Paavo Havas

Responses to harvesting intensity in a clonal dwarf shrub, the bilberry (Vaccinium myrtillus L.)

The effects of herbivory were simulated on stands of bilberry (Vaccinium myrtillus L.) in a boreal Empetrum-Myrtillus type forest. Five harvesting intensities were used (0% (A), 25% (B), 50% (C), 100% (D) of the bilberry ramets or all the ramets of all species (E)). Density and biomass of the stands, and growth of the ramets were monitored for five growth seasons, from 1986 to 1990. After damage new ramets emerged rapidly from dormant buds at the base of removed ramets. Between 70 and 97% of the density relative to the control level was regained by the final harvest. However, only between 11 and 64% of the biomass relative to the control level was recovered. Clipping reduced the branch growth, both in the new ramets and in the new parts of the old, unclipped ramets. Severe treatments (D and E) decreased the growth more than did light harvesting (B and C). Survival and fecundity of the ramets were not affected. The result therefore suggested that the bilberry is not able to recover totally from severe herbivory damage between the years of peak rodent population that shows a 3–4 year cycle. Nevertheless, extreme grazing pressure is rare in boreal ecosystems as alternative food is available for herbivores, and predators also limit the herbivore population. Hence the bilberry exhibits moderate tolerance of the usual level of herbivory damage.

The effect of air pollution on the radial growth of Scots pine (Pinus sylvestris L.)

Abstract The work described is primarily a methodological experiment of applying dendrochronology to determine the effect of air pollution on the radial growth of Pines within a distance of 0–1·5 km from a chemical installation producing fertilizers (Typpi Oy). This plant has been functioning for about 20 years, discharging fertilizer dust and certain toxins—mainly fluorine compounds. The diametric growth of Pines clearly varies in correlation with the functioning of the chemical plant. Younger trees (under 50 years old), in particular, are responsive to the action of the fertilizer dust. The harmful effects appear later, and can be seen even in fairly old trees (under 100 years old). The variation in radial growth can be regarded as a biological parameter that is significant in elucidating the effects of pollution in the coniferous zone and in predicting future development.

Above-ground growth response of the bilberry (Vaccinium myrtillus L.) to simulated herbivory

Summary To monitor growth response in the bilberry to herbivory caused by small rodents, a field branch cutting experiment was conducted. Two damage patterns were used. In the first, all annual branches except the oldest stem were removed (R1). In the second, only half of the branches were removed (R2). The above-ground growth and fecundity were monitored for three growth seasons. Survival was over 80 %. The above-ground vegetative growth was vigorous, being 1.3-1.4 or 1.7-fold for R1 and R2 ramets, respectively, as compared with the respective control ramets. Increase in biomass in R1 ramets was a consequence of the larger sizes of the annual branches and leaves, whereas in R2 ramets both the number and the size of the branches and leaves increased. Flower production decreased during the following growth seasons in R2 ramets, and fewer flowers developed into berries. Abundant sexual reproduction would apparently have been too costly for the stressed plants. The more pronounced treatment, R1, rejuvenated the ramets to a vegetative state and these started producing berries only in the third season following damage. In general, the main effect of the damage was clearly to cause rejuvenation in bilberry ramets. The reduced limitation imposed by old tissue overrode the negative effects of biomass loss, which indicates the existence of an efficient buffer system in this clonal species against stress.

Recovery of evergreen clonal dwarf shrubVaccinium vitis-idaea after simulated microtine herbivory in a boreal forest

The evergreen dwarf shrub lingonberry (Vaccinium vitis-idaea L.) was subjected to microtine herbivory simulations to investigate its recovery in a boreal forest. Beside the control (A), the study included three levels of herbivory: clipping of half the annual branches from 50% of ramets (B), removal of 50% of ramets (C), and removal of 100% of ramets (D). Density, growth, and fecundity of the ramets were monitored during the study. New ramets emerged rapidly from dormant basal buds at the base of the removed ramets in groups C and D. After three growth seasons, 60–117% and 42–112% of density and biomass, respectively, had been regained in the groups damaged relative to the control, the difference being insignificant between the treated groups apparently because of the small sample size. Survival, fecundity and net growth of ramets were not affected by the treatment. Mean dry weight of annual branches in new ramets was lower in the damaged groups than the control. The recovery of the lingonberry was unexpectedly good. The results suggest that, since natural herbivory seldom is as heavy as in this work, the time between population density peaks of microtine rodents is usually long enough for the lingonberry to recover in boreal ecosystems.

Effect of nitrogenous air pollutants on changes in protein spectra with the onset of winter in the leaves and shoots of the bilberry (Vaccinium myrtillus L.)

Electrophoretic profiles of 0.1 m Tris-HCl (pH 9.0)-soluble proteins in the leaves and stems of the bilberry (Vaccinium myrtillus L.) were investigated in the latter part of the growing season (July-October), in a highly-polluted industrial area with serious forest damage (main emissions NO(2), SO(2), NH(3), urea and fertilizer dust) in Oulu, northern Finland, and in an unpolluted control forest with the same climatic and edaphic conditions. About ten protein components in the leaves and seven in the stems increased in concentration in SDS-PAGE towards the autumn, while one to four other components decreased in concentration. The pollutants in the industrial area caused a considerable decrease in the concentrations of soluble proteins, particularly in the leaves in August and September. A decrease was obtained in six components in the leaves and three components in the stems, while increases were observed in one component in the leaves (10 kDa) and four components in the stems (10, 43, 50 and 65 kDa). One reason for the lowered cold-resistance in the bilberry caused by air pollutants could thus be the lowered concentrations of certain soluble cytoplasmic proteins that protect the plant against winter conditions.

Some Special Features of the Ecophysiological Effects of Air Pollution on Coniferous Forests during the Winter

The ecophysiological effects of air-borne pollutants have mostly been investigated in the region of temperate deciduous forests. We now present some observations from the area of northern coniferous forests. It seems to us that this area is characterized by some special features of the effects of air pollution on coniferous trees. We deal with this question mainly at the ecological level (i.e. we have been observing areas influenced by several polluting agents simultaneously, not by only acidic rain, for example). This is the normal case, and it is exceedingly difficult — often possibly even futile — to endeavour to estimate the effect of each polluting component separately; it is more important to strive to estimate the combined effects of pollutants in different climatic conditions.