Author(s): ROWLAND, L.; COSTA, A. C. L. da; OLIVEIRA, A. A. R.; OLIVEIRA, R. S.; BITTENCOURT, P. L.; COSTA, P. B.; GILES, A. L.; SOSA, A. I.; COUGHLIN, I.; GODLEE, J. L.; VASCONCELOS, S. S.; S. JUNIOR, J. A.; FERREIRA, L. V.; MENCUCCINI, M.; MEIR, P.

Summary: CO2 efflux from stems (CO2_stem) accounts for a substantial fraction of tropical forest gross primary productivity, but the climate sensitivity of this flux remains poorly understood. We present a study of tropical forest CO2_stem from 215 trees across wet and dry seasons, at the world?s longest running tropical forest drought experiment site. We show a 27% increase in wet season CO2_stem in the droughted forest relative to a control forest. This was driven by increasing CO2_stem in trees 10?40 cm diameter. Furthermore, we show that drought increases the proportion of maintenance to growth respiration in trees > 20 cm diameter, including large increases in maintenance respiration in the largest droughted trees, > 40 cm diameter. However, we found no clear taxonomic influence on CO2_stem and were unable to accurately predict how drought sensitivity altered ecosystem scale CO2_stem, due to substantial uncertainty introduced by contrasting methods previously employed to scale CO2_stem fluxes. Our findings indicate that under future scenarios of elevated drought, increases in CO2_stem may augment carbon losses, weakening or potentially reversing the tropical forest carbon sink. However, due to substantial uncertainties in scaling CO2_stem fluxes, stand-scale future estimates of changes in stem CO2 emissions remain highly uncertain.

Publication year: 2018

Types of publication: Journal article

Unit: Embrapa Eastern Amazon

Keywords: Carbono, Estresse hídrico, Floresta, Floresta Tropical