Current issue: 54(2)
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.
At immediate surroundings of a fiberglass plant in Central Sweden, vegetation shows toxicity symptoms. Soils and birch (Betula pendula Roth) leaves were sampled. The soil was analysed for water soluble and organic bound boron, carbon, nitrogen, and pH. Vegetation was analysed for total boron. Both fractions of boron in the soils increased towards the factory. Organic bound boron increased irregularly because of its strong correlation to carbon content which varied in the area. The C/N ratio increased nearer the industry due to the harmful effect of boron on the decomposition of organic matter. No relation between pH and the distance from the emission source was visible, but B/C ratio was found to increase with increasing pH of the soil. Boron levels in birch leaves were elevated very much close to the factory. The geographical distribution of high levels of boron in birch, corresponded well with high values in soils, and also with the main wind directions. The limit values for visible injury on birch were found to be around 5 ppm of water-soluble boron in soil and around 200 ppm in leaves.
Air pollution injury to vegetation often occurs near a fertilizer factory in Central Sweden. The causing incidence often occurs in the winter and the symptoms appear when metabolism starts in the spring. Deciduous and coniferous trees and bushes were injured in the spring of 1979. Samples of Scots pine (Pinus sylvestris L.) needles were analysed for sulphur, total fluorine and nitrogen content, some of them for nitrate and ammonium. All the compounds showed elevated levels, clearly connected with the degree of exposure of the sampling site. The levels were higher in the spring than later in the growing season, indicating involvement in metabolism or leaching. None of the compounds was significantly in excess, although, elevated to an extent to indicate the cause of injury. Most probably the nitrogen compounds were involved. The problems encountered in tracing the causing pollutant, when injury appeared long after the incidence, might be easier solved with regularly used technical monitoring and bioindicator technique.
Ultrastructure of mesophyll of second-year green needles of Picea abies (L.) H. Karst. and Pinus sylvestris (L.) has been studied in several polluted areas in Finland since 1976 (Soikkeli and Tuovinen 1979, Soikkeli 1981a). Four different types of injuries have been found. The types differ with the origin of the material:
1) In needles collected from areas pollute by S-communds the types with reduced grana and/or the with lightening of plastogobuli with simultaneous accumulation of lipid-like material are observed.
2) In needles expose to fluorides (alone or in addition to other pollutants) the type with swollen and/or that with curled thylakoids are found. Both of the latter have also stretched envelopes. In each type of the injury three stages of cell disruption have been described: slight-medium, severe and very severe. On the slight-medium stage the injuries are usually found only in chloroplasts. On severe stage other organelles show injuries, too. In very severe injury all cell organelles are badly disorganized or they disappear completely. The most abundant injuries are usually in needles collected after their second winter. The severity of cell injury depends on the closeness of emission source or on the measured concentration of SO2.
A forest damage was detected in spring 1931 near electro-chemical factory in Imatra in Eastern Finland. It was deduced that it was caused by a gas discharge from the factory. A survey was made to describe the damages. Forests in the damaged area of five hectares were Scots pine (Pinus sylvestris L.) dominated and 60-80 years old. According to the factory, the exhaust gases contained 0.4 mg chlorine per liter. In addition, chlorate containing liquids evaporated thorough the chimney, which seemed to have been the main cause of the damage. The chlorates may have concentrated in the snow covering the trees during the winter. The Scots pine trees had lost all the needles in spring, but grew new needles in the summer. In some trees the new needles were few or undeveloped. Some mild damages were noticed in pine and Betula sp. during the growing season. Forest edges and trees higher that the other trees were worst damaged. Pine was most sensitive to the emission. Pine weakened by the gas damages were attacked by insects, the most important being Pissodes sp. The secondary insect damage is likely to kill the surviving trees. The dying pines should be removed only if it is necessary to prevent the spreading of insect damage. The trees may hinder the spreading of further gas emissions. In future, other tree species should be preferred over pine.
The PDF includes a summary in German.