| Popis: |
Demographic data were gathered on populations of Viola incognita Brainard, V. pallens (Banks) Brainard, and V. adunca Ait. in Newfoundland. Density, recruitment, and mortality varied within and among species; but most populations expanded tremendously during the 4-year study period. Increasing density in V. pallens and V. incognita populations resulted in decreasing mean size of ramets. Density effects on plant size in V. adunca were obscured by the addition of many small seedlings to the populations. Seedling density and survivorship were relatively high, and disturbance appears to play an important role in violet population dynamics. Relative plant age (i.e., cohort) and plant size seldom were associated with plant survival over a 1-year period. An association between plant size and survival existed in V. adunca only because one-leaf plants had a higher mortality rate than plants with two or more leaves. Low survivorship was associated with reproduction in V. incognita, but no such association existed in the other species. Levels of herbivory were low, and herbivory and subsequent survival over 1 year were not associated. |
