Kang-Hyun Cho

Nutrient leaching from leaf litter of emergent macrophyte (Zizania latifolia) and the effects of water temperature on the leaching process

To quantify nutrient loading from emergent macrophytes through leaching in the littoral zones of Paldang Reservoir, we conducted incubation experiments using leaf litter of the emergent macrophyte, Zizania latifolia. To separate the leaching process from microbial decay, we used HgCl2 to suppress microbial activity during the experiment. We measured electric conductivity, absorbance at 280 nm, total nitrogen and dissolved inorganic nitrogen, total phosphorus and soluble reactive phosphorus, Na, K, Mg and Ca amounts in leaf litter and in water. In addition, we examined the effects of water temperature and ion concentrations of ambient water on the leaching process. A total of 6% of the initial ash‐ free dry mass of leaf litter was lost due to leaching during incubation (four days). Electric conductivity and A280 continued to increase and saturate during the incubation. To compare reaching rates of different nutrients, we fitted leaching dynamics with a hyperbolic saturation function [Y=A•X/(B+X)]. From these fittings, we found that ratios of leaching amounts to nutrient concentration in the litter were in the order of K>Na>Mg>P>Ca>N. Leaching from leaf litter of Z. latifolia was dependent on water temperature while it was not related with ion concentrations in the ambient water. Our results suggest that the leaching process of nutrients, especially phosphorus, from aquatic macrophytes provides considerable contribution to the eutrophication of the Paldang Reservoir ecosystem.

The Plant Community of Nanjido, a Representative Nonsanitary Landfill in South Korea: Implications for Restoration Alternatives

Vegetation and soil analyses of the slopes of the Nanjido, a nonsanitary landfill in South Korea, were conducted to investigate the colonization status of plant communities, and to suggest restoration alternatives by comparing the vegetation of the landfill and the nearby forests. The vegetation of the Nanjido landfill and the control sites was surveyed by using 10 ×: 10 m quadrats. The soils were analyzed for pH, electrical conductivity, organic matter content, Total-N, P, K, Ca, Mg, sand, silt, and clay. Canonical correspondence analysis (CCA) was performed by using the extent of cover for all the recorded species, and the physical and chemical variables of soil. Salix babylonica, Platanus orientalis, Rosa multiflora, Prunus persica,Albizzia julibrissin, Indigofera pseudo-tinctoria, Robinia pseudoacacia, Amorpha fruticosa, Ailanthus altissima, Forsythia koreana, and Paulownia tomentosa were the commonly found tree species.Quercus mongolica, considered to be the natural late successional species of temperate South Korea, was recorded at the Nanjido landfill. Levels of pH, the electrical conductivity and concentrations of P, Ca, and Mg in landfill soils were significantly higher than the forest control site soils (P < 0.05). In CCA ordination space, landfill quadrats clustered in less acidic soils, rich in Ca and Mg, while forest control site quadrats clustered in acidic, low P soils. This study found several indications that it is possible for a nonsanitary landfill to support succession to typical and natural forests. In addition, the landfill slope vegetation could function as a biological source for the restoration of the other landfill areas that remain barren, if planned efforts are made for conservation and rehabilitation.

Ecosystem responses to climate change in a large on-river reservoir, Lake Paldang, Korea

The impact of climate change on a large river reservoir ecosystem was investigated. Long-term meteorological data showed that recent climate change, including warmer winters, increased precipitation intensity and extended dry periods, may have influenced the basin of Lake Paldang, the most downstream reservoir of a series of on-river reservoirs. Extreme hydrologic events and climate warming, acting independently and in combination, appear to be related to changes in the Lake Paldang ecosystem. A significant increase in chlorophyll a concentrations in early spring corresponded to the timing of ice break-up. An increase in winter temperatures, which resulted in a shorter time period of ice-cover and earlier ice break-up, appears to have stimulated phytoplankton growth in winter and early spring. Repeated intensive and extended influxes of turbid water, associated with more frequent extreme rainfall events, have increased concentration of suspended solids and may have influenced the biotic community structure of Lake Paldang. In the mid-2000s, the area vegetated by submerged hydrophytes, the abundance and biomass of the phylum Mollusca, as well as the abundance of fish from the subfamily Acheilognathinae, which spawn in the body of bivalve molluscs, was all smaller than in the late 1980s and early 1990s. Together, these results suggest that climate change may have contributed directly and indirectly to changes in each trophic level of the Lake Paldang ecosystem.

Responses of riparian vegetation to flooding disturbance in a sand stream

This study compared vegetation map, transect, vegetation structure, and plant morphology before and after flooding in the Strea m Cheongmi, a sand stream, in order to investigate responses of riparian vegetation against flooding disturbance. Landform around channel was remarkably changed due to flooding disturbance in the sand stream. Erosion and deposition particularly provided new habitats to some riparian plants such asPhragmites japonica andRorippa islandica. As flow discharge increased due to flooding,Persicaria thunbergii community also increased in low landform adjacent to stream water.Miscanthus sacchariflorus with strong stem survived flooding disturbance.Humulus japonicus invaded abovePhragmites japonica community fallen by flooding disturbance. Major riparian vegetations in the Stream Cheongmi were quickly restored and sustained after flooding disturbance, giving little changes in community structure. Among annual and biennial plants,Persicaria nodosa adapted to flooding by forming aerenchyma in its stem internode, andRorippa islandica finished its life cycle before flooding.Phragmites japonica, Artemisia selengensis, andPhalaris arundinacea among perennial plants were restored by resprouting new shoots from stem node or rhizome of fallen or buried shoots by flooding disturbance.Miscanthus sacchariflorus resisted against flooding standing rather than being fallen. In conclusion, riparian vegetations in the Stream Cheongmi sustained their particular structures by getting adapted to repeated annual flooding disturbance.

Assessment of Gene Flow from Genetically Modified Anthracnose-Resistant Chili Pepper (Capsicum annuum L.) to a Conventional Crop

We conducted a 2-year field assessment of the gene flow from genetically modified (GM) chili pepper (Capsicum annuum L.), containing the PepEST (pepper esterase) gene, to a non-GM control line “WT512” and two commercial hybrid cultivars, “Manidda” and “Cheongpung Myeongwol (CM).” After seeds were collected from the pollen-recipient non-GM plants, hybrids between them and the GM peppers were screened by a hygromycin assay. PCR with the targeting hpt gene was performed to confirm the presence of transgenes in hygromycin-resistant seedlings. Out of 7,071 “WT512” seeds and 6,854 “Manidda” seeds collected in 2006, eight and 12 hybrids, respectively, were detected. In 2007, 33 hybrids from 3,456 “WT512” seeds and 50 hybrids from 3,457 “CM” seeds were found. The highest frequency of gene flow, 6.19%, was observed in that 2007 trial. These results suggest that a limited isolation distance would be sufficient to prevent gene flow from GM to conventionally bred chili peppers.

Recruitment and Succession of Riparian Vegetation in Alluvial River Regulated by Upstream Dams - Focused on the Nakdong River Downstream Andong and Imha Dams -

Changes of geomorphology in alluvial river and vegetation recruitment on its floodplain downstream from dams are investigated both qualitatively and quantitatively focusing on the downstream of Andong dam and Imha dam on the Nakdong River. Results of the analyses of river morphology and bed material in the study site show a general trend of riverbed degradation with a max scour of 3 m and bed material coarsening from pre-dam value of 1.5 mm in D50 to post-dam value of 2.5 mm. Decrease in bed shear stress due to the decrease in flood discharge have caused vegetation recruitment on the once-naked sandbars. As result, the ratio of area of vegetated bars over total area of bars has drastically changed from only 7% in 1971 before the Andong dam (constructed in 1976) to 25% after it, and increased to 43% only three year after the Imha dam (constructed in 1992) and eventually to 74% by 2005. Analysis of the vegetation succession at Wicjeol subreach, one of the three subreaches selected in this study for detailed investigation, has clearly shown a succession of vegetation on once-naked sand bars to a pioneering stage, reed and grass stage, willow shrub and eventually to willow tree stages. At the second subreach selected, two large point bars in front of Hahoe Village seem to have maintained their sand surfaces without a signifiant vegetation recruitment until 2005. The sand bars, however, seem to have been invaded by vegetation recently, which warns river managers to have a countermeasure to protect the sand bars from vegetation invasion in order to conserve them for the historical village of Hahoe. On the other hand, recruitment and establishment of vegetation on the sand bars by artificial disturbance of the river, such as damming, can create an unique habitat of backmarsh in the sandy river, as shown in the case of Gudam Wetland, and may increase the biodiversity as compared with relatively monotonous sand bars. Last, the premise in this study that decrease in flood discharge due to upstream dams and decrease in bed shear stress can induce vegetation recruitment on the naked sand bars in the river has been verified with the analyses of the distribution of dimensionless bed shear stress along the selected cross section in each subreach.

High Genetic Differentiation in Endangered Sedum ussuriense and Implications for Its Conservation in Korea

Sedum ussuriense Kom. (Crassulaceae) is a succulent perennial herb localized to rocky valleys in southeastern Korea. Although it is an important natural resource with high economic value as an ornamental plant, it is currently endangered because of land-use changes and illegal exploitation. To initiate a proper conservation plan, we selected four populations (Juwang, Okgye, Jeolgol, and Haok) around Mt. Juwang, characterized their phenotypic traits, and evaluated patterns of random amplified polymorphic DNA variation. Despite its small population size, Okgye had the greatest proportion of flowering plants and higher seed production than from the other populations. This population also harbored the greatest genetic diversity. However, recent fragmentation between Okgye and Haok appeared to cause genetic divergence, leading to close genetic relationships of Okgye to Juwang vs. Haok to Jeolgol. In the long term, this raises concerns about the loss of genetic variation and the possibility of a demographic crash in those fragmented populations. Because our results indicated a high degree of divergence among populations, we suggest that conservation activities should focus on maintaining and propagating all populations throughout this species’ range.

Analysis of Environmental Factors of Geomorphology, Hydrology, Water Quality and Shoreline Soil in Reservoirs of Korea.

In order to understand shoreline environment characteristics of Korean reservoirs, the interrelationships between environmental factors of geomorphology, hydrology, water quality and shoreline soil were analyzed, and the reservoir types were classified according to their environmental characteristics in the 35 reservoirs selected by considering the purpose of dam operations and annual water-level fluctuations. Geomorphological and hydrological characteristics of reservoirs were correlated with the altitude and the size scale of reservoirs. The annual range of water level fluctuation showed a wide variation from 1 m to 27 m in the various reservoirs in Korea. The levels of eutrophication of most reservoirs were mesotrophic or eutrophic. From the result of the soil texture analysis, sand contents were high in reservoir shorelines. Range, frequency and duration of water-level fluctuation were distinctive from the primary function of reservoirs. Flood control reservoirs had a wide range with low frequency and waterpower generation reservoirs had a narrow range with high frequency in the water-level fluctuation. According to the result of CART (classification and regression tree) analysis, the water quality of reservoirs was classified by water depth, range of water-level fluctuation and altitude. The result of PCA (principal component analysis) showed that the type of reservoirs was classified by reservoir size, water-level fluctuation, water quality, soil texture and soil organic matter. In conclusion, reservoir size, the water-level fluctuation, water quality and soil characteristics might be major factors in the environment of reservoir shorelines in Korea.

Genetic Diversity and Differentiation in Remnant Populations of Bupleurum latissimum Nakai, an Endangered Endemic Plant Species to Ulleung Island, Korea

Bupleurum latissimum is a narrowly endemic and endangered plant, restricted to only two small populations on steep cliffs of a small island, Ulleung Island, inKorea. The genetic diversity and population differentiation in the two remnant populations of the species were investigated using RAPD (random amplified polymorphic DNA) analysis. The Neis gene diversities were 0.146 in the smaller population of 45 individuals, and 0.151 in the larger population of 61 individuals. The geneticvariation was not significantly different between these two populations. Genetic diversity within populations was not low considering the very small size of populations. Analysis of molecular variance (AMOVA) revealed higher variation with in populations (65.9%) than genetic differentiation between them (34.1%). B. latissimum revealed higher population differentiation than other outbreeding species. The differentiation of the populations corresponded to low gene flow (Nem = 0.482). The cluster and principal coordination analyses provide strong support for high population differentiation, showing that all individuals of the two populations have built up population‐specific clusters. Although gene flow between the two populations ofß. latissimum was limited, they have preserved relatively high levels of genetic variation.

Difference in Shoreline Flora According to the Usage of Reservoirs in Korea

Differences in characteristics of flora and environmental factors of geomorphology, hydrology, water quality and soil were investigated in the shoreline of total 35 reservoirs according to their usages of waterpower generation, agricultural water supply, residential and industrial water supply and flood control in Korea. The number of plant species, floral structure and characteristics of species traits in the shoreline of reservoirs were different according to their usage. From the results of stepwise regression analysis, the total number of vascular plant species was increased at the environment of the higher flood frequency at the median water level and the longer exposure duration of the shoreline. The results of principal coordinates analysis and cluster analysis showed that the shoreline flora was classified as the 3 types of 1) flood control and residential and industrial water supply, 2) agricultural water supply and 3) waterpower generation reservoirs. The water level fluctuation, flood frequency at the median water level, lake water quality index and exposure duration of the shoreline were selected as important environmental factors affected on the characteristics of shoreline flora. The species richness of total flora and hydrophytes, especially submerged macrophytes, were much higher in the reservoirs for the purpose of the waterpower generation in which mesotrophic water quality and stable water levels were maintained. Annual or biennial ruderals were established on the ephemeral drawdown zone of flood control, residential and industrial water supply reservoirs which have oligotrophic or mesotrophic water quality and wide range of water level fluctuation. The floating hydrophytes were differentially dominated in the littoral zones of the agricultural water supply reservoirs with a mesotrophic or eutrophic water quality and a medium water level fluctuation. In conclusion environmental factors related to water level fluctuation and water quality were different and then the floral characteristics of shoreline were distinguishable according to usage of Korean reservoirs.