Ph.D. position plant - microfauna interactions

This Ph.D. project was started April 1st 2005 with Ph.D.-student Karen Andersen. The Ph.D. project is rooted in WP2.3 (Trophic interactions above-belowground) with links to WP2.2, WP3.2, WP3.3, and WP4.2.

Background
The soil microfauna (protozoa and nematodes) is an important component of the rhizosphere community and interacts intensively with plant growth. The microfauna consume rhizosphere bacteria thereby mineralising nutrients from organically bound to plant-available form. This bacterial consumption is to some extent selective and therefore affects the composition of the bacterial community in the rhizosphere. Moreover it is anticipated that the microfauna may interfere in the signal exchange between rhizosphere microbes and plant roots and an interaction rhizosphere microfauna - foliar herbivores has been demonstrated. These organisms are therefore important components in the functioning of the plant-soil system, and are most likely affected by global climate change. This effect may be indirect via the plant as in the case of elevated CO₂, or direct from the soil combined with indirect via the plant in the case of drought and elevated temperature.

The Project
The present project will focus on the microfauna and its interaction with microbial activity in the rhizosphere. The effect of an altered climate (elevated CO₂ and/or temperature, altered soil moisture) will be investigated in the field experiment at Brandbjerg (I). Test plants grown in the field plots will be the basis for growth chamber experimentation (II) on the interaction of the plant with its rhizosphere organisms and foliar herbivores as dependent on environmental factors such as soil nutrient status and the climatic origin of the plants. Two further laboratory experiments deal with (III) the consumption of carbon from the plant and the soil by rhizosphere organisms, and (IV) survival/activity of the microfauna when soil dries out.

The practical work consists of (a) cultivation of organisms from soil followed by quantification under the microscope (b) gas chromatography to determine microbial activity in the plant-soil system, (c) running experiments with plants and herbivores in a growth cabinet. During the project there will be cooperation with other partners of the consortium on labelling experiments with ¹³CO₂, and with Thure Hauser (Risø, KVL) on gene expression in plants. The final program will be settled in cooperation between the Ph.D.-student and the supervisor.