焼畑土地利用の履歴と休閑地の植生回復状況の解析-ミャンマー・バゴー山地におけるカレン焼畑の事例- (<特集>ミャンマー少数民族地域における生態資源利用と社会変容)

Abstract

In the Karen area of Myanmar, where the Karen have practiced traditional shifting cultivation since colonial times, we tried to reconstruct a land use history of their shifting cultivation practices using a combination of field observations, global positioning system (GPS) mapping, and interviews conducted during 2002-2006, as well as analyses of JERS and LANDSAT satellite images taken in 1989-2001. The vegetation recovery process during the fallow period was also analyzed using a supervised classification of high-resolution Quickbird satellite images taken in 2005. The satellite image analysis suggested that 65-75% of the shifting cultivation fields could be extracted from JERS images taken between November and January by using the normalized difference vegetation index (NDVI) as an indicator. The overlap of shifting cultivation fields from 1989 to 2006 showed that the fallow period of most shifting cultivation in this area exceeded 9-12 years. According to the vegetation recovery analysis, most fallow land was covered with bamboo within 5 years after the harvest, and that fallow land was reopened when a few tree species started to grow in the bamboo-dominated forests. Vegetation analysis showed that around 90% of the shifting cultivation fields were opened by slashing and burning bamboo-dominated forests in 2006, although more tree-dominated forests with a longer fallow period could have been opened. These results showed that the recovery of bamboo-dominated forests is a key factor in maintaining the practice of shifting cultivation in this area.