The fulltext of publications might not be freely accessible but require subscription. Please contact the authors to request reprints.
Publications in peer reviewed journals
Microbial utilization of mineral-associated nitrogen in soils2017 - 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 (amoA, narG, chiA) 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.
Phytosiderophore-induced mobilization and uptake of Cd, Cu, Fe, Ni, Pb and Zn by wheat plants grown on metal-enriched soils2017 - 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.