In Finland, Olkiluoto Island has been selected as the site for disposal of spent nuclear fuel. When creating biosphere models for the safety assessments, local main features and processes need to be taken into account. Characteristic of the site is land uplift (6 mm/a) exposing continuously new land for colonization by plant and animal communities. The forest vegetation succession on these stony, fine-grained till soils starts from deciduous shoreline vegetation and ends in almost pure Norway spruce forests. This has enabled to study processes in soils and forests of different developmental stages, to monitor forest condition and the factors affecting it in other land uplift sites. It has also made possible gradient studies of the succession of boreal mire ecosystems without waiting thousands of years. In this paper, a methodology is described to establish a descriptive model on the development of the biosphere to indicate possible ecosystem distributions and main characteristics on the area on the basis of above-mentioned studies carried out in the area of the Gulf of Bothnia, and of results of the site investigations at Olkiluoto. The description will be used as a basis for selection of appropriate ecosystem modules and parameter values in the subsequent assessment model systems.