Monitoring of defoliation in forest stands of the Czech Republic and its comparison with results of defoliation monitoring in other European countries

As a part of International Cooperative Programme on Assessment and Monitoring of Air Pollution Effect on Forests (ICP Forests), defoliation of forest stands has been assessed in the Czech Republic since 1986. Defoliation is one of the principal parameters reflecting the health of forest stands that is assessed on monitoring plots within this programme. Monitoring plots are distributed evenly according to woodiness of the area in a regular schematic network all over the Czech Republic. Even though there has been a long-term reduction of air pollution in most European countries, forest ecosystems reflect these changes with some delay. In the Czech Republic the trend of total defoliation of coniferous and deciduous forest stands has been increasing very moderately in the last 10 years. This trend appears to be partially analogous with some neighbouring countries. Compared to the whole of Europe the trend of defoliation of broadleaves is very similar, but differences have occurred in conifers in the last 10 years. There are significant differences in defoliation levels among the particular countries; in this comparison the Czech Republic is classified as one of the worst. Differences in these levels are very evident especially among the neighbouring countries. To partly eliminate these differences, regular international calibration courses are organized.