PhD in soil fauna physiology

The project is linked to WP 2.2, but includes elements of work packages 3 and 4 and Blog as well. The focus will be on desiccation tolerance in protozoa, nematodes, enchytraeids, Collembola and mites.

Background
Soil invertebrates are important components of soil ecosystems. This diverse group of animals cov-ers a range of taxa, the most important being protozoans, nematodes, oligochaete worms (earth-worms and enchytraeids), mites, springtails (Collembola) and a range of insects (mostly belonging to Diptera and Coleoptera) whose larval stages complete their development in the soil. Soil inverte-brates perform important functions in soil related to the growth conditions of plants. Soil meso-fauna, for example represented by enchytraeids, mites and Collembola, are grazers of bacteria and fungi, and are thought to stimulate microbial decomposition rates. At present there seems to be a consensus that the respiration of soil invertebrates amounts to little more than 10% of the total soil respiration (bacteria and fungi being the dominant biotic components), and often less than this. However, the indirect effects on soil respiration and decomposition, though difficult to quantify, may be substantial. A number of examples is showing that soil fauna may increase nitrogen miner-alisation with up to 25%.

One of the most important environmental factors determining the performance of soil fauna is the availability of water in the soil. In essence, there are three survival strategies open to soil fauna species during drought. Firstly, they may have evolved the ability to tolerate extensive loss of body water. The most extreme case of this is termed anhydrobiosis, a strategy utilized by nematodes and some collembolans. Secondly, they may have evolved resistance to desiccation by reducing the water permeability of their integument. This strategy has been adopted by many surface-dwelling species, whereas euedaphic species have little or no control of evaporation across the integument. Finally, species may migrate to moist micro-sites during drought periods, either vertically or horizon-tally. This last strategy may enable species to evade transient drought spells but longer lasting or extreme drought is likely to incur physiological stress.

Project description
The main focus of this PhD project will be on drought tolerance in soil fauna, preferably within enchytraeids and microarthropods. The studies should elucidate by which mechanisms selected organ-isms cope with low soil water potentials, identify critical stress levels and examine life-history traits under sub-optimal soil water potential. Also population recovery times after severe drought should be investigated. The main body of the project will be laboratory based experimental studies, but participation in field studies of soil mesofauna is also included using the CLIMAITE long-term field trial as a platform. Together, these studies should help to increase our understanding of soil fauna population and community responses in a changing climate.

This PhD project will have close interactions with other parallel CLIMAITE projects on plant physiology, plant community changes, microbiology, microfauna-plant interactions and biogeochemistry. The PhD candidate will be enrolled at the Institute of Biology, University of Copenhagen.

Terms of employment:
The tenure of the PhD will be limited to a period of three years (from 1 May 2026 or at the earliest convenience). Employment will be in accordance with entry about Ph.D.s to the current collective agreement of April 4, 2004, for state-employed academic staff.

Place of work: Silkeborg, Denmark.

Further information can be obtained from Professor Martin Holmstrup, Tel: +45 8920 1400. E-mail: [email protected]

Application including CV, relevant publications etc. should be marked "013/101-0172" and sub-mitted in four copies to:

National Environmental Research Institute
Frederiksborgvej 399
P.O. Box 358
DK-4000 Roskilde
Denmark

The application, which will be rated by an expert evaluation committee, should be received at NERI no later than 4th April 2005.

NERI encourages applications from all qualified candidates, regardless of gender, age or ethnic bak-ground.

The National Environmental Research Institute (NERI) is an independent research institute under the Danish Ministry of Environment.