Palaeobiodiversity of wetlands among buried protected biotopes and glacial relicts: preliminary palynological findings and time-based indicator species from the Teor-Campomolle palaeochannel sedge peatland (NE Italy)

The current global change is marked by an unprecedented loss of biodiversity, a major threat to ecosystems and human life. Past flora and its changes over time are increasingly vital to guide conservation efforts focused on plant biodiversity (1). Palynology is a powerful tool for studying past plant biodiversity: fossil pollen analysis can detect biodiversity shifts across centuries and millennia, along with floristic changes in relation to climate and human activity, in turn enabling to forecast future trends and thus the development of more solid ecosystem management strategies. Wetlands are among the most ecologically important areas on Earth, as initially recognized by the 1971 Convention on Wetlands. They host an incredible intersection of biodiversity, exclusive to these habitats. A long-term analysis of wetland flora is therefore essential to conservation efforts directed at them: the case study of the Teor-Campomolle meandering palaeochannel of the Tagliamento River in the distal sector of the Friuli Plain (province of Udine), which once was a sedge peatland, is exemplary in this sense. Pollen samples from a 6.5 m-long sediment core taken from the paleochannel, spanning the last 5000 years, were analysed. More than 190 pollen taxa were found throughout the series, highlighting a remarkable plant diversity, among which Cyperaceae are ubiquitous and by far the most abundant, marking this family as extremely important in this context. Three key species in this family appeared consistently and abundantly throughout the record, revealing a valuable buried biotope sealed by clay and silt deposits accumulated during the last approximately 2000 years. Traces of the EU-protected habitat type “Calcareous fens with Cladium mariscus and species of the Caricion davallianae” – now absent in the drilling area but documented elsewhere in the region – were present in the form of pollen of Cladium mariscus (L.) Pohl., the habitat’s flagship species, and of other taxa typical of the Caricion davallianae alliance, such as Carex, Eriophorum, Juncus, Lythrum salicaria L., and Schoenus. Pollen belonging to Rhynchospora alba (L.) Vahl. and R. fusca (L.) Vahl., glacial relict species present in the region and reportedly featured in the Caricion davallianae alliance in regional records (2), was also found, documenting the ancient local presence and long-term persistence of these important species. Additionally, statistical techniques, such as indicator species analysis (3), were applied to depth-based sample clusters (via CONISS), and allowed precise identification of species linked to specific single timeframes or groups of timeframes, and thus able to function as indicators of the pollen-based reconstruction of the past plant community in each of its main phases. 1) A.M. Mercuri, A. Florenzano, E. Clò, L. Braga, J. Zappa, M. Cremaschi, A. Zerboni (2025) Sci Rep, 15, 12587 2) G. Bertani, F. Martini (1992) Gortania – Atti Museo Friul. Storia Nat., 13 (’91), 123-136 3) M. De Cáceres, P. Legendre (2009) Ecology, 90, 3566-3574