Assessing forest productivity: Satellite versus terrestrial data-driven estimates in Austria

Forest productivity has always been A major issue within sustainable forest management. While in the past, terrestrial forest inventory data have been the major source for assessing forest productivity, recent developments of modeling techniques and satellite-derived information have become of increasing interest for productivity estimates. Using a mechanistic model enables us to analyze the pools and fluxes within a forest ecosystem. On the other hand, satellite data as they can be derived from, say, the Moderate Resolution Imaging Spectroradiometer (MODIS) Sensor may be used for monitoring global and/or regional Net Primary Production (NPP). In this study we first present the incorporation of management within a mechanistic ecosystem model and then use this approach for comparing satellite vs. terrestrial driven NPP based on different estimation procedures: (1) NPP estimates derived from MODIS satellite, (2) estimates from the species specific adaptation of Biome-BGC, and (3) NPP estimates derived from inventory data using biomass expansion functions (BEF). First results suggest that the scaling issue is of major concern since the area covered by the satellite images is much larger than the area which is commonly assumed to be represented by inventory plots. Thus, satellite-based approaches may overlook details which are covered by inventory data. After aggregating the available inventory information to ecological growth regions, the correlation between satellite vs. terrestrial data-driven NPP estimates improved substantially.