Survival and Flowering of Perennial Herbs. V Patterns of Flowering

Flowering patterns were analyzed for six perennial herbs - Orchis mascula (L.)L., Dactylorhiza sambucina (L.)Soó, Listera ovata R.Br., Hepatica nobilis Miller, Sanicula europaea L. and Primula veris L. - studied on permanent plots for time-spans ranging between 13 and 43 yr. Long-term trends due to changes in land use or other successional processes were major factors affecting flowering in many cases. However, this paper concentrates on short-term variations in flowering frequency. Multiple regression analysis indicates that summer drought negatively affected next year's flowering in Dactylorhiza, Listera and Sanicula. In Dactylorhiza and Primula there was some parallelism in flowering frequency between adjacent plots which may indicate biotic or abiotic influences other than those recorded by us or by standard meteorological observations. In Hepatica the effects of patchy disturbances were obvious. In Sanicula there was a strong tendency for ramets not to flower the year after they have flowered, interpreted as a high reproductive effort in flowering years causing fecundity costs of reproduction. This pattern, which is weak or absent in the other five species, seems to interact with the drought sensitivity to produce mast years. The usual explanation for the mast year phenomenon - predator satiation - is questioned.