• Weed & Turfgrass Science
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• v.2 no.4
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• pp.341-347
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• 2013

The survey of weed occurrence was conducted to identify problematic weed species on the paddy field. Total 524 sites of the 17 regions in Chungnam Province in Korea were investigated from June to August, 2013. In the whole region, 23 weed species were identified including 19 annuals and 4 perennials. The most dominant weed species in Chungnam paddy fields were Echinochloa crus-galli (25.3%), followed by Monochoria vaginalis (11.9%), Eleocharis kuroguwai (10.3%), Bidens tripartite (9.3%) and Aneilema japonicum (8.5%). The 95.2% of the investigation sites was determined under dominance value 1 (range of cover <10: numerous individuals) by Braun-Branquet indicating proper weed control in the paddy fields. This information could be useful for estimation of future weed occurrence, weed population dynamics and establishment of weed control methods in Chungnam Province in Korea.

• Weed & Turfgrass Science
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• v.2 no.4
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• pp.413-420
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• 2013

The climate change affects the growth and development of weeds as well as the outbreak of weeds. Especially, the occurrences of problematic paddy weeds due to climate change might cause the difficulties in weed control. This study therefore, investigated the current dominance and distribution of paddy weeds. As a result of the study on paddy weeds in northern Gyeonggi-do, there were total of 65 taxonomy groups including 23 family, 41 genus, 57 species, 7 subspecies and 1 variety. Among all the plants, 46 species were annual plants and 16 were perennial plants. Echinochloa crus-galli was the highest in importance analysis and the followings were in order of Ludwigia prostrate and Lemna paucicostata. The similarity of different paddy weeds in different regions observed through TWINSPAN analysis was distinguished by Fimbristylis miliacea, Rotala indica and Cyperus flaccidus. Regional differences shown in CCA analysis using weed species and soil environment revealed that Gimpo-si and Namyangju-si has difference soil and weeds, which are features that distinguished them from other regions. In northern Gyeonggi-do the result of paddy weed research showed the interregional difference not in dominant weeds but in distribution species.

• Journal of Environmental Science International
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• v.25 no.1
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• pp.57-65
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• 2016

This study's purpose was to provide basic data for the monitoring of ecological changes caused by change of vegetation structure of Abies koreana forest in a study site susceptible to climatic change in Yeongsil area of Hallasan Mountain, Jeju Island. Surveys revealed this: in Yeongsil area of Hallasan Mountain, per 1 ha of A. koreana forests, total number 1,781, and A. koreana number 989, accounting for 55.5% of the total number of trees. 190 A. koreana or 19.2% were found to be dead. For the number of individual trees by DBH, trees standing 5 cm - 10 cm tall formed the largest portion at 39.9%, and in the case of other trees except A. koreana, the number of individual trees below 5 cm accounted for 23.5% of the total number of trees. The survey of importance by height revealed this: at the top level, the importance of A. koreana was the highest at 106.23, but the sum of importance of temperate deciduous broad-leaved trees (Prunus maximowiczii, Quercus mongolica, and Taxus cuspidata) was higher at 142.84 than that of A. koreana. The analysis of species diversity revealed 0.645 species diversity for the tree layer and 0.817 for the shrub layer; for evenness, 0.549 for the tree layer and 0.664 for the shrub layer; for dominance value; 0.451 for the tree layer and 0.336 for the shrub layer. The analysis of tree vitality revealed that for the A. koreana forests in Yeongsil, the composition ratio of A. koreana by type is AS type>AL type>DS type>DB type, and that of the other trees is AL type>AS type>AF type>AB type. Compared with the forests in other areas, the A. koreana forests in the Yeongsil area have a very high occurrence rate of dead trees, and a high importance of trees is shown in the deciduous broad-leaved tree forests. Compared with the A. koreana forests in the Jindallaebat area, with the same level above sea, the vegetation structures are fast changing. Also, due to dryness and other non-physical environmental changes caused by a lack of rainwater and dry winds in winter, dead trees are fast increasing in number. Environmental changes such as climate change diversely affect the maintenance of A. koreana in individual areas, and if environmental changes are fast and continue long, of the A. koreana forest areas in the Hallasan Mountain, the A. koreana forests in the Yeongsil area will decrease fastest in number and will experience changes in the vegetation structure. Thus, it is necessary to survey the vegetation changes in A. koreana forests, which are distributed in all directions but are centered on Hallasan Mountain, and to thus conduct long-term monitoring and research.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.1
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• pp.70-78
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• 1991

Both long period of summer drought and unusual high water temperature in 1988 caused the harmfull effect to the aquacultural organisms in south coast of Korea. One of those was the mass mortality of arkshell seedlings in Jinhae Bay. The purpose of this study was to verify the effects of environmental factors on arkshell seedlings by investigating not only water quality and food organisms in culturing grounds, but also meteorological conditions. Water temperature in November was higher at $2.0^{\circ}C$ than mean water temperature and the concentration of total inorganic nitrogen and N/P ratio were $0.38{\mu}g-at/l,$ 0.98, respectively which indicated the exhaustion of nutrients, especially nitrogen in the study area. In analysis of phytoplankton population structure, species diversity index(H) , equitability-index(e), species richness $index(d_1)$ were low, but dominance $index({\delta}_2)$ was high at the value of 98.4 and dominant species was Nitzschia pungens. In conclusion, it seems that mass .mortality of arkshell seedlings in November was resulted from the metabolism disorder with poor food organism under the unstable marine environment.

• Journal of Environmental Impact Assessment
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• v.20 no.2
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• pp.187-198
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• 2011

The objective of this study is to analyze the flora and forest vegetation of trails with high visitor density at Molundae. Nine quadrats of $20{\times}20m$ were selected for the survey. The survey was conducted from April to October 2010. The obtained results are summarized as follows. Plot1, plot2, plot3, plot4, plot6, and plot7 were located at slopes of $5{\sim}20^{\circ}$, 17~40m above sea level, and were formed with the colony of Japanese black pine(Pinus thunbergii Parl) and Japanese black pine(Pinus thunbergii Parl)-white oak(Quercus aliena Blume). Tree layer had the height of 8~20m, and the coverage of 50~70%, while subtree layer had the height of 3-8m, and the coverage 30~80%. On the other hand, shrub layer had the height of 2~4m, and the coverage of 10~30%, and herb had the height of 0.2~1m and coverage 5~20%. Plot5, plot8, and plot9 were located at the summit areas of 57~78m above sea level, and $0^{\circ}$ slope. Japanese black pine(Pinus thunbergii Parl) formed a community there. Tree layer was 8~20m high, and covered 60~70%, of the area, and subtree layer was 6~8m high, and coverage 30~40%. Shrub layer had the height of 2~6m, and the coverage of 30%, while herb layer had the height 0.2~2m, and the coverage 20-80%. Succession does not occur in the surveyed areas which have high visitor density. Artificially planted sawtooth oak(Quercus acutissima) trees were found to disturb succession and formation of multi-layer vegetation, resulting in the ecologically unstable forest. Therefore, the researcher suggested the strategy of managing the vegetation in the conclusion. This study has the limit in that the plots selected for the survey reflected only part of various trails in the Molundae area. It is necessary to suggest the vegetation management plans by selecting more diverse trail areas in consideration of the visitor density and behaviors, and analyzing the changes in vegetation quantitatively in order to manage the vegetation in urban areas damaged by visitors more effectively.

• Journal of Digital Contents Society
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• v.17 no.5
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• pp.307-316
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• 2016

A user usually gets the same suggesting results as everyone else in most of the multimedia social services, nowadays. To address the challenging problem of personalization in the social network, we propose a method which exploits user's activities, user's moods, and user's friend relationships from the social network to build a decision-making system. Depending on a current state of the user's mood, this system infers the most appropriated video for the user. In the system, the user evaluates a set of the given recommendation methods which extract from the user's database social network and assigns a vague value to each method by a weight. Then, we find the fuzzy collection solution for the system and classify the set of methods into subsets, and order the subsets based on its local dominance to choose the best appropriate method. Finally, we conduct an experiment using the YouTube API with a lot of video types. The experiment result shows that the channel recommendation system appropriately affords the user's character, it is more satisfying than the current YouTube based on an evaluation of several users.

• Korean Journal of Plant Taxonomy
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• v.42 no.2
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• pp.116-125
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• 2012

The distribution, vegetation characteristics and an assessment of the conservation status of the Korea endemic species Coreanomecon hylomeconoides Nakai were investigated to collect biological basic data to formulate a conservation strategy. According to the distribution map of C. hylomeconoides based on the literature, specimen information, and local field surveys, natural populations of C. hylomeconoides are intensively distributed in the Southern regions of the peninsula, around Gyeongsangnam-do and Jeollanan-do. C. hylomeconoides was distributed in the middle and low slope adjacent to a valley. The altitude ranged from 227 m to 744 m, with inclinations of $5-10^{\circ}$. As a result of a vegetation survey within natural populations, a total of 238 taxa were identified from 29 quadrates in 8 natural populations. The importance value of C. hylomeconoides is 25.34% based on the coverage and frequency of the herbaceous layer with in the populations. The species diversity of the occurrence of the species in 8 natural populations was 1.52, while the averages of species evenness and the dominance values were calculated to be 0.83 and 0.17, respectively. As a result of assessing the conservation status through IUCN Red List criteria, C. hylomeconoides was evaluated as Near Threatened (NT). Conservation strategies are also discussed for the sustainable conservation of C. hylomeconoides.

• Korean Journal of Environment and Ecology
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• v.32 no.1
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• pp.66-76
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• 2018

This study surveyed the species and population of dragonflies in 20 study sites in the Junam wetland in May and July 2015 to investigate the relationship between the dragonflies and the inhabited environment. We measured the environmental factors such as the area of emergent plants, the area of floating and floating-leaved plants, the area of water surface, the area of water plants, and the nearby land-use type and analyzed the relationship to the dragonfly species, population, and diversity index. We found 757 dragonflies belonging to 21 species of 6 families. The area of floating and floating-leaved plants and the area of water surface affected the species diversity. The area of floating and floating-leaved plants and the area of surface water, in particular, showed the positive correlation with the species richness and the dominance value, respectively. The area of water surface showed the negative correlations with Shannon's diversity index and evenness. Among the type of surrounding land-uses, the dry fields and orchards showed significantly lower average species richness than wetlands. Among the species, Cercion calamorum and Crocothemis servilia were positively correlated with floating and floating-leaved plants. Cercion v-nigrum and Epophthalmia elegans were positively correlated with the area of water surface, and Ischnura asiatica and Ceriagrion nipponicum were negatively correlated. The recent uncontrolled proliferation of lotus colony in the Junam wetland is likely to affect greatly the species composition of dragonflies which have a close relationship with plant species.

• Korean Journal of Environment and Ecology
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• v.28 no.6
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• pp.725-740
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• 2014

To figure out the vegetation situation in the ridge of the Naknam-Jeongmaek, six intensive survey sites were selected considering environmental factors and human interferences, 132 quadrats (area $100m^2$) were installed to survey appearing species of trees and major environmental factors, and the characteristics of vegetation structures were analyzed. The surveyed plots were divided into six groups according to the analysis of classification by TWINSPAN; Quercus mongolica-Q. variabilis community, Pinus densiflora-Q. dentata community, Chamaecyparis obtusa community, Q. mongolica-P. densiflora community, P. densiflora-P. thunbergii community, P. koraiensis community, Rhododendron spp.-Lespedeza cyrtobotrya community. P. densiflora-Q. dentata community, Q. mongolica-P. densiflora community, and P. densiflora-P. thunbergii community are expected to be succeeded by deciduous oaks because the power of deciduous oaks is strong in their lower layer. C. obtusa community, P. densiflora community, and Rhododendron spp.-L.cyrtobotrya community are artificial forests that were artificially formed and are expected to be maintained in the current state for some time because the dominance value of planted species of trees is high. Most vegetations in Naknam-Jeongmaek were secondary forests or artificial forests formed for forest tree production and forestation for erosion control. In particular the top regions and hilly sections of the mountain were mostly dominated by deciduous oaks such as Q. mongolica, Q. variabilis showed some P. densiflora community competing with deciduous oaks. On the other hand, low sections and regions adjacent to the city showed severe artificial interference since exotic species such as P. thunbergiil, C. obtusa, P. koraiensis, and Rhododendron spp. were planted.

• Korean Journal of Plant Taxonomy
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• v.40 no.3
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• pp.135-144
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• 2010

This study intended to investigate environmental factors including soil and vegetation in order to understand the environmental and ecological characteristics of four different habitats of Abelia tyaihyoni. These habitats, according to investigations, are mostly located at elevations of 203 m to 297 m with angles of inclination ranging from 9 degrees to 17 degrees. The litter depth of habitats is 2 cm to 5 cm. A total of 113 vascular plant taxa are identified in seven quadrates of the four habitats. The life form of 113 species is H-$D_4$-$R_5$-e type. The importance value of Abelia tyaihyoni is 39.61%, and 4 highly ranked species such as Quercus dentata (6.27%), Spiraea blumei, Spiraea prunifolia for. simpliciflora (4.04%) and Ulmus davidiana var. japonica (3.84%) are considered to be an affinity with Abelia tyaihyoni in their habitats. The dominant species of woody plants in the four habitats are represented as Pinus densiflora (21.22%) and Quercus dentata (16.82%) in the subtree layer (T2), and Carex humilis var. nana (18.95%) and Carex lanceolata (17.63%) in the herbaceous layer (H). The degree of their average species diversity is 1.42, and that of dominance and evenness are 0.07 and 0.86, respectively. The type of soil is sandy loam, clay loam and loam, and the average field capacity of soil is 22.49%. Their average organic matter is 9.39%, soil pH 6.75, and available phosphorus is $1.23 {\mu}g/g$.