| dc.description.abstract | The Amazon Basin has experienced more variable climate over the last decade, with a severe and widespread drought in 2005 causing large basin-wide losses of biomass. A drought of similar climatological magnitude occurred again in 2010; however, there has been no basin-wide ground-based evaluation of effects on vegetation. We examine to what extent the 2010 drought affected forest dynamics using ground-based observations of mortality and growth from an extensive forest plot network. We find that during the 2010 drought interval, forests did not gain biomass (net change: −0.43 Mg ha−1, confidence interval (CI): −1.11, 0.19, n = 97), regardless of whether forests experienced precipitation deficit anomalies. This contrasted with a long-term biomass sink during the baseline pre-2010 drought period (1998 to pre-2010) of 1.33 Mg ha−1 yr−1 (CI: 0.90, 1.74, p < 0.01). The resulting net impact of the 2010 drought (i.e., reversal of the baseline net sink) was −1.95 Mg ha−1 yr−1 (CI:−2.77, −1.18; p < 0.001). This net biomass impact was driven by an increase in biomass mortality (1.45 Mg ha−1 yr−1 CI: 0.66, 2.25, p < 0.001) and a decline in biomass productivity (−0.50 Mg ha−1 yr−1, CI:−0.78, −0.31; p < 0.001). Surprisingly, the magnitude of the losses through tree mortality was unrelated to estimated local precipitation anomalies and was independent of estimated local pre-2010 drought history. Thus, there was no evidence that pre-2010 droughts compounded the effects of the 2010 drought. We detected a systematic basin-wide impact of the 2010 drought on tree growth rates across Amazonia, which was related to the strength of the moisture deficit. This impact differed from the drought event in 2005 which did not affect productivity. Based on these ground data, live biomass in trees and corresponding estimates of live biomass in lianas and roots, we estimate that intact forests in Amazonia were carbon neutral in 2010 (−0.07 Pg C yr−1 CI:−0.42, 0.23), consistent with results from an independent analysis of airborne estimates of land-atmospheric fluxes during 2010. Relative to the long-term mean, the 2010 drought resulted in a reduction in biomass carbon uptake of 1.1 Pg C, compared to 1.6 Pg C for the 2005 event. | en_GB |
| dc.description.sponsorship | Forest inventory data are curated in the ForestPlots database, https://www.forestplots.net. This paper is a product of the RAINFOR network, supported by Natural Environment Research Council (NERC) Urgency, Standard, and Consortium grants Assessing the impacts of the 2010 drought at the Amazon forest-savanna zone of tension (NE/I02982X/1), Niche Evolution of South American Trees (NE/I028122/1), AMAZONICA (NE/F005806/1), and TROBIT (NE/D005590/1), the European Union's Seventh Framework Programme project 282664, AMAZALERT, CNPq/PELD (403725/2012-7), a Gordon and Betty Moore Foundation grant, and ERC grant “Tropical Forests in the Changing Earth System.” Additional data were included from the Tropical Ecology Assessment and Monitoring (TEAM) Network, a collaboration between Conservation International, the Missouri Botanical Garden, the Smithsonian Institution, and the Wildlife Conservation Society, and partly funded by these institutions, the Gordon and Betty Moore Foundation, and other donors. T.R.F. was supported by a Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil, grant (177/2012). O.L.P. was supported by a European Research Council Advanced Grant and a Royal Society Wolfson Research Merit Award. J.C. and M.R.M. were supported by Investissement d'Avenir grants of the ANR (CEBA: ANR-10-LABX-25-01 and TULIP: ANR-10-LABX-0041) and from CNES funds (TOSCA). This is paper number 694 in the Biological Dynamics of Forest Fragments project. We thank I. Amaral, A. Araujo-Murakami, O.S. Bánki, J. Barichivich, P. C. Barros, P. Brando, L. Blanc, C. Doughty, T. Gaui, N. Higuchi, T.J. Killeen, E. Lenza, P.S. Morandi, A. Parada, M.C. Peñuela-Mora, N.C.A. Pitman, Z. Restrepo, A. Roopsind, C. Roth, D. Sasaki, A. Sota, J. Talbot, M. Toledo, R. K. Umetsu, and R. Zagt for their assistance with collection or sharing data and two anonymous referees for their helpful suggestions to improve the manuscript. T.R.F. performed analyses and wrote the paper with major input from O.L.P., R.B., J.L., and E.G. O.L.P., J.L., and Y.M. conceived the RAINFOR forest census plot network program, and E.G., T.R.B., T.R.F., and R.B. contributed to its development. O.L.P., T.R.F., J.L., Y.M., and E.G. conceived the study and received funding. O.L.P., T.R.F., R.J.W.B., and A.M.M. coordinated data collection with the help of most coauthors. T.R.F., R.B., A.M.M., O.L.P., and G.L.G. performed quality control on the data with the help of most coauthors. All remaining authors contributed data. All authors commented on the analysis, presentation of the data, and manuscript. | en_GB |
