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Seasonality and drought effects of Amazonian forests observed from multi-angle satellite data

Seasonality and drought effects of Amazonian forests observed from multi-angle satellite data
Seasonality and drought effects of Amazonian forests observed from multi-angle satellite data
Seasonality and drought in Amazon rainforests have been controversially discussed in the literature, partially due to a limited ability of current remote sensing techniques to detect its impacts on tropical vegetation. We use a multi-angle remote sensing approach to determine changes in vegetation structure from differences in directional scattering (anisotropy) observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) with data atmospherically corrected by the Multi-Angle Implementation Atmospheric Correction Algorithm (MAIAC). Our results show a strong linear relationship between anisotropy and field (r2 = 0.70) and LiDAR (r2 = 0.88) based estimates of LAI even in dense canopies (LAI ? 7 m2 m? 2). This allowed us to obtain improved estimates of vegetation structure from optical remote sensing. We used anisotropy to analyze Amazon seasonality based on spatially explicit estimates of onset and length of dry season obtained from the Tropical Rainfall Measurement Mission (TRMM). An increase in vegetation greening was observed during the beginning of dry season (across ~ 7% of the basin), which was followed by a decline (browning) later during the dry season (across ~ 5% of the basin). Anomalies in vegetation browning were particularly strong during the 2005 and 2010 drought years (~ 10% of the basin). We show that the magnitude of seasonal changes can be significantly affected by regional differences in onset and duration of the dry season. Seasonal changes were much less pronounced when assuming a fixed dry season from June through September across the Amazon Basin. Our findings reconcile remote sensing studies with field based observations and model results as they provide a sounder basis for the argument that tropical vegetation growth increases during the beginning of the dry season, but declines after extended drought periods. The multi-angle approach used in this work may help quantify drought tolerance and seasonality in the Amazonian forests.
amazon, anisotropy, browning, drought, greening, MAIAC, MODIS
0034-4257
278-290
Mendes de Moura, Yhasmin
5391f401-2f7c-4173-90f4-ed6e6d5324e4
Hilker, Thomas
c7fb75b8-320d-49df-84ba-96c9ee523d40
Lyapustin, Alexei, I.
6eb2d498-94ca-49b1-b0ab-89028d0e44c8
Soares Galvão, Lênio
215cfafc-c6de-4cee-a708-d81c6589502f
Roberto dos Santos, João
5e2ef154-246a-4413-8498-ea279ca292cb
Anderson, Liana O.
07be8e9d-0046-4e64-90d6-a8edc08125e4
Helder Resende de Sousa, Célio
38f65565-840b-4b84-b99d-04043cb65ad2
Arai, Egidio
f9acca09-79e5-4098-b37b-cbf7a1046605
Mendes de Moura, Yhasmin
5391f401-2f7c-4173-90f4-ed6e6d5324e4
Hilker, Thomas
c7fb75b8-320d-49df-84ba-96c9ee523d40
Lyapustin, Alexei, I.
6eb2d498-94ca-49b1-b0ab-89028d0e44c8
Soares Galvão, Lênio
215cfafc-c6de-4cee-a708-d81c6589502f
Roberto dos Santos, João
5e2ef154-246a-4413-8498-ea279ca292cb
Anderson, Liana O.
07be8e9d-0046-4e64-90d6-a8edc08125e4
Helder Resende de Sousa, Célio
38f65565-840b-4b84-b99d-04043cb65ad2
Arai, Egidio
f9acca09-79e5-4098-b37b-cbf7a1046605

Mendes de Moura, Yhasmin, Hilker, Thomas, Lyapustin, Alexei, I., Soares Galvão, Lênio, Roberto dos Santos, João, Anderson, Liana O., Helder Resende de Sousa, Célio and Arai, Egidio (2015) Seasonality and drought effects of Amazonian forests observed from multi-angle satellite data. Remote Sensing of Environment, 171, 278-290. (doi:10.1016/j.rse.2015.10.015).

Record type: Article

Abstract

Seasonality and drought in Amazon rainforests have been controversially discussed in the literature, partially due to a limited ability of current remote sensing techniques to detect its impacts on tropical vegetation. We use a multi-angle remote sensing approach to determine changes in vegetation structure from differences in directional scattering (anisotropy) observed by the Moderate Resolution Imaging Spectroradiometer (MODIS) with data atmospherically corrected by the Multi-Angle Implementation Atmospheric Correction Algorithm (MAIAC). Our results show a strong linear relationship between anisotropy and field (r2 = 0.70) and LiDAR (r2 = 0.88) based estimates of LAI even in dense canopies (LAI ? 7 m2 m? 2). This allowed us to obtain improved estimates of vegetation structure from optical remote sensing. We used anisotropy to analyze Amazon seasonality based on spatially explicit estimates of onset and length of dry season obtained from the Tropical Rainfall Measurement Mission (TRMM). An increase in vegetation greening was observed during the beginning of dry season (across ~ 7% of the basin), which was followed by a decline (browning) later during the dry season (across ~ 5% of the basin). Anomalies in vegetation browning were particularly strong during the 2005 and 2010 drought years (~ 10% of the basin). We show that the magnitude of seasonal changes can be significantly affected by regional differences in onset and duration of the dry season. Seasonal changes were much less pronounced when assuming a fixed dry season from June through September across the Amazon Basin. Our findings reconcile remote sensing studies with field based observations and model results as they provide a sounder basis for the argument that tropical vegetation growth increases during the beginning of the dry season, but declines after extended drought periods. The multi-angle approach used in this work may help quantify drought tolerance and seasonality in the Amazonian forests.

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More information

Accepted/In Press date: 22 October 2015
e-pub ahead of print date: 5 November 2015
Published date: 15 December 2015
Keywords: amazon, anisotropy, browning, drought, greening, MAIAC, MODIS
Organisations: Geography & Environment

Identifiers

Local EPrints ID: 384671
URI: https://eprints.soton.ac.uk/id/eprint/384671
ISSN: 0034-4257
PURE UUID: 14958887-8b67-4b66-b4f3-86821f61c593

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Date deposited: 11 Jan 2016 16:25
Last modified: 15 Jul 2019 20:55

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Contributors

Author: Yhasmin Mendes de Moura
Author: Thomas Hilker
Author: Alexei, I. Lyapustin
Author: Lênio Soares Galvão
Author: João Roberto dos Santos
Author: Liana O. Anderson
Author: Célio Helder Resende de Sousa
Author: Egidio Arai

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