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Publications in peer reviewed journals

5 Publications found
  • Microbial utilization of mineral-associated nitrogen in soils

    Turner S, Meyer-Stüve S, Schippers A, Guggenberger G, Schaarschmidt F, Wild B, Richter A, Dohrmann R, Mikutta R
    2017 - Soil Biology and Biochemistry, 104: 185-196


    In soils, a large portion of organic nitrogen (ON) is associated with minerals and thus, possibly stabilized against biological decay. We therefore tested if mineral-associated N is an important N source for soil microorganisms, and which soil parameters control its bioavailability. Microcosm experiments with mineral-associated organic matter, obtained as heavy fraction (HF) via density fractionation, and bulk soil from mineral topsoil of the Franz Josef chronosequence were conducted for 125 days. We examined the effects of O2 status, soil age (differences in mineralogical properties), as well as cellulose and phosphate additions on the turnover of mineral-associated N. Using a combination of activity measurements and quantitative PCR, microbial N transformation rates and abundances of N-related functional genes (amoAnarGchiA) were determined. Similar or higher values for microbial N cycling rates and N-related functional abundances in the HF compared to bulk soil indicated that mineral-associated N provides an important bioavailable N source for soil microorganism. The turnover of mineral-associated N was mainly controlled by the O2 status. Besides, soil mineralogical properties significantly affected microbial N cycling and related gene abundances with the effect depending on the N substrate type (ON, NH4+ or NO3). In contrast, cellulose or phosphate addition hardly enhanced microbial utilization of mineral-associated N. The results of our microcosm study indicate that mineral-associated N is highly bioavailable in mineral topsoils, but effects of the mineral phase differ between N cycling processes.

  • Rhizospheric microbial community of Caesalpinia spinosa (Mol.) Kuntze in conserved and deforested zones of the Atiquipa fog forest in Peru

    Cordero I, Ruiz-Diez B, Balaguer L, Richter A, Pueyo JJ, Rincon A
    2017 - Applied Soil Ecology, 114: 132-141


    Caesalpinia spinosa, tara, is the predominant fog catcher tree in the fog forest of Atiquipa, a biodiversity hotspot ecosystem within the coastal Peruvian desert highly threatened by intense land use over time. We investigated the impact of deforestation, as well as potential effects of the tree age (juveniles vs adults) and the type of tree (recruited vs planted), on the rhizospheric microbial communities of tara growing in contrasting landscapes (conserved vs deforested) of the Atiquipa forest.

    We used a phospholipid fatty acids analysis approach to study the microbial community associated with tara. Additionally, we isolated and sought for native rhizospheric bacteria with plant growth promoting (PGPR) traits to be used as potential inoculants for restoration projects.

    Deforestation profoundly altered the chemical and biological fertility of soils. All rhizospheric microorganisms were clearly reduced in abundance by deforestation, while the age or the type of trees had no effects. Both, deforestation and tree age influenced the assemblage of microbial communities, which tightly correlated with soil pH and organic matter among other soil properties. Adult trees harboured similar microbial communities in conserved and deforested soils being potential reservoirs of native microorganisms in the degraded areas. Some selected bacterial strains showed high plant growth promoting abilities, and PGPR traits were related with the isolation source of bacteria. The knowledge about key factors structuring the rhizospheric microbiota of tara and the identification of high-performing PGPR strains, provide a solid framework to formulate inocula for their use in restoration programmes in the Atiquipa fog forest.

  • Phytosiderophore-induced mobilization and uptake of Cd, Cu, Fe, Ni, Pb and Zn by wheat plants grown on metal-enriched soils

    Puschenreiter M, Gruber B, Wenzel WW, Schindlegger Y, Hann S, Spangl B, Schenkeveld WDC, Kraemer SM, Oburger E
    2017 - Environmental and Experimental Botany, 138: 67-76


    We investigated to which extent phytosiderophores (PS), released by grasses for the acquisition of iron, solubilize other metals in contaminated soils, and how this affects metal mobilization and uptake in wheat plants. A plant-based bioassay (‘RHIZOtest’) and batch extraction scheme were carried out for assessing metal mobilisation in soil, PS exudation and metal accumulation in wheat. Increased PS exudation was observed in Fe-deficient wheat, leading to enhanced Zn, Cu, Mn and Ni concentrations in wheat shoots on some soils. In contrast, plant Cd and Pb concentrations were not affected. Likewise, in the batch experiment, strongly increased extractable Cu, Ni and Zn concentrations were observed, in particular when 100 or 1000 μM PS were added. Our results suggest that Fe deficiency can enhance the accumulation of some metals in shoots of grass species. Although our results indicate that the risk of enhanced accumulation of Cd and Pb in Fe deficient wheat shoots is rather small, further experiments conducted on soil for the complete vegetation period would be needed to confirm this observation.

  • Decoupling of microbial carbon, nitrogen, and phosphorus cycling in response to extreme temperature events

    Mooshammer M, Hofhansl F, Frank AH, Wanek W, Hämmerle I, Leitner S, Schnecker J, Wild B, Watzka M, Keiblinger KM, Zechmeister­‐Boltenstern S, Richter A
    2017 - Science Advances, 3: 13


    Predicted changes in the intensity and frequency of climate extremes urge a better mechanistic understanding of the
    stress response of microbially mediated carbon (C) and nutrient cycling processes. We analyzed the resistance and
    resilience of microbial C, nitrogen (N), and phosphorus (P) cycling processes and microbial community composition
    in decomposing plant litter to transient, but severe, temperature disturbances, namely, freeze-thaw and heat. Disturbances
    led temporarily to a more rapid cycling of C and N but caused a down-regulation of P cycling. In contrast to the
    fast recovery of the initially stimulated C and N processes, we found a slow recovery of P mineralization rates, which
    was not accompanied by significant changes in community composition. The functional and structural responses to
    the two distinct temperature disturbances were markedly similar, suggesting that direct negative physical effects and
    costs associated with the stress response were comparable. Moreover, the stress response of extracellular enzyme
    activities, but not that of intracellular microbial processes (for example, respiration or N mineralization), was
    dependent on the nutrient content of the resource through its effect on microbial physiology and community
    composition. Our laboratory study provides novel insights into the mechanisms of microbial functional stress responses
    that can serve as a basis for field studies and, in particular, illustrates the need for a closer integration of
    microbial C-N-P interactions into climate extremes research.

  • Global patterns of phosphatase activity in natural soils

    Margalef O, Sardans J, Fernández-Martínez M, Molowny-Horas R, Janssens IA, Ciais P, Richter A, Obersteiner M, Asenio D, Peñuelas J
    2017 - Scientific Reports, 7: 13


    Soil phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for
    life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil
    traits on phosphatase activity in terrestrial systems using metadata analysis from published studies.
    This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest
    that organic P (Porg), rather than available P, is the most important P fraction in predicting phosphatase
    activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean
    annual temperature, thermal amplitude and total soil carbon as most available predictor variables
    explained up to 50% of the spatial variance in phosphatase activity. In this analysis, Porg could not be
    tested and among the rest of available variables, TN was the most important factor explaining the
    observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also
    found to be associated with climatic conditions and soil type across different biomes worldwide. The
    close association among different predictors like Porg, TN and precipitation suggest that P recycling is
    driven by a broad scale pattern of ecosystem productivity capacity.

Book chapters and other publications

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