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Investigation of relationships between biomass of different plant compartments is important because their varying turnover rates affect the amount and composition of aboveground and belowground litter, which has a direct effect on nutrient cycling and carbon accumulation in soil. A study of biomass partitioning amongst compartments of the bilberry (Vaccinium myrtillus L.), a common clonal dwarf shrub in boreal coniferous forests, was carried out at eleven study sites in Finland. We hypothesize that the biomass partitioning of bilberry follows a common pattern across a variety of edaphic conditions and geographic range, and this pattern can be modelled by the rank distribution of compartment biomasses. We found that the highest portion of the total biomass belonged to rhizomes, which were followed by shoot stems, roots and leaves. Furthermore, this pattern was observed regardless of the latitudinal zone (northern or southern Finland), site fertility level measured as soil C/N ratio and canopy-dominant tree species (pine or spruce). However, the observed ratios between biomass compartments varied between different sites. In particular, we found that the exact ratio between above- and belowground biomass was dependent on the C/N ratio of the soil organic layer (exponential model, R2 = 0.443), showing that bilberry allocates more biomass to belowground parts in the nutrient poor than in the nutrient-rich sites. The results suggested that there are uniform regularities in the structural organization within the plant species representing clonal growth form of dwarf shrubs. This observation enables us to use the rank distribution of compartments in modelling biomass partitioning of bilberry in a wide range of environmental conditions, although the mechanisms underlying such regularities require further investigation. [ABSTRACT FROM AUTHOR]

The effect of artificial shoot clipping on the vegetative growth and sexual reproduction of the evergreen bearberry, Arctostaphylos uva-ursi, and the deciduous bog bilberry, Vaccinium uliginosum, was studied in the vicinity of a copper-nickel smelter in SW Finland. According to the research hypothesis, heavy metal induced shoot death breaks the apical dominance in the clones growing in a polluted environment. This causes activation of dormant axillary and adventitious buds and an increase in branching on the older parts of the stem. Regrowth after shoot death was studied by clipping off all the current-year shoots from experimental branches in autumn (1994) and spring (1995). Within-clone and between-clone control branches were used to test the data. Both species displayed a considerable ability to activate dormant meristems after the damage. Regrowth of the current shoots during the next growing season (1995) was about 80% compared to the within-clone control in both species after autumn clipping. Shoot clipping in early summer was more detrimental for both species, and the regrowth of A. uva-ursi was less than that of V. uliginosum. Differences in the storage reserves and source-sink mechanisms of carbon allocation between evergreen and deciduous species probably explain their distinct response. When the removed biomass was added to the living biomass of the branches, there was overcompensation in the total dry weight of A. uva-ursi after autumn clipping, and the weight was almost 90% of the control after spring clipping. The total dry weight of V. uliginosum also equalled that of the control when the removed biomass was added. No berries developed on either species in the year following the autumn treatment, because clipping removed all the flower buds. Spring clipping had no effect on the sexual reproduction of A. uva-ursi, but decreased the berry production of V. uliginosum. The degree of compensatory growth of both species was only slightly affected by the distance from the smelter. It is suggested that dormant bud activation, rapid regrowth and plastic branching contribute to the resistance mechanism to heavy metals. [ABSTRACT FROM AUTHOR]