Modelling of Italian forest net primary productivity by the integration of remotely sensed and GIS data

This paper reports on the development and testing of a procedure for assessing large-scale patterns of forest net primary productivity (NPP) in Italy. The work was based on a straightforward forest productivity model (C-Fix) which uses the relationship between absorbed photosynthetically active radiation of plant canopies and relevant biomass productivity. The objective was to develop a procedure of simple implementation, based on widely available Earth Observation (SPOT Vegetation, VGT) and ancillary data, suitable for rapid assessment of forest net primary productivity on a national level. The original C-Fix methodology, which was proposed in 1994 and has been applied all over Europe, was improved by the use of more abundant ancillary information and more efficient techniques for NDVI data processing. In this way, the method was suited to evaluating mean productivity levels of existing forests. The accuracy of the model outputs was assessed through comparison with independent estimates of forest NPP. The results obtained were satisfactory, with some shortcomings mainly due to the limited spatial resolution of SPOT Vegetation VGT data with respect to the high heterogeneity of forest landscapes in Italy. After including correction factors which accounted for the mean canopy covers of existing forest types, the method allowed the computation of NPP estimates for all Italian forests.