Understanding the long-term dynamics of vegetation since 1953 in high-mountain regions

Alpine ecosystems, highly sensitive to climate change, are experiencing
shifts in species ranges and community structure. These changes are driven
by a complex interplay of climatic and environmental factors, land use
changes, geomorphological dynamics, and species interactions, which can
often lead to contrasted and sometimes unexpected dynamics. Historical
records provide a valuable opportunity to capture these complexities by
revealing long-term changes, opening a gateway to hypothesise about the
key underlying processes. We investigated changes in the floristic
composition of subalpine to nival vegetation communities by resurveying a
period of 70 years. To understand vegetation patterns, we (i) resampled
vegetation at plot level and remapped the areas, (ii) analysed the role of
driving climate, environmental, and land use factors on vegetation
distribution and vascular plant species richness, and (iii) modelled
plant-plant interactions from community data. The results reveal that
vegetation cover patterns were strongly influenced by local climate and
soil properties. The species richness is also influenced by the livestock
density and the flat morphology. It should be noted that climate change
caused wetland habitats to become drier and accelerated secondary
succession through upward migration and range-infilling processes.
Furthermore, a trend towards eutrophication was observed. The results
suggested that certain plant communities, particularly those found in
snowbeds, were more vulnerable to environmental changes that have occurred
over the past 70 years. Synthesis: This study highlighted the complexity
of vegetation dynamics. In addition to thermophilisation and aridisation,
changes in land use affect species composition, species richness, and
vegetation cover. Substrate conditions also play an important role.