ATBC 2012 49th Annual Meeting Bonito-MS, Brasil
S33.OC.05 Land use intensity affects biomass accumulation in Amazonian secondary forests Massoca PES1,2, Nogueira CLB1,2, Bentos TV2, Wiener E3, Mesquita RCG1,2 - 1National Institute of Science and Technology for the Environmental Services of Amazonia (INCT/Servamb), 2Instituto Nacional de Pesquisas da Amazônia (INPA) - Biological Dynamics of Forest Fragments Project (PDBFF), 3Ramapo College of New Jersey School of Theoretical and Applied Science Secondary forests or “capoeiras” accounted for 20% of the total deforested area in the Brazilian Amazon in 2006. This study relates land use history and biomass accumulation in a chronosequence of secondary forests in the Apuí municipality, one of the deforestation hotspots in the Amazon. Aboveground live biomass (ABGB) was estimated for trees in 16 secondary forests with ages ranging from 3-23 years of abandonment, and subjected to two previous land uses: eight areas were clearcut and used only once for small farm agriculture and then abandoned (low intensity); eight areas were maintained mainly as pasture experiencing several prescribed fires until abandonment (high intensity). Satellite imagery data between 1985 and 2010 was supplemented with landowner interviews in order to define the secondary forests age and their previous land use history. The point-centered quarter method was used for sampling trees in four diametric classes (1<5 cm, 5<10 cm, 10<20 cm, ≥20 cm dbh) in each quarter. The average accumulation of ABGB was 6.7 Mg.ha-1.year-1 and ranged between 10.9 - 193.0 Mg.ha-1 in the study area. As expected, biomass was positively related to the abandonment time of secondary forests for both land use intensities (F1,13=23.1, p<0.001; ANCOVA). However, high intensity land use prior to the abandonment resulted in a lower stock of biomass accumulated through time (F1,13=4.9, p=0.04; ANCOVA), revealing the loss of environmental conditions in supporting forest restoration after high intensity land uses. The results point to the negative effect of inadequate pasture maintenance practices in the Amazon. Depleting the poor soils of the region affects one of the main environmental services played by the secondary forests while reducing biomass accumulation and consequently the amount of carbon it removes from the atmosphere.
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