Multitemporal analysis of land use/land cover JERS-1 backscatter in the Brazilian tropical rainforest

Abstract

The temporal evolution of L-band microwave backscatter for several land cover types in the Tapajos National Forest is analysed using JERS-1. Five images were acquired from 1993 to 1997. Samples of the studied land cover types were identified after analysis of a Landsat Thematic Mapper (TM) dataset of 12 images obtained from 1984 to 1999. The following land cover types were investigated: bare soil, agriculture, pastures, forest regrowth from 1 to 23-year-old and primary forest. Backscatter behaviour of regrowth stands is influenced by the previous land use and by human impacts such as fire and selective logging. This selective logging can be mechanized or not, because people who live in the Amazon usually cut trees to build houses, bridges, fences, etc. Backscatter of young regrowth stands on sites immediately abandoned after slash and burn increases at a faster rate than young regrowth on sites abandoned after some years of agriculture. Backscatter of old regrowth stands also behaves differently where there are disturbances such as fire or selective logging. In the presence of such disturbances, one finds an oscillating pattern over time, while undisturbed forest shows either a progressive trend or a stable pattern, depending on the age of the stand.