Data Quality in Field Surveys: Methods and Results for Tree Condition, Phenology, Growth, Plant Diversity and Foliar Injury due to Ozone.

The response of forest vegetation to the variety of biotic and abiotic stressors can be evaluated by several methods and techniques.These investigations are based on measurements and visual assessments carried out in the field on a number of sample trees, which are both subject to the same source of errors (with sampling error and measurement error being particularly important). Here, we present the methodologies adopted within the ICP Forests to promote and control data quality in investigations based on field measurements and visual assessments, hereafter referred to as field-based investigations. Results from recent tests are also presented