A comparison of landsat TM and MODIS vegetation indices for estimating forage phenology in desert bighorn sheep (ovis canadensis nelsoni) habitat in the Sonoran desert, USA

Steven Edward Sesnie, Brett G Dickson, Steven Sheldon Rosenstock, Jill Marie Rundall

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Sonoran Desert bighorn sheep (Ovis canadensis mexicana) occupy rugged upland areas that experience irregular periods of vegetation growth associated with precipitation events. These episodic and often spatially limited events provide important forage and preformed water resources that may be important drivers of animal movement and habitat use. Habitat-use models that incorporate forage phenology would broaden our understanding of desert bighorn ecology and have considerable potential to inform conservation efforts for the species. Field-based methods are of limited utility to characterize vegetation phenology across large areas. Vegetation indices (VI) derived from satellite imagery are a viable alternative, but may be confounded by areas of high relief and shadow effects that can degrade VI values. The varying spatial and temporal resolutions of readily available satellite sensors, such as the Landsat thematic mapper (TM) and moderate-resolution imaging spectrometer (MODIS), present additional challenges. In this study, we sought to minimize degrading effects of terrain on TM- and MODIS-based estimates of vegetation phenology. We compared effects of high topographic relief on time series MODIS-and TM-based VI such as the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) using VI departures from average (DA) in shaded and unshaded areas. Sun elevation angle negatively impacted TM-derived NDVI and EVI values in areas of steep terrain. In contrast, MODIS-derived NDVI values were insensitive to sun elevation and terrain effects, whereas MODIS-derived EVI was degraded in areas of steep terrain. Time series MODIS NDVI and EVI DA values differed significantly during months of low sun elevation angle. Average MODIS EVI departure values were ≥20% lower than NDVI under these conditions, confounding time series estimates of plant phenology. Our best results were obtained from MODIS 16-day composited NDVI. These remote-sensing-based VI estimates of seasonal plant phenology and productivity can be used to inform models of habitat use and movements of desert bighorn over large areas.

Original languageEnglish (US)
Pages (from-to)276-286
Number of pages11
JournalInternational Journal of Remote Sensing
Volume33
Issue number1
DOIs
StatePublished - Jan 2012

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vegetation index
Landsat thematic mapper
sheep
phenology
MODIS
forage
desert
NDVI
habitat
habitat use
time series
vegetation
relief
comparison
satellite sensor
satellite imagery
water resource
ecology
remote sensing
productivity

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Cite this

A comparison of landsat TM and MODIS vegetation indices for estimating forage phenology in desert bighorn sheep (ovis canadensis nelsoni) habitat in the Sonoran desert, USA. / Sesnie, Steven Edward; Dickson, Brett G; Rosenstock, Steven Sheldon; Rundall, Jill Marie.

In: International Journal of Remote Sensing, Vol. 33, No. 1, 01.2012, p. 276-286.

Research output: Contribution to journalArticle

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