Quality assurance
High data quality is an essential prerequisite for the representativeness, evaluation and interpretation of the results of the National Forest Soil Invetory. To this end, the use of standardised methods across the country is a fundamental requirement. This applies in particular to the sampling network, the collection of samples, laboratory analysis and accompanying documentation.
To ensure reproducibility, both data collection and data management, as well as all procedures applied to each individual sample, must be documented. Furthermore, the harmonisation and further development of methods, comparative studies and accompanying analyses, as well as close consultation among participants, play a decisive role in the success of data management and data security.
Specific quality assurance requirements apply to the BZE’s field measurements in the forest, with the emphasis on comparable sampling and data collection. The comparability and reproducibility of a measurement or analysis result for a sample must be considered in conjunction with the recording and interpretation of the conditions during the on-site measurement of the parameter. The collection of a sample constitutes a mechanical intervention in a specific continuum that is associated with disturbances. For this reason, the method of sample collection must be precisely documented. This is particularly important in order to ensure that all subsequent processes, such as laboratory analysis, error analysis, evaluation or interpretation, can be carried out consistently and without errors.
The BZE working instructions (German language) contain all relevant information regarding laboratory analyses and field surveys. BZE Wald is making significant efforts in the areas of method development and harmonisation. To this end, numerous studies have been carried out to assess the comparability of different methods. In addition, existing methods have been further developed.
All analytical methods used by the National Forest Soil Inventory are documented under the auspices of the Expert Committee on Forestry Analysis and published in the Manual for Forestry Analytics (see here, German language). The quality assurance programme included accompanying interlaboratory tests and the inclusion of standard material for each survey parameter. A further quality criterion involves the verification of the coordinates of previous inventories as well as newly added survey points, insofar as these were known prior to the start of the inventory through preliminary clarification. As part of the field surveys, each point is georeferenced.
The field survey guidelines were drawn up in close consultation with experts and inventory managers. They provide a detailed explanation of the sampling design, the sampling procedure, the parameters to be recorded along with their corresponding units and formats, including the relevant code tables with permitted entries. The guidelines also contain the forms required for the field surveys.
To ensure data quality, there is a continuous exchange of experience between the inventory managers, representatives of the federal government, the participating laboratories and experts from the relevant specialist fields. To this end, regular federal-state meetings have been taking place since 2001. Further coordination on specific topics has taken place in numerous workshops, training sessions and pilot surveys. During the survey phase, federal representatives accompany the fieldwork in the various federal states so that any problems or deviations from the working instructions, particularly in the initial phase of sample collection, can be addressed directly on site.