Ecosystem dynamics triggered by climate change along a glacier foreland: a quantitative and functional approach on plant and arthropod assemblages.

We studied the succession of vascular plant and carabid beetle assemblages along a primary succession on the foreland of the Cedec Glacier (Northern Italy). We used a quantitative (species richness, vegetation cover) and qualitative (changes in morpho-functional attributes) approach. Ten sampling stations were positioned along a transect covering the entire proglacial area from the glacier terminus to the areas untouched by Holocene glacier advances; on each station both plant and carabid assemblages were recorded. For both plant and animal species some morpho-functional traits (canopy height, leaf dry matter content, leaf dry weight and specific leaf area for plants; wingless, autumn-breeders, predators and body length for carabid beetles) were measured. Quantitative and functional changes occur both on plant and carabid beetle assemblages along a primary succession on glacier forelands. These changes are not gradual throughout the succession, but experience at least one threshold. For plants, quantitative and functional changes are not synchronous: an abrupt increase in species richness and ground cover occurs between 41 and 156 years after deglaciation, while major functional changes occur at the very last step of the succession; the timing of this change is unknown, as it occurs in a lapse of time comprised between 156 and 10.000 years. Carabid assemblages change abruptly both from the quantitative and the functional point of view in correspondence of the quantitative changes of the plant community, thus suggesting a role for trophic availability.