In the paper, a preliminary model of the structure and function of a boreal mire ecosystem is presented. In addition, a research plan leading to the model is described. In the exploitation and management of natural resources, information about the ecosystem as a functional unit is needed, if ecological principles are to be applied. In Finland, mires (peatland ecosystems) have been subject to exceptionally severe exploitation since forest drainage and fertilization effectively started in the 1960's, However, mires represent one of the least known ecosystems.
The mire ecosystem has been defined according to Ellenberg's (1973) criteria as follows. A mire is an ecosystem maintained by cool and humid local climatic conditions and a high water table, which results in deficient decomposer activity and accumulation of organic matter (peat-forming process). The most striking features in the energetics of the system are a relatively ineffective input of energy and an even more ineffective use of it. This is indicated in the metabolism of the system by an excess production of oxygen and, in addition, by losses in the carbon, mineral, and nitrogen cycles.
A general model of the mire ecosystem is presented in Figure 1, which simultaneously serves as a framework for the study. The individual parts of the project are planned to be as follows:
(1) environmental factors, (2) plant community and primary production, (3) secondary production, in which (3a) energy flows through herbivores, and (3b) energy flows through decomposers, (4) nutrient cycle, (5) the accumulation of peat, and (6) succession in the mire ecosystem.
In (1), special attention has been paid to factors characteristic of mires, especially the factors connected with the water table. As the aim of the study is to obtain a dynamic model of a biotic phenomenon, emphasis has been put on the continuous observation of environmental factors.
In (2), a graphic model (Fig. 3) has been chosen as the primary goal. Graphic models of a few peatland site types based on preliminary studies already exist. When constructing dynamic ecosystem models, the growth rhythm of the plant communities is the most important study object. Some advances in the methodological development of measuring the growth of mire plants have been achieved. For instance, the problems involved in measuring the height growth of Sphagnum mosses in field conditions have partly been solved. An application of the IRGA-technique to studying the organic matter production of the Sphagnum — dwarf shrub community is ready for use in field conditions, but the methods for combining direct measurement data with IRGA results are still inadequate.
The main task in (3) is characterized by Figure 2, i.e. energy flow and material should be divided into biotic components. By using population studies, decomposition tests, and experimental respiration techniques, a more detailed quantitative model of these pathways can be constructed. Preliminary results for total decomposer activity and the role of soil animals in detritus energy flow have already been revealed.
Branches (4) and (5) are very closely connected with each other and with (3b). A detailed study into the different terms which make up the accumulation equations as a function of the environmental factors has been proposed.
In (6), the suitability of the mire ecosystem as a study object of stability and succession problems has been emphasized. The successio-nal stage of the ecosystem is very strongly affected by forest improvement measures. For this reason, the study of the regulation mechanisms of mire communities is important in Finland, where about 4.5 mill. ha. out of a total of 10 mill. ha. have been drained and partly fertilized so far for forestry purposes.
Finally, the future of the planned research project The structure and function of mire ecosystems and the effects of forest improvement on them is discussed. The working group consisting of biologists from the Finnish Forest Research Institute (Department of Peatland Forestry) and from a number of departments at Helsinki University (Botany, Zoology, Microbiology) is waiting for the research plan, now connected with the MAB-program of Finland, to be financed. The preliminary studies are continuing on a small scale.