SPP 1685:  "Ecosystem Nutrition: Forest Strategies for Limited Phosphorous Resources"

The focus of this study is the microbial utilization of Phosphorus in forest soil. Special areas of interest are the analytics of microbial transformation, utilization and metabolic rates concerning Phosphorus containing organic compounds.  

Current topic:

"Competition between roots and microorganisms for phosphorus"

While organic N mineralization exhibit clear seasonal uptake dynamics, knowledge about seasonal variation in microbial P uptake and mineralization is scarce. We hypothesize that dynamics of P uptake and mineralization by microorganisms in temperate forest soils exhibits a seasonality anti-cyclic to plant P uptake. To investigate this, F. sylvatica seedlings were grown in pots using soil from the Ah horizon of the sites Bad Brückenau and Lüss under controlled conditions over the course of a year and labeled by 33P.  For the first time we analyzed the 33P incorporation into total PLFA and consequently provide a new alternative for analysis of P uptake by microorganisms. This approach will enable the quantification of P fluxes through the microbial network and reveal the P cycling of relevant microbial groups.

Oncoming topic:

"Effects of soil P heterogeneity on P acquisition patterns and the P nutritional status and growth of forest trees on sites with low P availability"

At the moment, research is only covering effects of heterogeneous vs. homogeneous distribution of total P concentrations (same P species) on root development and growth of non-woody plants. No information is available concerning the effects of a homogenous vs. heterogeneous distribution of (a) the soil total P content and (b) different P species (given level of average P soil stock) on P acquisition, the P nutritional status and the growth of forest trees on sites with low P availability. These questions shall be answered by studying root development and root-induced changes of rhizosphere chemistry in a rhizotron study.

Possible master thesis:

A participation in the aforementioned rhizotron experiment opens numerous possibilities for analytical work. Extensive analyses of the shoots concerning biomass and element levels as well as changes in the soil chemistry and soil fauna (PLFA) will be performed and can be the foundation of a master thesis.  Additionally, an interested master student could take part in advanced instrumental analytics.