Secondary vegetation in central Amazonia: Land-use history effects on aboveground biomass

• Secondary forests in abandoned pastures grow slower than in agricultural fallows.
• Greater length of use as pasture and number of burns reduce biomass growth rates.
• Amazonian secondary forests on sites with typical use histories grow slowly.
• Brazil’s national inventory of GHG emissions greatly overestimates carbon uptake.
• Secondary forests in family-farming have carbon benefits that could be rewarded.

Growth of secondary forest (capoeira) is an important factor in absorption of carbon from the atmosphere. Estimates of this absorption vary greatly, in large part due to the effect of different land-use histories on the estimates available in the literature. We relate land-use history to aboveground biomass accumulation of secondary vegetation in plots on land that had been used for agriculture (unmechanized manioc and maize) and for pasture in small rural properties in the Tarumã-Mirim settlement near Manaus in central Amazonia, Brazil. We evaluated influence of (a) age of the second growth vegetation, (b) time of use as agriculture or pasture and (c) number of times the area was burned. Biomass data were obtained by destructive sampling of all plants with diameter at breast height >1 cm in 24 parcels of secondary vegetation ranging from 1 to 15 years of age in abandoned pasture (n = 9) and agriculture (n = 15). As compared to secondary vegetation in abandoned agricultural fields, vegetation in abandoned cattle pasture (the predominant use history for Amazonian secondary vegetation) grows 38% more slowly to age 6 years. Number of burns also negatively affects biomass recovery. Applying the growth rates we measured to the secondary forests reported in Brazil’s Second National Communication to the United Nations Framework Convention on Climate Change suggests that carbon uptake by this vegetation is overestimated by a factor of four in the report.