Yi S.,Korea Institute of Geoscience and Mineral Resources |
Kim S.-J.,Korea Polar Research Institute KOPRI
Geosciences Journal | Year: 2010
Age-controlled pollen record from wetland sediments of Hanam, western central Korean Peninsula (KP), reveals vegetation dynamics response to climate changes during the last glacial, 26.1-20.1 cal kyr BP. The Hanam pollen assemblages are dominated by conifers, Picea and Pinus and cold tolerant deciduous broadleaved Betula, together with common xerophytic herb like Artemisia and Gramineae. Principal taxa are similar to those of subalpine forest in modern vegetation of KP. Humidity variation reconstructed by semi aridity index (AI) indicates that, during 26.1-22.7 cal kyr BP, cold and dry conditions were prevailed with an expansion of subalpine coniferous forest and high value of AI. From 22.5 to 20.5 cal kyr BP, cool and wet conditions were reconstructed with low value of AI due to climatic amelioration, enhanced conifers and temperate deciduous broadleaved mixed forests flourished. Between 20.3 and 20.1 cal kyr BP, an abundance of Picea and Betula associated with high value of AI infers that subalpine conifers forest colonized again in hinterland montane along with open, low grassland under colder and drier conditions owing to climatic deterioration. The principal pollen taxa suggest that prevailing climate conditions were annual mean temperature about 5-6 °C colder and annual mean precipitation 40% drier than today. © 2010 The Association of Korean Geoscience Societies.
Changes in CO2, 13C abundance, inorganic nitrogen, β-glucosidase, and oxidative enzyme activities of soil during the decomposition of switchgrass root carbon as affected by inorganic nitrogen additions
Jung J.Y.,Korea Polar Research Institute KOPRI |
Lal R.,Ohio State University |
Ussiri D.A.N.,Ohio State University
Biology and Fertility of Soils | Year: 2011
This study was conducted to investigate the effect of inorganic nitrogen (N) and root carbon (C) addition on decomposition of organic matter (OM). Soil was incubated for 200 days with nine treatments (three levels of N (no addition (N0) = 0, low N (NL) = 0. 021, high N (NH) = 0. 083 mg N g-1 soil) × three levels of C (no addition (C0) = 0, low C (CL) = 5, high C (CH) = 10 mg root g-1 soil)). The carbon dioxide (CO2) efflux rates, inorganic N concentration, pH, and potential activities of β-glucosidase and oxidative enzyme were measured during incubation. At the beginning and the end of incubation, the native soil organic carbon (SOC) and root-derived SOC were quantified by using a natural labeling technique based on the differences in δ13C between C3 and C4 plants. Overall, the interaction between C and N was not significant. The decomposition of OM in the NH treatment decreased. This could be attributed to the formation of recalcitrant OM by N because the potentially mineralizable C pool was significantly lower in the NH treatment (3. 1 mg C g-1) than in the N0 treatment (3. 6 mg C g-1). In root C addition treatments, the CO2 efflux rate was generally in order of CH > CL > C0 over the incubation period. Despite no differences in the total SOC concentration among C treatments, the native SOC in the CH treatment (18. 29 mg C g-1) was significantly lower than that in the C0 treatment (19. 16 mg C g-1). © 2011 Springer-Verlag.
Kim I.,Seoul National University |
Kim I.,Korea Polar Research Institute KOPRI |
Kim G.,Seoul National University
Marine Chemistry | Year: 2015
The concentrations of both the total dissolved (<0.45μm) and colloidal (10kDa-0.45μm) phases of trace elements and rare earth elements (REEs) in coastal groundwater were measured to evaluate the role of colloids in transporting trace elements and REEs to the ocean through submarine groundwater discharge (SGD). Samples were collected from two different hydrogeological conditions, Hampyeong Bay in the southwestern coast of Korea and Jeju Island, Korea. The average colloidal proportions of Al, Mn, Zn, Ni, Cu, Cd, Pb, 210Po, and 210Pb were 35-45% of the total dissolved phase, which were relatively higher than those of Cr, Fe, Co, and REEs (10-30%), although hydrogeological conditions were variable. Most of the colloidal trace elements (including 210Pb and REEs), except Mn, correlate most significantly with Fe, indicating that their presence is dependent on Fe-containing oxide minerals in the subterranean estuary (STE). On the other hand, the colloidal Mn and 210Po correlated more significantly with dissolved organic carbon (DOC), indicating that dissolved organic matter (DOM) cycling associated with bacterial activity plays an important role in their presence in the colloidal phase in the STE. Our results suggest that the fluxes of trace elements through SGD are greatly dependent on the presence of Fe (for Al, Zn, Ni, Cu, Cd, Pb, and REEs) and DOM (for 210Po and Mn) in coastal groundwater. © 2015 Elsevier B.V.
Kim M.-K.,Sun Moon University |
Park H.,Korea Polar Research Institute KOPRI |
Oh T.-J.,Sun Moon University
Polish Journal of Microbiology | Year: 2014
Although many scientists have been studying lichens, the bacterial communities among lichens have not been fully explored. In this study, the biological activities of bacterial isolates from Arctic lichen Ochrolechia sp. were screened. Cell cultures were extracted using ethyl acetate, and these cultures were tested for antibacterial and antioxidant activities. To evaluate the antibacterial activities, we carried out a disk diffusion test and minimum inhibitory concentration assay. The inhibition zone diameter (mm) was 8 to 12, and its MIC value ranged from 222.0 to > 1000 ìg/ml (control antibiotic ampicillin ranged from 0.31 to 0.58 ìg/ml). PAMC26625 (Sphingomonas sp., sequence similarity: 99.108%) showed a high amount of total phenolic and total flavonoid contents within 5 extracts and also exhibited 77.23% and 80.02% in the 1,1-diphenyl-2-picryl-hydrazyl assay and the 2,2'-azino-bis(3-ethyl benzothiazoline-6-sulphonic acid) assay, respectively. In the ferric reducing antioxidant power assay, it was determined that PAMC26625 contained a higher amount of ferrous ion [8.72 mM Fe(II)/mg extract] than control ascorbic acid [6.21 mM Fe(II)/mg extract]. Our data indicated that they had potential to be novel sources of antibacterials and antioxidants.
Chung T.W.,Sejong University |
Yoshimoto K.,Yokohama City University |
Yun S.,Korea Polar Research Institute KOPRI
Bulletin of the Seismological Society of America | Year: 2010
For the separation of intrinsic (Q i -1) and scattering attenuation Q (s -1) in South Korea, coda observations represented by the multiple-lapse time windows method were numerically simulated using the direct simulation Monte Carlo method. The simulation showed that the depth-dependent velocity model separated by crust and mantle fit better than the uniform velocity model. Under a uniform attenuation assumption, the Q i -1 and total Q t -1 in South Korea represent the lowest values among current global measurements. These low attenuation values can be explained by the inactive seismicity of South Korea corresponding to those of the seismically stable area such as a shield.