP (coenzyme) ; amino acid sequences ; biocatalysis ; carbon dioxide ; carboxylation ; enzymes ; hydrides ; hydrogen ; phylogeny ; prediction ; protein engineering ; sequence analysis ; solvents ; stereochemistry
    Language English
    Dates of publication 2009-0602
    Size p. 8871-8876.
    Publishing place National Academy of Sciences
    Document type Article
    ZDB-ID 209104-5
    ISSN 1091-6490 ; 0027-8424
    ISSN (online) 1091-6490
    ISSN 0027-8424
    DOI 10.1073/pnas.0903939106
    Database NAL-Catalogue (AGRICOLA)

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  7. Article: Single Nanocrystals of Platinum Prepared by Partial Dissolution of Au-Pt Nanoalloys

    Schrinner, Marc / Ballauff, Matthias / Breu, Josef / Kauffmann, Yaron / Möller, Michael / Talmon, Yeshayahu / Thun, Jürgen

    Science. 2009 Jan. 30, v. 323, no. 5914

    2009  

    Abstract: Small metal nanoparticles that are also highly crystalline have the potential for showing enhanced catalytic activity. We describe the preparation of single nanocrystals of platinum that are 2 to 3 nanometers in diameter. These particles were generated ... ...

    Abstract Small metal nanoparticles that are also highly crystalline have the potential for showing enhanced catalytic activity. We describe the preparation of single nanocrystals of platinum that are 2 to 3 nanometers in diameter. These particles were generated and immobilized on spherical polyelectrolyte brushes consisting of a polystyrene core (diameter of ~100 nanometers) onto which long chains of a cationic polyelectrolyte were affixed. In a first step, a nanoalloy of gold and platinum (a solid solution) was generated within the layer of cationic polyelectrolyte chains. In a second step, the gold was slowly and selectively dissolved by cyanide ions in the presence of oxygen. Cryogenic transmission electron microscopy, wide-angle x-ray scattering, and high-resolution transmission electron microscopy showed that the resulting platinum nanoparticles are faceted single crystals that remain embedded in the polyelectrolyte-chain layer. The composite systems of the core particles and the platinum single nanocrystals exhibit an excellent colloidal stability, as well as high catalytic activity in hydrogenation reactions in the aqueous phase.
    Keywords alloy nanoparticles ; brushes ; catalytic activity ; cyanides ; electrolytes ; gold ; hydrogenation ; ions ; nanocrystals ; oxygen ; platinum ; polystyrenes ; transmission electron microscopy ; X-radiation
    Language English
    Dates of publication 2009-0130
    Size p. 617-620.
    Publishing place American Association for the Advancement of Science
    Document type Article
    ZDB-ID 128410-1
    ISSN 1095-9203 ; 0036-8075
    ISSN (online) 1095-9203
    ISSN 0036-8075
    DOI 10.1126/science.1166703
    Database NAL-Catalogue (AGRICOLA)

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  8. Article: Profiling of promoter occupancy by PPARα in human hepatoma cells via ChIP-chip analysis

    van der Meer, David L.M / Degenhardt, Tatjana / Väisänen, Sami / de Groot, Philip J / Heinäniemi, Merja / de Vries, Sacco C / Müller, Michael / Carlberg, Carsten / Kersten, Sander

    Nucleic acids research. 2010 May, v. 38, no. 9

    2010  

    Abstract: The transcription factor peroxisome proliferator-activated receptor α (PPARα) is an important regulator of hepatic lipid metabolism. While PPARα is known to activate transcription of numerous genes, no comprehensive picture of PPARα binding to ... ...

    Abstract The transcription factor peroxisome proliferator-activated receptor α (PPARα) is an important regulator of hepatic lipid metabolism. While PPARα is known to activate transcription of numerous genes, no comprehensive picture of PPARα binding to endogenous genes has yet been reported. To fill this gap, we performed Chromatin immunoprecipitation (ChIP)-chip in combination with transcriptional profiling on HepG2 human hepatoma cells treated with the PPARα agonist GW7647. We found that GW7647 increased PPARα binding to 4220 binding regions. GW7647-induced binding regions showed a bias around the transcription start site and most contained a predicted PPAR binding motif. Several genes known to be regulated by PPARα, such as ACOX1, SULT2A1, ACADL, CD36, IGFBP1 and G0S2, showed GW7647-induced PPARα binding to their promoter. A GW7647-induced PPARα-binding region was also assigned to SREBP-targets HMGCS1, HMGCR, FDFT1, SC4MOL, and LPIN1, expression of which was induced by GW7647, suggesting cross-talk between PPARα and SREBP signaling. Our data furthermore demonstrate interaction between PPARα and STAT transcription factors in PPARα-mediated transcriptional repression, and suggest interaction between PPARα and TBP, and PPARα and C/EBPα in PPARα-mediated transcriptional activation. Overall, our analysis leads to important new insights into the mechanisms and impact of transcriptional regulation by PPARα in human liver and highlight the importance of cross-talk with other transcription factors.
    Keywords agonists ; chromatin ; genes ; hepatoma ; humans ; lipid metabolism ; liver ; nucleic acids ; peroxisome proliferator-activated receptors ; precipitin tests ; transcription (genetics) ; transcriptional activation
    Language English
    Dates of publication 2010-05
    Size p. 2839-2850.
    Document type Article
    ZDB-ID 186809-3
    ISSN 0301-5610 ; 0305-1048
    ISSN 0301-5610 ; 0305-1048
    DOI 10.1093/nar/gkq012
    Database NAL-Catalogue (AGRICOLA)

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  9. Article: Identifying the missing steps of the autotrophic 3-hydroxypropionate CO₂ fixation cycle in Chloroflexus aurantiacus

    Zarzycki, Jan / Brecht, Volker / Müller, Michael / Fuchs, Georg

    Proceedings of the National Academy of Sciences of the United States of America

    Volume v. 106,, Issue no. 5

    Abstract: The phototrophic bacterium Chloroflexus aurantiacus uses a yet unsolved 3-hydroxypropionate cycle for autotrophic CO₂ fixation. It starts from acetyl-CoA, with acetyl-CoA and propionyl-CoA carboxylases acting as carboxylating enzymes. In a first cycle, ...

    Abstract The phototrophic bacterium Chloroflexus aurantiacus uses a yet unsolved 3-hydroxypropionate cycle for autotrophic CO₂ fixation. It starts from acetyl-CoA, with acetyl-CoA and propionyl-CoA carboxylases acting as carboxylating enzymes. In a first cycle, (S)-malyl-CoA is formed from acetyl-CoA and 2 molecules of bicarbonate. (S)-Malyl-CoA cleavage releases the CO₂ fixation product glyoxylate and regenerates the starting molecule acetyl-CoA. Here we complete the missing steps devoted to glyoxylate assimilation. In a second cycle, glyoxylate is combined with propionyl-CoA, an intermediate of the first cycle, to form β-methylmalyl-CoA. This condensation is followed by dehydration to mesaconyl-C1-CoA. An unprecedented CoA transferase catalyzes the intramolecular transfer of the CoA moiety to the C4 carboxyl group of mesaconate. Mesaconyl-C4-CoA then is hydrated by an enoyl-CoA hydratase to (S)-citramalyl-CoA. (S)-Citramalyl-CoA is cleaved into acetyl-CoA and pyruvate by a tri-functional lyase, which previously cleaved (S)-malyl-CoA and formed β-methylmalyl-CoA. Thus, the enigmatic disproportionation of glyoxylate and propionyl-CoA into acetyl-CoA and pyruvate is solved in an elegant and economic way requiring only 3 additional enzymes. The whole bicyclic pathway results in pyruvate formation from 3 molecules of bicarbonate and involves 19 steps but only 13 enzymes. Elements of the 3-hydroxypropionate cycle may be used for the assimilation of small organic molecules. The 3-hydroxypropionate cycle is compared with the Calvin-Benson-Bassham cycle and other autotrophic pathways.
    Language English
    Document type Article
    ISSN 0027-8424
    Database AGRIS - International Information System for the Agricultural Sciences and Technology

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