Implications of land-use history for forest regeneration in the Brazilian Amazon

Understanding the dynamics of forest regeneration on abandoned agricultural land in the Amazon has often been restricted by limited knowledge of historical land use. This study compared time-series classifications of mature forest, nonforest, and regrowth generated from Landsat sensor data for areas north of the Brazilian cities of Manaus (1973-2003) and Santarem (1984-2003) to chronicle land histories and forest age. At Manaus, active land use prior to abandonment ranged from 10-15 years with burning. Few forests were recleared on more than three occasions. From the mid-1980s, land was increasingly abandoned and, in 2003, over 75% of the deforested area supported regenerating forests, with several being older than 20 years. South of Santarem, forests were cleared up to seven times. In 2003, few regenerating forests were older than 10 years, and all land covers, but particularly mature forest, were damaged by extensive wildfires in 1993 and 1998. Based on previous research, the study concludes that the capacity of regenerating forests to recover biomass and tree species diversity will be reduced where prior land use is more intense, as in Santarem and some clearings north of Manaus.