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USA-NPN Strategy and Activities for LSP/RS
With these issues in mind, the remote sensing group of NPN constructed short- and medium-term strategies for implementing the remote sensing component of NPN. The short-term strategy includes plans for both in situ validation/characterization pilot studies of LSP at intensive observation sites (in cooperation with several LTERs) and an observation protocol for cooperating extensive observation sites that will make broader-scale observations. The pilot experiment will involve collecting weekly measurements (including digital photographs) of community greenness at fixed transect sites that can be compared to Landsat and MODIS observed fractional greenness. The extensive observations will provide information on the spatial patterns of stages of vegetation community phenology that can be compared to both remote sensing and species level observations to forge a stronger link between the two approaches. The mid-term goals include development of a web site for the group, initiation of a field validation study of the intensive observation sites (developed from lessons learned during the pilot study), and development of proposals involving validation techniques, algorithm intercomparison studies, and forecast model development.
A wealth of remote-sensing research fields will be opened with the availability of the NPN data sets, including: 1) comparative studies of alternative phenology characterization techniques; 2) techniques to validate remote sensing phenology parameters; 3) characterization of relationships of key phenology parameters to climatic variables; 4) characterization of relationships of remote sensing-based phenology parameters to indicator species and natural vegetation; and 5) scaling studies. Phenological data collected by the various tiers of the NPN will be a critical source for validating land surface phenology estimates from satellite sensors and, conversely, estimates from remote sensing can fill gaps between ground observations to produce a continuous surface of phenology estimates at the continental scale.