Lopes, DM, Aranha, JT, Walford, N, O'Brien, J, Lucas, N (2009). Accuracy of remote sensing data versus other sources of information for estimating net primary production in Eucalyptus globulus Labill. and Pinus pinaster Ait. ecosystems in Portugal. CANADIAN JOURNAL OF REMOTE SENSING, 35(1), 37-53.
Net primary production (NPP) quantifies vegetation growth. It reflects the impact of biotic and abiotic factors over an ecosystem and is an important ecological variable for monitoring the impact of human activity on ecosystems. Though conceptually simple, NPP can be very difficult to measure accurately. In this paper, different temporal and spatial NPP products are compared, improving our understanding of the accuracy of these methods for measuring NPP in small forested areas of Eucalyptus globulus Labill. and Pinus pinaster Ait. stands. The Moderate-Resolution Imaging Spectroradiometer (MODIS) NPP products were compared with NPP values obtained from FOREST-BGC (a well-known ecophysiological model) and field measurements. The paper also examines the possibility of estimating the leaf area index (LAI), a key FOREST-BGC input, using remote sensing techniques. The results indicate that the most accurate estimates were achieved using the FOREST-BGC model, which is normally applied at the stand level. Since LAI can be estimated from remotely sensed data, this ecophysiological model may now be regarded as suitable for use at the regional and global scales. The results also showed that, although average NPP values are similar to field measurements, MODIS NPP products are inefficient for identifying extreme NPP values.