Comparison of leaf area indices for grasslands within the Alpine upland based on multi-scale satellite data time series and radiation transfer modeling

In this study, the leaf area index (LAI) of grasslands in the Bavarian Alpine uplands has been derived using inverted radiation transfer modeling (RTM) on original as well as simulated remote sensing data time series. The spatial resolutions of the data sets range from 6.5 to 250 m. While the high resolution data are available for four points in the vegetation period, the medium resolution time series consist of weekly scenes. The aim is to investigate the performance of the inverse RTM when applied to satellite data of different spatial and temporal resolutions. Further, we determine the adequate resolutions of remote sensing data for LAI retrieval in a heterogeneous landscape. All results were validated using in situ measurements. While the algorithm proves to be generally applicable in this challenging landscape on different scales, retrieval accuracy increases with higher spatial resolution. Satellite images with a spatial resolution up to 20 m are identified as a good compromise between accurate results and spatial detail. The 250 m resolution LAI time series on the other hand provides valuable information on the phenology and sudden LAI reductions caused by harvest, which are not captured by the high spatial resolution time series with few scenes.