The Soil Sciences at the Martin Luther University Halle offer a doctoral researcher position by 1 December 2013 for three years. Salary is TV-L E13 (65%), according to the German TV-L system.
Background
With rock phosphorus resources becoming increasingly depleted, development of more efficient use of phosphorus is a major near-future research task. In response, Deutsche Forschungsgemeinschaft - DFG sponsors a large-scale research programme on Ecosystem Nutrition: Forest Strategies for Limited Phosphorus Resources, aiming at studying the mechanisms of the relative efficient phosphorus cycling
within forest ecosystems.
Objectives and work schedule
With mineral sources of phosphorus become increasingly scarce with progressing ecosystem development, forests start recycling organic phosphorus. Inorganic phosphorus forms tend to be bound strongly to secondary minerals, thus, it is hardly available to plants but also not leached from soil. Instead, phosphorus leaching losses tend to be governed by mobile organic forms, whatever state the ecosystem is in. Microbial compounds such as nucleotides and nucleic acids seem to form the most mobile fraction of dissolved organic phosphorus in soils,
while plant-derived compounds such as phytate are less prone to leaching. However, those potentially mobile microbial compounds are labile to enzymatic hydrolysis, thus, the phosphorus contained may be taken up by plants, thus, minimizing the phosphorus leaching losses of recycling ecosystems.
Background
With rock phosphorus resources becoming increasingly depleted, development of more efficient use of phosphorus is a major near-future research task. In response, Deutsche Forschungsgemeinschaft - DFG sponsors a large-scale research programme on Ecosystem Nutrition: Forest Strategies for Limited Phosphorus Resources, aiming at studying the mechanisms of the relative efficient phosphorus cycling
within forest ecosystems.
Objectives and work schedule
With mineral sources of phosphorus become increasingly scarce with progressing ecosystem development, forests start recycling organic phosphorus. Inorganic phosphorus forms tend to be bound strongly to secondary minerals, thus, it is hardly available to plants but also not leached from soil. Instead, phosphorus leaching losses tend to be governed by mobile organic forms, whatever state the ecosystem is in. Microbial compounds such as nucleotides and nucleic acids seem to form the most mobile fraction of dissolved organic phosphorus in soils,
while plant-derived compounds such as phytate are less prone to leaching. However, those potentially mobile microbial compounds are labile to enzymatic hydrolysis, thus, the phosphorus contained may be taken up by plants, thus, minimizing the phosphorus leaching losses of recycling ecosystems.
The proposed research aims at understanding the chemical characteristics of dissolved organic phosphorus compounds controlling their mobility, the controls on the composition of dissolved organic phosphorus, and if dissolved organic phosphorus is plant available. We will collect forest floor seepage water and solutions from mineral soils along a gradient of phosphorus availability. These solutions will be analyzed for chemical organic phosphorus species, using
spectroscopic methods (basically NMR, complemented by XPS and XANES analyses on selected samples), and for enzymatic release of the phosphorus contained (in combination with spectroscopic methods). This approach will inform on mobile and labile dissolved organic phosphorus compounds. Similar analyses will be carried out on solutions deriving from other proposed experiments on potential controls (drought, pH) on dissolved phosphorus release, in order to track changes in composition, thus, chemical and biological reactivity of dissolved
organic phosphorus. Laboratory assays will be used to address the potential mobility of organic phosphorus species (sorption experiments, in combination with spectroscopic methods) as well as experiments with labelled compounds. The latter will address the potential plant uptake of dissolved organic phosphorus, either after enzymatic hydrolysis or by direct of small molecules.
Requested qualifications
M. Sc. or equivalent degree in forest science, agricultural sciences, geosciences, geoecology, environmental sciences or related disciplines, preferably with a strong background in soil science or geoscience, as well as experiences in field and laboratory studies. The field work requires a stable physical condition and a certain degree of flexibility to adapt to different working environments.
For further details and questions Dr. Klaus Kaiser
(klaus.kaiser@landw.uni-halle.de).
Complete applications, including a summary of M.Sc. thesis, shall be submitted to
Dr. Klaus Kaiser
Martin Luther University Halle-Wittenberg
Soil Sciences
von-Seckendorff-Platz 3
06120 Halle (Saale)
Germany
Phone: +49-345-55-22530
E-mail: klaus.kaiser@landw.uni-halle.de
Applications will be considered until 1 November 2013 or until the position is filled.
Application Deadline : 1 November 2013
