Two different types of field work are undertaken at the IM sites: site description and monitoring. Site description refers to basic site characteristics, such as geographical situation, climate, land use history and distribution of soil types, plant communities and tree stands. The description may be supplemented with inventories over the whole site of for example soil types and plant species. Site information is essential for scaling results obtained in the monitoring subprogrammes to the site as a whole, and its importance should not be underestimated. The monitoring is carried out at permanent stations, the locations of which are carefully selected according to the subprogrammes described in Chapter 7. A central aim of integrated monitoring is to establish the relationships between chemical, physical and biological parameters. This is best achieved by carrying out the subprogrammes as close to each other as possible within the main habitat type(s) at the site.