Seasonal Dynamics of Boreal Forest Structure and Reflectance

Global-scale plant phenology observations are needed to understand the seasonality of biosphere-atmosphere interactions and the ecological consequences of an altered growing period. Satellite remote sensing offers an efficient means for making spatially and temporally continuous observations of vegetation dynamics. Our project focuses on quantifying the seasonal dynamics of boreal forest ecosystems and linking the different vegetation phases to satellite reflectance data. We present (to our knowledge) the first, seasonal in situ measurements of boreal forest canopy leaf area index (LAI) for a range of forest types as well as seasonal reflectance trajectories of boreal forest understory species. The measurements were carried out during 2009 and 2010 in Hyytiala (Finland); Hyytiala represents typical, Scots pine and Norway spruce dominated vegetation of the southern boreal zone in Europe. We compare our ground reference data to reflectance factors, spectral vegetation indices and vegetation products obtained from a time series of MODIS satellite images for the same area. Finally, we discuss possible sources of error in predicting the phenological phases of a boreal forest area using satellite remote sensing data.