Habitat demands and population characteristics of the rare plant species Gladiolus imbricatus L. in the Frenštát region (NE Moravia, the Czech Republic)

The sword lily (Gladiolus imbricatus L.) is an endangered species belonging to plant communities of wet meadows. Such meadows decreased in area in central Europe during the second half of the 20th century, and unsuitable biotope management has led to recent decreases in sword lily abundance. The conservation of geophytes (i.e. perennial plants with underground storage organ) like the sword lily requires knowledge of their essential environmental factors and population dynamics. Five populations of the sword lily were assessed at sites near Frenštát pod Radhoštěm (the Czech Republic). From 2008-2010 all individuals (generative, vegetative, juvenile) were counted, biometric data was measured (leaves, flowers, fruits number, and stalk height), a transient matrix was created, and vegetation (relevés) evaluated.

The number of all individuals in generative, vegetative and juvenile stage at these sites underwent year-to-year variability. Nevertheless, the influence of management practices was documented, and was also slightly reflected in both biometric parameters and population abundance. The height, number of leaves and number of blossoms did not show clear temporal or site variability. High reproductive success in this gladiolus was found (61.8-77.8 %), yet seed recruitment is crucial for population stability. In contrast to orchids, each flowering individual had a high probability of flowering to the next season (40 %) and did not switch to the dormant or vegetative stage. About 50 % of individuals tended to stay in dormancy for two years. Unfortunately, the short observation period and inability to estimate the number of dormant individuals made it impossible to determine the length of dormancy, an accurate population structure, and long-term population responses to climate factors. Still, our results confirm the ecological linkage of gladiolus with a broad gradient of moisture, and their connection with mesic Arrhenatherum meadows and intermittently wet Molinia meadows. Long-term regular extensive management is essential for the persistence of populations at all study sites. Self-sowing tree species should be pruned away and herb vegetation cut down each season to provide safe sites for gladiolus seed recruitment.