Current issue: 56(4)
Under compilation: 57(1)
The results of the Finnish forest condition survey carried out during 1986–90 in background areas are presented. The same 3,388 forest trees (1,897 Scots pines (Pinus sylvestris L.), 1,289 Norway spruces (Picea abies (L.) H. Karst. And 202 broadleaves) on 450 mineral soil sample plots were examined annually. Growth characteristics (defoliation, the number of needle age classes, branch damage and needle discolouration), fertility and abiotic and biotic damage express the general vitality of the trees and are not specific for air pollutants. A correlative approach was applied in analysing the factors which may explain the regional pattern and changes in defoliation.
Average tree-specific degree of defoliation was 9% in pine, 21% in spruce and 12% in broadleaves in 1990. Altogether 11% of the pines, 42% of the spruces and 16% of the broadleaves have lost over 20% of their needles or leaves. Defoliation in spruce was the same as in the previous year, but in pine and broadleaves it had slightly decreased. Defoliation had increased by 5 %-units in pine, 16 %-units in spruce and 7 %-units in broadleaves during the whole study period 1986–90.
High stand age and different weather and climatic factors greatly affected forest defoliation in background areas in Finland. Pine cancer (Ascocalyx abietina) has enhanced defoliation in pine in the western part of the country. Air pollutants have evidently contributed to the increase of defoliation in the most polluted parts of Southern Finland. In pine a significant positive correlation was found between modelled sulphur deposition and the average stand-specific degree of defoliation as well as with the increase in average 5-year defoliation in Southern Finland. It is suspected that green algae growing on needles of spruce in Southern Finland indicates elevated nitrogen deposition levels.
The PDF includes an abstract in Finnish.
Different sampling methods (the percentage cover scale, the graphical method, two-point quadrat methods, the five-, nine- and twelve-class cover scales, and the biomass harvesting) were used in estimating abundance of ground vegetation in clear-cut areas and on an abandoned field in Southern and Central Finland. The results are examined with the help of DCA ordinations. In addition, the species numbers and diversity indices obtained by different sampling methods are compared.
There were no large differences in DCA configurations between the sampling methods. According to all the sampling methods, a complex soil fertility-moisture gradient (a forest site type) was interpreted as the main ordination gradient in the vegetation data for clear-cut areas. However, different sampling methods did not give similar estimates of species numbers and diversity indices.
The PDF includes a summary in Finnish.