The threats posed by air pollution and climate change have resulted in considerable public debate about forest condition and growth during the past two decades. Despite the massive input ofresearch resources, no clear answers have been found to these global questions. Although there have been substantial advances in our knowledge of the effects of air pollutants on the forests, many of the questions associated with forest condition are still open. Monitoring of forest condition at the national level started in Finland in 1985 in accordance with the methodology drawn up by the International Co-operative Programme on Assessments and Monitoring of Air Pollution Effects on Forests (ICP Forests, UN/ECE). Since then, research into forest condition and vitality has been one of the key areas in the research carried out by the Finnish Forest Research Institute. Three basic questions formed the starting point for the multidisciplinary, Forest Condition Research Programme: What changes are taking place in our forests? Why does forest condition vary, and why do trees appear to be suffering? How can forest condition be maintained through appropriate forest management? This report covers forest condition and changes in environmental factors on the of the latest findings, publications and expertise of researchers participated in basis the Forest Condition Research Programme. In addition to researchers from the Finnish Forest Research Institute, a large number of scientists from domestic and foreign universities and research institutes also made a considerable contribution to the research programme.

Inhalt
Importance of forests in Finland.- Finland's forest resources in 19891994 and changes compared to 1951.- Growth variation.- Climate change.- Weather conditions during 19801995 and tree damage directly attributable to weather.- Air pollutants Emissions, air quality and acidifying deposition.- Heavy metal loading.- Soil factors.- Tree tolerance, resistance and defence.- Tree nutrient status.- Air pollutants and frost-hardiness of conifer needles.- Effects of ozone on trees and forest insects.- Cellular and tissue changes in needles.- Crown condition.- Dynamics of defoliation, biotic and abiotic damage during 19861998.- Forest condition in relation to environmental factors.- Changes in abundance of some forest floor mosses.- Epiphytic lichens as indicators of air quality.- Abundance of epiphytic lichens in litterfall during 19671994.- Changes in lichen abundance and index of atmospheric purity during 19851995.- Structure and functioning of forest ecosystems.- Effects of acidic deposition on soil solution quality and nutrient leaching in forest soils.- Effects of acidic deposition on forest soil microbiology.- Fine roots and soil properties.- Dependence of tree annual diameter growth on weather factors.- Functioning of forest ecosystem as an indicator of environmental change.- Functioning of forest ecosystems under nitrogen loading.- Areas polluted by heavy metals.- Effects of heavy metal deposition on soil fertility.- Effects of heavy metals on soil microflora.- Response of understorey vegetation to heavy metal loading.- Crowberry (Empetrum nigrum L.), a copper-tolerant dwarf shrub.- Response of tree stands to heavy metal loading.- Variation in radial growth of Scots pines exposed to heavy metal and sulphur emissions from the Cu-Ni smelter at Monchegorsk,NW Russia.- Role of tree species in determining soil fertility.- Prescribed burning as a soil amelioration measure.- Improving forest condition by means of slow-release fertilisers.- Effects of fertilisation on soil microbes.- Liming of forest soils.- Effect of nutrient availability on pest resistance of trees.- VI. Forest Condition in Finland Concluding Remarks.- Appendices.- Abbreviations for Finnish forest site types.- Author index.