Abstract
The threat of climate change on alpine vegetation is becoming more and more evident and the assessment of the vulnerability of alpine plant species’ under altered climatic conditions is an urgent task. This thesis wants to contribute to climate change research with three studies. The first (chapter I) is a literature review about the effects of climate change on the vegetation in Italy. The second (chapter II) is a case study on intraspecific functional plant response to advanced snowmelt in highly specialized alpine snowbed ecosystems. These systems are characterized by a long duration of snow cover, up to ten months per year. The third study (chapter III) investigated the intraspecific functional trait variability of subalpine species growing in microrefugia at lower elevations, i.e. ice holes, as well as in the alpine climatic zone. The approach adopted for both case studies discussed in the second and the third chapter was the assessment of intraspecific variation of functional traits (ITV) between areas with different environmental conditions. Given the importance of plant functional traits for individual plant performance, ITV represents a fundamental mechanism for species’ adaptation to changing environments. As results of the first chapter, we found that climate warming probably enhances plant growth in Italy but the magnitude of this effect differs among climatic zones. Drought can override the stimulating effect of higher temperatures, especially in Mediterranean and sub-Mediterranean climatic zones, but even in the temperate one. Moreover, our review revealed major research gaps regarding, first, possible modifications of species composition and its effects on ecosystem functioning and, second, relations between climate- and land-use change regarding vegetation changes. In the second chapter, we showed how already little changes in snowmelt timing induced by climate warming could improve the growth of snowbed species. However, seeds’ production under advanced snowmelt was lower. The consequent possible reduction of dispersal ability together with improved growth conditions may make snowbed species less capable to face future probable invasions of more competitive and generalist species. Finally, in the third study, the analysis of leaf traits showed that two species in ice holes exhibited a tendency towards acquisitive leaf economics on siliceous bedrock. Two other species on the same bedrock expressed instead a more conservative economics in ice holes, indicating that there is still space for them for additional adjustments to ice holes environmental conditions. On calcareous bedrock, species performance depended on soil characteristics. The species on more developed soil showed a better growth performance if compared to subalpine habitat. We conclude that some species harbored by ice holes’ microrefugia might represent a possible effective source for future colonization in case of climatic deterioration. The findings of the presented thesis generally confirm ITV as a valid approach to detect the direction of plants’ response to climate and environmental alterations.