• Journal of Ecology and Environment
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• 제44권4호
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• pp.241-255
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• 2020

Background: The stem exclusion stage is a stage of forest development that is important for understanding the subsequent understory reinitiation stage and maturation stage during which horizontal heterogeneity is formed. Over the past 11 years (2009-2019), we observed a deciduous broad-leaved forest in the Albongbunji Basin in Ulleungdo, South Korea in its stem exclusion stage, where Fagus engleriana (Engler's beech) is the dominant species, thereby analyzing the changes in the structure (density and size distributions), function (biomass and species richness), and demographics. Results: The mean stem density data presented a bell-shaped curve with initially increasing, peaking, and subsequently decreasing trends in stem density over time, and the mean biomass data showed a sigmoidal pattern indicating that the rate of biomass accumulation slowed over time. Changes in the density and biomass of Fagus engleriana showed a similar trend to the changes in density and biomass at the community level, which is indicative of the strong influence of this species on the changing patterns of forest structure and function. Around 2015, a shift between recruitment and mortality rates was observed. Deterministic processes were the predominant cause of tree mortality in our study; however, soil deposition that began in 2017 in some of the quadrats resulted in an increase in the contribution of stochastic processes (15% in 2019) to tree mortality. The development of horizontal heterogeneity was observed in forest gaps. Conclusions: Our observations showed a dramatic shift between the recruitment and mortality rates in the stem exclusion stage, and that disturbance increases the uncertainty in forest development increases. The minor changes in species composition are likely linked to regional species pool and the limited role of the life-history strategy of species such as shade tolerance and habitat affinity. Our midterm records of ecological succession exhibited detailed demographic dynamics and contributed to the improvement of an ecological perspective in the stem exclusion stage.

• 한국환경농학회지
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• 제30권3호
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• pp.234-242
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• 2011

BACKGROUND: Cultivation of winter cover crops is strongly recommended to increase land utilization efficiency, animal feeding material self-production, and to improve soil and environmental quality. METHODS AND RESULTS: Four major winter crops (barley, Chinese milk vetch, hairy vetch, and rye) having different C/N ratio were seeded in silt loam paddy soil in the November 2007 and the aboveground biomass was harvested on the late May 2008 to evaluate its effectiveness as green manure, and root biomass distribution was characterized at the different depth (0-60 cm) to study its effect on physical properties and carbon sequestration in soil. During this experiment, the naturally growing weed in the rice paddy soil in Korea, short awn foxtail (Alopecurus aequalis Sobol), was considered as control treatment. Above-ground biomass of all cover crops selected was significantly higher than that of the control treatment (2.8 Mg/ha). Comparatively higher above-ground biomass productivity of rye and barley (15.8 and 13.5 Mg/ha, respectively) suggested that these cover crops possibly had the highest potential as a green manure and animal feeding material. Root biomass production of different cover crops followed the same trend as that for their above ground biomass. Rye (Secale cereal) might have the highest potential for soil C accumulation (7893 C kg/ha) by root biomass development, and then followed by barley (6985 C kg/ha), hairy vetch (6467 C kg/ha), Chinese milk vetch (6671 C kg/ha), and control (5791 C kg/ha). CONCLUSION(s): Cover crops like rye and barley having high biomass productivity might be the most effective winter cover crops to increase organic carbon distribution in different soil aggregates which might be beneficial to improve soil structure, aeration etc. and C sequestration.

• 한국환경생태학회지
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• 제30권6호
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• pp.1022-1031
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• 2016

본 연구는 강원도 점봉산에 분포하고 있는 신갈나무군락에서 군락의 지상부 생물량과 생물종 다양성, 그리고 군락 구조의 다양성 간의 관계 특성을 밝히기 위하여 수행되었다. 이를 위해, 2004년부터 2013년까지 점봉산 신갈나무군락에서 측정한 지상부 생물량은 총 $311.1ton{\cdot}ha^{-1}$였으며, 종 별 생물량 및 구성 비율은 신갈나무 $206.3ton{\cdot}ha^{-1}$(66.3%),까치박달 $36.9ton{\cdot}ha^{-1}$(11.9%),피나무 $30.6ton{\cdot}ha^{-1}$(9.8%)등의 순으로 적었다. 신갈나무의 지상부 생물량이 가장 많은 것은 전체에 비해 임목 밀도가 많지 않지만, 평균 흉고직경(DBH)이 50cm 이상인 개체수 비율이 다른 수종에서 보다 월등히 높기 때문인 것으로 판단된다. 이 군락의 종 다양성 지수(H')와 종 균등도(J')를 추정해 본 결과 각각 2.015~2.166과 0.673~0.736의 범위 내에서 시간에 따른 점진적인 증가를 보여 주고 있다. 위의 종 다양성 지수와 종 균등도는 지상부 생물량과 높은 양의 상관관계를 나타내는데, 이는 시간이 변함에 따라 신갈나무군락의 지상부 생물량이 공간적으로 균일해진다는 것과 이러한 현상이 다양한 수종에 걸쳐 나타나고 있다는 것을 의미한다. 또한, 생물량-종 다양성 지수(BS)와 종 풍부도-생물량-종 다양성 지수(ABS)도 각각 3.746~3.811, 4.781~5.028 범위 내에서 시간에 따른 점진적인 증가를 보여주고 있었으며, 이들 지수와 지상부 생물량 높은 양의 상관관계가 관찰되었다. 이는 신갈나무군락의 지상부 생물량이 다양한 수종에서 뿐만 아니라 다양한 직경급에 따라 균일해 지고 있음을 나타낸다. 그리고 점봉산 신갈나무군락은 군락의 구조적 다양성을 통하여 생산성과 탄소 저장 능력이 더욱 효율화 되어, 자원이 풍부한 생태계로서의 역할을 수행 할 것으로 예상된다. 또한 복원된 산림의 생물다양성과 생산성의 유지를 위하여 생태적 특성을 고려한 다양한 수종과 다양한 DBH 수목의 선택적 식재를 제안한다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.247-250
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• 2008

Biomass gasification is a promising technology for producing a fuel gas which is useful for power generation systems. In biomass gasification processes, tar formation often causes some problems such as pipeline plugging. Thus, proper tar treatment is necessary. So far, nickel (Ni)-based catalysts have been intensively studied for the catalytic tar removal. However, the deactivation of Ni-based catalysts takes place because of coke deposition and sintering of Ni metal particles. To overcome these problems, we have been using ruthenium (Ru)-based catalyst for tar removal. It is reported by Okada et al., that a Ru/$Al_2O_3$ catalyst is very effective for preventing the carbon deposition during the steam reforming of hydrocarbons. Also, this catalyst is more active than the Ni-based catalyst at a low steam to carbon ratio (S/C). Benzene was used for the tar model compound because it is the main constituent of biomass tar and also because it represents a stable aromatic structure apparent in tar formed in biomass gasification processes. The steam reforming process transforms hydrocarbons into gaseous mixtures constituted of carbon dioxide ($CO_2$), carbon monoxide (CO), methane ($CH_4$) and hydrogen ($H_2$).

• 한국농림기상학회지
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• 제5권2호
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• pp.101-109
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• 2003

The study area, Kwangneung Experiment Forest (KEF) is located on the west-central portion of Korean peninsula and belongs to a cool-temperate broadleaved forest Bone. At the old-growth deciduous forest near Soribong-peak (533.1 m) in KEF, we have established a 1 ha permanent plot ($100m{\times}100m$) and a flux tower, and the site was registered as a KLTER(Korean long-term ecological research network) and DK site of KoFlux. In this site, we made a stemmap of trees and analyzed forest stand structure and physical and chemical soil characteristics, and estimated carbon budgets by forest components (tree biomass, soils, litter and so on). Dominant tree species were Quercus serrata and Carpinus laxiflora, and accompanied by Q. aliena, Carpinus cordata, and so on. As a result of a field survey of the plot, density of the trees larger than 2 cm in DBH was 1,473 trees per ha, total biomass 261.2 tons/ha, and basal area $28.0m^2$/ha. Parent rock type is granite gneiss. Soil type is brown forest soil (alfisols in USDA system), and the depth is from 38 to 66 cm. Soil texture is loam or sandy loam, and its pH was f개m 4.2 to 5.0 in the surface layer, and from 4.8 to 5.2 in the subsurface layer. Seasonal changes in LAI were measured by hemispherical photography at the 1.2 m height, and the maximum was 3.65. And the spatial distributions of volumetric soil moisture contents and LAIs of the plot were measured. The carbon pool in living tree biomass including below ground biomass was 136 tons C/ha, and 5.6 tons C/ha is stored in the litter layer, and about 92.0 tons C/ha in the soil to the 30 cm in depth. Totally more than about 233.6 tons C/ha was stored in DK site. These ground survey and monitoring data will give some important parameters and validation data for the forest dynamics models or biogeochemical dynamics models to predict or interpolate spatially the changes in forest ecosystem structure and function.

• Ocean and Polar Research
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• 제33권spc3호
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• pp.337-347
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• 2011

We investigated latitudinal changes in mesozooplankton community structure during a cruise between October 16 and November 30 of 2007 from four distinctive regions in the northwestern Pacific Ocean: Warm pool area (longitude $135^{\circ}$ line), Philippine EEZ (PEEZ), Japan EEZ (JEEZ), and East China Sea (ECS). Major taxa of numerical importance were Clausocalanidae (Clausocalanus spp.), Oncaeidae (Oncaea spp.), and Oithonidae (Oithona spp.) in oligotrophic regions, however Paracalanidae (Paracalanus spp.) was the most abundant group in the ECS. Mesozooplankton size group of <1 mm dominated in PEEZ and WP (48% and 56%, respectively), but mesozooplankton (>1 mm) were of importance in the JEEZ and ECS (34% and 38%, respectively). Mesozooplankton biomass and abundance were high in the JEEZ and ECS, and low in the oligotrophic WP and PEEZ waters, with positive relationship with both total Chl-a and heterotrophic protist biomass. Latitudinal change in mesozooplankton community structure was related with water temperature, with copepods such as Lucicutia spp. and Pleuromamma spp. being present only in warm waters. The geographical expansion of mesozooplankton with a preference for warmer waters could potentially be useful as an indicator for detecting ocean warming.

• 자연과학논문집
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• 제11권1호
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• pp.75-84
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• 1999

1995년 5월부터 1996년 6월까지 한강 하류지역을 대상으로 Ponar grab과 basket sampler 등을 이용하여 저서동물상을 조사하였다.그 결과 총 3문 7강 8목 12과 14종이 서식하고 있는 것으로 나타났다. 이중 환형동물은 3종, 연체동물은 4종, 절지동물은 7종으로 나타났다. 환형동물은 전 조사정점에서 출현하였으며 참갯지렁이(Neanthe japonica)가 우점종으로 나타났다. 현존량은 정점 4를 기점으로 상류와 하류로 갈수록 감소하는 양상을 보였고, 시기별로는 1995년 5월부터 감소하기 시작하여 1995년 10월에 급격히 감소하였다가 1996년부터 약간 증가하는 양상을 보였으나 대체적으로 생물상이 불안정한 상태를 보였다.

• Ocean Science Journal
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• 제41권2호
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• pp.121-124
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• 2006

Argo drifters provide information of the vertical structure in the water column and have a potential for the improvement of understanding phytoplankton primary production and biogeochemical cycles in combination with ocean color satellite data, which can obtain the horizontal distribution of phytoplankton biomass in the surface layer. Our examples show that using Argo drifters with satellite-measured horizontal distribution of phytoplankton biomass at the sea surface allow an improved understanding of the development of the spring bloom. The other possible uses of Argo drifter are discussed.

• 생태와환경
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• 제56권1호
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• pp.83-93
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• 2023

This study compares the abundance and community structure of zooplankton organisms from pelagic regions, and considers particularly the trophic levels vs. zooplankton abundances and biomass. Zooplankton samples were collected three times from May to November 2022, at 30 temperate lakes and reservoirs, which belong to four different river basins. The total zooplankton abundance, biomass and species index were showed considerable spatial variation. The spatial pattern of rotifer abundance was similar to that of total zooplankton abundance, while there were not showed similar patterns of zooplankton biomass (㎍ L^-1) in lentic ecosystems. The rotifer strongly dominated the zooplankton assemblage in smaller lentic system than that of larger. A total of 130 species of zooplankton were identified (83 rotifers, 34 cladocerans and 13 copepods). The total average of zooplankton abundance and biomass were 213.7±342.3 Ind. L^-1 (n=129) and 1382.8±1850.4 ㎍ L^-1, respectively. Total and average of zooplankton abundance were usually dominated by the rotifers (>56.9%), while those of zooplankton biomass were dominated by the cladocerans and copepods (>73.6%) in lentic ecosystems. Considering the Trophic State Index (TSI), the factors of zooplankton abundance and biomass were included in between meso- and eutrophic states(27 lakes, 90% of all). The mean abundance and biomass of zooplankton in eutrophic systems were higher than that of meso- and hypertrophic systems. From this result, we suggest that management strategy for the lentic ecosystem water environment has to be focused more on small-sized lakes and reservoirs, in terms of zooplankton assemblages.

• 한국환경과학회지
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• 제26권3호
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• pp.325-334
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• 2017

To understand the changes in physical parameters and phytoplankton size structure caused by tides, a fixed station in the Youngsan River estuary was monitored at 2-h intervals, on April 28, 2012 and August 12, 2012. No clear relationship was observed between the temperature and salinity changes and tidal levels in April. However, in August, temperature decreased during the ebb tide and increased during the flood tide, while salinity showed the opposite trend. In addition, there was no specific change in the phytoplankton biomass corresponding to tidal levels in April. In August, the total chlorophyll a and the biomass of net phytoplankton (>$20{\mu}m$) increased almost 20 times during the ebb tide and decreased during the flood tide. The biomass of nanophytoplankton (<$20{\mu}m$) showed a similar variation in response to tidal level changes. In April, the relationship between percent contributions of phytoplankton size structure and tidal levels was not clear. In August, the net phytoplankton was dominant in the early stage and nanophytoplankton was dominant in the later stage, while contribution of nanophytoplankton and net phytoplankton increased at high tide and low tide, respectively. Therefore, in April, other factors such as freshwater discharge were more important than the tide, whereas in August, when no freshwater discharge was recorded, the changes in semidiurnal tides influenced the physical parameters and phytoplankton dynamics. These results could contribute to the understanding of phytoplankton dynamics in the Youngsan River estuary.