334 publications from this institution
Author: von Blanckenburg, F. et al.; Genre: Other; Finally published : 2019; Keywords: Animation, Plants, Forests, Roots, Ecosystems, Geology, Rock, Soil, Weathering, Recycling, Leaf litter, litter decomposition, Fungus, Mycorrhiza, Nutrients, Phosphorus, Climate, Climate Change, Carbon Cycle, Photosynthesis, Soil Organic Carbon, Critical Zone; Title: Do rocks feed plants? [Film]
When multiple metabolic pathways lead to the same product, compound-specific isotope analysis may not provide enough information to quantify the activities of the contributing pathways. Instead, identification of where in the molecule the 13C is incorporated is required. Here we show how knowledge of position-specific 13C incorporation in fatty acids (FA) and FA fragments can be used to quantitatively estimate the fluxes through the central C metabolic network. We developed a method to measure 13C enrichment of FA and FA fragments (ethanoate, propionate) using electron impact GC–MS. We tested the accuracy and repeatability of the measurements using natural abundance and position-specific 13C labelled standards and FA extracted from Bacillus licheniformis and Pseudomonas fluorescens grown with labelled and unlabelled glucose. The molecular ions of FA generally reflected theoretical predictions of mass isotopomer distributions for natural abundance values, but that of the associated FA fragments deviated from expected values, likely associated with McLafferty rearrangements of hydrogen. After correction for naturally occurring isotopes, 13C enrichments of FA and FA fragments showed good agreement with expected isotope composition of FA standards (root mean square error < 0.044 at%; δ13C of ∼ 40‰), natural abundance and labelled glucose. The unsaturated FA extracted from P. fluorescens deviated from expected values likely associated with problems of co-elution and ion suppression and were excluded from analysis. The ratio of glucose-1-13C to glucose-3-13C incorporation into FA fragments was high for B. licheniformis, but low for P. fluorescens. Metabolic flux modelling based on the 13C enrichment of ethanoate and propionate fragments showed that B. licheniformis used Embden-Meyerhof-Parnas and pentose phosphate pathway (66% and 30%, respectively), whereas P. fluorescens utilized Entner-Doudoroff and pentose phosphate pathway (72% and 27%, respectively). FA fragment analysis is therefore a promising tool to study central C metabolic network activities of co-occurring groups of microbes in intact and complex environmental communities.
No abstract is provided for this article.
Anaerobic oxidation of methane (AOM) is a globally important CH4 sink. However, the AOM pathways in paddy soils, the largest agricultural source of methane emissions (31 Mio tons per year) are not yet well described. Here, a combination of 13C isotope tracer, phospholipid fatty acids (PLFA) analyses, and microbial community analysis was used to identify AOM pathways in fertilized (pig manure, biochar, NPK, and the control) paddy soils amended with alternative electron acceptors (AEAs) (NO3 −, Fe3+, SO4 2−, humic acids, and the reference without AEAs addition). After 84 days of anaerobic incubation, the microbial co-occurrence network got tightened and became more complex relative to unincubated samples. Fertilization and AEAs addition led to a strong divergence of the microbial community structure as indicated by abundances of AOM-related microbiota and 13C incorporation into microbial PLFA, thus suggesting an environmental niche differentiation of AOM-involved microorganisms. Comparative analyses revealed a set of major and minor AOM pathways with synergistic relations to complementary anaerobic microbial groups. NO3 −-driven AOM, performed by members of the candidate group ANME-2d, was the major AOM pathway. Minor AOM pathways involved NO2 − reduction by NC10, reduction of humic acids and Fe3+ by Geobacter species, and SO4 2− reduction by sulfate-reducing bacteria linked with anaerobic methanotrophs. As identified by the network analysis, these active AOM pathways compensated a fraction of CH4 produced during ongoing methanogenesis. From a broader ecological perspective, nitrogen-driven AOM will become a more important methane sink in the future with the increases of nitrogen fertilization and deposition.
No abstract is provided for this article.
No abstract is provided for this article.
Climate change projections indicate that significant areas of the current cocoa cultivation areas in West Africa are likely to experience unfavorable climatic conditions by 2050. Water use efficient agroforestry systems are considered to be an important option to adapt cocoa to climate change. Water use efficiency and complementary soil water use between cocoa and shade trees have been reported in previous studies in Indonesia but in our previous study in Ghana, popular native shade tree species Albizia ferruginea and Antiaris toxicaria were found to have a strong competitive water use advantage over cocoa plants during an extreme drought experienced during 2015/16. Cocoa plants under no shade were relatively more resilient with higher survival rate and post drought recovery.While past research studies &#160;&#160;were each limited to few selected shade tree species being investigated despite the huge numbers within cocoa landscapes. To overcome this limitation, an approach based on functional traits of trees in terms of water use is proposed to understand their effect on water use efficiency and drought resilience in cocoa agroforestry systems rather than describing individual species. We apply this concept across temporal and spatial scales in a marginally suitable cocoa climate in Ghana. Shade tree species have been categorized into phenological trait groups (evergreen, deciduous, or brevi-deciduous) under which detailed above- and belowground traits interactions with cocoa plant and effect on water use has been evaluated.The following hypotheses are being tested: (i) shade trees in the three phenological trait groups exhibit significant difference in their root and water uptake depth, and, thus, affect environmental conditions relevant for cocoa, (ii) cocoa plant above- and belowground morphological and physiological traits are influenced by shade tree phenological and morphological traits and their modification by micro-climatic (light, temperature, relative humidity and VPD), and soil (water and nutrients) conditions over different seasons.Replicated plots of 19 shade tree species distributed across the three phenological trait groups have been established for analysis of functional traits interactions in such a multi-species agroforestry system. We determine root specific traits through direct sampling, stable isotope analysis for assessment of water use portioning between the various shade tree groups and cocoa plants. Soil moisture, temperature and relative humidity and light sensors were installed in each plot. Cocoa plants under different micro-climatic impact zones of the shade trees have been monitored for a full production cycle. &#160;The shade trees impact on the cocoa plant productivity (morphology and yield traits) has been evaluated. Complementary and non-complementary shade tree species with respect to their trait interactions and effect on cocoa plant productivity have been identified.
No abstract is provided for this article.
No abstract is provided for this article.
Land use change and agricultural intensification in developing countries affect terrestrial carbon (C) stocks, CO2 efflux, microbial communities and overall soil health. This study assesses the effects of four land use types typical for northern Ethiopia (forests, exclosures, grazing lands and intensively cultivated croplands) on various soil health indicators. We quantified and compared microbial biomass carbon (MBC), water extractable organic carbon (WOC), metabolic quotient (qCO2), substrate use efficiency (SUE) and dynamics of 14C-labelled glucose added to soil. Irrespective of the land use, MBC but not SUE decreased 2- to 8-fold with increasing depth, demonstrating the C limitation of subsoil microbial communities under all land use forms. Sandy soils, however, which permit seepage and leaching of WOC into lower layers and promote subsoil microbial communities, adapted to frequent input of easily accessible C substrates. Significantly higher qCO2 were recorded in subsoils compared to topsoils, especially in croplands with low MBC. In croplands, high glucose-14C incorporation (≈20%) into their low microbial biomass indicates a high SUE and reflects a better nutrient supply of these microbial communities. Mineralization of up to 95% of 14C-labeled glucose in topsoils of forest and grazing lands was higher than in croplands, and exclosures never reached the level of natural ecosystems. This demonstrates that 6–10 years of exclosure establishment does not result in soil microbial communities and soil C dynamics resembling those of natural forests. Our study demonstrates that land use can negatively affect the ecological performance of microbial communities and that these impacts are more severe in sandy than in clayey soils. Mitigation strategies such as minimum tillage or residue retention in intensively cultivated croplands can increase microbial abundance and activity and help ensure environmental sustainability and mitigation of climate change. Nonetheless, such measures need to be carefully accompanied by monitoring indicators of soil health to confirm the sustainability of the chosen mitigation strategies.
No abstract is provided for this article.
To explore carbon (C), nitrogen (N), and phosphorus (P) dynamics during leaf litter decomposition, we investigated the temporal variability of soil microbial biomass and associated soil enzyme activities. Our 342-day leaf litter (Quercus wutaishanica) decomposition experiment at the Loess Plateau (China) sheds light on how soil microorganisms – mainly the soil microbial biomass C, N, P, and soil enzyme activities – maintain element homeostasis of C, N, and P by producing soil enzymes during various phases of litter decomposition. Overall, the highest soil enzyme activities were measured in summer, whereas soil microbial biomass carbon (MBC) and soil microbial biomass nitrogen (MBN) were highest in winter. Soil water content and soil temperature had significant effects on soil enzyme activities and stoichiometry. The results indicate that the stoichiometry of extracellular enzyme activities (lnBG:lnNAG:lnAP) changes significantly between individual stages of litter decomposition. The resources available for microorganisms were restricted by C and P, while P limitation progressively decelerated during decomposition and C limitation was enhanced at the latest stage. Strong positive correlations between ecological indicators of microbial element limitation and soil enzyme activities indicated that microbes allocate C and nutrients towards soil enzyme production to mine for scarce nutrients. This adaptation strategy enabled the soil microorganisms to maintain element homeostasis. Soil MBC, MBN, soil microbial biomass phosphorus (MBP), MBC:MBN, MBC:MBP, and MBN:MBP rarely showed significant correlations with soil or leaf litter C, N, P, C:N, C:P, and N:P. This suggests no resource dependency of microbial element composition but supports the concept of element homeostasis of soil microorganisms. Besides compensating for element imbalances by adjusting soil enzyme production, the microorganisms also adjusted element use efficiencies such as C use efficiency. We conclude that the maintenance of element homeostasis by soil microorganisms induces a tight co-regulation of enzymes involved in covering their C and nutrient supply during successive litter degradation.
No abstract is provided for this article.
