Population dynamics, energetic cost of flowering and survival of Spiranthes spiralis in regularly managed National Nature Monument "Pastviště u Fínů"
Abstract
Population biology of critically endangered species Spiranthes spiralis was studied in one of the two remaining Czech localities (National Nature Monument Pastviště u Fínů). In years 1985-2010, the total number of flowering plants varied from 15 to 181 individuals.
Since 1998, we have gradually marked 540 positions with the occurrence of individual plants or dense clumps. Survival of marked individuals and their growth characteristics (plant height, number of flowers, length and width of leaves) were recorded annually from 2000 to 2010.
Long-term observation enabled calculation of transition probabilities between life stages. Dormancy (survival without an appearance of the above-ground parts in one or more growing seasons) was a very rare event recorded eight times in six plants.
Sterile plants were more likely to remain sterile in a subsequent year (65.5%) than becoming flowering (15.4%) or dead (19.1%). Flowering plants were prone to sterility in the following season (63.7%), rarely dying (8.6%).
Despite the energy loss in favour of flowering, the probability of flowering over two consecutive years was 27.6%. The flowering plants had a significantly smaller leaf area in the following season compared to the previous one, while the leaf area of sterile plants remained similar.