The use of forest mosses as bioindicators was tested with transplanted experiments. One transplantation experiment was made to study effects of air pollutants on two forest moss species, Hylocomnium splendens (Hedw.) Schimp. and Pleurozium schreberi (Willd. ex Brid.) Mitt. Another transplantation was used to study the nitrogen fixation capacity of blue-green algae in the Hylocomnium and Pleurozium moss layers. The surface structure of the moss species was studied by scanning electron microscopy. The air pollution induced changes in the surface structure of moss cells were observable soon after the transplantation. In polluted industrial areas the fertilizing effect of air-borne nitrogen compounds increased the photosynthetic activity of mosses before their destruction. Stress respiration was also observable in polluted areas. The nitrogen fixing capacity decreased or was almost inhibited in all the air-polluted environments.
Several studies of air polluted forest environments have shown that dwarf shrubs suffer from air pollution. In many cases the disturbances have been attributed to the susceptibility of the dwarf shrubs, while in some cases the vegetational competition factor has been discussed. The growth pattern of dwarf shrubs is very complicated and a single individual can cover large areas due to vegetative reproduction. Since dwarf shrub individuals cannot be transplanted for the purpose of laboratory or field tests, the only possibility is to use small cuttings for the bioindication studies. Some preliminary results are discussed.
The symposium of ’Air pollutants as additional stress factors under northern conditions’ was held in Oulu in Northern Finland during November 11–13, 1980. The symposium had four sessions: 1) the ecophysiology of air pollution effects and long-term risks of air pollution effects, 2) bioindication in forest ecosystems, 3) particle and metal problems, and 4) a general poster session mainly related to current research, and the results of the research programme on the dispersion and effects of air pollutants in forest environments financed by the Academy of Finland. Most of the posters and papers presented at the symposium have been included in the proceedings. The rest of the results presented are reviewed in research report of the programme and in the related scientific papers.
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The development of the stomatal area wax structure of Scots pine (Pinus sylvestris L.) needles was studied in flushing needles with a scanning electron microscope. The needles were obtained from eleven Finnish plus tree progenies. The needles were taken from trees that were either nearly uninfected or heavily infected by Lophodermella sulcigena (Rostr.) Höhn.
No difference in the early developmental stages of stomatal vax structure were observed between the southern Finnish, central Finnish and northern Finnish progenies. The general structure differed in the stomatal cavity chamber size. The stomatal openings were larger in heavily infected trees than in healthy trees. This might have an influence on the mechanical penetration of the fungal hyphae.
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The success of certain Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) H. Karst.) provenances from Northern Finland was studied in a tree damage area occasioned by air pollution in the town of Oulu over the period of 1972-76. The pine strains from more northerly and easterly areas and the spruce strains from the immediate vicinity of the site itself were being observed to thrive best. The results point in a similar direction to those of other comparable experiments, except that the mortality rate amongst the saplings was exceptionally high and the proportion of healthy saplings in good condition was found to be unusually low. Structural properties suggestive of resistance to pollution were observable selectively in certain provenances, these including the xeromorphy of needles or thickness of the epidermis. The chief cause of mortality amongst the saplings was found to be the damage inflicted by pollution during the winter, while that arising in the summer months was relatively slight.
The PDF includes a summary in Finnish.