How Did Deciduous Rubber Plantations Expand Spatially in China's Xishuangbanna Dai Autonomous Prefecture During 1991-2016?

Rubber plantations have experienced continuous expansion in Xishuangbanna, in southwestern China, since the 1950s. However, the question of how the establishment of adventive rubber trees has spatially expanded in the margin of the Asian tropics in recent decades is not clearly understood. Here, a robust phenology-based algorithm--namely the change rate of the Landsat-derived normalized burn ratio--was modified based on tri-windows (i.e., predefoliation, defoliation, and foliation) and then used to discriminate deciduous rubber plantations from other land cover types by applying a threshold of 1.0 and combining Landsat-based forest masks every five years during 1991-2016. Deciduous rubber plantations increased more than 6.6 times, approximately 3074 km2 in 2016, or at an annual rate of about 8% (104 km2/year) in Xishuangbanna over that period, showing two typical expansion trends toward both higher (over 1000 m) and lower (below 600 m) elevations and increasingly spread to borderlands with Laos and Myanmar. [ABSTRACT FROM AUTHOR]