La risposta degli ecosistemi della Rete LTER-Italia alla variabilità climatica e antropica

The LTER-Italy network encompasses 79 sites distributed in terrestrial, freshwater and marine domains and reflects the great variety and biodiversity of environments present in Italy and in two extraterritorial areas under Italian responsibility. The research activities carried out at these sites allow following and understanding the short and long term ecosystem dynamics. This chapter provides a synthetic overview of the results achieved by researches focused on the environmental changes detected in the different types of ecosystems. Studies of the terrestrial sites have shown changes, even on relatively short scales, due to the increase in temperature and the variation in the rainfall regime, and the decrease in snow cover. It has been observed an increase in: i) vegetation cover at medium and high altitudes, ii) distribution of thermophilic species, and iii) microbial biomass in the soil. In addition, variations have been recorded in the composition of insect communities and aquatic fauna. On the other hand, variations observed in the fragile environments of coastal dunes seem to be caused more by anthropogenic activities than by climate change. In the freshwater ecosystems, the most evident effect in large and medium-sized lakes is related to temperature increase, which has affected the winter mixing, especially in large lakes, and the production and seasonal cycle of plankton. In contrast, the decreased impact of reduced acid and non-acid atmospheric depositions and the appearance of alien species, especially in the benthic systems, are connected to the anthropic activities. In marine and transitional ecosystems, plankton seem to respond to the climatic variation with changes in phenology and variations in production, which is, however, also linked to anthropogenic impact such as external nutrient supply. Benthic systems show a more marked response, likely due to a tight interplay of climatic variation and anthropogenic pressure, such as the introduction and establishment of alien species mainly linked to commercial use. Terrestrial and aquatic systems, especially the marine ones, respond differently to climate change and anthropogenic activity even if both systems show responses to the temperature increasing. However, it is still difficult to completely disentangle anthropogenic from natural factors that tightly interplay and affect ecosystem components and dynamics.