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Landscape-Scale Dynamics of Carbon in Live and Dead Biomass Pools

Gregory Santoni, Harvard University,
Lucy Hutyra, Harvard University, (Presenting)
Elizabeth Hammond-Pyle, Harvard University,
Daniel Curran, Harvard University,
Plinio B. de Camargo, CENA,
Simone Vieira, CENA,
Henrique Nascimento, INPA,
William Laurance, Smithsonian Tropical Research Institute,
Scott Saleska, University of Arizona,
Steven Wofsy, Harvard University,

Carbon sequestration dynamics in Amazonian forests remain controversial. Inventories tend to be spatially and/or temporally limited and often fail to integrate coarse woody debris (CWD) in their estimates. A set of four 10-ha transects were established across the Tapajós National Forest (TNF) to determine whether the 19.75-ha plots in the eddy flux tower footprint (km67) were representative of the TNF as a whole. Analysis revealed that the km67 site was indistinguishable from the TNF, with live biomass estimates (trees ≥ 10cm DBH) of 152.8 ± 6.0 MgC/ha/yr and 156.1 ± 7.0 MgC/ha/yr, respectively. The net increase in carbon stored in live wood biomass at km67 was 1.68 ± .68 MgC/ha/yr (1999-2001) and 0.59 ± .29 MgC/ha/yr (2001-2005), comparable to the net average increase of 1.59 ± 0.32 MgC/ha/yr across the Tapajós. Gains in live wood biomass, however, were exceeded by decomposition losses from CWD at km67, resulting in a net carbon source to the atmosphere of -1.6 MgC/ha/yr during the1999 to 2001 period and a net zero or small source of -0.47 MgC/ha/yr during the 2001 to 2005 time-step. Between 2003 and 2005, a net zero or small source of -0.21 MgC/ha/yr was observed as the landscape mean across the Tapajós. Dynamics across the Tapajós were compared to established Amazonian forest plots at the BDFFP project near Manaus, Brazil. The BDFFP plots showed a mean live biomass increase of 0.27 MgC/ha/yr from 1998 to 2002. When decomposition losses from CWD were estimated, the sites were a carbon sink of 1.18 MgC/ha/yr. While mortality at the Tapajós and BDFFP were comparable, the decay states of the CWD differed substantially accounting for the low carbon losses through decomposition at the BDFFP plots. This reiterates the importance of CWD and decomposition in carbon sequestration measurements as an analysis of live biomass without CWD would suggest that both the Tapajós and the BDFFP plots were carbon sinks.

Science Theme:  CD (Carbon Dynamics)

Presentation Type:  Poster

Abstract ID: 112

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