ENSO effects on the transpiration of eastern Amazon trees

Abstract

Tree transpiration is important in the recycling of precipitation in the Amazon and might be negatively affected by El Nino-Southern Oscillation (ENSO)-induced droughts. To investigate the relative importance of soil moisture deficits versus increasing atmospheric demand (VPD) and determine if these drivers exert different controls over tree transpiration during the wet season versus the dry season (DS), we conducted sap flow measurements in a primary lowland tropical forest in eastern Amazon during the most extreme ENSO-induced drought (2015/2016) recorded in the Amazon. We also assessed whether trees occupying different canopy strata contribute equally to the overall stand transpiration (Tstand). Canopy trees were the primary source of Tstand. However, subcanopy trees are still important as they transpired an amount similar to other biomes around the globe. Tree water use was higher during the DS, indicating that during extreme drought trees did not reduce transpiration in response to low soil moisture. Photosynthetically active radiation and VPD exerted an overriding effect on water use patterns relative to soil moisture during extreme drought, indicating that light and atmospheric constraints play a critical role in controlling ecosystem fluxes of water. Our study highlights the importance of canopy and subcanopy trees to the regional water balance and highlights the resilience to droughts that these trees show during an extreme ENSO event.This article is part of a discussion meeting issue 'The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

Keywords

drought; hysteresis; sap flow; vapour pressure deficit; El Nino

Published in

Philosophical Transactions B: Biological Sciences
2018, Volume: 373, number: 1760, article number: 20180085

Sustainable Development Goals

SDG7 Affordable and clean energy
SDG13 Climate action


UKÄ Subject classification

Forest Science


Publication identifier

DOI: https://doi.org/10.1098/rstb.2018.0085

Permanent link to this page (URI)

https://res.slu.se/id/publ/111183