Currently, the Bulgarian LTER network is built from 9 sites and their associated infrastructures. The sites cover the main biogeographic regions and some of the main ecosystem types in the country: Forest – 4 (“Belasitsa” – forests dominated by common chestnut, “Petrohan-Ponor” and “Plana” – mainly beech and mixed forests and “Yundola” – coniferous forests ); Marine Macrosite – 1 (Black Sea); Coastal Zone -1 (Sozopol Bay); Surface standing water – 1 (Srebarna Lake) and water currents – 1 (Mesta River). The Bulgarian Antarctic Base “St. Kliment Ohridski”, located on Livingston Island, falls outside national borders but is managed entirely by bulgarian research personnel. This site is of particular strategic and political importance and its scientific agenda strongly supports research on climate change and its impact on ecosystems.
Depending on the research approach applied, their infrastructure, data and users, the sites have different status and classification within the LTER-Europe network (https://deims.org/network/bulgaria-lter-bulgaria). To date, apart from standard and extensive, there are two potential sites in Bulgaria: “Plana” – near a large urban area and Mount Belasitsa, promising as a platform for socio-environmental research (LTSER), which is developing towards a higher category. There is also a newly proposed forest site – “Parangalitsa”, which is being prepared for admission to the National Network and LTER-Europe.