Discrimination of the Respective Contributions of Understory and Tree Canopy to the Seasonal Dynamics of Reflectance of Maritime Pine Forest in Southwest France

The objective of this study is to estimate the potential of remote sensing observations over forests in order to distinguish the seasonal dynamic of LAI and fAPAR of understory and tree canopy over the large maritime pine forest "Les Landes" in south-western France. First, we measured the seasonal dynamic of the vegetation index PVI using a time series of seasonal reflectance data acquired from 2002 to 2007 with the VEGETATION radiometer. Also, we monitored the seasonal changes of LAI and fAPAR of the understory and tree canopy layers from ground measurements with hemispherical photographs and PAR sensors on four sites, which were representative of the different ecological conditions found in "Les Landes". Finally, we compared the seasonal dynamic of PVI with the seasonal dynamic of LAI and fAPAR measured for both layers. The first results showed that the seasonal variation of PVI could mainly be explained by the seasonal variation of LAI and fAPAR of understory vegetation.