| Abstract [eng] |
This dissertation presents the results of a study of three endangered woodland plant species in Lithuania: Cephalanthera longifolia and C. rubra (Orchidaceae) and Cardamine bulbifera (Brassicaceae). The aim of the study was to assess the effect of habitats on population structure, plant traits and reproductive success. A standardised, trait-based approach was used, combining single-census assessments with observational studies of natural fruit set (2021–2023), as well as an experiment on simulated autogamy and allogamy (2022). The analysis revealed that C. longifolia is expanding and successfully colonising habitats ranging from shaded forests to early-successional tree stands. In contrast, C. rubra is significantly rarer and confined to four localities; it is also more sensitive to habitat change. Within C. longifolia populations, the density of individuals varied widely, being higher in more open habitats and lower in shaded forests. Vegetative individuals dominated populations (58.7–85.1%), whereas generative individuals comprised 14.9–40.1%. Cardamine bulbifera populations were dominated by juvenile and immature individuals (89.2% combined), indicating predominant vegetative reproduction by axillary bulbils. The highest density of individuals was found in broadleaved forests, while hornbeam forests supported the highest percentage of mature individuals. Across Cephalanthera populations, the rate of natural fruit set was consistently low (11.8% on average for C. longifolia and 15.2% for C. rubra), with many individuals producing no fruit. Flowers in lower positions set fruit more frequently than those in higher positions. Fruit set was weakly related to display traits in C. longifolia and moderately related to them in C. rubra. Bryophyte cover negatively affected fruit set in both species, more open habitats favoured reproduction in C. rubra, soil pH correlated positively, and mean June temperature correlated negatively with fruit set rate. Pollination experiments showed that assured pollination (both self- and cross-) increased the percentage of fruits set to 69–70% in C. longifolia and 88–97% in C. rubra. This confirmed self-compatibility and ruled out resource limitation as the cause of the low natural fruit set. The results of the study refine the understanding of the demography of long-lived rhizomatous plants by showing that the ratios of maturity groups primarily reflect the current suitability of the habitat (e.g. sunlight availability, disturbance and community composition) rather than the developmental trends of the population. The study provides evidence-based guidance for conservation, including habitat management (e.g. controlling the canopy and plant debris) and the targeted use of hand pollination. It also highlights the importance of single-census assessments alongside longer-term population studies. |
