Management of forest vegetation data series: the role of database in the frame of Quality Assurance procedure

If data from diachronic records on permanent areas are to be made available, the quality of the historic sequences must be standardised, preserved, organised and checked in such a way as to permit continuous input and comparison. The "Ground Vegetation Assessment" group of the CONECOFOR programme designed a database with extended search capability to ensure rapid and precise access to data. The vegetation is analysed within a network of permanent plots, based on field surveys conducted at community and population level. Assessments include specific, stratified and overall cover estimates as well as detailed cover scores and density of aboveground shoots (respectively on 24 100 m2 and 100 0.25 m2 sampling units). In addition to archiving data, the database runs functions to check their validity. The integrity of the dataset and its conformation to the user defined range can be assessed, and the entire sequence can be validated before the new data is saved in the database. Subsequent cross-checks among attributes allow further tests of validity and precision. These functions are an integral part of the overall Quality Assurance Control system. The data are organised into seasonal surveys, plots and sampling units. Each species has a field code, with reference to a second archive of coded nomenclature established at a European level. A section for addition and deletion of data makes output available according to the appropriate EC regulations. The system guarantees the visualisation of a certain number of simple statistics, and also permits export of analytic data to external statistical tools.