A central task of the Nature Conservation and Plant Ecology Group is to carry out ecological research on ecosystem- and population-level processes and to utilise the acquired knowledge in directing nature conservation. A major part of the research activities will analyse the quantitatively important interactions between the different components of the ecosystem. These interactions include competition between plant species, plant-herbivore interactions, and the influence of the plants on soil and atmosphere. Incorporating these interactions, numerical simulation models are an important tool to formulate hypotheses about the long-term changes in species composition and biodiversity when environmental conditions change or when species invade, are introduced or go extinct. The hypotheses are tested in empirical studies on the long-term dynamics of ecosystems and plant populations in the field. In addition, whole ecosystem manipulation experiments are carried out. Based on the results of these experiments, we hope to acquire the scientific knowledge that allows us to predict the effects of changes in the deposition of nitrogen- and sulphur-compounds, the CO2-level and the temperature of the atmosphere, as well as changes in the hydrology of ecosystems, and the densities of herbivores and predators.