A comparative germination study among different alpine habitats

If species inhabit in a specific habitat two conditions should be befallen: first seeds must be present through dispersal or in the soil seed bank and secondly, conditions for germination must occurred. If suitable germination niche is not met, germination will not occur and, consequently, species will not be present. In an alpine context, the large species and microhabitats pool found have resulted in a variety of germination and dormancy patterns, which make it difficult to define a common alpine germination niche or behaviour. Therefore, to better understand germination ecology in alpine environment and their functional role in filtering the regional species pools into local communities a habitat-related germination study is needed. A habitat-related approach will contribute to a better comprehension of which are the key factors affecting germination in alpine habitats and define the different alpine germination niches. To this end, a germination study of species inhabiting in two Sites of Community Interest (SCI) “Passo dello Stelvio (46° 32’N, 10° 25’E)” and “Val Viola, Dosde (46º 24’N, 10º12E)”, located in the Alps of Lombardy (Sondrio, Northern Italy) was done. These SCI belong to two habitats types defined by the European Habitat Directive Natura 2000 classification: Habitat #6230- Nardus-rich species grasslands” or “siliceous habitat”; and Habitat #6170- Alpine calcareous grasslands’ or “calcareous habitat”. Firstly, I described and compare the type and level of seed dormancy and assessed species’ germination strategies of 53 alpine species growing in two different habitats. Results showed that calcareous and siliceous species showed different germination strategies, with a slow, mostly overwinter germination on calcareous species’, and with fast and undifferentiated timing germination for siliceous ones. Moreover, specialized regenerative strategies were observed among microhabitats with species mostly occurring in heats showing high overwinter germination. In conclusion, alpine species use different germination strategies depending on habitat provenance, species’ main microhabitat and chorotype. Subsequently I defined the germination and vegetative traits of seven pairs of closely related species inhabiting in these habitats. Results showed some germination traits dissimilarities according to habitat provenience. Conversely, other germination traits and vegetative traits were similar in both habitats. The high vegetative traits convergence hints at small differentiations in adult plants between habitats. However, the separate habitat clusters when using germination traits suggest that species occurrence in the two habitats may be limited at the earliest stages of plant development, particularly by germination. Finally, I predict species germination timing in the field using thermalmodels. Results showed species were dormant when dispersal and different germination timings were predicted for each specie. The different dormancy types detected here indicate that dormancy may play a significant role in controlling germination, always awarding risk-averse strategies to escape winter. The different germination timing detected reduce probability to overlap species’ germination niche, thus having different timings species do not compete for the same resources. In conclusion, this thesis describes germination ecology on alpine habitats and identify the main factors affecting species’ specific germination behavior. Special attention was putted on the possible functional role of germination and dormancy on driving species distribution and community assembly. Finally, all outputs reached here and future outputs that new research will bring hint at important implication in developing good practices for restoration and conservation activities in alpine habitats and contribute to a better understanding of the response of alpine plants in the regeneration from seeds due to global warming.