Spatial identification by satellite imagery of the crop–fallow rotation cycle in northern Laos

摘要: In the mountainous regions of northern Laos, shifting cultivation, or slash-and-burn agriculture, is widely practiced. However, crop–fallow rotation cycle becoming shorter owing to forest conservation policies and population pressure, causing loss productivity that deleteriously affects farmers’ livelihoods in region. To investigate regional land use conditions, we have developed a method identifying from Landsat Thematic Mapper (TM) Enhanced Mapper+ (ETM+) data. We assessed impact identified on plant production measured by Normalized Difference Vegetation Index (NDVI). The study site was an area Luang Prabang Province. Using eight TM ETM+ images acquired annually 1995 2003, except for 1998, when cloud-free data were not collected, classified each year as crop fallow presence vegetation late dry season. Conformity with age determined field investigation 69.1%. cultivation frequency 2002 showed 77,000 ha (17.3% site) had been used cropping during period, but 41,000 ha (9.2%) every year. Of site, 129,000 ha (29.1%) cultivated one two times, 83,000 ha (18.7%) three four 54,000 ha (12.2%) five six times. NDVI crops November did provide sufficient evidence prove assumption longer period would result better yields. Instead, regeneration evidenced higher values after fallow. More than 8 years be needed reach same forest. From produced maps indicating frequency, found areas high potential decreased increased. Areas near rivers intensively used, length accordingly short. Low-potential western basin Mekong River. This spatial information can detect where biomass at risk deteriorating.