What makes the soil environment special? Most nutrients and energy come from dead organic matter (plant and animal parts), soil pores are filled with air and water, for instance rain water that transports particles downwards, and plant roots that penetrate the soil matrix form pores and exudate organic substances. In this dynamic system, fungal mycelia, bacteria, actinomycetes and invertebrates spend most of their life cycles. The intriguing interactions between soil organisms, the responses of soil organisms to the environment, the distribution of the organisms, and the impact of the environment on populations and communities parameters (also anthropogenic ones) are dealt with within soil ecology.

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MIXTOX is financed within the EU programme "Environment and Climate" and is a cooperation between the Netherlands, England and Sweden. The objectives are to assess the effects of two toxicant mixtures (Cu and the fungicides Carbendazim and Iprodione, and Cu, Zn, Pb and Cd) on soil organisms and to look for general concepts which are applicable for different groups of compounds. The same mixtures will be tested on invertebrates with different uptake routes under standardized conditions. Chemical speciation, transformation and sorption will also be studied. Basic concepts for mixture toxicity in soil will be identified from the experimental work and used for the development of mixture toxicity models for soil invertebrates.

The project started in October 1997 and will last until September 2000. I am responsible for the Swedish part of the project which includes the testing of different chemical mixtures on enchytraeids, investigating exposure routes and uptake rates. Together we will develop models for mixture toxicity based on sub-lethal effects on enchytraeids, earthworms, nematodes and springtails.

Development and improvement of test systems for assessing sublethal effects of harmful chemicals (Anna-Karin Augustsson, Sten Rundgren, Maria Sjögren Öhrn)

Changing land usage, enhancement of community stability and ecosystem development on set-aside land (CLUE) (Katarina Hedlund Dagmar Gormsen)

The project was granted by the EU within the Terrestrial Ecosystem Research Initiative (TERI) in the Environment and Climate programme and the the Swedish Environmental Protection Agency (SNV). The project focusses on the transformation of set-aside agricultural land to restored natural ecosystems. The main aim of the project is to study links and driving forces between plant diversity and soil organism communities at succession, but also to experimentally find ways to increase the rates of succession. Within CLUE I am (KH) responsible for a the Swedish group and a work package concerning soil fauna and colonization processes. In addition to this EU project I have national funding for a joint project from the Swedish Environmental Protection Agency (SNV). http://www.nioo.knaw.nl/cto/clue/clue.htm

Gene flow between natural populations of soil microarthropods. (Katarina Hedlund, Dagmar Gormsen, Sten Rundgren, Göran Bengtsson).

Knowledge of geneflow and dispersal in soil microarthropods is practically unknown today. The project aims at studying geneflow of soil collembolans on a local and a continental level. Knowledge of geneflow on a local level can be used to study local adaptations of soil microarthropods to natural and antropogenically disturbed sites. On a continental level, the phylogeography of soil microarthropods can be studied. With PCR based DNA techniques there are today methods that have proved to be efficient for this type of studies. The project has started with populations around the Baltic sea and has now been extended to include Artic species. It has been extended in 1999, as the project participates in the Polar expedition Tundra North West -99. (länk här till Polars hemsida).

Tritrophic interactions (Katarina Hedlund)

Interactions among plants, herbivores and their natural enemies (predators, parasitoids and parasites) can be considered in a tritrophic context in which traits of a plant can influence the reproductive success of a herbivore and a predator's possibility of finding and profiting on its prey (Price et al. 1980) This project aims at studying interactions among tritrophic levels in a soil community by investigating the mechanisms of prey location of a soil predator. The two mains topics are: Means of communication between trophic levels and trophic interactions in soil ecosystems.

Torsten Gunnarsson. 1987. Soil arthropods and their food: choice, use and consequences.

Lena Tranvik. 1992. To sustain in a stressed environment: a study of soil Collembola.

Katarina Hedlund. 1993. Animal-microbial interactions: the fungivorous Collembola.

Maria Sjögren. 1994. Dispersal in and ectomycorrhizal grazing by soil invertebrates.