Ecosystem N cycling and N uptake by plants

A central assumption of ecosystem N cycling has been that organic nitrogen (N) must be converted to inorganic N (ammonium and nitrate) to be available for plant uptake, and thus N mineralization has been viewed as the bottleneck in plant N nutrition. We are investigating the new hypothesis that plants can bypass the mineralization bottleneck by taking up organic N. This project is using stable isotopes of N and C to investigate uptake of a variety of different forms of organic N (several amino acids, peptides, proteins).
Examination of uptake of N by plants is being accompanied by extensive studies of fluxes and pools of N in soil. We are using and developing analytical techniques fro rapid measurements of different forms of N, e.g. amino acids by capillary electrophoresis with laser-induced fluorescence, nitrate and ammonium by microplate methods. Recently we have begun adapting metabolomics methods for use on soil extracts and soil solutions.

Location: Field experiments in Tasmania (Warra, long-term ecological research site), Victoria (Eucalyptus spp. trials in Gippsland) and the Snowy Mountains.

Funding: ARC-Linkage grant with Forestry Tasmania

Uptake of glycine

Uptake of double-labeled (15N, 13C) glycine by Eucalyptus regnans