• Title/Summary/Keyword: Value diversity

Search Result 1,181, Processing Time 0.037 seconds

Distribution of Benthic Macrofauna in subtidal area and on sand flat of Sindu-ri coast, Korea (신두리 해안의 조하대와 모래 갯벌에 서식하는 대형저서동물의 분포)

  • Koo, Bon Joo;Shin, Sang Ho;Woo, Han Jun
    • Journal of Wetlands Research
    • /
    • v.7 no.2
    • /
    • pp.69-88
    • /
    • 2005
  • Distribution of benthic macrofauna was surveyed in the subtidal area and on the sand flat of Sindu-ri coast during July 2002. A total of 134 species, 3,511 individuals and 388g biomass of macrobenthos were sampled inclusively from the study sites. 109 species with a mean density of $1,298ind./m^2$ and biomass of $69.4g/m^2$ were collected from 10 stations established in the subtidal area. Polychaetes were represented as a dominant faunal group of the subtidal area in both species richness and density with values of 54 species and $813ind./m^2$. Cluster analysis based on the faunal composition showed that the subtidal area could be divided into four stational groups according to sedimentary characteristics: Cirrophorus armatus - Lumbrineris longifolia association on the mud sediment with pebbles near aqua-farms; Aonides oxycephala association on the rocky bed; Scoloplos armiger - Grandifoxus cuspis association on the sand-dominated sediment along the lowest low water; a association with higher evenness on the sand-dominated sediment in the depth. Although having characteristics of high value in species richness, density and species diversity, the macrobenthic association around the farming area was dominated by the opportunistic species such as Lumbrineris longifolia and Tharyx sp. Natural community represented by S. armiger and G. cuspis was developed in most sand-dominated areas. 50 species were sampled with a mean density of $2,443ind./m^2$ and biomass of $381.3g/m^2$ from eight+ stations along two transects on Sindu-ri sand flat. Mollusks were represented as a dominant faunal group of the sand flat in species richness, density and biomass with values of 20 species, $1,345ind./m^2$ and $350.4g/m^2$, respectively. Umbonium thomasi, Veneridae sp., Mandibulophoxus mai, Armandia lanceolata, Eohaustorius spinigerus, Urothoe convexa were dominant species and these species accounted for over 83% of total individuals. There were three distinct zones of macrobenthos on Sindu-ri sand flat according to the extent of exposure time. The upper zone was dominated by Scopimera globosa, the middle zone was characterized by M. mai, and the lower zone was dominated by E. spinigerus. Sindu-ri coastal area was considered as a healthy habitat for macrobenthos, except for around the farming area. It was considered that Sindu-ri coastal area including the sand flat connected to the sand dune of natural monument was a valuable habitat as a protected site in having no pollution source and no artificial structure.

  • PDF

Characteristics of Indigenous Rhizobium to Korean Soils -II. Symbiotic and Serological Characteristics of Bradyrhizobium japonicum Naturalized in Yeongnam Soils (우리나라 토착근류균(土着根瘤菌)의 제(諸) 특성(特性) 연구 -II. 영남지역(嶺南地域) 토착(土着) Bradyrhizobium japonicum의 공생(共生) 및 혈청학적(血淸學的) 특성(特性))

  • Kang, Ui-Gum;Jung, Yeun-Tae;Somasegaran, Padma;Hoben, H.;Bohlool, B. Ben
    • Korean Journal of Soil Science and Fertilizer
    • /
    • v.24 no.1
    • /
    • pp.61-68
    • /
    • 1991
  • Thirty Bradyrhizobium japonicum isolates (10 strains per each soil) from 1 uncultivated [Sangnam(Soil 1), Milyang]- and 2 cultivated [Dong(Soil 2)and Chinbuk(Soil 3), Changweon] upland soils in Yeongnam area were evaluated on their symbiotic effectiveness to soybean [Glycin max (L.)] cv. Korean Jangbaekkong and American Clark and examined on their serological diversity. The results obtained were summarized as follows : 1. On symbiotic effectiveness of B. japonicum with plant genotypes, isolates showed a relatively high value of nodule mass in Jangbaekkong cv. and of shoot dry weight and total nitrogen in Clark cv. demonstrating the order of Soil 1> Soil 2> Soil 3 isolates. 2. Among 30 B. japonicum isolates, YCK 141 showed the best effectiveness on mean nitrogen fixation of two cultivars. 3. Thirty indigenous B. japonicum showed 6 types of serological diversities in the immunoblot analysis which were present in various proportions at Soil 2(5) and Soil 3(5) except Soil 1 where all isolates fell into the YCK 117 serogroup. And their distribution order was serotype YCK 117( 12 strains) > USDA 1l0(5strains), USDA 123(5 strains) > YCK 150(4 strains) > YCK 141(3 strains) > YCK 226(1 strain). 4. Especially, 10 isolates from Soil 1, an uncultivated orchard, showed a very homologous pattern in not only effectiveness but serological distribution. It seemed to indicate that the isolates were typically affected by numerous physical and environmental factors of the soil.

  • PDF

Geographic Variations and DNA Polymorphisms in Gizzard-shad (Konosirus punctatus) (전어 (Konosirus punctatus)의 지리적 변이와 DNA 다형성)

  • Park, Su-Young;Kim, Jong-Yeon;Yoon, Jong-Man
    • Korean Journal of Ichthyology
    • /
    • v.18 no.4
    • /
    • pp.300-310
    • /
    • 2006
  • Genomic DNA isolated from three geographical gizzard-shad (Konosirus punctatus) populations in Seocheon (SC), Busan (BS) and Gochang (GC) collected in the West Sea and the southern sea, respectively, off the Korean Peninsula, were PCR-amplified repeatedly. Eight selected decamer and 20-mer primers generated a total of 713 loci in the SC population, 791 in the BS population, and 732 in the GC population, with a DNA fragment size ranging from 100 bp to 2,800 bp. We identified 50 unique loci for the SC population, 70 unique loci for the BS population and 130 for the GC population: 120 shared loci for the three populations. There were 108 specific loci (15.1%) for the SC population, 74 (9.4%) for the BS population, and 67 (9.2%) for the GC population. Eight primers also generated 48 polymorphic loci (6.7%) for the SC population, 26 (3.3%) for the BS population, and 16 (2.2%) for the GC population. The similarity matrix ranged from 0.756 to 0.936 for the SC population, from 0.800 to 0.938 for the BS population, and from 0.731 to 0.959 for the GC population. The dendrogram obtained by the eight primers indicates three genetic clusters: cluster 1 (SEOCHEON 01~SEOCHEON 10), cluster 2 (BUSAN 11~BUSAN 20 and GOCHANG 23~GOCHANG 24), and cluster 3 (GOCHANG 21, 22, 25, 26, 27, 28, 29 and 30). As stated above, some individuals of the GC population appear to belong in BS population. When seeing this result, it was thought with the fact that some individuals of 2 populations seem to come and go partially. Thus, RAPD-PCR analysis revealed a significant genetic distance between the three geographical gizzard-shad populations. Using various decamer and 20-mer primers, RAPD-PCR may be applied to identify specific/polymorphic markers that are particular to a species and geographic population, and to define genetic diversity, polymorphisms, and similarities among geographical gizzard-shad populations.

The Perception of Aseptic Foods in Cancer Patients (멸균식 개발에 대한 암환자의 인식조사)

  • Lee, Kyung-A;Son, Eun-Joo;Song, Beom-Seok;Kim, Jae-Hun;Lee, Ju-Woon;Lyu, Eun-Soon
    • Journal of the Korean Society of Food Science and Nutrition
    • /
    • v.42 no.2
    • /
    • pp.203-211
    • /
    • 2013
  • The purpose of this study was to investigate the perception of aseptic foods (sterilized foods with radiation technology) in cancer patients in Busan. The subjects were 192 cancer patients at a hospital. This study was performed through interviews using questionnaires. Patients had perception scores on the need to develop aseptic foods (4.30 points out of 5.00), use aspetic foods (4.06/5.00), and intake aseptic foods (4.04/5.00). Patients less than 59 years old had significantly higher perception scores than those over 60 years old (p<0.05). The scores on aseptic food indicated the importance of various factors, including sanitation (4.86/5.00), good materials (4.82/5.00), nutritional value (4.79/5.00), unused of monosodium glutamate (MSG) (4.66/5.00), taste (4.61/5.00), and reasonable prices (4.60/5.00). The patients who were college graduates showed significantly higher scores and importance in good materials, proper packaging unit, simple cooking methods, food diversity, and familiar foods (p<0.05). In the aseptic menu items, patients wanted to include seasoned raw vegetables (4.11/5.00), a set menu (including cooked grain, soup, and a side dish) (4.08/5.00), seasoned cooked vegetables (4.04/5.00), low sodium kimchi (3.98/5.00), and fermented sauces (3.92/5.00). The patients with gastrointestinal cancer and other cancers (e.g. breast, thyroid, and renal cancer) had significantly higher necessity scores than lung patients for stew, seasoned raw vegetables, salad, low sodium kimchi, and a set menu (p<0.05).

A Study on the Tendencies and Characteristics When Constructing Landscape Architectural Archives in the US (미국 조경 아카이브 구축 동향과 특성 연구)

  • Lee, Myeong-Jun;Kim, Jung-Hwa;Seo, Young-Ai
    • Journal of the Korean Institute of Landscape Architecture
    • /
    • v.47 no.6
    • /
    • pp.1-11
    • /
    • 2019
  • This study aims to understand the tendencies and characteristics when constructing landscape architectural archives in the United States, and to find implications for creating Korean landscape architectural archives. Focusing on seven American landscape architectural archives operated by public institutes, universities, and research institutes, this study examines the background, mission, scope, subject, acquisition, arrangement, and application of the programs in the archives. The results show that the characteristics of the American landscape architectural archives are as follows: first, the recognition of the value and importance of the landscape plays a major role in the establishment of archives; second, the purpose of the archives is to educate and encourage people to find diversity or significance of landscapes; third, the subject and scope of the archives vary according to the purpose of each operating institution; fourth, the main acquisitional method is to receive a donation and to purchase materials or documents; fifth, the classification systems of each archive differs depending on the subject and scope; and sixth, the archives were built on the basis of participation and collaboration with various experts and organizations with stable and sustainable financial resources. These characteristics offer three implications for constructing landscape architectural archives in Korea. First, a long-term vision for landscape architectural archives and the establishment of differentiated themes are required. Second, appropriate methods of material collection and systems of classification, recording, and digitization are necessary and therefore research and pilot archives are required. Third, it is necessary to secure the sustainability of archives by developing ways to utilize the archives in connection with academic and educational programs, thereby securing financial resources and allowing for the establishment of appropriate policies. As basic research, this study is significant as it provides a basis for further research concerning the development of landscape architectural archives in Korea.

A Study on Teaching-Learning and Evaluation Methods of Environmental Studies in the Middle School (중학교 "환경" 교과의 교수.학습 및 평가 방법 연구)

  • 남상준
    • Hwankyungkyoyuk
    • /
    • v.7 no.1
    • /
    • pp.1-17
    • /
    • 1994
  • This study was performed to determine appropriate teaching-learning and evaluation methods for Environmental Studies. To promote the relevance of our study to the needs of the schools and concerned educational communities of environmental education, we reviewed related literature, conducted questionnaire surveys, interviewed related teachers and administrator, held meetings with experts, and field-tested our findings. For selecting and developing teaching-learning methods of Environmental Studies, findings of educational research in general are considered. moreover, principles of environmental education, general aim of environmental education, orientations of environmental education, and developmental stages of middle school students in educational psychology were attended. In addition, relevance to the purpose of the Environmental Studies curriculum, appropriateness for value inquiry as well as knowledge inquiry, small group centered class organization, social interaction centered teaching-learning process, regional environmental situation, significance of personal environment, evaluation methods of Environmental Studies, multi- and inter-disciplinary contents of the Environmental Studies textbook, suitability to the evaluation methods of Environmental Studies, and emphasis on the social interaction in teaching-learning process were regarded. It was learned the Environmental Studies can be taught most effectively in via of holding discussion sessions, conducting actual investigation, doing experiment-practice, doing games and plate, role-playing and carrying out simulation activities, and doing inquiry. These teaching-learning methods were field-tested and proved appropriate methods for the subject. For selecting and developing evaluation method of Environmental Studies, such principles and characteristics of Environmental Studies as objective domains stated in the Environmental Studies curriculum, diversity of teaching-learning organization, were appreciated. We categorized nine evaluation methods: the teacher may conduct questionnaire surveys, testings, interviews, non-participatory observations; they may evaluate student's experiment-practice performances, reports preparation ability, ability to establish a research project, the teacher may ask the students to conduct a self-evaluation, or reciprocal evaluation. To maximize the effect of these methods, we further developed an application system. It considered three variables, that is, evaluates, evaluation objectives domains, and evaluation agent, and showed how to choose the most appropriate methods and, when necessary, how to combine uses of different methods depending on these variables. A sample evaluation instrument made on the basis of this application system was developed and tested in the classes. The system proved effective. Pilot applications of the teaching-learning methods and evaluation method were made simultaneously; and the results and their implications are as follows. Discussion program was applied in a lesson dealing with the problems of waste disposal, in which students showed active participation and creative thinking. The evaluation method used in this lesson was a multiple-choice written test for knowledge and skills. It was shown that this evaluation method and device are effective in helping students' revision of the lesson and in stimulating their creative interpretations and responces. Pupils showed great interests in the actual investigation program, and this programme was proved to be effective in enhancing students' participation. However, it was also turned out that there must be pre-arranged plans for the objects, contents and procedures of survey if this program is to effective. In this lesson, non-participatory observation methods were used with a focus on the attitudes of students. A scaled reported in general description rather than in grade. Experiment-practice programme was adopted in a lesson for purifying contaminated water and in this lesson, instruction objectives were properly established, the teaching-learning process was clearly specified and students were highly motivated. On the other hand, however, it was difficult to control the class when some groups of students require more times to complete their experiment, and sometimes different results. As regards to evaluation, performance observation test were used for assessing skills and attitudes. If teachers use well-prepared Likert scale, evaluation of all groups within a reasonablely short period of time will be possible. The most effective and successful programme in therms of students' participation and enjoyment, was the 'ah-nah-bah-dah-market' program, which is kind of game of the flea market. For better organized program of this kind, however, are essential, In this program, students appraise their own attitudes and behavior by responding to a written questionnaire. In addition, students were asked to record any anecdotes relating to self-appraisal of changes on one's own attitudes and behaviours. Even after the lesson, students keep recording those changes on letters to herself. Role-playing and simulation game programme was applied to a case of 'NIMBY', in which students should decide where to located a refuse dumping ground. For this kind of programme to e successful, concepts and words used in the script should be appropriate for students' intellectual levels, and students should by adequately introduced into the objective and the procedures of the lessons. Written questionnaire was used to assess individual students' attitudes after the lesson, but in order to acquire information on the changes of students' attitudes and skills, pre-test may have to be made. Doing inquiry programme, in which advantages in which students actually investigated the environmental influence of the areas where school os located, had advantages in developing students' ability to study the environmental problems and to present the results of their studies. For this programme to be more efficient, areas of investigation should be clearly divided and alloted to each group so that repetition or overlap in areas of study and presentation be avoided, and complementary wok between groups bee enhanced. In this programme, teacher assessed students' knowledge and attitudes on the basis of reports prepared by each group. However, there were found some difficults in assessing students' attitudes and behaviours solely on the grounds of written report. Perhaps, using a scaled checklist assessing students' attitudes while their presentation could help to relieve the difficulties.

  • PDF

Potential of River Bottom and Bank Erosion for River Restoration after Dam Slit in the Mountain Stream

  • Kang, Ji-Hyun;So, Kazama
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2011.05a
    • /
    • pp.46-46
    • /
    • 2011
  • Severe sediment erosion during floods occur disaster and economic losses, but general sediment erosion is basic mechanism to move sediment from upstream to downstream river. In addition, it is important process to change river form. Check dam, which is constructed in mountain stream, play a vital role such as control of sudden debris flow, but it has negative aspects to river ecosystem. Now a day, check dam of open type is an alternative plan to recover river biological diversity and ecosystem through sediment transport while maintaining the function of disaster control. The purpose of this paper is to verify sediment erosion progress of river bottom and bank as first step for river restoration after dam slit by cross-sectional shear stress and critical shear stress. Study area is upstream reach of slit check dam in mountain stream, named Wasada, in Japan. The check dam was slit with two passages in August, 2010. The transects were surveyed for four upstream cross-sections, 7.4 m, 34 m, 86 m, and 150 m distance from dam in October 2010. Sediment size was surveyed at river bottom and bank. Sediment of cobble size was found at the wetted bottom, and small size particles of sand to medium gravel composed river bank. Discharge was $2.5\;m^3/s$ and bottom slope was 0.027 m/m. Excess shear stress (${\tau}_{ex}$) was calculated for hydraulic erosion by subtracting the values of critical shear stress (${\tau}_{c}$) from the value of shear stress (${\tau}$) at river bottom and bank (${\tau}_{ex}=\tau-{\tau}_c$). Shear stress of river bottom (${\tau}_{bottom}$) was calculated using the cross-sectional shear stress, and bank shear stress (${\tau}_{bank}$) was calculated from the method of Flintham and Carling (1988). $${\tau}_{bank}={\tau}^*SF_{bank}((B+P_{bed})/(2^*P_{bank}))$$ where $SF_{bank}=1.77(P_{bed}/p_{bank}+1.5)^{-1.4}$, B is the water surface width, $P_{bed}$ and $P_{bank}$ are wetted parameter of the bed and bank. Estimated values for ${\tau}_{bottom}$ for a flow of $2.5\;m^3/s$ were lower as 25.0 (7.5 m cross-section), 25.7 (34 m), 21.3 (86 m) and 19.8 (150 m), in N/$m^2$, than critical shear stress (${\tau}_c=62.1\;N/m^2$) with cobble of 64 mm. The values were insufficient to erode cobble sediment. In contrast, even if the values of ${\tau}_{bank}$ were lower than the values for ${\tau}_{bottom}$ as 18.7 (7.5 m), 19.3 (34 m), 16.1 (86 m) and 14.7 (150 m), in N/$m^2$, excess shear stresses were calculated at the three cross-sections of 7.5 m, 34 m, and 86 m distances compare with ${\tau}_c$ is 15.5 N/$m^2$ of 16mm gravel. Bank shear stresses were sufficient for erosion of the medium gravel to sand. Therefore there is potential to erode lateral bank than downward erosion in a flow of $2.5\;m^3/s$. Undercutting of the wetted bank can causes bank scour or collapse, therefore this channel has potential to become wider at the same time. This research is about a potential of sediment erosion, and the result could not verify with real data. Therefore it need next step for verification. In addition an erosion mechanism for river restoration is not simple because discharge distribution is variable by snow-melting or rainy season, and a function for disaster control will recover by big precipitation event. Therefore it needs to consider the relationship between continuous discharge change and sediment erosion.

  • PDF

Microbial Community Composition Associated with Anaerobic Oxidation of Methane in Gas Hydrate-Bearing Sediments in the Ulleung Basin, East Sea (동해 울릉분지 가스 하이드레이트 매장 지역의 메탄산화 미생물 군집 조성 및 분포)

  • Cho, Hyeyoun;Kim, Sung-Han;Shin, Kyung-Hoon;Bahk, Jang-Jun;Hyun, Jung-Ho
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
    • /
    • v.20 no.1
    • /
    • pp.53-62
    • /
    • 2015
  • To elucidate the microbial consortia responsible for the anaerobic methane oxidation in the methane hydrate bearing sediments, we compared the geochemical constituents of the sediment, the rate of sulfate reduction, and microbial biomass and diversity using an analysis of functional genes associated with the anaerobic methane oxidation and sulfate reduction between chimney site (UBGH2-3) on the continental slope and non-chimney site (UBGH2-10) on the basin of the Ulleung Basin. From the vertical profiles of geochemical constituents, sulfate and methane transition zone (SMTZ) was clearly defined between 0.5 and 1.5 mbsf (meters below seafloor) in the UBGH2-3, and between 6 and 7 mbsf at the UBGH2-10. At the UBGH2-3, the sulfate reduction rate (SRR) in the SMTZ exhibited was appeared to be $1.82nmol\;cm^{-3}d^{-1}$ at the depth of 1.15 mbsf. The SRR in the UBHG2-10 showed a highest value ($4.29nmol\;cm^{-3}d^{-1}$) at the SMTZ. The 16S rRNA gene copy numbers of total Prokaryotes, mcrA, (methyl coenzyme M reductase subunit A), and dsrA (dissimilatory sulfite reductase subunit A) showed the peaks in the SMTZ at both sites, but the maximum mcrA gene copy number of the UBGH2-10 appeared below the SMTZ (9.8 mbsf). ANME-1 was a predominant ANME (Anaerobic MEthanotroph) group in both SMTZs of the UBGH2-3 and -10. However, The sequences of ANME-2 were detected only at 2.2 mbsf of the UBGH2-3 where high methane flux was observed because of massive amount of gas hydrate at shallow depth. And Desulfosarcina-Desulfococcus (DSS) that is associated with ANME-2 was detected in 2.2 mbsf of the UBHG2-3. Overall results demonstrate that ANME-1 and ANME-2 are considered as significant archaeal groups related to methane cycle in the subsurface sediment of the East Sea, and ANME-2/DSS consortia might be more responsible for methane oxidation in the methane seeping region than in non-seeping region.

A Study on the Applicability of Chinese Steamed Dumpling with Korean Food Stuffing - Focusing on Jiangsu Residents - (중국 만두소의 한국음식 적용가능성 연구 - 중국 강소성 지역 주민을 대상으로 -)

  • Wu, Di;Joo, Nami
    • Korean journal of food and cookery science
    • /
    • v.31 no.3
    • /
    • pp.344-351
    • /
    • 2015
  • The purpose of this study is to improve Korean food market competitiveness in China, and to develop product diversity. Therefore, the paper will discuss and analyze the feasibility of combining Korean and Chinese cuisines. The paper is based on a SPSS-analyzed survey of 255 Jiangsu residents focusing on the concept of breakfast, and the recognition of and preference for Korean food. The result showed a high level of eating out for breakfast in Jiangsu province and the expectation of many options. The respondents generally preferred porridge, steamed stuffed dumplings, noodles and other options that are relatively convenient. Korean foods such as bulgogi, samgyeopsal, tteokbokki and bibimbap generally enjoyed a high degree of recognition and preference. This study selected bulgogi, jeyukbokkeum, dakgalbi and japchae as the stuffings for steamed dumplings and an evaluation of sensory attributes including saltiness, sweetness, spiciness, and gravy was conducted using 30 professionals. Relatively high scores were recorded in all aspects. Compared with the reference product, the dumplings with Korean food stuffing achieved higher scores. As a new development and attempt, the steamed dumplings with Korean food filling evaluated during this test demonstrated feasibility and enormous market potential. The study provides a new direction and reference value for the Chinese breakfast market and for the penetration of Korean food into the Chinese market.

Weed Flora Diversity and Composition on Upland Field of Korea (우리나라 밭작물 재배지 잡초 발생 및 분포현황)

  • Lee, In-Yong;Oh, Young-Ju;Hong, Sun-Hee;Choi, Jun-Keun;Heo, Su-Jeoung;Lee, Chae-Young;Hwang, Ki-Seon;Park, Kee-Woong;Cho, Seng-Hyun;Kwon, Oh-Do;Im, Il-Bin;Kim, Sang-Kuk;Seong, Deok-Gyeong;Chung, Young-Jae;Kim, Chang-Seok;Lee, Jeongran;Seo, Hyun-A;Jang, Hyung-Mok
    • Weed & Turfgrass Science
    • /
    • v.4 no.3
    • /
    • pp.159-175
    • /
    • 2015
  • Surveys of weed species on upland fields were conducted in Korea to investigate the occurrence of weed flora from April to May 2014 for winter crop fields and from July to August 2014 for summer crop fields. From the nation-wide survey, 375 weed species in 50 families were identified and classified to 162 annuals, 78 biennials and 135 perennials. Based on the occurrence ratio, the most weed species belonged to Compositae (73 species). 44 and 25 weed species belonged to Poaceae and Polygonaceae, respectively, and these 183 weed species in the most five families accounted for 49% of total weed occurrence. While 287 weed species in 45 families occurred in the winter crop fields, 339 weed species in 47 families occurred in summer crop fields. The most dominant weed species in Korean upland fields were Digitaria ciliaris, followed by Portulaca oleracea, Acalypha australis, Chenopodium album, Rorippa palustris etc. 129 weed species in 25 families were considered as exotic weeds. Based on the importance analysis, the highest value was C. album followed by Amaranthus lividus, Conyza canadensis etc. This information could be useful for estimation of future weed occurrence, weed population dynamics and establishment of weed control methods in upland fields of Korea.