A 20-year study of NDVI variability over the Northeast Region of Brazil

Barbosa, HA; Huete, AR; Baethgen, WE

A 20-year study of NDVI variability over the Northeast Region of Brazil

Barbosa, HA Huete, AR

Baethgen, WE

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Publication Type:: Journal Article
Citation:: Journal of Arid Environments, 2006, 67 (2), pp. 288 - 307
Issue Date:: 2006-10-01

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Field	Value	Language
dc.contributor.author	Barbosa, HA	en_US
dc.contributor.author	Huete, AR https://orcid.org/0000-0003-2809-2376	en_US
dc.contributor.author	Baethgen, WE	en_US
dc.date.issued	2006-10-01	en_US
dc.identifier.citation	Journal of Arid Environments, 2006, 67 (2), pp. 288 - 307	en_US
dc.identifier.issn	0140-1963	en_US
dc.identifier.uri	http://hdl.handle.net/10453/8543
dc.description.abstract	The natural ecosystems of the Northeast Region of Brazil (NEB) have experienced persistent drought episodes and environmental degradation during the past two decades. In this study, we examined the spatial heterogeneity and temporal dynamics of the NEB using a 20-year time series of Normalized Difference Vegetation Index (NDVI) observations, derived from the National Oceanographic and Atmospheric Administration (NOAA)-Advanced Very High Resolution Radiometer (AVHRR) instrument. A set of 12 000 spatially distributed NDVI values was analysed to investigate significant deviations from the mean-monthly values of the base period (1982-2001) in the study area. Various statistical analyses involving minimum, mean and maximum values, coefficient of variation (CV), standardized anomalies (Z-scores), and 36-month running mean were applied to monthly NDVI values to identify spatial and temporal variations in vegetation dynamics. We found strong seasonal oscillations in the vegetation-growing season (February-May) over the NEB study area, with maximum NDVI observed in April-May and seasonal variations, expressed by the CV, ranging from 14% to 32%. In addition, a consistent upward trend in vegetation greenness occurred over the period 1984-1990, and was strongly reversed in the subsequent period 1991-1998. These upward and downward trends in vegetation greenness followed an inter-annual oscillation of ∼7-8 years. We also found that dry season peak (September) latitudinal variations in NDVI were 20-25% greater in 1991-1999 than 1982-1990 across the study region. The results of this study suggest that patterns in NEB vegetation variability were a result of the impact of enhanced aridity occurring over the last decade of the 20th century. © 2006 Elsevier Ltd. All rights reserved.	en_US
dc.relation.ispartof	Journal of Arid Environments	en_US
dc.relation.isbasedon	10.1016/j.jaridenv.2006.02.022	en_US
dc.subject.classification	Ecology	en_US
dc.title	A 20-year study of NDVI variability over the Northeast Region of Brazil	en_US
dc.type	Journal Article
utslib.citation.volume	2	en_US
utslib.citation.volume	67	en_US
utslib.for	0602 Ecology	en_US
utslib.for	0502 Environmental Science and Management	en_US
utslib.for	04 Earth Sciences	en_US
utslib.for	05 Environmental Sciences	en_US
utslib.for	06 Biological Sciences	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.issue	2	en_US
pubs.publication-status	Published	en_US
pubs.volume	67	en_US

Abstract:

The natural ecosystems of the Northeast Region of Brazil (NEB) have experienced persistent drought episodes and environmental degradation during the past two decades. In this study, we examined the spatial heterogeneity and temporal dynamics of the NEB using a 20-year time series of Normalized Difference Vegetation Index (NDVI) observations, derived from the National Oceanographic and Atmospheric Administration (NOAA)-Advanced Very High Resolution Radiometer (AVHRR) instrument. A set of 12 000 spatially distributed NDVI values was analysed to investigate significant deviations from the mean-monthly values of the base period (1982-2001) in the study area. Various statistical analyses involving minimum, mean and maximum values, coefficient of variation (CV), standardized anomalies (Z-scores), and 36-month running mean were applied to monthly NDVI values to identify spatial and temporal variations in vegetation dynamics. We found strong seasonal oscillations in the vegetation-growing season (February-May) over the NEB study area, with maximum NDVI observed in April-May and seasonal variations, expressed by the CV, ranging from 14% to 32%. In addition, a consistent upward trend in vegetation greenness occurred over the period 1984-1990, and was strongly reversed in the subsequent period 1991-1998. These upward and downward trends in vegetation greenness followed an inter-annual oscillation of ∼7-8 years. We also found that dry season peak (September) latitudinal variations in NDVI were 20-25% greater in 1991-1999 than 1982-1990 across the study region. The results of this study suggest that patterns in NEB vegetation variability were a result of the impact of enhanced aridity occurring over the last decade of the 20th century. © 2006 Elsevier Ltd. All rights reserved.

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http://hdl.handle.net/10453/8543