ENSO Drives interannual variation of forest woody growth across the tropics

Citation

Rifai SW, Girardin CAJ, Berenguer E, del Aguila-Pasquel J, Dahlsjö CAL, Doughty CE, Jeffery KJ, Moore S, Oliveras I, Riutta T, Rowland LM, Murakami AA, Addo-Danso SD, Abernethy KA & White LJT (2018) ENSO Drives interannual variation of forest woody growth across the tropics. Philosophical Transactions of the Royal Society B: Biological Sciences, 373 (1760), Art. No.: 20170410. https://doi.org/10.1098/rstb.2017.0410

Abstract
Meteorological extreme events such as El Niño events are expected to affect tropical forest net primary production (NPP) and woody growth, but there has been no large-scale empirical validation of this expectation. We collected a large high–temporal resolution dataset (for 1–13 years depending upon location) of more than 172 000 stem growth measurements using dendrometer bands from across 14 regions spanning Amazonia, Africa and Borneo in order to test how much month-to-month variation in stand-level woody growth of adult tree stems (NPPstem) can be explained by seasonal variation and interannual meteorological anomalies. A key finding is that woody growth responds differently to meteorological variation between tropical forests with a dry season (where monthly rainfall is less than 100 mm), and aseasonal wet forests lacking a consistent dry season. In seasonal tropical forests, a high degree of variation in woody growth can be predicted from seasonal variation in temperature, vapour pressure deficit, in addition to anomalies of soil water deficit and shortwave radiation. The variation of aseasonal wet forest woody growth is best predicted by the anomalies of vapour pressure deficit, water deficit and shortwave radiation. In total, we predict the total live woody production of the global tropical forest biome to be 2.16 Pg C yr−1, with an interannual range 1.96–2.26 Pg C yr−1 between 1996–2016, and with the sharpest declines during the strong El Niño events of 1997/8 and 2015/6. There is high geographical variation in hotspots of El Niño–associated impacts, with weak impacts in Africa, and strongly negative impacts in parts of Southeast Asia and extensive regions across central and eastern Amazonia. Overall, there is high correlation (r = −0.75) between the annual anomaly of tropical forest woody growth and the annual mean of the El Niño 3.4 index, driven mainly by strong correlations with anomalies of soil water deficit, vapour pressure deficit and shortwave radiation.

Keywords
General Biochemistry, Genetics and Molecular Biology; General Agricultural and Biological Sciences

Notes
Additional co-authors: Paulo Brando, Chad Burton, Fidèle Evouna Ondo, Akwasi Duah-Gyamfi, Filio Farfán Amézquita, Renata Freitag, Fernando Hancco Pacha, Walter Huaraca Huasco, Forzia Ibrahim, Armel T Mbou, Vianet Mihindou Mihindou, Karine S Peixoto, Wanderley Rocha, Liana C Rossi, Marina Seixas, Javier E Silva-Espejo, Stephen Adu-Bredu, Jos Barlow, Antonio C. L. da Costa, Beatriz S. Marimon, Ben H Marimon-Junior, Patrick Meir, Daniel B Metcalfe, Oliver L. Phillips,Yadvinder Malhi

Journal
Philosophical Transactions of the Royal Society B: Biological Sciences: Volume 373, Issue 1760

• Accepted manuscript