| Summary: | Climate is a major determinant of the distribution of ecosystems on earth and influences the latitudinal and altitudinal distribution of both plant species and vegetation. Over the least decades, global warming has been affecting ecosystems worldwide, especially cold regions such as the arctic and alpine biomes. European mountains are considered hotspots of biodiversity, hosting approximately 20% of the continent's native vascular flora, with a high number of endemic species. Yet, these rich and diverse environments are projected to experience one of the highest rates of climate warming, compared to other regions of the world. Climate change has direct impact on plant species, causing species migration and extinction. Consequence, vegetation dynamics in these cold adapted ecosystems are difficult to predict. In this Thesis, I firstly investigated the variation of species richness, α-diversity, β-diversity and total cover of plant functional types on an alpine long-term monitoring site (belonging to the GLORIA network, https://www.gloria.ac.at), with the aim to promote a better understanding of climate-driven changes of alpine vegetation. I identified significant increment in plant species richness, along with trend of biodiversity loss and signals of biotic homogenization: Cold-adapted and rare species declined while dominant species like nitrophilous graminoids and shrubs increased. The results obtained highlight that long-term vegetation monitoring activities paired with multiple measures of diversity are required to properly assess biodiversity and to obtain useful indications for future conservation activities in alpine environments. Secondly, I investigated the germination ecology of 75 alpine plants of interest, to evaluate the role of seed germination as a driver for plant species population dynamics in response to climate warming. One of the key processes in determining the species capacity to migrate, establish and persist is, in fact, seed dispersal, followed by seed germination and seedling ...
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