Introduction

The area of Lithuania is 65,200 km2. The relief of the country is flat or slightly hilly. Lowlands cover more than 70% of the territory. Lithuania is located in the moderate climate zone. The climate is humid and comparatively cold. A rather high diversity of ecosystems is characteristic of the country. Forests cover about 29% of the territory. A characteristic feature of Lithuanian forests is high diversity of tree species in stands. Mixed stands occupy 56% of forests. According to composition of tree species, pine (37.6%), spruce (24%) and birch (19.5%) stands prevail in Lithuanian forests. Bogs and mires of all types cover about 5% of the territory of Lithuania. Some parts of large mire complexes are almost pristine, never used for agriculture or intensive forestry – the kind of nature that has already been destroyed for many years in Western Europe. There are about 3,200 lakes in Lithuania. They cover about 1.5% of the whole territory. Only 14 lakes are larger than 1,000 ha. Among 758 rivers (longer than 10 km) and numerous streams there are many unregulated or moderately modified rivers with naturally flooded land. The total length of unregulated rivers and streams – 17,000 km. Coastal wetlands (near-shore marine waters, the Curonian Lagoon and the Nemunas River delta area) are distinguished by particularly mosaic habitats. Preservation of such areas of extraordinary richness of flora and fauna is particularly important.

Lithuanian core nature areas play an important role in the regulation of hydrological regime and are the key elements for maintaining the biological diversity.

During the last five decades, intensification of industrial and agricultural activities, and a rapid expansion of urban zones have resulted in rapid ecosystem changes. The global climate change is also a major factor affecting Lithuanian ecosystems during the last decades.

Protected areas now cover more than 12% of the territory of Lithuania. The network of protected areas consists of one Biosphere Strict Nature Reserve, three State Strict Nature Reserves, five National Parks, 30 Regional Parks, 254 State Nature Reserves, 410 Objects of Nature Heritage (including 159 Monuments of Nature) and about 273 Municipality Reserves. The Natura 2000 network in Lithuania is under development.

Ecological research in Lithuania has a long tradition. Detailed ecological investigations of certain ecosystems in Lithuania were performed since the end of the 19th – early 20th century. Several multidisciplinary studies have been performed since the 1950s. These large-scale research programs resulted in a series of monographs and publications on the geology, geography, hydrology, meteorology, botany and zoology of certain core nature areas of Lithuania.

Large-scale multidisciplinary investigations were performed as part of the EU 5th Framework, European Science Foundation, Global Environmental Facility, PHARE, NATO, HELCOM and other international programs by several research institutes and universities during the last decades.

It was important to develop a nation-wide network to integrate the results of separate ecological investigations implemented by various research institutes and universities. The network of sites with long-term ecological research (LTER) in Lithuania was initiated and organized by the Institute of Ecology of Vilnius University in 2004, with the support of the US State Department and International Long Term Ecological Research (ILTER) group.

Four sites were designated for LTER program in Lithuania:

• Lithuanian coastal area (including inshore marine waters, the Curonian Lagoon, the Curonian Spit and the Nemunas River delta),

• Cepkeliai State Strict Nature Reserve and the Katra River,

• Kamanos State Strict Nature Reserve,

• Lake Druksiai with adjacent wetlands.

These sites are representative examples of ecosystems characteristic of different regions of Lithuania and have proper scientific background from earlier and ongoing multidisciplinary research.

They are internationally important nature areas, included in the list of UNESCO World Cultural and Natural Heritage (the Kursiu Nerija (Curonian Spit) National Park) and in the list of Wetlands of International Importance (Cepkeliai and Kamanos State Strict Nature Reserves, and the Nemunas River Delta Regional Park).

Site-based long-term multidisciplinary ecological research has central role in the network. The key research topics are the following:

• The role of biological diversity in ecosystem functions;

• Effects of the global change on structure and dynamics of ecosystems;

• Long-term changes of ecological communities;

• Invasive species and their role in ecosystems;

• Ecology of rare species of flora and fauna;

• Biological effects of environmental pollution of ecosystems;

• Geo-ecological state of ecosystems;

• Long-term (since Late Glacial and Holocene) development of LTER sites.

Scientists from the Institute of Ecology of Vilnius University, Institute of Botany and Institute of Geology and Geography, Vilnius University, Klaipeda University, in collaboration with other organizations, implement the scientific program of the network.

Institute of Ecology of Vilnius University (Akademijos 2, LT-08412 Vilnius-21, Lithuania) coordinates the LTER network in Lithuania.