Research Papers

Forest leaf area index in an Alpine valley from medium resolution satellite imagery and in situ data

[+] Author Affiliations
Daniela Stroppiana, Mirco Boschetti, Pietro A. Brivio

Istituto per il Rilevamento Elettromagnetico dell’Ambiente, IREA-CNR, Via Bassini 15, 20133 Milano, Italy

Luca Nizzetto

University of Lancaster, Lancaster Environment Centre, Center for Chemicals Management, Lancaster LA1 4YQ, England

Norwegian Institute for Water Research, Brekkevein 19, N-0349 Oslo, Norway

Antonio Di Guardo

University of Insubria, Department of Science and High Technology, Via Valleggio 11, 22100 Como, Italy

J. Appl. Remote Sens. 6(1), 063528 (Apr 23, 2012). doi:10.1117/1.JRS.6.063528
History: Received September 26, 2011; Revised March 8, 2012; Accepted March 19, 2012
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Abstract.  Leaf area index (LAI) is a key variable for modeling the interaction between vegetation and the atmosphere. We collected field LAI measurements over 12 sites in 2005 in the Lys valley, Northern Italy, to calibrate regressive models using normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), and wide dynamic range vegetation index (WDRVI) products derived from 250-m moderate resolution imaging spectroradiomete (MODIS) imagery. Field data were compared to the 1 km MODIS leaf area index—fraction of photosynthetically active radiation (LAI/fAPAR) product to show that regressive techniques are better suited for local applications. We investigated these LAI-vegetation index (VI) regressive models to 1. test the sensitivity of the model to forest type and phenology, 2. identify the most suitable VI for LAI retrieval, and 3. verify the feasibility of using a linear model. Results show that in our experimental conditions the LAI-VI relationship is primarily influenced by phenology and that the leaf constant period (maximum LAI) is significantly different compared to the other phenological phases. Among the indices, EVI yielded the poorest performance (R2<0.41) and the linear regressive models for NDVI and WDRVI derived by pooling together data from different phenological phases show a good correlation with field data (R2>0.65); the use of a logarithmic model does not improve the performance. The LAI-WDRVI and LAI-NDVI models were inverted and applied to 2004 MODIS data and model performance was assessed by comparing predicted and measured LAI. Results show that WDRVI performs best in a linear regressive model, yielding a relative root mean square error <23%.

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© 2012 Society of Photo-Optical Instrumentation Engineers

Citation

Daniela Stroppiana ; Mirco Boschetti ; Pietro A. Brivio ; Luca Nizzetto and Antonio Di Guardo
"Forest leaf area index in an Alpine valley from medium resolution satellite imagery and in situ data", J. Appl. Remote Sens. 6(1), 063528 (Apr 23, 2012). ; http://dx.doi.org/10.1117/1.JRS.6.063528


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