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Identification of hyperspectral vegetation indices for Mediterranean pasture characterization

Fava, Francesco and Colombo, Roberto and Bocchi, Stefano and Meroni, Michele and Sitzia, Maria and Fois, Nicola and Zucca, Claudio (2009) Identification of hyperspectral vegetation indices for Mediterranean pasture characterization. International Journal of Applied Earth Observation and Geoinformation, Vol. 11 (4), p. 233-243. ISSN 0303-2434. Article.

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DOI: 10.1016/j.jag.2009.02.003

Abstract

A field experiment was carried out to assess biomass and nitrogen status in Mediterranean pastures by means of hyperspectral high resolution field radiometric data. Spectral and agronomic measurements were collected at three different pasture growth stages and in grazed–ungrazed plots distributed over an area of 14 ha. Reflectance-based vegetation indices such as simple ratio indices (SR[i,j]) and normalized difference vegetation indices (NDVI[i,j]) were calculated using all combinations of two wavelengths i and j in the spectral range 400–1000 nm. The performances of these indices in predicting green biomass (GBM, t ha−1), leaf area index (LAI, m2 m−2), nitrogen content (N, kg ha−1) and nitrogen concentration (NC, %) were evaluated by linear regression analysis using the cross validated coefficient of determination (R2CV) and root mean squared error (RMSECV). SR involving bands in near-infrared (i = 770–930 nm) and in the red edge (j = 720–740 nm) yielded the best performance for GBM (R2CV = 0.73, RMSECV = 2.35 t ha−1), LAI (R2CV = 0.73, RMSECV = 0.37 m2 m -2), and N (R2CV = 0.73, RMSECV= 7.36 kg ha−1). The best model performances for NC (R2CV = 0.54, RMSECV = 0.35%) were obtained using SR involving near-infrared bands (i = 775–820 nm) and longer wavelengths of the red edge (j = 740–770 nm). The defined indices lead to significant improvements in model predictive capability compared to the traditional SR [near-infrared, red] and NDVI [near-infrared, red] and to broad-band indices. The possibility of exploiting these results gathered at field level with high resolution spectral data (FWHM 3.5 nm) also at landscape level by means of hyperspectral airborne or satellite sensors was explored. Model performances resulted extremely sensitive to band position, suggesting the importance of using hyperspectral sensors with contiguous spectral bands.

Item Type:Article
ID Code:2659
Status:Published
Refereed:Yes
Uncontrolled Keywords:Pasture, remote sensing, hyperspectral indices, biomass, leaf area index, nitrogen
Subjects:Area 07 - Scienze agrarie e veterinarie > AGR/14 Pedologia
Divisions:001 Università di Sassari > 01 Dipartimenti > Scienze zootecniche
001 Università di Sassari > 02 Centri > Centro interdipartimentale Nucleo di ricerca sulla desertificazione
Publisher:Elsevier
ISSN:0303-2434
Deposited On:18 Aug 2009 10:08

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