Drought stress and tree size determine stem CO2 efflux in a tropical forest.
2018
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. | Lucy Rowland, University of Exeter; Antonio C. L. da Costa, UFPA; Alex A. R. Oliveira, MPEG; Rafael S. Oliveira, UNICAMP; Paulo L. Bittencourt, UNICAMP; Patricia B. Costa, UNICAMP; Andre L. Giles, UNICAMP; Azul I. Sosa, UNICAMP; Ingrid Coughlin, USP; John L. Godlee, University of Edinburgh; STEEL SILVA VASCONCELOS, CPATU; João A. S. Junior, UFPA; Leandro V. Ferreira, MPEG; Maurizio Mencuccini, CREAF / ICREA; Patrick Meir, University of Edinburgh / Australian National University.
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.
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