Comparative seed germination traits in bog and fen mire wetlands

Abstract

Mires are continental wetlands of high scientific and conservation interest. Understanding the seed germination traits of mire species is essential for comprehending their regeneration ecology and conducting active restoration policies. Here, a comparative study of seed germination traits was performed with 34 plant species from bog and fen communities, including many of the European indicators of these habitats. Freshly collected seeds were exposed to a laboratory germination experiment designed to characterize their response to (1) cold stratification and (2) simulated field temperatures. Germination strategy groups were interpreted according to these responses, and the relation between these groups and different mire types was discussed. Seeds of all tested species had physiological dormancy. Most of them showed conditional type 2 non-deep physiological dormancy: fresh seeds could germinate only at warm temperature, but attained the ability to germinate at colder temperature as they lost dormancy. Most mire species from bogs, poor fens and base-rich fens followed a warm germination strategy analogous to that of other wetland species. Species from this warm group responded to very warm temperatures which rarely occur in the field, and this was interpreted as a gap-detecting mechanism. In contrast, species from calcareous springs and flushes had a cold germination strategy, which would fit with the cold and stable soils where they occur. Finally, a group of species associated with the pioneer Rhynchosporion vegetation of bare peat areas have very low germination, suggesting an intermediate or deep seed dormancy and a long term seed bank.