• Journal of the Korean association of regional geographers
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• v.4 no.2
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• pp.31-47
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• 1998

This paper deals with the historical geography of land-use and agriculture along the Lower Nam-River floodplains. The reclamation process of the river floodplains, the cultivation methods on the reclaimed lands, and the land-use patterns and processes are investigated. The Nam River, one of the major tributaries of the Nakdong River, flows through the boundary between Ham-An and Eu-Ryong Guns. Larger floodplains are located in Ham-An Gun. The floodplains of Ham-An Gun have been surveyed intensively in this study. In South Korea, the alluvial plains, mostly located along the river valleys, have been reclaimed to provide fertile agricultural lands. Those along the upper river valleys were reclaimed before those along the lower river valleys. The flood-plains of Han-An Gun were reclaimed to be the largest agricultural lands of the Gun. The natural levees along the Lower Nam-River Valley were identified before the reclamation processes but now hardly identified. Relatively larger floodplains are located along the tributary streams of the Nam River. Often there are low-lying back swamps between the natural levees and the hills/mountains that rise above the floodplains. The back swamps, called 'natural bog lands' in this region, have been reduced in size and in number through reclamation for the purpose of agricultural and industrial land-uses. Now about ten 'natural bog lands' are found in the Ham-An floodplains, and some of them are being reclaimed for the industrial land-use. This study suggests the emergent need of conservation for the remaining 'natural bog lands' in terms of ecology. Seven agricultural fields of large size, originated from the Nam-River floodplains, are identified in this study: Kun(큰들), Chung-Am(정암들), Chang-chi(장지들), Baek-San(백산들), Ha-Ki(하기들), Gu-Hae(구혜들), and Chang-Po(장포들) fields. The Kun field was reclaimed during the Japanese control and the Gu-Hae, in the 1950s. All of those except the above two fields were reclaimed after the mid-1960s. The Nam-River Dam in Chinju, completed in 1969, contributed the reclamation processes along the Lower Nam-River floodplains. The rice acreage of the region has been reduced slowly since 1970 but the rice production of the region has been relatively stable (Table 4). Rice culture had been the most important agriculture on the reclaimed lands for decades before the greenhouse vegetable cultivation became more important in the 1980s. Among the vegetables cultivated in the greenhouse, the watermelon is the dominantly leading one. Watermelons are usually harvested two or three times in a year though it is possible to harvest four times in one year. The rotation of watermelons and rice is common in the region. It is known the physical conditions of the Nam-River floodplains in Ham-An Gun is the most suitable for watermelon cultivation in South Korea.

• Journal of fish pathology
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• v.8 no.1
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• pp.13-21
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• 1995

Four species of Actinosporeans, Aurantiactinomyxon sp. A, B, C and Neoctinomyxon sp. D were released from Oligochaete, Branchiura sowerbyi captured from three reserviors, where intestinal giant-cystic disease in carp had occured from June to September, 1994. All part of the intestinal epithelial tissue from the gullet to the anus of B. sowerbyi were infected by Actino-sporeans, and many mature Actinosporean were seen more easily at the posterior parts of the body. Just before releasing, mature Actinosporean sporozoites were divied into each individual from the intestinal epithelial tissue of Oligochaete, while immature ones had 6 spores ($20{\times}25{\mu}m$ in size) per each in the oocyst ($60{\times}65{\mu}m$ in size). A total of 1, 762 of B. sowerbyi were investigated in three reservoirs, 86 individuals (4.88%) of them were infected; 0. 74% (13 ind.) of Aurantiactinomyxon sp. A, 2. 27% (40 ind.) of Aurantiactinomyxon sp. B, 1. 59% (28 ind.) of Aurantiactinomyxon sp. C, and 0. 28% (5 ind.) of Neoactinomyxon sp. D. At the room temperature of 22.6-$30.7^{\circ}C$, number of extrusion dates of Actinosporeans from B. sowerbyi for 32 days are 1 day (23.3% of total, 1 time) or 5 days (11.7%. 5 times), and the majority was finished within 15 days, however, 6.7% of total were released for 32 days.