A new framework for mapping time series rubber plantation in Southeast Asia

Accurate yield estimation and appropriate planting management policies for rubber plantations require their precise information on spatiotemporal change data. Previous studies on mapping of rubber plantations did not employ the dynamic rubber phenology features and had difficulty in obtaining historical samples. Here we attempted to develop a new mapping framework through taking historical sample migration, dynamic phenology, and change detection variables into the classification procedure. An automatic sample migration algorithm was first proposed to generate historical samples. Then, two new variable types, dynamic phenology indices and change detection variables, were developed. Another four commonly used variable types -spectral bands, yearly composite spectral indices, terrains, and textures were also extracted. Five combinations of variable types were designed to explore key variable types. Subsequently, the framework with recommended variable types was applied at an experimental site in China and was finally evaluated to two test sites in Myanmar and Thailand for examining its transferability. Results showed that the average overall accuracy of historically migrated samples reached over 97% at the experimental site. Dynamic phenology indices and change detection variables were found as two crucial variable types for rubber plantations mapping. The average rubber plantations mapping accuracy during 2003-2022 reached 93.68%. Transferring the proposed framework to two test sites confirmed the independent roles of change detection variables and dynamic phenology indices. Their average rubber plantations mapping accuracy during 2003-2022 reached 94.34% and 93.73%, respectively. Good spatial consistency between the classified maps and Google Earth images was observed, displaying clear boundaries between rubber plantations and farmland, evergreen broadleaf forest, and shrub. Overall, the proposed framework has great potential for time series rubber plantations mapping in Southeast Asia.