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Spatiotemporal variation in the terrestrial vegetation phenology of Iraq and its relation with elevation

Spatiotemporal variation in the terrestrial vegetation phenology of Iraq and its relation with elevation
Spatiotemporal variation in the terrestrial vegetation phenology of Iraq and its relation with elevation
Iraq contains the Great Mesopotamian alluvial plain of the Euphrates and Tigris rivers. Its regional vegetation phenological patterns are worthy of investigation because relatively little is known about the phenology of semi-arid environments, and because their inter-annual variation is expected to be driven by uncertain rainfall and varied topography. The aim of this research was to assess and map the spatial variation in key land surface phenology (LSP) parameters over the last decade and their relation with elevation. It is the first study mapping land surface phenology during last decade over the whole of Iraq, and one of only a few studies on vegetation phenology in a semi-arid environment. Time-series of Moderate Resolution Imaging Spectroradiometer (MODIS) normalised difference vegetation index (NDVI) data at 250 m spatial resolution and 8 day temporal resolution, were employed to map the spatial variation in three LSP parameters for the major vegetation types in Iraq during 2001–2012. LSP parameters were defined by inflection points after smoothing the vegetation phenological signals using the Fourier technique. The estimated key LSP parameters indicated that the relatively shorter length of season (LOS) in the north of Iraq resulted from a delayed start of season (SOS). Greater spatial variation occurred in the SOS than end of season (EOS), which may be due to the spatial distribution of rainfall and temperature as a function of elevation. A positive correlation was observed for SOS and EOS with elevation for all major land cover types with EOS producing the largest positive correlation (R2 = 0.685, R2 = 0.638 and R2 = 0.588, p < 0.05 in shrubland, cropland and grassland, respectively). The magnitude of delay in SOS and EOS increased in all land cover types along a rising elevation gradient where for each 500 m increase, SOS was delayed by around 25 or more days and EOS delayed by around 22 or more days, except for grassland. The SOS and EOS also varied temporally during the last decade, particularly the SOS in the lowland, north of the country where the standard deviation was around 80 to 120 days, due mainly to the practice of crop rotation and the traditional biennial cropping system. Thus, the results of this research emphasize the effect of elevation on key LSP parameters over Iraq, for all major vegetation types.
Phenology Time–series Iraq NDVI Elevation
0303-2434
107-117
Qader, Sarchil
b1afb647-aeff-4bb8-84f2-56865c4eb9e4
Atkinson, Peter
96e96579-56fe-424d-a21c-17b6eed13b0b
Dash, Jadunandan
51468afb-3d56-4d3a-aace-736b63e9fac8
Qader, Sarchil
b1afb647-aeff-4bb8-84f2-56865c4eb9e4
Atkinson, Peter
96e96579-56fe-424d-a21c-17b6eed13b0b
Dash, Jadunandan
51468afb-3d56-4d3a-aace-736b63e9fac8

Qader, Sarchil, Atkinson, Peter and Dash, Jadunandan (2015) Spatiotemporal variation in the terrestrial vegetation phenology of Iraq and its relation with elevation. International Journal of Applied Earth Observation and Geoinformation, 41, 107-117. (doi:10.1016/j.jag.2015.04.021).

Record type: Article

Abstract

Iraq contains the Great Mesopotamian alluvial plain of the Euphrates and Tigris rivers. Its regional vegetation phenological patterns are worthy of investigation because relatively little is known about the phenology of semi-arid environments, and because their inter-annual variation is expected to be driven by uncertain rainfall and varied topography. The aim of this research was to assess and map the spatial variation in key land surface phenology (LSP) parameters over the last decade and their relation with elevation. It is the first study mapping land surface phenology during last decade over the whole of Iraq, and one of only a few studies on vegetation phenology in a semi-arid environment. Time-series of Moderate Resolution Imaging Spectroradiometer (MODIS) normalised difference vegetation index (NDVI) data at 250 m spatial resolution and 8 day temporal resolution, were employed to map the spatial variation in three LSP parameters for the major vegetation types in Iraq during 2001–2012. LSP parameters were defined by inflection points after smoothing the vegetation phenological signals using the Fourier technique. The estimated key LSP parameters indicated that the relatively shorter length of season (LOS) in the north of Iraq resulted from a delayed start of season (SOS). Greater spatial variation occurred in the SOS than end of season (EOS), which may be due to the spatial distribution of rainfall and temperature as a function of elevation. A positive correlation was observed for SOS and EOS with elevation for all major land cover types with EOS producing the largest positive correlation (R2 = 0.685, R2 = 0.638 and R2 = 0.588, p < 0.05 in shrubland, cropland and grassland, respectively). The magnitude of delay in SOS and EOS increased in all land cover types along a rising elevation gradient where for each 500 m increase, SOS was delayed by around 25 or more days and EOS delayed by around 22 or more days, except for grassland. The SOS and EOS also varied temporally during the last decade, particularly the SOS in the lowland, north of the country where the standard deviation was around 80 to 120 days, due mainly to the practice of crop rotation and the traditional biennial cropping system. Thus, the results of this research emphasize the effect of elevation on key LSP parameters over Iraq, for all major vegetation types.

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More information

Accepted/In Press date: 29 April 2015
e-pub ahead of print date: 16 May 2015
Published date: September 2015
Keywords: Phenology Time–series Iraq NDVI Elevation
Organisations: Geography & Environment

Identifiers

Local EPrints ID: 377741
URI: https://eprints.soton.ac.uk/id/eprint/377741
ISSN: 0303-2434
PURE UUID: 14831c8c-0d2c-4005-ab07-2ccf11852a68
ORCID for Peter Atkinson: ORCID iD orcid.org/0000-0002-5489-6880
ORCID for Jadunandan Dash: ORCID iD orcid.org/0000-0002-5444-2109

Catalogue record

Date deposited: 16 Jun 2015 16:17
Last modified: 10 Sep 2019 00:54

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