Investigation of air pollution impact on tree condition indicates the greatest correlation between pine defoliation and SO2, SO4 and NH4 concentration in the air, NH4 load with precipitation and its pH in the eastern part of Lithuania. In the southern part significant correlation was found between defoliation and SO4 concentration in the air and SO4, NH4 load with precipitation and its pH. No significant correlation was found in the western region of the country, which includes seaside part. Tree age and tree development classes have an essential effect on the correlation significance

The results indicate that it is possible to reach a good level of reproducibility in a relatively short time. However, quality assurance procedures allow to know the real status of reliability of the field data. More attention must be given to the Level II indices, to select the really useful and informative ones, and to concentrate on these the didactic efforts

The assessment of O3-like foliar symptoms is increasingly considered in monitoring programs aimed at evaluating air pollution effects on forests. The results showed considerable spatial and temporal variation of O3-like foliar symptoms: year, subplot adn the interaction between year and plot were found significant factors. Symptoms resulted lower in 2001; there were differences of foliar symptoms between different subplot and overall the variation between years are considerably different according to the plot being considered. These findings suggest that O3-like foliar symptoms recorded on a small plot selected without a formal statistical approach and with no consideration of the apparently high variability of symptoms expression risk to introduce a serious bias in the evaluation of the potential ozone impact at a given site and its trend

A FORest Monitoring System (FORMS) has been implemented in Denmark in order to gain and deliver knowledge and information for operational and strategic decisions concerning nature and environment. FORMS integrate four national monitoring programmes. Forest condition monitoring is performed on 52 permanent plots distributed on a 16 x 16 km grid. FORMS gives a systematic and representative assessment of the resources in and development of the forests in Denmark, includes the monitoring of important processes in the forest ecosystem and follows the use of forest for recreational purposes

The present paper presents a list of probabilistic sampling procedures and subsequent statistical analysis, which may achieve this goal without a considerable increase of field effort

Following the objective to provide an overview on the spatial and temporal variation in forest condition on a European scale, an extensive systematic survey on more than 6000 so called Level I plots throughout Europe is carried out. Results show a recuparation of crown condition in the mid nineties and a resuming deterioration with nearly a quarter of the sample trees classified as damaged in 2001. Results of statistical evaluations explain the observed variation mainly by weather extremes, insects, fungi and indirect effects of air pollutants via soil acidification or changes in the nutritional status of trees