The soil ecosystem and its interaction with C fluxes on the isle of Pianosa

The atmospheric CO2 concentration can be considered as an instigator of climate changes, and at the same time the natural rates of C fluxes are strongly influenced by climatic conditions. The evaluation of the C balance is an important stage in the study of ecosystem vulnerability. The Isle of Pianosa, in the Tuscan Archipelago National Park (Italy), is especially suited to this kind of investigation, because of its particular flat topography and the absence of anthropic activity and C emissions (it was once a prison settlement and was abandoned four years ago). These conditions allow the evaluation of total gas exchanges of the whole island's ecosystem, which consists of a complex mosaic of natural Mediterranean and previously managed areas. An integrated study by several Italian research groups is in progress to assess: i) the C stored in soil, litter and vegetation, ii) how the soil ecosystem constituents affect storage and fluxes of C, and iii) the biospheric-atmospheric CO2 fluxes, in order to determine the C balance of the island. These measurements will then be used to validate models that simulate environmental and climatic effects on biospheric gas exchange processes. The work of our research team is concentrated on the study of the Pianosa soil ecosystem by assessing the chemical, physical and biological properties of the soil. Soils of Pianosa, which are substantially homogeneous with regard to the parent material and to their pedological evolution, have a different agronomic history and the effects of agricultural activities on the soil and vegetation are still easily recognisable. Preliminary physical and chemical results showed evidence of the impact of human activity on soil fertility. Modifications in soil structure were observed and a considerable reduction in soil C and N amounts was recorded both in the previously ex-cultivated areas and in the previously pastured land. Nevertheless, biochemical results showed a good biochemical recovery of the soil previously subjected to agriculture. This demonstrates the good resilience of the Pianosa soil ecosystem, with the relative implications on C storage and fluxes.