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We assessed the naturalness of rivers based on the riparian vegetation index throughout the national territory of South Korea as a preparatory process for restoration to improve the ecological quality of rivers. The riparian vegetation index was obtained by incorporating the diversity of species and community, vegetation profile, and ratios of the number of species and areas occupied by exotic, obligate upland, and annual plants. The evaluation was conducted based on both the riparian vegetation index and each vegetation component. The result of the evaluation based on the riparian vegetation index showed that more than 70% of the river reaches were graded as less than “moderate” and exotic and obligate upland plants were more common than endemic aquatic plants. The reaches recorded as “very good” and “good” grades were usually restricted around the upstream of the north and central-eastern parts, whereas reaches of the other areas showed “poor” naturalness (less than “moderate”). The vegetation components selected for the evaluation showed a significant correlation with each other as well as the riparian vegetation index. The degree of contribution of each vegetation component showed that the vegetation profile played the most significant role, followed by species diversity, community diversity, and the ratio of area occupied by annual plants. The riparian vegetation index revealed a significant correlation with the indices based on other taxa such as benthic invertebrates, periphytic algae, and fish, habitat conditions in the waterway, and water quality based on biochemical oxygen demand (BOD). The diagnostic evaluation results imply that most reaches need ecological restoration. The reference information was prepared by incorporating the vegetation condition with the highest score in each reach in the diagnostic evaluation. The river reach was divided into five reaches of upper and lower valley streams, upstream, midstream, and downstream. Information on the reference vegetation for restoration was prepared with the stand profile including both horizontal and vertical arrangements of riparian vegetation and species composition classified by the reach divided into five types. The levels of restoration were determined based on the diagnostic evaluation results. The lower the naturalness grade, the higher the level of restorative treatment was recommended.

Seoul's Cheonggye Stream Reconstruction Project removed the concrete road surface that had covered the stream basin for decades to allow sunlight to the stream, reconstructed the stream's channel, restored the surface flow of water by pumping water from the river's downstream to its upstream area, and reintroduced riparian vegetation. Although the project did not fulfill the conditions of ecological restoration, there were a few ecological effects that this project brought. The reconstructed Cheonggye stream has enhanced species diversity and decreased the percentage of exotic species compared to an unrestored urban stream. Also, the species composition of the reintroduced riparian vegetation of the Cheonggye stream has since grown to more closely resemble the natural reference streams, whereas dissimilar to the degraded urban reference site. The re-established vegetation has attracted numerous animal species, and thereby increasing the size and diversity of the biota from 17 species before reconstruction to approximately 400 species. Consequently, the naturalness of the reconstructed Cheonggye stream, as indicated by morphological and ecological characteristics, has improved markedly. In addition, the reconstruction project also improved the water quality, as reflected by the biochemical oxygen demand (BOD). But the restoration of the Cheonggye stream is still underway and several requirements still need to be met to fully actualize true restoration. First, the river zone should be extended and linked to the surrounding terrestrial ecosystems to create an ecological network based on ecological information from the reference area. Second, more diverse microhabitats should be created within the waterway to support greater biodiversity. Flooding during the rainy season produces various microhabitats and human assistance can aid this natural occurrence. Finally, species composition and its spatial arrangement were focused on landscaping during the reconstruction; this approach should be changed to reflect the principles of ecological restoration.

We evaluated the restoration effect by introducing willows as a means of controlling invasions of giant ragweed (Ambrosia trifida L.) on a riparian site. Our preliminary survey demonstrated that a problematic exotic species, giant ragweed and the representative riparian species, Salix koreensis are in competitive exclusive relationship. We planted willows at 1 m intervals on the bank of the Dongmun stream at Munsan, Paju, in Central Western Korea as an experimental restoration practice. We installed two 50 m ⅹ 5 m sized restored and non-restored for this experimental study. The non-restored plots were located on river banks, which were covered with concrete blocks and left in itself without any treatment. The height of willow was measured after each of three consecutive growing seasons and compared with the height of the giant ragweed. Although the height of Salix gracilistyla did not achieve the height of the giant ragweed, the height of S. koreensis surpassed that of giant ragweed in the third year after introduction. The results were also reflected in the relative light intensity on the herb layer of willow stand, and thereby the relative light intensities of stands, which were dominated by S. koreensis or restored by introducing S. koreensis, 1.99 ± 0.33 (%, mean ± SD) and 1.92 ± 0.50 (%, mean ± SD), respectively were lower than those in the stands treated by S. gracilistyla, 3.01 ± 0.43 (%, mean ± SD). The giant ragweed stands receive full sunlight as there are no any vegetation layers higher than the herb layer formed by the giant ragweed. As the result of Detrended Correspondence analysis ordination based on naturally established vegetation, the stands dominated by willows and giant ragweed showed different species composition between both stands. The species composition of the restoratively treated sites resembled the reference sites more than the non-treated sites. The species diversity (H’) of the sites restored by introducing S. koreensis and S. gracilistyla was higher than the non-restored site dominated by A. trifida . On the basis of our results, the restoration of riparian vegetation equipped with integrated features could contribute not only to the control of exotic plants including giant ragweed but also to ensure the diversity and stability of riverine ecosystems.

Lammas growth, a rare phenomenon for Korean red pine (Pinus densiflora), occurred in 2006. Lammas shoots showed higher frequency and longer length in Seoul`s hotter urban center than in urban boundary or suburban forest sites. Frequency and length showed a close correlation with urbanization density and vegetation cover expressed in NDVI. Air temperature in the late summer of 2006 was more than higher than an average year. Of the predominant environmental signals that modulate bud flush, only temperature changed significantly during the year. Differences in temperature between the urban centers, urban boundaries and suburban forests correlated with varying land-use density. The rise in temperature likely spurred lammas growth of the Korean red pine. Symptoms of climate change are being detected throughout the world, and its consequences will be clearer in the future. Considerate interest in the responses of ecological systems to the variable changes is required to prepare for unforeseeable crises. Monitoring of diverse ecological phenomena at Long Term Ecological Research sites could offer harbingers of change.