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Vegetation in the urban area showed not only a difference in species composition but also lower diversity compared with that of the natural area. Successional trend was normal in natural area, but that in urban areas showed a retrogressive pattern. Korean mountain ash (Sorbus alnifolia (Siebold & Zucc.) K.Koch), a shade intolerant species, dominated such a retrogressive succession. The vegetation decline is due to changes of mesoclimate and soil properties that imbalanced distribution of green space induced as the result of urbanization. In recent years, new environmental stress due to climate change is imposed additively to this forest decline. Drought is the very environmental stress. Drought-induced plant damage started from withering of leaves of plants introduced for landscaping in the urban area. Over time, branches died and death of the whole plant body followed. In particular, damage of Korean mountain ash, the product of retrogressive succession, was remarkable. As retrogressive succession has already progressed much, thus such phenomenon could be recognized as crisis of urban forest.

Background The creation of the National Institute of Ecology began as a national alternative project to preserve mudflats instead of constructing the industrial complexes by reclamation, and achieve regional development. On the other hand, at the national level, the research institute for ecology was needed to cope with the worsening conditions for maintaining biodiversity due to accelerated climate change such as global warming and increased demand for development. In order to meet these needs, the National Institute of Ecology has the following objectives: (1) carries out studies for ecosystem change due to climate change and biodiversity conservation, (2) performs ecological education to the public through exhibition of various ecosystem models, and (3) promotes regional development through the ecological industry. Furthermore, to achieve these objectives, the National Institute of Ecology thoroughly followed the basic principles of ecology, especially restoration ecology, in the process of its construction. We introduce the principles and cases of ecological restoration applied in the process. Results We minimized the impact on the ecosystem in order to harmonize with the surrounding environment in all the processes of construction. We pursued passive restoration following the principle of ecological restoration as a process of assisting the recovery of an ecosystem degraded for all the space except in land where artificial facilities were introduced. Reference information was applied thoroughly in the process of active restoration to create biome around the world, Korean peninsula forests, and wetland ecosystems. In order to realize true restoration, we pursued the ecological restoration in a landscape level as the follows. We moved the local road 6 and high-voltage power lines to underground to ensure ecological connectivity within the National Institute of Ecology campus. To enhance ecological diversity, we introduced perch poles and islands as well as floating leaved, emerged, wetland, and riparian plants in wetlands and mantle communities around the forests of the Korean Peninsula in the terrestrial ecosystem. Furthermore, in order to make the public aware of the importance of the intact nature, the low-lying landscape elements, which have disappeared due to excessive land use in most areas of Korea, was created by imitating demilitarized zone (DMZ) landscape that has these landscape elements. Conclusions The National Institute of Ecology was created in an eco-friendly way by thoroughly reflecting the principles of ecology to suit its status and thus the impact on the existing ecosystem was minimized. This concept was also designed to be reflected in the process of operation. The results have become real, and a result of analysis on carbon budget analysis is approaching the carbon neutrality.

This study was carried out to assess the carbon budget of local governments in South Korea. The carbon budget was obtained from the difference between net ecosystem productivity (NEP) that the natural ecosystem displays, and carbon dioxide emissions calculated from energy consumption in each local government. NEP was obtained from the difference between net primary productivity, measured by an allometric method, and soil respiration, measured with EGM-4 in natural forests and artificial plantations. Heterotrophic respiration was adjusted to 55% level of the total soil respiration based on existing research results. A field survey to obtain information for components of the carbon cycle was conducted in Cheongju (central Korea) and Yeosu (southern Korea). Pinus densiflora, Quercus acutissima, and Quercus mongolica (central Korea) and P. densiflora and Q. acutissima (southern Korea) forests were selected as the natural forests. Pinus rigida and Larix kaempferi (central Korea) and P. rigida (southern Korea) plantations were selected as the artificial plantations. Vegetation types were classified by analyzing LandSat images by applying a GIS program. CO2 emissions were the highest in Pohang, Gwangyang, and Yeosu, where the iron and the petrochemical industrial complexes are located. CO2 emissions per unit area were the highest in Seoul, followed by Pohang and Gwangyang. CO2 absorption was the highest in the Gangwon province, where the forest area ratio to the total area is the highest, and the lowest in the metropolitan areas such as Seoul, Incheon, Daegu, Daejeon, and Gwangju. The number of local governments in which the amount of absorption is more than the emission amount was highest in Gangwon-do, where 10 local governments showed a negative carbon budget. Eight, seven, five, five, three, and three local governments in Gyeongsangbuk-do, Jeollanam-do, Gyeongsangnam-do, Jeollabuk-do, Gyeonggi-do, and Chungcheongbuk-do, respectively, showed a negative carbon budget where the amount of carbon absorption was greater than the emission amount. The carbon budget showed a very close correlation with carbon emission, and the carbon emission showed a significant correlation with population size. Moreover, the amount of carbon absorption showed a negative correlation with population size, population density, and non-forest area, and a positive correlation with the total area of the forest, coniferous forest area, and broad-leaved forest area. Considering the reality that carbon emissions exceed their absorption, measures to secure absorption sources should be considered as important as measures to reduce carbon emissions to achieve carbon neutrality in the future. As a measure to secure absorption sources, it is proposed to improve the quality of existing absorption sources, secure new absorption sources such as riparian forests, and efficiently arrange absorption sources.

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