Enhanced canopy growth precedes senescence in 2005 and 2010 Amazonian droughts

Liu, YY; van Dijk, AIJM; Miralles, DG; McCabe, MF; Evans, JP; de Jeu, RAM; Gentine, P; Huete, A; Parinussa, RM; Wang, L; Guan, K; Berry, J; Restrepo-Coupe, N

Enhanced canopy growth precedes senescence in 2005 and 2010 Amazonian droughts

Liu, YY van Dijk, AIJM Miralles, DG McCabe, MF Evans, JP de Jeu, RAM Gentine, P Huete, A

Parinussa, RM Wang, L Guan, K Berry, J Restrepo-Coupe, N

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Publication Type:: Journal Article
Citation:: Remote Sensing of Environment, 2018, 211 pp. 26 - 37
Issue Date:: 2018-06-15

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Field	Value	Language
dc.contributor.author	Liu, YY	en_US
dc.contributor.author	van Dijk, AIJM	en_US
dc.contributor.author	Miralles, DG	en_US
dc.contributor.author	McCabe, MF	en_US
dc.contributor.author	Evans, JP	en_US
dc.contributor.author	de Jeu, RAM	en_US
dc.contributor.author	Gentine, P	en_US
dc.contributor.author	Huete, A https://orcid.org/0000-0003-2809-2376	en_US
dc.contributor.author	Parinussa, RM	en_US
dc.contributor.author	Wang, L	en_US
dc.contributor.author	Guan, K	en_US
dc.contributor.author	Berry, J	en_US
dc.contributor.author	Restrepo-Coupe, N https://orcid.org/0000-0003-3921-1772	en_US
dc.date.issued	2018-06-15	en_US
dc.identifier.citation	Remote Sensing of Environment, 2018, 211 pp. 26 - 37	en_US
dc.identifier.issn	0034-4257	en_US
dc.identifier.uri	http://hdl.handle.net/10453/130290
dc.description.abstract	© 2018 Unprecedented droughts hit southern Amazonia in 2005 and 2010, causing a sharp increase in tree mortality and carbon loss. To better predict the rainforest's response to future droughts, it is necessary to understand its behavior during past events. Satellite observations provide a practical source of continuous observations of Amazonian forest. Here we used a passive microwave-based vegetation water content record (i.e., vegetation optical depth, VOD), together with multiple hydrometeorological observations as well as conventional satellite vegetation measures, to investigate the rainforest canopy dynamics during the 2005 and 2010 droughts. During the onset of droughts in the wet-to-dry season (May–July) of both years, we found large-scale positive anomalies in VOD, leaf area index (LAI) and enhanced vegetation index (EVI) over the southern Amazonia. These observations are very likely caused by enhanced canopy growth. Concurrent below-average rainfall and above-average radiation during the wet-to-dry season can be interpreted as an early arrival of normal dry season conditions, leading to enhanced new leaf development and ecosystem photosynthesis, as supported by field observations. Our results suggest that further rainfall deficit into the subsequent dry season caused water and heat stress during the peak of 2005 and 2010 droughts (August–October) that exceeded the tolerance limits of the rainforest, leading to widespread negative VOD anomalies over the southern Amazonia. Significant VOD anomalies were observed mainly over the western part in 2005 and mainly over central and eastern parts in 2010. The total area with significant negative VOD anomalies was comparable between these two drought years, though the average magnitude of significant negative VOD anomalies was greater in 2005. This finding broadly agrees with the field observations indicating that the reduction in biomass carbon uptake was stronger in 2005 than 2010. The enhanced canopy growth preceding drought-induced senescence should be taken into account when interpreting the ecological impacts of Amazonian droughts.	en_US
dc.relation.ispartof	Remote Sensing of Environment	en_US
dc.relation.isbasedon	10.1016/j.rse.2018.03.035	en_US
dc.subject.classification	Geological & Geomatics Engineering	en_US
dc.title	Enhanced canopy growth precedes senescence in 2005 and 2010 Amazonian droughts	en_US
dc.type	Journal Article
utslib.citation.volume	211	en_US
utslib.for	0406 Physical Geography and Environmental Geoscience	en_US
utslib.for	0909 Geomatic Engineering	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Faculty of Science/School of Life Sciences
pubs.organisational-group	/University of Technology Sydney/Strength - CAMGIS - Centre for Advanced Modelling and Geospatial lnformation Systems
utslib.copyright.status	closed_access
pubs.publication-status	Published	en_US
pubs.volume	211	en_US

Abstract:

© 2018 Unprecedented droughts hit southern Amazonia in 2005 and 2010, causing a sharp increase in tree mortality and carbon loss. To better predict the rainforest's response to future droughts, it is necessary to understand its behavior during past events. Satellite observations provide a practical source of continuous observations of Amazonian forest. Here we used a passive microwave-based vegetation water content record (i.e., vegetation optical depth, VOD), together with multiple hydrometeorological observations as well as conventional satellite vegetation measures, to investigate the rainforest canopy dynamics during the 2005 and 2010 droughts. During the onset of droughts in the wet-to-dry season (May–July) of both years, we found large-scale positive anomalies in VOD, leaf area index (LAI) and enhanced vegetation index (EVI) over the southern Amazonia. These observations are very likely caused by enhanced canopy growth. Concurrent below-average rainfall and above-average radiation during the wet-to-dry season can be interpreted as an early arrival of normal dry season conditions, leading to enhanced new leaf development and ecosystem photosynthesis, as supported by field observations. Our results suggest that further rainfall deficit into the subsequent dry season caused water and heat stress during the peak of 2005 and 2010 droughts (August–October) that exceeded the tolerance limits of the rainforest, leading to widespread negative VOD anomalies over the southern Amazonia. Significant VOD anomalies were observed mainly over the western part in 2005 and mainly over central and eastern parts in 2010. The total area with significant negative VOD anomalies was comparable between these two drought years, though the average magnitude of significant negative VOD anomalies was greater in 2005. This finding broadly agrees with the field observations indicating that the reduction in biomass carbon uptake was stronger in 2005 than 2010. The enhanced canopy growth preceding drought-induced senescence should be taken into account when interpreting the ecological impacts of Amazonian droughts.

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http://hdl.handle.net/10453/130290